[1mInter-Client Communication Conventions Manual[0m
[1mVersion 2.0.xf86.1[0m
[1mXFree86 4.0.2[0m
[1mXFree86, Inc.[0m
[4mbased[24m [4mon[0m
[1mVersion 2.0[0m
[1mX Consortium Standard[0m
[1mX Version 11, Release 6.4[0m
David Rosenthal
Sun Microsystems, Inc.
Version 2 edited by Stuart W. Marks
SunSoft, Inc.
X Window System is a trademark of X Consortium, Inc.
Copyright (C) 1988, 1991, 1993, 1994 X Consortium
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documenta-
tion files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or
sell copies of the Software, and to permit persons to whom
the Software is furnished to do so, subject to the following
conditions:
The above copyright notice and this permission notice shall
be included in all copies or substantial portions of the
Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PUR-
POSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSOR-
TIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
OR OTHER DEALINGS IN THE SOFTWARE.
Except as contained in this notice, the name of the X Con-
sortium shall not be used in advertising or otherwise to
promote the sale, use or other dealings in this Software
without prior written authorization from the X Consortium.
Copyright (C) 1987, 1988, 1989, 1993, 1994 Sun Microsystems,
Inc.
Permission to use, copy, modify, and distribute this docu-
mentation for any purpose and without fee is hereby granted,
provided that the above copyright notice and this permission
notice appear in all copies. Sun Microsystems makes no rep-
resentations about the suitability for any purpose of the
information in this document. This documentation is pro-
vided as is without express or implied warranty.
ii
vi
[1mPreface to Version 2.0[0m
The goal of the ICCCM Version 2.0 effort was to add new
facilities, to fix problems with earlier drafts, and to
improve readability and understandability, while maintaining
compatibility with the earlier versions. This document is
the product of over two years of discussion among the mem-
bers of the X Consortium's [1mwmtalk [22mworking group. The fol-
lowing people deserve thanks for their contributions:
Gabe Beged-Dov Bill Janssen Chan Ben-
son Vania Joloboff Jordan
Brown Phil Karlton Larry
Cable Kaleb Keithley Ellis
Cohen Mark Manasse Donna Con-
verse Ralph Mor Brian
Cripe Todd Newman Susan
Dahlberg Bob Scheifler Peter Dai-
fuku Keith Taylor Andrew
deBlois Jim VanGilder Clive
Feather Mike Wexler Stephen
Gildea Michael Yee Christian Jacobi
It has been a privilege for me to work with this fine group
of people.
Stuart W. Marks
December 1993
vii
[1mPreface to Version 1.1[0m
David Rosenthal had overall architectural responsibility for
the conventions defined in this document; he wrote most of
the text and edited the document, but its development has
been a communal effort. The details were thrashed out in
meetings at the January 1988 MIT X Conference and at the
1988 Summer Usenix conference, and through months (and
megabytes) of argument on the mail alias. Thanks are due to
everyone who contributed, and especially to the following
people.
For the Selection section:
Jerry Farrell Phil Karlton Loretta Guarino Reid Mark Manasse
Bob Scheifler
For the Cut-Buffer section:
Andrew Palay
For the Window and Session Manager sections:
Todd Brunhoff Matt Landau Ellis
Cohen Mark Manasse Jim Ful-
ton Bob Scheifler Hania Gajew-
ska Ralph Swick Jordan Hub-
bard Mike Wexler Kerry Kim-
brough Glenn Widener Audrey
Ishizaki
For the Device Color Characterization section: Keith Packard
In addition, thanks are due to those who contributed to the
public review:
Gary Combs John Irwin Errol
Crary Vania Joloboff Nancy
Cyprych John Laporta John Dia-
mant Ken Lee Clive
Feather Stuart Marks Burns
Fisher Alan Mimms Richard
Greco Colas Nahaboo Tim Green-
wood Mark Patrick Kee Hinck-
ley Steve Pitschke Brian
Holt Brad Reed John Inter-
rante John Thomas
viii
It was an explicit design goal of X Version 11 to specify
mechanism, not policy. As a result, a client that converses
with the server using the protocol defined by the [4mX[24m [4mWindow[0m
[4mSystem[24m [4mProtocol[24m, [4mVersion[24m [4m11[24m may operate correctly in isola-
tion but may not coexist properly with others sharing the
same server.
Being a good citizen in the X Version 11 world involves
adhering to conventions that govern inter-client communica-
tions in the following areas:
+o Selection mechanism
+o Cut buffers
+o Window manager
+o Session manager
+o Manipulation of shared resources
+o Device color characterization
This document proposes suitable conventions without attempt-
ing to enforce any particular user interface. To permit
clients written in different languages to communicate, these
conventions are expressed solely in terms of protocol opera-
tions, not in terms of their associated Xlib interfaces,
which are probably more familiar. The binding of these
operations to the Xlib interface for C and to the equivalent
interfaces for other languages is the subject of other docu-
ments.
In the interests of timely acceptance, the [4mInter-Client[24m [4mCom-[0m
[4mmunication[24m [4mConventions[24m [4mManual[24m (ICCCM) covers only a minimal
set of required conventions. These conventions will be
added to and updated as appropriate, based on the experi-
ences of the X Consortium.
As far as possible, these conventions are upwardly compati-
ble with those in the February 25, 1988, draft that was dis-
tributed with the X Version 11, Release 2, of the software.
In some areas, semantic problems were discovered with those
conventions, and, thus, complete upward compatibility could
not be assured. These areas are noted in the text and are
summarized in Appendix A.
In the course of developing these conventions, a number of
minor changes to the protocol were identified as desirable.
They also are identified in the text, are summarized in Ap-
pendix B, and are offered as input to a future protocol
revision process. If and when a protocol revision incorpo-
rating these changes is undertaken, it is anticipated that
the ICCCM will need to be revised. Because it is difficult
[1m1[0m
[1mInter-Client Communication Conventions X11, Release 6.4[0m
to ensure that clients and servers are upgraded simultane-
ously, clients using the revised conventions should examine
the minor protocol revision number and be prepared to use
the older conventions when communicating with an older
server.
It is expected that these revisions will ensure that clients
using the conventions appropriate to protocol minor revision
[4mn[24m will interoperate correctly with those that use the con-
ventions appropriate to protocol minor revision [4mn[24m + 1 if the
server supports both.
Many of the conventions use atoms. To assist the reader,
the following sections attempt to amplify the description of
atoms that is provided in the protocol specification.
At the conceptual level, atoms are unique names that clients
can use to communicate information to each other. They can
be thought of as a bundle of octets, like a string but with-
out an encoding being specified. The elements are not nec-
essarily ASCII characters, and no case folding happens.1
The protocol designers felt that passing these sequences of
bytes back and forth across the wire would be too costly.
Further, they thought it important that events as they
appear on the wire have a fixed size (in fact, 32 bytes) and
that because some events contain atoms, a fixed-size repre-
sentation for them was needed.
To allow a fixed-size representation, a protocol request was
provided to register a byte sequence with the server, which
returns a 32-bit value (with the top three bits zero) that
maps to the byte sequence. The inverse operator is also
available
The protocol specifies a number of atoms as being prede-
fined:
Predefined atoms are not strictly necessary and
may not be useful in all environments, but they
will eliminate many requests in most applications.
Note that they are predefined only in the sense of
having numeric values, not in the sense of having
required semantics.
Predefined atoms are an implementation trick to avoid the
cost of interning many of the atoms that are expected to be
used during the startup phase of all applications. The
results of the requests, which require a handshake, can be
-----------
1 The comment in the protocol specification for
that ISO Latin-1 encoding should be used is in the
nature of a convention; the server treats the
string as a byte sequence.
[1m2[0m
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assumed [4ma[24m [4mpriori[24m.
Language interfaces should probably cache the atom-name map-
pings and get them only when required. The CLX interface,
for instance, makes no distinction between predefined atoms
and other atoms; all atoms are viewed as symbols at the
interface. However, a CLX implementation will typically
keep a symbol or atom cache and will typically initialize
this cache with the predefined atoms.
The built-in atoms are composed of uppercase ASCII charac-
ters with the logical words separated by an underscore char-
acter (_), for example, WM_ICON_NAME. The protocol specifi-
cation recommends that atoms used for private vendor-spe-
cific reasons should begin with an underscore. To prevent
conflicts among organizations, additional prefixes should be
chosen (for example, _DEC_WM_DECORATION_GEOMETRY).
The names were chosen in this fashion to make it easy to use
them in a natural way within LISP. Keyword constructors
allow the programmer to specify the atoms as LISP atoms. If
the atoms were not all uppercase, special quoting conven-
tions would have to be used.
The core protocol imposes no semantics on atoms except as
they are used in FONTPROP structures. For further informa-
tion on FONTPROP semantics, see the [4mX[24m [4mLogical[24m [4mFont[24m [4mDescrip-[0m
[4mtion[24m [4mConventions[24m.
The protocol defines six distinct spaces in which atoms are
interpreted. Any particular atom may or may not have some
valid interpretation with respect to each of these name spa-
ces.
l l lw(3.6i). _
[1mSpace Briefly Examples[0m
[1m_[0m
Property name Name WM_HINTS, WM_NAME, RGB_BEST_MAP, ...
Property type Type WM_HINTS, CURSOR, RGB_COLOR_MAP, ...
Selection name Selection PRIMARY, SECONDARY, CLIPBOARD
Selection target Target FILE_NAME, POSTSCRIPT,
PIXMAP, ... Font property QUAD_WIDTH, POINT_SIZE, ...
T{ type T} T{ T} T{ WM_SAVE_YOURSELF, _DEC_SAVE_EDITS,
... T}
_
Sometimes a protocol requires an arbitrary number of similar
objects that need unique names (usually because the objects
are created dynamically, so that names cannot be invented in
advance). For example, a colormap-generating program might
use the selection mechanism to offer colormaps for each
screen and so needs a selection name for each screen. Such
names are called "discriminated names" and are discriminated
[1m3[0m
[1mInter-Client Communication Conventions X11, Release 6.4[0m
by some entity. This entity can be:
A screen
An X resource (a window, a colormap, a visual, etc.)
A client
If it is only necessary to generate a fixed set of names for
each value of the discriminating entity, then the discrimi-
nated names are formed by suffixing an ordinary name accord-
ing to the value of the entity.
If [4mname[24m is a descriptive portion for the name, [4md[24m is a deci-
mal number with no leading zeroes, and [4mx[24m is a hexadecimal
number with exactly 8 digits, and using uppercase letters,
then such discriminated names shall have the form:
lB lB lB l l l . _
Name Discriminated by Form Example
_
screen number [4mname[24m_S[4md[24m WM_COMMS_S2 X
resource [4mname[24m_R[4mx[24m GROUP_LEADER_R1234ABCD
_
To discriminate a name by client, use an X resource ID cre-
ated by that client. This resource can be of any type.
Sometimes it is simply necessary to generate a unique set of
names (for example, for the properties on a window used by a
MULTIPLE selection). These names should have the form:
U[4md[24m (e.g., U0 U1 U2 U3 ...)
if the names stand totally alone, and the form:
[4mname[24m_U[4md[24m (e.g., FOO_U0 BAR_U0 FOO_U1 BAR_U1 ...)
if they come in sets (here there are two sets, named "FOO"
and "BAR"). The stand-alone U[4md[24m form should be used only if
it is clear that the module using it has complete control
over the relevant namespace or has the active cooperation of
all other entities that might also use these names. (Naming
properties on a window created specifically for a particular
selection is such a use; naming properties on the root win-
dow is almost certainly not.)
In a particularly difficult case, it might be necessary to
combine both forms of discrimination. If this happens, the U
form should come after the other form, thus:
[1m4[0m
[1mInter-Client Communication Conventions X11, Release 6.4[0m
FOO_R12345678_U23
Existing protocols will not be changed to use these naming
conventions, because doing so will cause too much disrup-
tion. However, it is expected that future protocols -- both
standard and private -- will use these conventions.
Selections are the primary mechanism that X Version 11
defines for the exchange of information between clients, for
example, by cutting and pasting between windows. Note that
there can be an arbitrary number of selections (each named
by an atom) and that they are global to the server. Section
2.6 discusses the choice of an atom. Each selection is
owned by a client and is attached to a window.
Selections communicate between an owner and a requestor.
The owner has the data representing the value of its selec-
tion, and the requestor receives it. A requestor wishing to
obtain the value of a selection provides the following:
+o The name of the selection
+o The name of a property
+o A window
+o The atom representing the data type required
+o Optionally, some parameters for the request
If the selection is currently owned, the owner receives an
event and is expected to do the following:
+o Convert the contents of the selection to the requested
data type
+o Place this data in the named property on the named win-
dow
+o Send the requestor an event to let it know the property
is available
Clients are strongly encouraged to use this mechanism. In
particular, displaying text in a permanent window without
providing the ability to select and convert it into a string
is definitely considered antisocial.
Note that all data transferred between an owner and a
requestor must usually go by means of the server in an X
Version 11 environment. A client cannot assume that another
client can open the same files or even communicate directly.
The other client may be talking to the server by means of a
completely different networking mechanism (for example, one
client might be DECnet and the other TCP/IP). Thus, passing
[1m5[0m
[1mInter-Client Communication Conventions X11, Release 6.4[0m
indirect references to data (such as, file names, host
names, and port numbers) is permitted only if both clients
specifically agree.
A client wishing to acquire ownership of a particular selec-
tion should call which is defined as follows:
[4mselection[24m: ATOM
[4mowner[24m: WINDOW or
[4mtime[24m: TIMESTAMP or
The client should set the specified selection to the atom
that represents the selection, set the specified owner to
some window that the client created, and set the specified
time to some time between the current last-change time of
the selection concerned and the current server time. This
time value usually will be obtained from the timestamp of
the event that triggers the acquisition of the selection.
Clients should not set the time value to because if they do
so, they have no way of finding when they gained ownership
of the selection. Clients must use a window they created so
that requestors can route events to the owner of the selec-
tion.2 Clients attempting to acquire a selection must set
the time value of the request to the timestamp of the event
triggering the acquisition attempt, not to A zero-length
append to a property is a way to obtain a timestamp for this
purpose; the timestamp is in the corresponding event.
If the time in the request is in the future relative to the
server's current time or is in the past relative to the last
time the specified selection changed hands, the request
appears to the client to succeed, but ownership is not actu-
ally transferred.
Because clients cannot name other clients directly, the
specified owner window is used to refer to the owning client
in the replies to in and events, and possibly as a place to
put properties describing the selection in question. To
discover the owner of a particular selection, a client
should invoke which is defined as follows:
[4mselection[24m: ATOM
->
-----------
2 At present, no part of the protocol requires
requestors to send events to the owner of a selec-
tion. This restriction is imposed to prepare for
possible future extensions.
[1m6[0m
[1mInter-Client Communication Conventions X11, Release 6.4[0m
owner: WINDOW or
Clients are expected to provide some visible confirmation of
selection ownership. To make this feedback reliable, a
client must perform a sequence like the following:
SetSelectionOwner(selection=PRIMARY, owner=Window,
time=timestamp) owner = GetSelectionOwner(selection=PRIMARY)
if (owner != Window) Failure
If the request succeeds (not merely appears to succeed), the
client that issues it is recorded by the server as being the
owner of the selection for the time period starting at the
specified time.
When a requestor wants the value of a selection, the owner
receives a event, which is defined as follows:
[4mowner[24m: WINDOW
[4mselection[24m: ATOM
[4mtarget[24m: ATOM
[4mproperty[24m: ATOM or
[4mrequestor[24m: WINDOW
[4mtime[24m: TIMESTAMP or
The specified owner and selection will be the values that
were specified in the request. The owner should compare the
timestamp with the period it has owned the selection and, if
the time is outside, refuse the by sending the requestor
window a event with the property set to (by means of a
request with an empty event mask).
More advanced selection owners are free to maintain a his-
tory of the value of the selection and to respond to
requests for the value of the selection during periods they
owned it even though they do not own it now.
If the specified property is the requestor is an obsolete
client. Owners are encouraged to support these clients by
using the specified target atom as the property name to be
used for the reply.
Otherwise, the owner should use the target to decide the
form into which the selection should be converted. Some
targets may be defined such that requestors can pass parame-
ters along with the request. The owner will find these
parameters in the property named in the selection request.
The type, format, and contents of this property are depen-
dent upon the definition of the target. If the target is
not defined to have parameters, the owner should ignore the
property if it is present. If the selection cannot be con-
verted into a form based on the target (and parameters, if
[1m7[0m
[1mInter-Client Communication Conventions X11, Release 6.4[0m
any), the owner should refuse the as previously described.
If the specified property is not the owner should place the
data resulting from converting the selection into the speci-
fied property on the requestor window and should set the
property's type to some appropriate value, which need not be
the same as the specified target. All properties used to
reply to events must be placed on the requestor window.
In either case, if the data comprising the selection cannot
be stored on the requestor window (for example, because the
server cannot provide sufficient memory), the owner must
refuse the as previously described. See also section 2.5.
If the property is successfully stored, the owner should
acknowledge the successful conversion by sending the
requestor window a event (by means of a request with an
empty mask). is defined as follows:
[4mrequestor[24m: WINDOW
[4mselection[24m, [4mtarget[24m: ATOM
[4mproperty[24m: ATOM or
[4mtime[24m: TIMESTAMP or
The owner should set the specified selection, target, time,
and property arguments to the values received in the event.
(Note that setting the property argument to indicates that
the conversion requested could not be made.) The selection,
target, time, and property arguments in the event should be
set to the values received in the event.
If the owner receives more than one event with the same
requestor, selection, target, and timestamp it must respond
to them in the same order in which they were received. It
is possible for a requestor to have multiple outstanding
requests that use the same requestor window, selection, tar-
get, and timestamp, and that differ only in the property.
If this occurs, and one of the conversion requests fails,
the resulting event will have its property argument set to
This may make it impossible for the requestor to determine
which conversion request had failed, unless the requests are
responded to in order.
The data stored in the property must eventually be deleted.
A convention is needed to assign the responsibility for
doing so. Selection requestors are responsible for deleting
properties whose names they receive in events (see section
2.4) or in properties with type MULTIPLE.
A selection owner will often need confirmation that the data
comprising the selection has actually been transferred.
(For example, if the operation has side effects on the
[1m8[0m
[1mInter-Client Communication Conventions X11, Release 6.4[0m
owner's internal data structures, these should not take
place until the requestor has indicated that it has success-
fully received the data.) Owners should express interest in
events for the specified requestor window and wait until the
property in the event has been deleted before assuming that
the selection data has been transferred. For the MULTIPLE
request, if the different conversions require separate con-
firmation, the selection owner can also watch for the dele-
tion of the individual properties named in the property in
the event.
When some other client acquires a selection, the previous
owner receives a event, which is defined as follows:
[4mowner[24m: WINDOW
[4mselection[24m: ATOM
[4mtime[24m: TIMESTAMP
The timestamp argument is the time at which the ownership
changed hands, and the owner argument is the window the pre-
vious owner specified in its request.
If an owner loses ownership while it has a transfer in
progress (that is, before it receives notification that the
requestor has received all the data), it must continue to
service the ongoing transfer until it is complete.
If the selection value completely changes, but the owner
happens to be the same client (for example, selecting a
totally different piece of text in the same [1mxterm [22mas
before), then the client should reacquire the selection own-
ership as if it were not the owner, providing a new time-
stamp. If the selection value is modified, but can still
reasonably be viewed as the same selected object,3 the owner
should take no action.
Clients may either give up selection ownership voluntarily
or lose it forcibly as the result of some other client's
actions.
To relinquish ownership of a selection voluntarily, a client
should execute a request for that selection atom, with owner
specified as and the time specified as the timestamp that
was used to acquire the selection.
Alternatively, the client may destroy the window used as the
owner value of the request, or the client may terminate. In
both cases, the ownership of the selection involved will
-----------
3 The division between these two cases is a mat-
ter of judgment on the part of the software devel-
oper.
[1m9[0m
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revert to
If a client gives up ownership of a selection or if some
other client executes a for it and thus reassigns it
forcibly, the previous owner will receive a event. For the
definition of a event, see section 2.2.
The timestamp is the time the selection changed hands. The
specified owner is the window that was specified by the cur-
rent owner in its request.
A client that wishes to obtain the value of a selection in a
particular form (the requestor) issues a request, which is
defined as follows:
[4mselection[24m, [4mtarget[24m: ATOM
[4mproperty[24m: ATOM or
[4mrequestor[24m: WINDOW
[4mtime[24m: TIMESTAMP or
The selection argument specifies the particular selection
involved, and the target argument specifies the required
form of the information. For information about the choice
of suitable atoms to use, see section 2.6. The requestor
should set the requestor argument to a window that it cre-
ated; the owner will place the reply property there. The
requestor should set the time argument to the timestamp on
the event that triggered the request for the selection
value. Note that clients should not specify Clients should
not use for the time argument of a request. Instead, they
should use the timestamp of the event that caused the
request to be made.
The requestor should set the property argument to the name
of a property that the owner can use to report the value of
the selection. Requestors should ensure that the named
property does not exist on the window before issuing the
request.4 The exception to this rule is when the requestor
intends to pass parameters with the request (see below). It
is necessary for requestors to delete the property before
issuing the request so that the target can later be extended
to take parameters without introducing an incompatibility.
Also note that the requestor of a selection need not know
the client that owns the selection nor the window on which
the selection was acquired.
-----------
4 This requirement is new in version 2.0, and,
in general, existing clients do not conform to
this requirement. To prevent these clients from
breaking, no existing targets should be extended
to take parameters until sufficient time has
passed for clients to be updated. Note that the
[1m10[0m
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Some targets may be defined such that requestors can pass
parameters along with the request. If the requestor wishes
to provide parameters to a request, they should be placed in
the specified property on the requestor window before the
requestor issues the request, and this property should be
named in the request.
Some targets may be defined so that parameters are optional.
If no parameters are to be supplied with the request of such
a target, the requestor must ensure that the property does
not exist before issuing the request.
The protocol allows the property field to be set to in which
case the owner is supposed to choose a property name. How-
ever, it is difficult for the owner to make this choice
safely.
1. Requestors should not use for the property argument of
a request.
2. Owners receiving requests with a property argument of
are talking to an obsolete client. They should choose
the target atom as the property name to be used for the
reply.
The result of the request is that a event will be received.
For the definition of a event, see section 2.2.
The requestor, selection, time, and target arguments will be
the same as those on the request.
If the property argument is the conversion has been refused.
This can mean either that there is no owner for the selec-
tion, that the owner does not support the conversion implied
by the target, or that the server did not have sufficient
space to accommodate the data.
If the property argument is not then that property will
exist on the requestor window. The value of the selection
can be retrieved from this property by using the request,
which is defined as follows:
[4mwindow[24m: WINDOW
[4mproperty[24m: ATOM
[4mtype[24m: ATOM or
[4mlong-offset[24m, [4mlong-length[24m: CARD32
[4mdelete[24m: BOOL
-----------
MULTIPLE target was defined to take parameters in
version 1.0 and its definition is not changing.
There is thus no conformance problem with MULTI-
PLE.
[1m11[0m
[1mInter-Client Communication Conventions X11, Release 6.4[0m
->
type: ATOM or
format: {0, 8, 16, 32}
bytes-after: CARD32
value: LISTofINT8 or LISTofINT16 or LISTofINT32
When using to retrieve the value of a selection, the prop-
erty argument should be set to the corresponding value in
the event. Because the requestor has no way of knowing
beforehand what type the selection owner will use, the type
argument should be set to Several requests may be needed to
retrieve all the data in the selection; each should set the
long-offset argument to the amount of data received so far,
and the size argument to some reasonable buffer size (see
section 2.5). If the returned value of bytes-after is zero,
the whole property has been transferred.
Once all the data in the selection has been retrieved (which
may require getting the values of several properties -- see
section 2.7), the requestor should delete the property in
the request by using a request with the delete argument set
to As previously discussed, the owner has no way of knowing
when the data has been transferred to the requestor unless
the property is removed. The requestor must delete the
property named in the once all the data has been retrieved.
The requestor should invoke either or after it has success-
fully retrieved all the data in the selection. For further
information, see section 2.5.
Selections can get large, which poses two problems:
+o Transferring large amounts of data to the server is
expensive.
+o All servers will have limits on the amount of data that
can be stored in properties. Exceeding this limit will
result in an error on the request that the selection
owner uses to store the data.
The problem of limited server resources is addressed by the
following conventions:
1. Selection owners should transfer the data describing a
large selection (relative to the maximum-request-size
they received in the connection handshake) using the
INCR property mechanism (see section 2.7.2).
2. Any client using to acquire selection ownership should
arrange to process errors in property change requests.
For clients using Xlib, this involves using the func-
tion to override the default handler.
[1m12[0m
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3. A selection owner must confirm that no error occurred
while storing the properties for a selection before
replying with a confirming event.
4. When storing large amounts of data (relative to maxi-
mum-request-size), clients should use a sequence of
requests for reasonable quantities of data. This
avoids locking servers up and limits the waste of data
an error would cause.
5. If an error occurs during the storing of the selection
data, all properties stored for this selection should
be deleted and the request should be refused (see sec-
tion 2.2).
6. To avoid locking servers up for inordinate lengths of
time, requestors retrieving large quantities of data
from a property should perform a series of requests,
each asking for a reasonable amount of data. Single-
threaded servers should take care to avoid locking up
during large data transfers.
Defining a new atom consumes resources in the server that
are not released until the server reinitializes. Thus,
reducing the need for newly minted atoms is an important
goal for the use of the selection atoms.
There can be an arbitrary number of selections, each named
by an atom. To conform with the inter-client conventions,
however, clients need deal with only these three selections:
+o PRIMARY
+o SECONDARY
+o CLIPBOARD
Other selections may be used freely for private communica-
tion among related groups of clients.
The selection named by the atom PRIMARY is used for all com-
mands that take only a single argument and is the principal
means of communication between clients that use the selec-
tion mechanism.
The selection named by the atom SECONDARY is used:
+o As the second argument to commands taking two arguments
(for example, "exchange primary and secondary selec-
tions")
+o As a means of obtaining data when there is a primary
selection and the user does not want to disturb it
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The selection named by the atom CLIPBOARD is used to hold
data that is being transferred between clients, that is,
data that usually is being cut and then pasted or copied and
then pasted. Whenever a client wants to transfer data to
the clipboard:
+o It should assert ownership of the CLIPBOARD.
+o If it succeeds in acquiring ownership, it should be pre-
pared to respond to a request for the contents of the
CLIPBOARD in the usual way (retaining the data to be
able to return it). The request may be generated by the
clipboard client described below.
+o If it fails to acquire ownership, a cutting client
should not actually perform the cut or provide feedback
that would suggest that it has actually transferred data
to the clipboard.
The owner should repeat this process whenever the data to be
transferred would change.
Clients wanting to paste data from the clipboard should
request the contents of the CLIPBOARD selection in the usual
way.
Except while a client is actually deleting or copying data,
the owner of the CLIPBOARD selection may be a single, spe-
cial client implemented for the purpose. This client main-
tains the content of the clipboard up-to-date and responds
to requests for data from the clipboard as follows:
+o It should assert ownership of the CLIPBOARD selection
and reassert it any time the clipboard data changes.
+o If it loses the selection (because another client has
some new data for the clipboard), it should:
- Obtain the contents of the selection from the new
owner by using the timestamp in the event.
- Attempt to reassert ownership of the CLIPBOARD
selection by using the same timestamp.
- Restart the process using a newly acquired time-
stamp if this attempt fails. This timestamp should
be obtained by asking the current owner of the
CLIPBOARD selection to convert it to a TIMESTAMP.
If this conversion is refused or if the same time-
stamp is received twice, the clipboard client
should acquire a fresh timestamp in the usual way
(for example by a zero-length append to a prop-
erty).
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+o It should respond to requests for the CLIPBOARD contents
in the usual way.
A special CLIPBOARD client is not necessary. The protocol
used by the cutting client and the pasting client is the
same whether the CLIPBOARD client is running or not. The
reasons for running the special client include:
+o Stability - If the cutting client were to crash or ter-
minate, the clipboard value would still be available.
+o Feedback - The clipboard client can display the contents
of the clipboard.
+o Simplicity - A client deleting data does not have to
retain it for so long, thus reducing the chance of race
conditions causing problems.
The reasons not to run the clipboard client include:
+o Performance - Data is transferred only if it is actually
required (that is, when some client actually wants the
data).
+o Flexibility - The clipboard data may be available as
more than one target.
The atom that a requestor supplies as the target of a
request determines the form of the data supplied. The set
of such atoms is extensible, but a generally accepted base
set of target atoms is needed. As a starting point for
this, the following table contains those that have been sug-
gested so far.
lw(1.8i) lw(1i) lw(3i) . _
[1mAtom Type Data Received[0m
_
l s s . ADOBE_PORTABLE_DOCUMENT_FORMAT lw(1.8i) lw(1i)
lw(3i) . STRING T{ [1] T}
APPLE_PICT APPLE_PICT T{ [2] T} BACK-
GROUND PIXEL A list of pixel values BITMAP BIT-
MAP A list of bitmap IDs CHARACTER_POSITION SPAN T{ The
start and end of the selection in bytes T}
CLASS TEXT (see section 4.1.2.5) CLIENT_WINDOW WIN-
DOW T{ Any top-level window owned by the selection owner
T} COLORMAP COLORMAP A list of colormap IDs COLUMN_NUM-
BER SPAN T{ The start and end column numbers T} COM-
POUND_TEXT COMPOUND_TEXT Compound Text DELETE NULL (see
section 2.6.3.1) DRAWABLE DRAWABLE A list of drawable IDs
l s s . ENCAPSULATED_POSTSCRIPT lw(1.8i) lw(1i) lw(3i) .
STRING T{ [3], Appendix H5 T}
l s s . ENCAPSULATED_POSTSCRIPT_INTERCHANGE lw(1.8i) lw(1i)
lw(3i) . STRING T{ [3], Appendix H T}
FILE_NAME TEXT The full path name of a file
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lw(1.8i) lw(1i) lw(3i) . _
[1mAtom Type Data Received[0m
_
FOREGROUND PIXEL T{ A list of pixel values T}
HOST_NAME TEXT (see section 4.1.2.9) INSERT_PROP-
ERTY NULL (see section 2.6.3.3) INSERT_SELEC-
TION NULL (see section 2.6.3.2) LENGTH INTEGER T{
The number of bytes in the selection6 T} LINE_NUM-
BER SPAN T{ The start and end line numbers T}
LIST_LENGTH INTEGER T{ The number of disjoint parts of
the selection T} MODULE TEXT T{ The name of the selected
procedure T} MULTIPLE ATOM_PAIR T{ (see the discussion that
follows) T} NAME TEXT (see section 4.1.2.1) ODIF TEXT T{ ISO
Office Document Interchange Format T} OWNER_OS TEXT T{ The
operating system of the owner client T} PIXMAP T{ PIXMAP7
T} T{ A list of pixmap IDs T} POSTSCRIPT STRING T{
[3] T} PROCEDURE TEXT T{ The name of the selected procedure
T} PROCESS INTEGER, TEXT T{ The process ID of the owner
T} STRING STRING ISO Latin-1 (+TAB+NEWLINE) text TAR-
GETS ATOM A list of valid target atoms TASK INTEGER,
TEXT T{ The task ID of the owner T} TEXT TEXT T{ The text
in the owner's choice of encoding T} TIMESTAMP INTEGER T{
The timestamp used to acquire the selection T} USER TEXT T{
The name of the user running the owner T}
UTF8_STRING TEXT T{ UTF-8 text T}
_
References:
[1] Adobe Systems, Incorporated. [4mPortable[24m [4mDocument[24m [4mFormat[0m
[4mReference[24m [4mManual.[24m Reading, MA, Addison-Wesley, ISBN
-----------
5 Earlier versions of this document erroneously
specified that conversion of the PIXMAP target
returns a property of type DRAWABLE instead of
PIXMAP. Implementors should be aware of this and
may want to support the DRAWABLE type as well to
allow for compatibility with older clients.
6 The targets ENCAPSULATED_POSTSCRIPT and ENCAP-
SULATED_POSTSCRIPT_INTERCHANGE are equivalent to
the targets _ADOBE_EPS and _ADOBE_EPSI (respec-
tively) that appear in the selection targets reg-
istry. The _ADOBE_ targets are deprecated, but
clients are encouraged to continue to support them
for backward compatibility.
7 This definition is ambiguous, as the selection
may be converted into any of several targets that
may return differing amounts of data. The
requestor has no way of knowing which, if any, of
these targets corresponds to the result of LENGTH.
Clients are advised that no guarantees can be made
about the result of a conversion to LENGTH; its
use is thus deprecated.
[1m16[0m
[1mInter-Client Communication Conventions X11, Release 6.4[0m
0-201-62628-4.
[2] Apple Computer, Incorporated. [4mInside[24m [4mMacintosh,[24m [4mVolume[0m
[4mV.[24m Chapter 4, "Color QuickDraw," Color Picture Format.
ISBN 0-201-17719-6.
[3] Adobe Systems, Incorporated. [4mPostScript[24m [4mLanguage[24m [4mRef-[0m
[4merence[24m [4mManual.[24m Reading, MA, Addison-Wesley, ISBN
0-201-18127-4.
It is expected that this table will grow over time.
Selection owners are required to support the following tar-
gets. All other targets are optional.
+o TARGETS - The owner should return a list of atoms that
represent the targets for which an attempt to convert
the current selection will succeed (barring unforseeable
problems such as errors). This list should include all
the required atoms.
+o MULTIPLE - The MULTIPLE target atom is valid only when a
property is specified on the request. If the property
argument in the event is and the target is MULTIPLE, it
should be refused.
When a selection owner receives a request, the contents
of the property named in the request will be a list of
atom pairs: the first atom naming a target and the sec-
ond naming a property is not valid here). The effect
should be as if the owner had received a sequence of
events (one for each atom pair) except that:
- The owner should reply with a only when all the
requested conversions have been performed.
- If the owner fails to convert the target named by
an atom in the MULTIPLE property, it should replace
that atom in the property with
The entries in a MULTIPLE property must be processed in
the order they appear in the property. For further
information, see section 2.6.3.
The requestor should delete each individual property
when it has copied the data from that conversion, and
the property specified in the MULTIPLE request when it
has copied all the data.
The requests are otherwise to be processed indepen-
dently, and they should succeed or fail independently.
The MULTIPLE target is an optimization that reduces the
amount of protocol traffic between the owner and the
requestor; it is not a transaction mechanism. For exam-
ple, a client may issue a MULTIPLE request with two
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targets: a data target and the DELETE target. The
DELETE target will still be processed even if the con-
version of the data target fails.
+o TIMESTAMP - To avoid some race conditions, it is impor-
tant that requestors be able to discover the timestamp
the owner used to acquire ownership. Until and unless
the protocol is changed so that a request returns the
timestamp used to acquire ownership, selection owners
must support conversion to TIMESTAMP, returning the
timestamp they used to obtain the selection.
Some targets (for example, DELETE) have side effects. To
render these targets unambiguous, the entries in a MULTIPLE
property must be processed in the order that they appear in
the property.
In general, targets with side effects will return no infor-
mation, that is, they will return a zero length property of
type NULL. (Type NULL means the result of on the string
"NULL", not the value zero.) In all cases, the requested
side effect must be performed before the conversion is
accepted. If the requested side effect cannot be performed,
the corresponding conversion request must be refused.
1. Targets with side effects should return no information
(that is, they should have a zero-length property of
type NULL).
2. The side effect of a target must be performed before
the conversion is accepted.
3. If the side effect of a target cannot be performed, the
corresponding conversion request must be refused. The
need to delay responding to the request until a further
conversion has succeeded poses problems for the Intrin-
sics interface that need to be addressed.
These side-effect targets are used to implement operations
such as "exchange PRIMARY and SECONDARY selections."
When the owner of a selection receives a request to convert
it to DELETE, it should delete the corresponding selection
(whatever doing so means for its internal data structures)
and return a zero-length property of type NULL if the dele-
tion was successful.
When the owner of a selection receives a request to convert
it to INSERT_SELECTION, the property named will be of type
ATOM_PAIR. The first atom will name a selection, and the
second will name a target. The owner should use the selec-
tion mechanism to convert the named selection into the named
target and should insert it at the location of the selection
for which it got the INSERT_SELECTION request (whatever
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doing so means for its internal data structures).
When the owner of a selection receives a request to convert
it to INSERT_PROPERTY, it should insert the property named
in the request at the location of the selection for which it
got the INSERT_SELECTION request (whatever doing so means
for its internal data structures).
The names of the properties used in selection data transfer
are chosen by the requestor. The use of property fields in
requests (which request the selection owner to choose a
name) is not permitted by these conventions.
The selection owner always chooses the type of the property
in the selection data transfer. Some types have special
semantics assigned by convention, and these are reviewed in
the following sections.
In all cases, a request for conversion to a target should
return either a property of one of the types listed in the
previous table for that target or a property of type INCR
and then a property of one of the listed types.
Certain selection properties may contain resource IDs. The
selection owner should ensure that the resource is not
destroyed and that its contents are not changed until after
the selection transfer is complete. Requestors that rely on
the existence or on the proper contents of a resource must
operate on the resource (for example, by copying the con-
tents of a pixmap) before deleting the selection property.
The selection owner will return a list of zero or more items
of the type indicated by the property type. In general, the
number of items in the list will correspond to the number of
disjoint parts of the selection. Some targets (for example,
side-effect targets) will be of length zero irrespective of
the number of disjoint selection parts. In the case of
fixed-size items, the requestor may determine the number of
items by the property size. Selection property types are
listed in the table below. For variable-length items such
as text, the separators are also listed.
l c l. _
[1mType Atom Format Separator[0m
_
APPLE_PICT 8 T{ Self-sizing T} ATOM 32 Fixed-size
ATOM_PAIR 32 Fixed-size BITMAP 32 Fixed-size
C_STRING 8 T{ Zero T} COLORMAP 32 T{ Fixed-size T}
COMPOUND_TEXT 8 Zero DRAWABLE 32 Fixed-size
INCR 32 Fixed-size INTEGER 32 Fixed-size
PIXEL 32 T{ Fixed-size T} PIXMAP 32 Fixed-size
SPAN 32 Fixed-size STRING 8 Zero
UTF8_STRING 8 Zero WINDOW 32 Fixed-size
_
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It is expected that this table will grow over time.
In general, the encoding for the characters in a text string
property is specified by its type. It is highly desirable
for there to be a simple, invertible mapping between string
property types and any character set names embedded within
font names in any font naming standard adopted by the Con-
sortium.
The atom TEXT is a polymorphic target. Requesting conver-
sion into TEXT will convert into whatever encoding is conve-
nient for the owner. The encoding chosen will be indicated
by the type of the property returned. TEXT is not defined
as a type; it will never be the returned type from a selec-
tion conversion request.
If the requestor wants the owner to return the contents of
the selection in a specific encoding, it should request con-
version into the name of that encoding.
In the table in section 2.6.2, the word TEXT (in the Type
column) is used to indicate one of the registered encoding
names. The type would not actually be TEXT; it would be
STRING or some other ATOM naming the encoding chosen by the
owner.
STRING as a type or a target specifies the ISO Latin-1 char-
acter set plus the control characters TAB (hex 09) and NEW-
LINE (hex 0A). The spacing interpretation of TAB is context
dependent. Other ASCII control characters are explicitly
not included in STRING at the present time.
COMPOUND_TEXT as a type or a target specifies the Compound
Text interchange format; see the [4mCompound[24m [4mText[24m [4mEncoding[24m.
UTF8_STRING as a type or a target specifies an UTF-8 encoded
string, with NEWLINE (U+000A, hex 0A) as end-of-line marker.
There are some text objects where the source or intended
user, as the case may be, does not have a specific character
set for the text, but instead merely requires a zero-termi-
nated sequence of bytes with no other restriction; no ele-
ment of the selection mechanism may assume that any byte
value is forbidden or that any two differing sequences are
equivalent.8 For these objects, the type C_STRING should be
used. An example of the need for C_STRING is to transmit
the names of files; many operating systems do not interpret
filenames as having a character set. For example, the same
-----------
8 Note that this is different from STRING, where
many byte values are forbidden, and from COM-
POUND_TEXT, where, for example, inserting the
sequence 27, 40, 66 (designate ASCII into GL) at
the start does not alter the meaning.
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character string uses a different sequence of bytes in ASCII
and EBCDIC, and so most operating systems see these as dif-
ferent filenames and offer no way to treat them as the same.
Thus no character-set based property type is suitable.
Type STRING, COMPOUND_TEXT, UTF8_STRING, and C_STRING prop-
erties will consist of a list of elements separated by null
characters; other encodings will need to specify an appro-
priate list format.
Requestors may receive a property of type INCR9 in response
to any target that results in selection data. This indi-
cates that the owner will send the actual data incremen-
tally. The contents of the INCR property will be an inte-
ger, which represents a lower bound on the number of bytes
of data in the selection. The requestor and the selection
owner transfer the data in the selection in the following
manner.
The selection requestor starts the transfer process by
deleting the (type==INCR) property forming the reply to the
selection.
The selection owner then:
+o Appends the data in suitable-size chunks to the same
property on the same window as the selection reply with
a type corresponding to the actual type of the converted
selection. The size should be less than the maximum-
request-size in the connection handshake.
+o Waits between each append for a event that shows that
the requestor has read the data. The reason for doing
this is to limit the consumption of space in the server.
+o Waits (after the entire data has been transferred to the
server) until a event that shows that the data has been
read by the requestor and then writes zero-length data
to the property.
The selection requestor:
+o Waits for the event.
+o Loops:
- Retrieving data using with the delete argument
-----------
9 These properties were called INCREMENTAL in an
earlier draft. The protocol for using them has
changed, and so the name has changed to avoid con-
fusion.
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- Waiting for a with the state argument
+o Waits until the property named by the event is zero-
length.
+o Deletes the zero-length property.
The type of the converted selection is the type of the first
partial property. The remaining partial properties must
have the same type.
Requestors may receive properties of type PIXMAP, BITMAP,
DRAWABLE, or WINDOW, which contain an appropriate ID. While
information about these drawables is available from the
server by means of the request, the following items are not:
+o Foreground pixel
+o Background pixel
+o Colormap ID
In general, requestors converting into targets whose
returned type in the table in section 2.6.2 is one of the
DRAWABLE types should expect to convert also into the fol-
lowing targets (using the MULTIPLE mechanism):
+o FOREGROUND returns a PIXEL value.
+o BACKGROUND returns a PIXEL value.
+o COLORMAP returns a colormap ID.
Properties with type SPAN contain a list of cardinal-pairs
with the length of the cardinals determined by the format.
The first specifies the starting position, and the second
specifies the ending position plus one. The base is zero.
If they are the same, the span is zero-length and is before
the specified position. The units are implied by the target
atom, such as LINE_NUMBER or CHARACTER_POSITION.
Certain clients, often called managers, take on responsibil-
ity for managing shared resources. A client that manages a
shared resource should take ownership of an appropriate
selection, named using the conventions described in sections
1.2.3 and 1.2.6. A client that manages multiple shared
resources (or groups of resources) should take ownership of
a selection for each one.
The manager may support conversion of various targets for
that selection. Managers are encouraged to use this tech-
nique as the primary means by which clients interact with
the managed resource. Note that the conventions for inter-
acting with the window manager predate this section; as a
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result many interactions with the window manager use other
techniques.
Before a manager takes ownership of a manager selection, it
should use the request to check whether the selection is
already owned by another client, and, where appropriate, it
should ask the user if the new manager should replace the
old one. If so, it may then take ownership of the selec-
tion. Managers should acquire the selection using a window
created expressly for this purpose. Managers must conform
to the rules for selection owners described in sections 2.1
and 2.2, and they must also support the required targets
listed in section 2.6.2.
If a manager loses ownership of a manager selection, this
means that a new manager is taking over its responsibili-
ties. The old manager must release all resources it has
managed and must then destroy the window that owned the
selection. For example, a window manager losing ownership
of WM_S2 must deselect from on the root window of screen 2
before destroying the window that owned WM_S2.
When the new manager notices that the window owning the
selection has been destroyed, it knows that it can success-
fully proceed to control the resource it is planning to man-
age. If the old manager does not destroy the window within
a reasonable time, the new manager should check with the
user before destroying the window itself or killing the old
manager.
If a manager wants to give up, on its own, management of a
shared resource controlled by a selection, it must do so by
releasing the resources it is managing and then by destroy-
ing the window that owns the selection. It should not first
disown the selection, since this introduces a race condi-
tion.
Clients who are interested in knowing when the owner of a
manager selection is no longer managing the corresponding
shared resource should select for on the window owning the
selection so they can be notified when the window is
destroyed. Clients are warned that after doing a and
selecting for they should do a again to ensure that the
owner did not change after initially getting the selection
owner and before selecting for
Immediately after a manager successfully acquires ownership
of a manager selection, it should announce its arrival by
sending a event. This event should be sent using the proto-
col request with the following arguments:
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l lw(4.5i) . _
[1mArgument Value[0m
_
destination: T{ the root window of screen 0, or the root
window of the appropriate screen if the manager is managing
a screen-specific resource T} propagate: False event-
mask: T{ T} event: T{ T} type: MANAGER for-
mat: 32 T{ data[0]:10 T} timestamp
data[1]: manager selection atom data[2]: the
window owning the selection data[3]: manager-selec-
tion-specific data data[4]: manager-selection-specific
data
_
Clients that wish to know when a specific manager has
started should select for on the appropriate root window and
should watch for the appropriate MANAGER
The cut buffer mechanism is much simpler but much less pow-
erful than the selection mechanism. The selection mechanism
is active in that it provides a link between the owner and
requestor clients. The cut buffer mechanism is passive; an
owner places data in a cut buffer from which a requestor
retrieves the data at some later time.
The cut buffers consist of eight properties on the root of
screen zero, named by the predefined atoms CUT_BUFFER0 to
CUT_BUFFER7. These properties must, at present, have type
STRING and format 8. A client that uses the cut buffer
mechanism must initially ensure that all eight properties
exist by using requests to append zero-length data to each.
A client that stores data in the cut buffers (an owner)
first must rotate the ring of buffers by plus 1 by using
requests to rename each buffer; that is, CUT_BUFFER0 to
CUT_BUFFER1, CUT_BUFFER1 to CUT_BUFFER2, ..., and
CUT_BUFFER7 to CUT_BUFFER0. It then must store the data
into CUT_BUFFER0 by using a request in mode
A client that obtains data from the cut buffers should use a
request to retrieve the contents of CUT_BUFFER0.
In response to a specific user request, a client may rotate
the cut buffers by minus 1 by using requests to rename each
buffer; that is, CUT_BUFFER7 to CUT_BUFFER6, CUT_BUFFER6 to
CUT_BUFFER5, ..., and CUT_BUFFER0 to CUT_BUFFER7.
-----------
10 We use the notation data[n] to indicate the
nth element of the LISTofINT8, LISTofINT16, or
LISTofINT32 in the data field of the according to
the format field. The list is indexed from zero.
[1m24[0m
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Data should be stored to the cut buffers and the ring
rotated only when requested by explicit user action. Users
depend on their mental model of cut buffer operation and
need to be able to identify operations that transfer data to
and fro.
To permit window managers to perform their role of mediating
the competing demands for resources such as screen space,
the clients being managed must adhere to certain conventions
and must expect the window managers to do likewise. These
conventions are covered here from the client's point of
view.
In general, these conventions are somewhat complex and will
undoubtedly change as new window management paradigms are
developed. Thus, there is a strong bias toward defining
only those conventions that are essential and that apply
generally to all window management paradigms. Clients
designed to run with a particular window manager can easily
define private protocols to add to these conventions, but
they must be aware that their users may decide to run some
other window manager no matter how much the designers of the
private protocol are convinced that they have seen the "one
true light" of user interfaces.
It is a principle of these conventions that a general client
should neither know nor care which window manager is running
or, indeed, if one is running at all. The conventions do
not support all client functions without a window manager
running; for example, the concept of Iconic is not directly
supported by clients. If no window manager is running, the
concept of Iconic does not apply. A goal of the conventions
is to make it possible to kill and restart window managers
without loss of functionality.
Each window manager will implement a particular window man-
agement policy; the choice of an appropriate window manage-
ment policy for the user's circumstances is not one for an
individual client to make but will be made by the user or
the user's system administrator. This does not exclude the
possibility of writing clients that use a private protocol
to restrict themselves to operating only under a specific
window manager. Rather, it merely ensures that no claim of
general utility is made for such programs.
For example, the claim is often made: "The client I'm writ-
ing is important, and it needs to be on top." Perhaps it is
important when it is being run in earnest, and it should
then be run under the control of a window manager that rec-
ognizes "important" windows through some private protocol
and ensures that they are on top. However, imagine, for
example, that the "important" client is being debugged.
Then, ensuring that it is always on top is no longer the
appropriate window management policy, and it should be run
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under a window manager that allows other windows (for exam-
ple, the debugger) to appear on top.
In general, the object of the X Version 11 design is that
clients should, as far as possible, do exactly what they
would do in the absence of a window manager, except for the
following:
+o Hinting to the window manager about the resources they
would like to obtain
+o Cooperating with the window manager by accepting the
resources they are allocated even if they are not those
requested
+o Being prepared for resource allocations to change at any
time
A client's [4mtop-level[24m [4mwindow[24m is a window whose override-redi-
rect attribute is It must either be a child of a root win-
dow, or it must have been a child of a root window immedi-
ately prior to having been reparented by the window manager.
If the client reparents the window away from the root, the
window is no longer a top-level window; but it can become a
top-level window again if the client reparents it back to
the root.
A client usually would expect to create its top-level win-
dows as children of one or more of the root windows by using
some boilerplate like the following:
win = XCreateSimpleWindow(dpy, DefaultRootWindow(dpy),
xsh.x, xsh.y, xsh.width, xsh.height, bw,
bd, bg);
If a particular one of the root windows was required, how-
ever, it could use something like the following:
win = XCreateSimpleWindow(dpy, RootWindow(dpy, screen),
xsh.x, xsh.y, xsh.width, xsh.height, bw,
bd, bg);
Ideally, it should be possible to override the choice of a
root window and allow clients (including window managers) to
treat a nonroot window as a pseudo-root. This would allow,
for example, the testing of window managers and the use of
application-specific window managers to control the subwin-
dows owned by the members of a related suite of clients.
Doing so properly requires an extension, the design of which
is under study.
From the client's point of view, the window manager will
regard its top-level window as being in one of three states:
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+o Normal
+o Iconic
+o Withdrawn
Newly created windows start in the Withdrawn state. Transi-
tions between states happen when the top-level window is
mapped and unmapped and when the window manager receives
certain messages. For further details, see sections 4.1.2.4
and 4.1.4.
Once the client has one or more top-level windows, it should
place properties on those windows to inform the window man-
ager of the behavior that the client desires. Window man-
agers will assume values they find convenient for any of
these properties that are not supplied; clients that depend
on particular values must explicitly supply them. The win-
dow manager will not change properties written by the
client.
The window manager will examine the contents of these prop-
erties when the window makes the transition from the With-
drawn state and will monitor some properties for changes
while the window is in the Iconic or Normal state. When the
client changes one of these properties, it must use mode to
overwrite the entire property with new data; the window man-
ager will retain no memory of the old value of the property.
All fields of the property must be set to suitable values in
a single mode request. This ensures that the full contents
of the property will be available to a new window manager if
the existing one crashes, if it is shut down and restarted,
or if the session needs to be shut down and restarted by the
session manager. Clients writing or rewriting window man-
ager properties must ensure that the entire content of each
property remains valid at all times.
Some of these properties may contain the IDs of resources,
such as windows or pixmaps. Clients should ensure that
these resources exist for at least as long as the window on
which the property resides.
If these properties are longer than expected, clients should
ignore the remainder of the property. Extending these prop-
erties is reserved to the X Consortium; private extensions
to them are forbidden. Private additional communication
between clients and window managers should take place using
separate properties. The only exception to this rule is the
WM_PROTOCOLS property, which may be of arbitrary length and
which may contain atoms representing private protocols (see
section 4.1.2.7).
The next sections describe each of the properties the
clients need to set, in turn. They are summarized in the
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table in section 4.4.
The WM_NAME property is an uninterpreted string that the
client wants the window manager to display in association
with the window (for example, in a window headline bar).
The encoding used for this string (and all other uninter-
preted string properties) is implied by the type of the
property. The type atoms to be used for this purpose are
described in section 2.7.1.
Window managers are expected to make an effort to display
this information. Simply ignoring WM_NAME is not acceptable
behavior. Clients can assume that at least the first part
of this string is visible to the user and that if the infor-
mation is not visible to the user, it is because the user
has taken an explicit action to make it invisible.
On the other hand, there is no guarantee that the user can
see the WM_NAME string even if the window manager supports
window headlines. The user may have placed the headline
off-screen or have covered it by other windows. WM_NAME
should not be used for application-critical information or
to announce asynchronous changes of an application's state
that require timely user response. The expected uses are to
permit the user to identify one of a number of instances of
the same client and to provide the user with noncritical
state information.
Even window managers that support headline bars will place
some limit on the length of the WM_NAME string that can be
visible; brevity here will pay dividends.
The WM_ICON_NAME property is an uninterpreted string that
the client wants to be displayed in association with the
window when it is iconified (for example, in an icon label).
In other respects, including the type, it is similar to
WM_NAME. For obvious geometric reasons, fewer characters
will normally be visible in WM_ICON_NAME than WM_NAME.
Clients should not attempt to display this string in their
icon pixmaps or windows; rather, they should rely on the
window manager to do so.
The type of the WM_NORMAL_HINTS property is WM_SIZE_HINTS.
Its contents are as follows:
lw(1i) lw(1i) lw(2i). _
[1mField Type Comments[0m
[1m_[0m
flags CARD32 (see the next table) pad 4*CARD32 For
backwards compatibility min_width INT32 If missing,
assume base_width min_height INT32 If missing,
assume base_height max_width INT32 max_height INT32
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lw(1i) lw(1i) lw(2i). _
[1mField Type Comments[0m
[1m_[0m
width_inc INT32 height_inc INT32
min_aspect (INT32,INT32) max_aspect (INT32,INT32)
base_width INT32 If missing, assume min_width
base_height INT32 If missing, assume min_height
win_gravity INT32 T{ If missing, assume T}
_
The WM_SIZE_HINTS.flags bit definitions are as follows:
lw(1i) nw(.5i) lw(3i). _
[1mName Value Field[0m
[1m_[0m
T{ T} 1 User-specified x, y T{ T} 2 User-specified
width, height T{ T} 4 Program-specified position T{
T} 8 Program-specified size T{ T} 16 Program-speci-
fied minimum size T{ T} 32 Program-specified maximum
size T{ T} 64 Program-specified resize increments T{
T} 128 Program-specified min and max aspect ratios T{
T} 256 Program-specified base size T{ T} 512 Program-
specified window gravity
_
To indicate that the size and position of the window (when a
transition from the Withdrawn state occurs) was specified by
the user, the client should set the and flags, which allow a
window manager to know that the user specifically asked
where the window should be placed or how the window should
be sized and that further interaction is superfluous. To
indicate that it was specified by the client without any
user involvement, the client should set and
The size specifiers refer to the width and height of the
client's window excluding borders.
The win_gravity may be any of the values specified for
WINGRAVITY in the core protocol except for (1), (2), (3),
(4), (5), (6), (7), (8), and (9). It specifies how and
whether the client window wants to be shifted to make room
for the window manager frame.
If the win_gravity is the window manager frame is positioned
so that the inside border of the client window inside the
frame is in the same position on the screen as it was when
the client requested the transition from Withdrawn state.
Other values of win_gravity specify a window reference
point. For and the reference point is the specified outer
corner of the window (on the outside border edge). For and
the reference point is the center of the specified outer
edge of the window border. For the reference point is the
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center of the window. The reference point of the window
manager frame is placed at the location on the screen where
the reference point of the client window was when the client
requested the transition from Withdrawn state.
The min_width and min_height elements specify the minimum
size that the window can be for the client to be useful.
The max_width and max_height elements specify the maximum
size. The base_width and base_height elements in conjunc-
tion with width_inc and height_inc define an arithmetic pro-
gression of preferred window widths and heights for non-neg-
ative integers [4mi[24m and [4mj[24m:
width ~ = ~ base_width ~ + ~ ( i ~ times ~ width_inc )
height ~ = ~ base_height ~ + ~ ( j ~ times ~ height_inc )
Window managers are encouraged to use [4mi[24m and [4mj[24m instead of
width and height in reporting window sizes to users. If a
base size is not provided, the minimum size is to be used in
its place and vice versa.
The min_aspect and max_aspect fields are fractions with the
numerator first and the denominator second, and they allow a
client to specify the range of aspect ratios it prefers.
Window managers that honor aspect ratios should take into
account the base size in determining the preferred window
size. If a base size is provided along with the aspect
ratio fields, the base size should be subtracted from the
window size prior to checking that the aspect ratio falls in
range. If a base size is not provided, nothing should be
subtracted from the window size. (The minimum size is not
to be used in place of the base size for this purpose.)
The WM_HINTS property (whose type is WM_HINTS) is used to
communicate to the window manager. It conveys the informa-
tion the window manager needs other than the window geome-
try, which is available from the window itself; the con-
straints on that geometry, which is available from the
WM_NORMAL_HINTS structure; and various strings, which need
separate properties, such as WM_NAME. The contents of the
properties are as follows:
l l l. _
[1mField Type Comments[0m
[1m_[0m
flags CARD32 (see the next table)
input CARD32 The client's input model ini-
tial_state CARD32 The state when first mapped
icon_pixmap PIXMAP The pixmap for the icon image
icon_window WINDOW The window for the icon image
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l l l. _
[1mField Type Comments[0m
[1m_[0m
icon_x INT32 The icon location icon_y INT32
icon_mask PIXMAP The mask for the icon shape win-
dow_group WINDOW The ID of the group leader window
_
The WM_HINTS.flags bit definitions are as follows:
lw(1.5i) nw(.5i) lw(1.5i). _
[1mName Value Field[0m
[1m_[0m
T{ T} 1 input T{ T} 2 initial_state T{
T} 4 icon_pixmap T{ T} 8 icon_window T{
T} 16 icon_x & icon_y T{ T} 32 icon_mask T{
T} 64 window_group T{ T} 128 (this bit is obsolete)
T{ T} 256 urgency
_
Window managers are free to assume convenient values for all
fields of the WM_HINTS property if a window is mapped with-
out one.
The input field is used to communicate to the window manager
the input focus model used by the client (see section
4.1.7).
Clients with the Globally Active and No Input models should
set the input flag to Clients with the Passive and Locally
Active models should set the input flag to
From the client's point of view, the window manager will
regard the client's top-level window as being in one of
three states:
+o Normal
+o Iconic
+o Withdrawn
The semantics of these states are described in section
4.1.4. Newly created windows start in the Withdrawn state.
Transitions between states happen when a top-level window is
mapped and unmapped and when the window manager receives
certain messages.
The value of the initial_state field determines the state
the client wishes to be in at the time the top-level window
is mapped from the Withdrawn state, as shown in the follow-
ing table:
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l n l. _
[1mState Value Comments[0m
[1m_[0m
T{ T} 1 The window is visible. T{ T} 3 The icon
is visible.
_
The icon_pixmap field may specify a pixmap to be used as an
icon. This pixmap should be:
+o One of the sizes specified in the WM_ICON_SIZE property
on the root if it exists (see section 4.1.3.2).
+o 1-bit deep. The window manager will select, through the
defaults database, suitable background (for the 0 bits)
and foreground (for the 1 bits) colors. These defaults
can, of course, specify different colors for the icons
of different clients.
The icon_mask specifies which pixels of the icon_pixmap
should be used as the icon, allowing for icons to appear
nonrectangular.
The icon_window field is the ID of a window the client wants
used as its icon. Most, but not all, window managers will
support icon windows. Those that do not are likely to have
a user interface in which small windows that behave like
icons are completely inappropriate. Clients should not
attempt to remedy the omission by working around it.
Clients that need more capabilities from the icons than a
simple 2-color bitmap should use icon windows. Rules for
clients that do are set out in section 4.1.9.
The (icon_x,icon_y) coordinate is a hint to the window man-
ager as to where it should position the icon. The policies
of the window manager control the positioning of icons, so
clients should not depend on attention being paid to this
hint.
The window_group field lets the client specify that this
window belongs to a group of windows. An example is a sin-
gle client manipulating multiple children of the root win-
dow.
1. The window_group field should be set to the ID of the
group leader. The window group leader may be a window
that exists only for that purpose; a placeholder group
leader of this kind would never be mapped either by the
client or by the window manager.
2. The properties of the window group leader are those for
the group as a whole (for example, the icon to be shown
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when the entire group is iconified).
Window managers may provide facilities for manipulating the
group as a whole. Clients, at present, have no way to oper-
ate on the group as a whole.
The messages bit, if set in the flags field, indicates that
the client is using an obsolete window manager communication
protocol,11 rather than the WM_PROTOCOLS mechanism of sec-
tion 4.1.2.7.
The flag, if set in the flags field, indicates that the
client deems the window contents to be urgent, requiring the
timely response of the user. The window manager must make
some effort to draw the user's attention to this window
while this flag is set. The window manager must also moni-
tor the state of this flag for the entire time the window is
in the Normal or Iconic state and must take appropriate
action when the state of the flag changes. The flag is oth-
erwise independent of the window's state; in particular, the
window manager is not required to deiconify the window if
the client sets the flag on an Iconic window. Clients must
provide some means by which the user can cause the flag to
be set to zero or the window to be withdrawn. The user's
action can either mitigate the actual condition that made
the window urgent, or it can merely shut off the alarm.
This mechanism is useful for alarm dialog boxes or reminder
windows, in cases where mapping the window is not enough
(e.g., in the presence of multi-workspace or virtual desktop
window managers), and where using an override-redirect win-
dow is too intrusive. For example, the window manager may
attract attention to an urgent window by adding an indicator
to its title bar or its icon. Window managers may also take
additional action for a window that is newly urgent, such as
by flashing its icon (if the window is iconic) or by raising
it to the top of the stack.
The WM_CLASS property (of type STRING without control char-
acters) contains two consecutive null-terminated strings.
These specify the Instance and Class names to be used by
both the client and the window manager for looking up
resources for the application or as identifying information.
This property must be present when the window leaves the
Withdrawn state and may be changed only while the window is
in the Withdrawn state. Window managers may examine the
property only when they start up and when the window leaves
-----------
11 This obsolete protocol was described in the
July 27, 1988, draft of the ICCCM. Windows using
it can also be detected because their WM_HINTS
properties are 4 bytes longer than expected. Win-
dow managers are free to support clients using the
obsolete protocol in a backwards compatibility
mode.
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the Withdrawn state, but there should be no need for a
client to change its state dynamically.
The two strings, respectively, are:
+o A string that names the particular instance of the
application to which the client that owns this window
belongs. Resources that are specified by instance name
override any resources that are specified by class name.
Instance names can be specified by the user in an oper-
ating-system specific manner. On POSIX-conformant sys-
tems, the following conventions are used:
- If "-name NAME" is given on the command line, NAME
is used as the instance name.
- Otherwise, if the environment variable
RESOURCE_NAME is set, its value will be used as the
instance name.
- Otherwise, the trailing part of the name used to
invoke the program (argv[0] stripped of any direc-
tory names) is used as the instance name.
+o A string that names the general class of applications to
which the client that owns this window belongs.
Resources that are specified by class apply to all
applications that have the same class name. Class names
are specified by the application writer. Examples of
commonly used class names include: "Emacs", "XTerm",
"XClock", "XLoad", and so on.
Note that WM_CLASS strings are null-terminated and, thus,
differ from the general conventions that STRING properties
are null-separated. This inconsistency is necessary for
backwards compatibility.
The WM_TRANSIENT_FOR property (of type WINDOW) contains the
ID of another top-level window. The implication is that
this window is a pop-up on behalf of the named window, and
window managers may decide not to decorate transient windows
or may treat them differently in other ways. In particular,
window managers should present newly mapped WM_TRANSIENT_FOR
windows without requiring any user interaction, even if map-
ping top-level windows normally does require interaction.
Dialogue boxes, for example, are an example of windows that
should have WM_TRANSIENT_FOR set.
It is important not to confuse WM_TRANSIENT_FOR with over-
ride-redirect. WM_TRANSIENT_FOR should be used in those
cases where the pointer is not grabbed while the window is
mapped (in other words, if other windows are allowed to be
active while the transient is up). If other windows must be
prevented from processing input (for example, when
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implementing pop-up menus), use override-redirect and grab
the pointer while the window is mapped.
The WM_PROTOCOLS property (of type ATOM) is a list of atoms.
Each atom identifies a communication protocol between the
client and the window manager in which the client is willing
to participate. Atoms can identify both standard protocols
and private protocols specific to individual window man-
agers.
All the protocols in which a client can volunteer to take
part involve the window manager sending the client a event
and the client taking appropriate action. For details of
the contents of the event, see section 4.2.8. In each case,
the protocol transactions are initiated by the window man-
ager.
The WM_PROTOCOLS property is not required. If it is not
present, the client does not want to participate in any win-
dow manager protocols.
The X Consortium will maintain a registry of protocols to
avoid collisions in the name space. The following table
lists the protocols that have been defined to date.
l c l. _
[1mProtocol Section Purpose[0m
[1m_[0m
WM_TAKE_FOCUS 4.1.7 Assignment of input focus
WM_SAVE_YOURSELF Appendix C Save client state request
(deprecated) WM_DELETE_WINDOW 4.2.8.1 Request to delete
top-level window
_
It is expected that this table will grow over time.
The WM_COLORMAP_WINDOWS property (of type WINDOW) on a top-
level window is a list of the IDs of windows that may need
colormaps installed that differ from the colormap of the
top-level window. The window manager will watch this list
of windows for changes in their colormap attributes. The
top-level window is always (implicitly or explicitly) on the
watch list. For the details of this mechanism, see section
4.1.8.
The client should set the WM_CLIENT_MACHINE property (of one
of the TEXT types) to a string that forms the name of the
machine running the client as seen from the machine running
the server.
The properties that were described in the previous section
are those that the client is responsible for maintaining on
its top-level windows. This section describes the proper-
ties that the window manager places on client's top-level
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windows and on the root.
The window manager will place a WM_STATE property (of type
WM_STATE) on each top-level client window that is not in the
Withdrawn state. Top-level windows in the Withdrawn state
may or may not have the WM_STATE property. Once the top-
level window has been withdrawn, the client may re-use it
for another purpose. Clients that do so should remove the
WM_STATE property if it is still present.
Some clients (such as [1mxprop[22m) will ask the user to click over
a window on which the program is to operate. Typically, the
intent is for this to be a top-level window. To find a top-
level window, clients should search the window hierarchy
beneath the selected location for a window with the WM_STATE
property. This search must be recursive in order to cover
all window manager reparenting possibilities. If no window
with a WM_STATE property is found, it is recommended that
programs use a mapped child-of-root window if one is present
beneath the selected location.
The contents of the WM_STATE property are defined as fol-
lows:
l l l. _
[1mField Type Comments[0m
_
state CARD32 (see the next table) icon WINDOW ID
of icon window
_
The following table lists the WM_STATE.state values:
l n. _
[1mState Value[0m
_
T{ T} 0 T{ T} 1 T{ T} 3
_
Adding other fields to this property is reserved to the X
Consortium. Values for the state field other than those
defined in the above table are reserved for use by the X
Consortium.
The state field describes the window manager's idea of the
state the window is in, which may not match the client's
idea as expressed in the initial_state field of the WM_HINTS
property (for example, if the user has asked the window man-
ager to iconify the window). If it is the window manager
believes the client should be animating its window. If it
is the client should animate its icon window. In either
state, clients should be prepared to handle exposure events
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from either window.
When the window is withdrawn, the window manager will either
change the state field's value to or it will remove the
WM_STATE property entirely.
The icon field should contain the window ID of the window
that the window manager uses as the icon for the window on
which this property is set. If no such window exists, the
icon field should be Note that this window could be but is
not necessarily the same window as the icon window that the
client may have specified in its WM_HINTS property. The
WM_STATE icon may be a window that the window manager has
supplied and that contains the client's icon pixmap, or it
may be an ancestor of the client's icon window.
A window manager that wishes to place constraints on the
sizes of icon pixmaps and/or windows should place a property
called WM_ICON_SIZE on the root. The contents of this prop-
erty are listed in the following table.
l l l. _
[1mField Type Comments[0m
[1m_[0m
min_width CARD32 The data for the icon size series
min_height CARD32 max_width CARD32 max_height CARD32
width_inc CARD32 height_inc CARD32
_
For more details see section 14.1.12 in [4mXlib[24m [4m-[24m [4mC[24m [4mLanguage[24m [4mX[0m
[4mInterface[24m.
From the client's point of view, the window manager will
regard each of the client's top-level windows as being in
one of three states, whose semantics are as follows:
+o - The client's top-level window is viewable.
+o - The client's top-level window is iconic (whatever that
means for this window manager). The client can assume
that its top-level window is not viewable, its icon_win-
dow (if any) will be viewable and, failing that, its
icon_pixmap (if any) or its WM_ICON_NAME will be dis-
played.
+o - Neither the client's top-level window nor its icon is
visible.
In fact, the window manager may implement states with seman-
tics other than those described above. For example, a win-
dow manager might implement a concept of an "inactive" state
in which an infrequently used client's window would be rep-
resented as a string in a menu. But this state is invisible
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to the client, which would see itself merely as being in the
Iconic state.
Newly created top-level windows are in the Withdrawn state.
Once the window has been provided with suitable properties,
the client is free to change its state as follows:
+o Withdrawn -> Normal - The client should map the window
with WM_HINTS.initial_state being
+o Withdrawn -> Iconic - The client should map the window
with WM_HINTS.initial_state being
+o Normal -> Iconic - The client should send a event as
described later in this section.
+o Normal -> Withdrawn - The client should unmap the window
and follow it with a synthetic event as described later
in this section.
+o Iconic -> Normal - The client should map the window.
The contents of WM_HINTS.initial_state are irrelevant in
this case.
+o Iconic -> Withdrawn - The client should unmap the window
and follow it with a synthetic event as described later
in this section.
Only the client can effect a transition into or out of the
Withdrawn state. Once a client's window has left the With-
drawn state, the window will be mapped if it is in the Nor-
mal state and the window will be unmapped if it is in the
Iconic state. Reparenting window managers must unmap the
client's window when it is in the Iconic state, even if an
ancestor window being unmapped renders the client's window
unviewable. Conversely, if a reparenting window manager
renders the client's window unviewable by unmapping an
ancestor, the client's window is by definition in the Iconic
state and must also be unmapped. Clients can select for on
their top-level windows to track transitions between Normal
and Iconic states. Receipt of a event will indicate a tran-
sition to the Normal state, and receipt of an event will
indicate a transition to the Iconic state.
When changing the state of the window to Withdrawn, the
client must (in addition to unmapping the window) send a
synthetic event by using a request with the following argu-
ments:
l lw(3.5i). _
[1mArgument Value[0m
[1m_[0m
destination: The root propagate: T{ T} event-
mask: T{ T} T{ event: an with: T} T{ T}
[1m38[0m
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event: The root window: The window itself
from-configure: T{ T}
_
The reason for requiring the client to send a synthetic
event is to ensure that the window manager gets some notifi-
cation of the client's desire to change state, even though
the window may already be unmapped when the desire is
expressed. For compatibility with obsolete clients, window
managers should trigger the transition to the Withdrawn
state on the real rather than waiting for the synthetic one.
They should also trigger the transition if they receive a
synthetic on a window for which they have not yet received a
real
When a client withdraws a window, the window manager will
then update or remove the WM_STATE property as described in
section 4.1.3.1. Clients that want to re-use a client win-
dow (e.g., by mapping it again or reparenting it elsewhere)
after withdrawing it must wait for the withdrawal to be com-
plete before proceeding. The preferred method for doing
this is for clients to wait for the window manager to update
or remove the WM_STATE property.12
If the transition is from the Normal to the Iconic state,
the client should send a event to the root with:
+o Window == the window to be iconified
+o Type13 == the atom WM_CHANGE_STATE
+o Format == 32
+o Data[0] == IconicState The format of this event does not
match the format of in section 4.2.8. This is because
they are sent by the window manager to clients, and this
message is sent by clients to the window manager.
Other values of data[0] are reserved for future extensions
to these conventions. The parameters of the request should
-----------
12 Earlier versions of these conventions prohib-
ited clients from reading the WM_STATE property.
Clients operating under the earlier conventions
used the technique of tracking events to wait for
the top-level window to be reparented back to the
root window. This is still a valid technique;
however, it works only for reparenting window man-
agers, and the WM_STATE technique is to be pre-
ferred.
13 The type field of the event (called the mes-
sage_type field by Xlib) should not be confused
with the code field of the event itself, which
will have the value 33
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be those described for the synthetic event. Clients can
also select for events on their top-level or icon windows.
They will then receive a event when the window concerned
becomes completely obscured even though mapped (and thus,
perhaps a waste of time to update) and a event when it
becomes even partly viewable. When a window makes a transi-
tion from the Normal state to either the Iconic or the With-
drawn state, clients should be aware that the window manager
may make transients for this window inaccessible. Clients
should not rely on transient windows being available to the
user when the transient owner window is not in the Normal
state. When withdrawing a window, clients are advised to
withdraw transients for the window.
Clients can resize and reposition their top-level windows by
using the request. The attributes of the window that can be
altered with this request are as follows:
+o The [x,y] location of the window's upper left-outer cor-
ner
+o The [width,height] of the inner region of the window
(excluding borders)
+o The border width of the window
+o The window's position in the stack
The coordinate system in which the location is expressed is
that of the root (irrespective of any reparenting that may
have occurred). The border width to be used and win_gravity
position hint to be used are those most recently requested
by the client. Client configure requests are interpreted by
the window manager in the same manner as the initial window
geometry mapped from the Withdrawn state, as described in
section 4.1.2.3. Clients must be aware that there is no
guarantee that the window manager will allocate them the
requested size or location and must be prepared to deal with
any size and location. If the window manager decides to
respond to a request by:
+o Not changing the size, location, border width, or stack-
ing order of the window at all.
A client will receive a synthetic event that describes
the (unchanged) geometry of the window. The (x,y) coor-
dinates will be in the root coordinate system, adjusted
for the border width the client requested, irrespective
of any reparenting that has taken place. The bor-
der_width will be the border width the client requested.
The client will not receive a real event because no
change has actually taken place.
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+o Moving or restacking the window without resizing it or
changing its border width.
A client will receive a synthetic event following the
change that describes the new geometry of the window.
The event's (x,y) coordinates will be in the root coor-
dinate system adjusted for the border width the client
requested. The border_width will be the border width
the client requested. The client may not receive a real
event that describes this change because the window man-
ager may have reparented the top-level window. If the
client does receive a real event, the synthetic event
will follow the real one.
+o Resizing the window or changing its border width
(regardless of whether the window was also moved or
restacked).
A client that has selected for events will receive a
real event. Note that the coordinates in this event are
relative to the parent, which may not be the root if the
window has been reparented. The coordinates will
reflect the actual border width of the window (which the
window manager may have changed). The request can be
used to convert the coordinates if required.
The general rule is that coordinates in real events are in
the parent's space; in synthetic events, they are in the
root space. Clients cannot distinguish between the case
where a top-level window is resized and moved from the case
where the window is resized but not moved, since a real
event will be received in both cases. Clients that are con-
cerned with keeping track of the absolute position of a top-
level window should keep a piece of state indicating whether
they are certain of its position. Upon receipt of a real
event on the top-level window, the client should note that
the position is unknown. Upon receipt of a synthetic event,
the client should note the position as known, using the
position in this event. If the client receives a or event
on the window (or on any descendant), the client can deduce
the top-level window's position from the difference between
the (event-x, event-y) and (root-x, root-y) coordinates in
these events. Only when the position is unknown does the
client need to use the request to find the position of a
top-level window.
Clients should be aware that their borders may not be visi-
ble. Window managers are free to use reparenting techniques
to decorate client's top-level windows with borders contain-
ing titles, controls, and other details to maintain a con-
sistent look-and-feel. If they do, they are likely to over-
ride the client's attempts to set the border width and set
it to zero. Clients, therefore, should not depend on the
top-level window's border being visible or use it to display
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any critical information. Other window managers will allow
the top-level windows border to be visible. Clients should
set the desired value of the border-width attribute on all
requests to avoid a race condition.
Clients that change their position in the stack must be
aware that they may have been reparented, which means that
windows that used to be siblings no longer are. Using a
nonsibling as the sibling parameter on a request will cause
an error. Clients that use a request to request a change in
their position in the stack should do so using in the sib-
ling field.
Clients that must position themselves in the stack relative
to some window that was originally a sibling must do the
request (in case they are running under a nonreparenting
window manager), be prepared to deal with a resulting error,
and then follow with a synthetic event by invoking a request
with the following arguments:
l lw(3.5i). _
[1mArgument Value[0m
[1m_[0m
destination: The root propagate: T{ T} event-
mask: T{ T} T{ event: a with: T} T{ T}
event: The root window: The window itself T{
... T} T{ Other parameters from the request T}
_
Window managers are in any case free to position windows in
the stack as they see fit, and so clients should not rely on
receiving the stacking order they have requested. Clients
should ignore the above-sibling field of both real and syn-
thetic events received on their top-level windows because
this field may not contain useful information.
The attributes that may be supplied when a window is created
may be changed by using the request. The window attributes
are listed in the following table:
l l l c. _
[1mAttribute Private to Client[0m
[1m_[0m
Background pixmap Yes Background pixel Yes Border
pixmap Yes Border pixel Yes Bit gravity Yes Window
gravity No Backing-store hint Yes Save-under hint No
Event mask No Do-not-propagate mask Yes Override-redi-
rect flag No Colormap Yes Cursor Yes
_
Most attributes are private to the client and will never be
interfered with by the window manager. For the attributes
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that are not private to the client:
+o The window manager is free to override the window grav-
ity; a reparenting window manager may want to set the
top-level window's window gravity for its own purposes.
+o Clients are free to set the save-under hint on their
top-level windows, but they must be aware that the hint
may be overridden by the window manager.
+o Windows, in effect, have per-client event masks, and so,
clients may select for whatever events are convenient
irrespective of any events the window manager is select-
ing for. There are some events for which only one
client at a time may select, but the window manager
should not select for them on any of the client's win-
dows.
+o Clients can set override-redirect on top-level windows
but are encouraged not to do so except as described in
sections 4.1.10 and 4.2.9.
There are four models of input handling:
+o No Input - The client never expects keyboard input. An
example would be or another output-only client.
+o Passive Input - The client expects keyboard input but
never explicitly sets the input focus. An example would
be a simple client with no subwindows, which will accept
input in mode or when the window manager sets the input
focus to its top-level window (in click-to-type mode).
+o Locally Active Input - The client expects keyboard input
and explicitly sets the input focus, but it only does so
when one of its windows already has the focus. An exam-
ple would be a client with subwindows defining various
data entry fields that uses Next and Prev keys to move
the input focus between the fields. It does so when its
top-level window has acquired the focus in mode or when
the window manager sets the input focus to its top-level
window (in click-to-type mode).
+o Globally Active Input - The client expects keyboard
input and explicitly sets the input focus, even when it
is in windows the client does not own. An example would
be a client with a scroll bar that wants to allow users
to scroll the window without disturbing the input focus
even if it is in some other window. It wants to acquire
the input focus when the user clicks in the scrolled
region but not when the user clicks in the scroll bar
itself. Thus, it wants to prevent the window manager
from setting the input focus to any of its windows.
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The four input models and the corresponding values of the
input field and the presence or absence of the WM_TAKE_FOCUS
atom in the WM_PROTOCOLS property are listed in the follow-
ing table:
l l l l c c. _
[1mInput Model Input Field WM_TAKE_FOCUS[0m
[1m_[0m
T{ No Input T} T{ T} T{ Absent T} T{ Passive T} T{
T} T{ Absent T} T{ Locally Active T} T{ T} T{ Present
T} T{ Globally Active T} T{ T} T{ Present T}
_
Passive and Locally Active clients set the input field of
WM_HINTS to which indicates that they require window manager
assistance in acquiring the input focus. No Input and
Globally Active clients set the input field to which
requests that the window manager not set the input focus to
their top-level window.
Clients that use a request must set the time field to the
timestamp of the event that caused them to make the attempt.
This cannot be a event because they do not have timestamps.
Clients may also acquire the focus without a corresponding
Note that clients must not use in the time field.
Clients using the Globally Active model can only use a
request to acquire the input focus when they do not already
have it on receipt of one of the following events:
+o
+o
+o Passive-grabbed
+o Passive-grabbed
In general, clients should avoid using passive-grabbed key
events for this purpose, except when they are unavoidable
(as, for example, a selection tool that establishes a pas-
sive grab on the keys that cut, copy, or paste).
The method by which the user commands the window manager to
set the focus to a window is up to the window manager. For
example, clients cannot determine whether they will see the
click that transfers the focus.
Windows with the atom WM_TAKE_FOCUS in their WM_PROTOCOLS
property may receive a event from the window manager (as
described in section 4.2.8) with WM_TAKE_FOCUS in its
data[0] field and a valid timestamp (i.e., not in its
data[1] field. If they want the focus, they should respond
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with a request with its window field set to the window of
theirs that last had the input focus or to their default
input window, and the time field set to the timestamp in the
message. For further information, see section 4.2.7.
A client could receive WM_TAKE_FOCUS when opening from an
icon or when the user has clicked outside the top-level win-
dow in an area that indicates to the window manager that it
should assign the focus (for example, clicking in the head-
line bar can be used to assign the focus).
The goal is to support window managers that want to assign
the input focus to a top-level window in such a way that the
top-level window either can assign it to one of its subwin-
dows or can decline the offer of the focus. For example, a
clock or a text editor with no currently open frames might
not want to take focus even though the window manager gener-
ally believes that clients should take the input focus after
being deiconified or raised.
Clients that set the input focus need to decide a value for
the revert-to field of the request. This determines the
behavior of the input focus if the window the focus has been
set to becomes not viewable. The value can be any of the
following:
+o - In general, clients should use this value when assign-
ing focus to one of their subwindows. Unmapping the
subwindow will cause focus to revert to the parent,
which is probably what you want.
+o - Using this value with a click-to-type focus management
policy leads to race conditions because the window
becoming unviewable may coincide with the window manager
deciding to move the focus elsewhere.
+o - Using this value causes problems if the window manager
reparents the window, as most window managers will, and
then crashes. The input focus will be and there will
probably be no way to change it.
Note that neither nor is really safe to use. Clients that
invoke a request should set the revert-to argument to
A convention is also required for clients that want to give
up the input focus. There is no safe value set for them to
set the input focus to; therefore, they should ignore input
material. Clients should not give up the input focus of
their own volition. They should ignore input that they
receive instead.
The window manager is responsible for installing and unin-
stalling colormaps on behalf of clients with top-level win-
dows that the window manager manages.
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Clients provide the window manager with hints as to which
colormaps to install and uninstall. Clients must not
install or uninstall colormaps themselves (except under the
circumstances noted below). When a client's top-level win-
dow gets the colormap focus (as a result of whatever col-
ormap focus policy is implemented by the window manager),
the window manager will ensure that one or more of the
client's colormaps are installed.
Clients whose top-level windows and subwindows all use the
same colormap should set its ID in the colormap field of the
top-level window's attributes. They should not set a
WM_COLORMAP_WINDOWS property on the top-level window. If
they want to change the colormap, they should change the
top-level window's colormap attribute. The window manager
will track changes to the window's colormap attribute and
install colormaps as appropriate.
Clients that create windows can use the value to inherit
their parent's colormap. Window managers will ensure that
the root window's colormap field contains a colormap that is
suitable for clients to inherit. In particular, the col-
ormap will provide distinguishable colors for and
Top-level windows that have subwindows or override-redirect
pop-up windows whose colormap requirements differ from the
top-level window should have a WM_COLORMAP_WINDOWS property.
This property contains a list of IDs for windows whose col-
ormaps the window manager should attempt to have installed
when, in the course of its individual colormap focus policy,
it assigns the colormap focus to the top-level window (see
section 4.1.2.8). The list is ordered by the importance to
the client of having the colormaps installed. The window
manager will track changes to this property and will track
changes to the colormap attribute of the windows in the
property.
If the relative importance of colormaps changes, the client
should update the WM_COLORMAP_WINDOWS property to reflect
the new ordering. If the top-level window does not appear
in the list, the window manager will assume it to be of
higher priority than any window in the list.
WM_TRANSIENT_FOR windows can either have their own WM_COL-
ORMAP_WINDOWS property or appear in the property of the win-
dow they are transient for, as appropriate. An alternative
design was considered for how clients should hint to the
window manager about their colormap requirements. This
alternative design specified a list of colormaps instead of
a list of windows. The current design, a list of windows,
was chosen for two reasons. First, it allows window man-
agers to find the visuals of the colormaps, thus permitting
visual-dependent colormap installation policies. Second, it
allows window managers to select for events on the windows
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concerned and to ensure that colormaps are only installed if
the windows that need them are visible. The alternative
design allows for neither of these policies. Clients should
be aware of the min-installed-maps and max-installed-maps
fields of the connection setup information, and the effect
that the minimum value has on the "required list" defined by
the Protocol in the description of the request. Briefly,
the min-installed-maps most recently installed maps are
guaranteed to be installed. This value is often one;
clients needing multiple colormaps should beware.
Whenever possible, clients should use the mechanisms
described above and let the window manager handle colormap
installation. However, clients are permitted to perform
colormap installation on their own while they have the
pointer grabbed. A client performing colormap installation
must notify the window manager prior to the first installa-
tion. When the client has finished its colormap installa-
tion, it must also notify the window manager. The client
notifies the window manager by issuing a request with the
following arguments:
tab(/) ; lB lB l lw(3.5i) _
Argument/Value
_ destination:/T{ the root window of the screen on which the
colormap is being installed T} propagate:/T{ T} event-
mask:/T{ T} T{ event: a with: T} window:/the root window,
as above type:/WM_COLORMAP_NOTIFY format:/32
data[0]:/T{ the timestamp of the event that caused the
client to start or stop installing colormaps T}
data[1]:/T{ 1 if the client is starting colormap installa-
tion, 0 if the client is finished with colormap installation
T} data[2]:/reserved, must be zero data[3]:/reserved,
must be zero data[4]:/reserved, must be zero
_
This feature was introduced in version 2.0 of this document,
and there will be a significant period of time before all
window managers can be expected to implement this feature.
Before using this feature, clients must check the compliance
level of the window manager (using the mechanism described
in section 4.3) to verify that it supports this feature.
This is necessary to prevent colormap installation conflicts
between clients and older window managers.
Window managers should refrain from installing colormaps
while a client has requested control of colormap installa-
tion. The window manager should continue to track the set
of installed colormaps so that it can reinstate its colormap
focus policy when the client has finished colormap installa-
tion.
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This technique has race conditions that may result in the
colormaps continuing to be installed even after a client has
issued its notification message. For example, the window
manager may have issued some requests that are not executed
until after the client's and requests, thus uninstalling the
client's colormaps. If this occurs while the client still
has the pointer grabbed and before the client has issued the
"finished" message, the client may reinstall the desired
colormaps. Clients are expected to use this mechanism for
things such as pop-up windows and for animations that use
override-redirect windows.
If a client fails to issue the "finished" message, the win-
dow manager may be left in a state where its colormap
installation policy is suspended. Window manager implemen-
tors may want to implement a feature that resets colormap
installation policy in response to a command from the user.
A client can hint to the window manager about the desired
appearance of its icon by setting:
+o A string in WM_ICON_NAME.
All clients should do this because it provides a fall-
back for window managers whose ideas about icons differ
widely from those of the client.
+o A into the icon_pixmap field of the WM_HINTS property
and possibly another into the icon_mask field.
The window manager is expected to display the pixmap
masked by the mask. The pixmap should be one of the
sizes found in the WM_ICON_SIZE property on the root.
If this property is not found, the window manager is
unlikely to display icon pixmaps. Window managers usu-
ally will clip or tile pixmaps that do not match
WM_ICON_SIZE.
+o A window into the icon_window field of the WM_HINTS
property.
The window manager is expected to map that window when-
ever the client is in the Iconic state. In general, the
size of the icon window should be one of those specified
in WM_ICON_SIZE on the root, if it exists. Window man-
agers are free to resize icon windows.
In the Iconic state, the window manager usually will ensure
that:
+o If the window's WM_HINTS.icon_window is set, the window
it names is visible.
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+o If the window's WM_HINTS.icon_window is not set but the
window's WM_HINTS.icon_pixmap is set, the pixmap it
names is visible.
+o Otherwise, the window's WM_ICON_NAME string is visible.
Clients should observe the following conventions about their
icon windows:
1. The icon window should be an child of the root.
2. The icon window should be one of the sizes specified in
the WM_ICON_SIZE property on the root.
3. The icon window should use the root visual and default
colormap for the screen in question.
4. Clients should not map their icon windows.
5. Clients should not unmap their icon windows.
6. Clients should not configure their icon windows.
7. Clients should not set override-redirect on their icon
windows or select for events on them.
8. Clients must not depend on being able to receive input
events by means of their icon windows.
9. Clients must not manipulate the borders of their icon
windows.
10. Clients must select for events on their icon window and
repaint it when requested.
Window managers will differ as to whether they support input
events to client's icon windows; most will allow the client
to receive some subset of the keys and buttons.
Window managers will ignore any WM_NAME, WM_ICON_NAME,
WM_NORMAL_HINTS, WM_HINTS, WM_CLASS, WM_TRANSIENT_FOR,
WM_PROTOCOLS, WM_COLORMAP_WINDOWS, WM_COMMAND, or
WM_CLIENT_MACHINE properties they find on icon windows.
Clients that wish to pop up a window can do one of three
things:
1. They can create and map another normal top-level win-
dow, which will get decorated and managed as normal by
the window manager. See the discussion of window
groups that follows.
2. If the window will be visible for a relatively short
time and deserves a somewhat lighter treatment, they
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can set the WM_TRANSIENT_FOR property. They can expect
less decoration but can set all the normal window man-
ager properties on the window. An example would be a
dialog box.
3. If the window will be visible for a very short time and
should not be decorated at all, the client can set
override-redirect on the window. In general, this
should be done only if the pointer is grabbed while the
window is mapped. The window manager will never inter-
fere with these windows, which should be used with cau-
tion. An example of an appropriate use is a pop-up
menu. The user will not be able to move, resize,
restack, or transfer the input focus to override-redi-
rect windows, since the window manager is not managing
them. If it is necessary for a client to receive key-
strokes on an override-redirect window, either the
client must grab the keyboard or the client must have
another top-level window that is not override-redirect
and that has selected the Locally Active or Globally
Active focus model. The client may set the focus to
the override-redirect window when the other window
receives a WM_TAKE_FOCUS message or one of the events
listed in section 4.1.7 in the description of the Glob-
ally Active focus model.
Window managers are free to decide if WM_TRANSIENT_FOR win-
dows should be iconified when the window they are transient
for is. Clients displaying WM_TRANSIENT_FOR windows that
have (or request to have) the window they are transient for
iconified do not need to request that the same operation be
performed on the WM_TRANSIENT_FOR window; the window manager
will change its state if that is the policy it wishes to
enforce.
A set of top-level windows that should be treated from the
user's point of view as related (even though they may belong
to a number of clients) should be linked together using the
window_group field of the WM_HINTS structure.
One of the windows (that is, the one the others point to)
will be the group leader and will carry the group as opposed
to the individual properties. Window managers may treat the
group leader differently from other windows in the group.
For example, group leaders may have the full set of decora-
tions, and other group members may have a restricted set.
It is not necessary that the client ever map the group
leader; it may be a window that exists solely as a place-
holder.
It is up to the window manager to determine the policy for
treating the windows in a group. At present, there is no
way for a client to request a group, as opposed to an
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individual, operation.
The window manager performs a number of operations on client
resources, primarily on their top-level windows. Clients
must not try to fight this but may elect to receive notifi-
cation of the window manager's operations.
Clients must be aware that some window managers will repar-
ent their top-level windows so that a window that was cre-
ated as a child of the root will be displayed as a child of
some window belonging to the window manager. The effects
that this reparenting will have on the client are as fol-
lows:
+o The parent value returned by a request will no longer be
the value supplied to the request that created the
reparented window. There should be no need for the
client to be aware of the identity of the window to
which the top-level window has been reparented. In par-
ticular, a client that wishes to create further top-
level windows should continue to use the root as the
parent for these new windows.
+o The server will interpret the (x,y) coordinates in a
request in the new parent's coordinate space. In fact,
they usually will not be interpreted by the server
because a reparenting window manager usually will have
intercepted these operations (see section 4.2.2).
Clients should use the root coordinate space for these
requests (see section 4.1.5).
+o requests that name a specific sibling window may fail
because the window named, which used to be a sibling, no
longer is after the reparenting operation (see section
4.1.5).
+o The (x,y) coordinates returned by a request are in the
parent's coordinate space and are thus not directly use-
ful after a reparent operation.
+o A background of will have unpredictable results.
+o A cursor of will have unpredictable results.
Clients that want to be notified when they are reparented
can select for events on their top-level window. They will
receive a event if and when reparenting takes place. When a
client withdraws a top-level window, the window manager will
reparent it back to the root window if the window had been
reparented elsewhere.
If the window manager reparents a client's window, the
reparented window will be placed in the save-set of the par-
ent window. This means that the reparented window will not
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be destroyed if the window manager terminates and will be
remapped if it was unmapped. Note that this applies to all
client windows the window manager reparents, including tran-
sient windows and client icon windows.
Clients must be aware that some window managers will arrange
for some client requests to be intercepted and redirected.
Redirected requests are not executed; they result instead in
events being sent to the window manager, which may decide to
do nothing, to alter the arguments, or to perform the
request on behalf of the client.
The possibility that a request may be redirected means that
a client cannot assume that any redirectable request is
actually performed when the request is issued or is actually
performed at all. The requests that may be redirected are
and The following is incorrect because the request may be
intercepted and the output made to an unmapped window:
MapWindow A
PolyLine A GC <point> <point> ...
The client must wait for an event before drawing in the win-
dow.14
This next example incorrectly assumes that the request is
actually executed with the arguments supplied:
ConfigureWindow width=N height=M
<output assuming window is N by M>
The client should select for on its window and monitor the
window's size by tracking events.
Clients must be especially careful when attempting to set
the focus to a window that they have just mapped. This
sequence may result in an X protocol error:
MapWindow B
SetInputFocus B
If the request has been intercepted, the window will still
be unmapped, causing the request to generate the error. The
-----------
14 This is true even if the client set the back-
ing-store attribute to The backing-store attribute
is a only a hint, and the server may stop main-
taining backing store contents at any time.
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solution to this problem is for clients to select for on the
window and to delay the issuance of the request until they
have received a event indicating that the window is visible.
This technique does not guarantee correct operation. The
user may have iconified the window by the time the request
reaches the server, still causing an error. Or the window
manager may decide to map the window into Iconic state, in
which case the window will not be visible. This will delay
the generation of the event indefinitely. Clients must be
prepared to handle these cases.
A window with the override-redirect bit set is immune from
redirection, but the bit should be set on top-level windows
only in cases where other windows should be prevented from
processing input while the override-redirect window is
mapped (see section 4.1.10) and while responding to events
(see section 4.2.9).
Clients that have no non-Withdrawn top-level windows and
that map an override-redirect top-level window are taking
over total responsibility for the state of the system. It
is their responsibility to:
+o Prevent any preexisting window manager from interfering
with their activities
+o Restore the status quo exactly after they unmap the win-
dow so that any preexisting window manager does not get
confused
In effect, clients of this kind are acting as temporary
window managers. Doing so is strongly discouraged because
these clients will be unaware of the user interface policies
the window manager is trying to maintain and because their
user interface behavior is likely to conflict with that of
less demanding clients.
If the window manager moves a top-level window without
changing its size, the client will receive a synthetic event
following the move that describes the new location in terms
of the root coordinate space. Clients must not respond to
being moved by attempting to move themselves to a better
location.
Any real event on a top-level window implies that the win-
dow's position on the root may have changed, even though the
event reports that the window's position in its parent is
unchanged because the window may have been reparented. Note
that the coordinates in the event will not, in this case, be
directly useful.
The window manager will send these events by using a request
with the following arguments:
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l l. _
[1mArgument Value[0m
[1m_[0m
destination: The client's window propagate: T{ T}
event-mask: T{ T}
_
The client can elect to receive notification of being
resized by selecting for events on its top-level windows.
It will receive a event. The size information in the event
will be correct, but the location will be in the parent win-
dow (which may not be the root).
The response of the client to being resized should be to
accept the size it has been given and to do its best with
it. Clients must not respond to being resized by attempting
to resize themselves to a better size. If the size is
impossible to work with, clients are free to request to
change to the Iconic state.
A top-level window that is not Withdrawn will be in the Nor-
mal state if it is mapped and in the Iconic state if it is
unmapped. This will be true even if the window has been
reparented; the window manager will unmap the window as well
as its parent when switching to the Iconic state.
The client can elect to be notified of these state changes
by selecting for events on the top-level window. It will
receive a event when it goes Iconic and a event when it goes
Normal.
Clients that wish to be notified of their colormaps being
installed or uninstalled should select for events on their
top-level windows and on any windows they have named in
WM_COLORMAP_WINDOWS properties on their top-level windows.
They will receive events with the new field FALSE when the
colormap for that window is installed or uninstalled.
Clients can request notification that they have the input
focus by selecting for events on their top-level windows;
they will receive and events. Clients that need to set the
input focus to one of their subwindows should not do so
unless they have set WM_TAKE_FOCUS in their WM_PROTOCOLS
property and have done one of the following:
+o Set the input field of WM_HINTS to and actually have the
input focus in one of their top-level windows
+o Set the input field of WM_HINTS to and have received a
suitable event as described in section 4.1.7
+o Have received a WM_TAKE_FOCUS message as described in
section 4.1.7
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Clients should not warp the pointer in an attempt to trans-
fer the focus; they should set the focus and leave the
pointer alone. For further information, see section 6.2.
Once a client satisfies these conditions, it may transfer
the focus to another of its windows by using the request,
which is defined as follows:
[4mfocus[24m: WINDOW or or
[4mrevert-to[24m:
[4mtime[24m: TIMESTAMP or
1. Clients that use a request must set the time argument
to the timestamp of the event that caused them to make
the attempt. This cannot be a event because they do
not have timestamps. Clients may also acquire the
focus without a corresponding event. Clients must not
use for the time argument.
2. Clients that use a request to set the focus to one of
their windows must set the revert-to field to
There is no way for clients to prevent themselves being sent
events.
Top-level windows with a WM_PROTOCOLS property may be sent
events specific to the protocols named by the atoms in the
property (see section 4.1.2.7). For all protocols, the
events have the following:
+o WM_PROTOCOLS as the type field
+o Format 32
+o The atom that names their protocol in the data[0] field
+o A timestamp in their data[1] field
The remaining fields of the event, including the window
field, are determined by the protocol.
These events will be sent by using a request with the fol-
lowing arguments:
l l. _
[1mArgument Value[0m
[1m_[0m
destination: The client's window propagate: T{ T}
event-mask: () empty event: As specified by the proto-
col
_
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Clients, usually those with multiple top-level windows,
whose server connection must survive the deletion of some of
their top-level windows, should include the atom
WM_DELETE_WINDOW in the WM_PROTOCOLS property on each such
window. They will receive a event as described above whose
data[0] field is WM_DELETE_WINDOW.
Clients receiving a WM_DELETE_WINDOW message should behave
as if the user selected "delete window" from a hypothetical
menu. They should perform any confirmation dialog with the
user and, if they decide to complete the deletion, should do
the following:
+o Either change the window's state to Withdrawn (as
described in section 4.1.4) or destroy the window.
+o Destroy any internal state associated with the window.
If the user aborts the deletion during the confirmation dia-
log, the client should ignore the message.
Clients are permitted to interact with the user and ask, for
example, whether a file associated with the window to be
deleted should be saved or the window deletion should be
cancelled. Clients are not required to destroy the window
itself; the resource may be reused, but all associated state
(for example, backing store) should be released.
If the client aborts a destroy and the user then selects
DELETE WINDOW again, the window manager should start the
WM_DELETE_WINDOW protocol again. Window managers should not
use requests on a window that has WM_DELETE_WINDOW in its
WM_PROTOCOLS property.
Clients that choose not to include WM_DELETE_WINDOW in the
WM_PROTOCOLS property may be disconnected from the server if
the user asks for one of the client's top-level windows to
be deleted.
Normal clients can use the redirection mechanism just as
window managers do by selecting for events on a parent win-
dow or events on a window itself. However, at most, one
client per window can select for these events, and a conven-
tion is needed to avoid clashes. Clients (including window
managers) should select for and events only on windows that
they own.
In particular, clients that need to take some special action
if they are resized can select for events on their top-level
windows. They will receive a event if the window manager
resizes their window, and the resize will not actually take
place. Clients are free to make what use they like of the
information that the window manager wants to change their
size, but they must configure the window to the width and
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height specified in the event in a timely fashion. To
ensure that the resize will actually happen at this stage
instead of being intercepted and executed by the window man-
ager (and thus restarting the process), the client needs
temporarily to set override-redirect on the window. Clients
receiving events must respond by doing the following:
+o Setting override-redirect on the window specified in the
event
+o Configuring the window specified in the event to the
width and height specified in the event as soon as pos-
sible and before making any other geometry requests
+o Clearing override-redirect on the window specified in
the event
If a window manager detects that a client is not obeying
this convention, it is free to take whatever measures it
deems appropriate to deal with the client.
For each screen they manage, window managers will acquire
ownership of a selection named WM_S[4mn[24m, where [4mn[24m is the screen
number, as described in section 1.2.6. Window managers
should comply with the conventions for "Manager Selections"
described in section 2.8. The intent is for clients to be
able to request a variety of information or services by
issuing conversion requests on this selection. Window man-
agers should support conversion of the following target on
their manager selection:
l l lw(3.5i) . _
[1mAtom Type Data Received[0m
_
VERSION INTEGER T{ Two integers, which are the major and
minor release numbers (respectively) of the ICCCM with which
the window manager complies. For this version of the ICCCM,
the numbers are 2 and 0.15 T}
_
The window manager properties are summarized in the follow-
ing table (see also section 14.1 of [4mXlib[24m [4m-[24m [4mC[24m [4mLanguage[24m [4mX[0m
[4mInterface[24m).
-----------
15 As a special case, clients not wishing to
implement a selection request may simply issue a
request on the appropriate WM_S[4mn[24m selection. If
this selection is owned, clients may assume that
the window manager complies with ICCCM version 2.0
or later.
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l l n c. _
[1mName Type Format See Section[0m
[1m_[0m
WM_CLASS STRING 8 4.1.2.5
WM_CLIENT_MACHINE TEXT 4.1.2.9 WM_COLORMAP_WIN-
DOWS WINDOW 32 4.1.2.8 WM_HINTS WM_HINTS 32 4.1.2.4
WM_ICON_NAME TEXT 4.1.2.2
WM_ICON_SIZE WM_ICON_SIZE 32 4.1.3.2
WM_NAME TEXT 4.1.2.1 WM_NOR-
MAL_HINTS WM_SIZE_HINTS 32 4.1.2.3 WM_PROTO-
COLS ATOM 32 4.1.2.7 WM_STATE WM_STATE 32 4.1.3.1
WM_TRANSIENT_FOR WINDOW 32 4.1.2.6
_
This section contains some conventions for clients that par-
ticipate in session management. See [4mX[24m [4mSession[24m [4mManagement[0m
[4mProtocol[24m for further details. Clients that do not support
this protocol cannot expect their window state (e.g.,
WM_STATE, position, size, and stacking order) to be pre-
served across sessions.
Each session participant will obtain a unique client identi-
fier (client-ID) from the session manager. The client must
identify one top-level window as the "client leader." This
window must be created by the client. It may be in any
state, including the Withdrawn state. The client leader
window must have a SM_CLIENT_ID property, which contains the
client-ID obtained from the session management protocol.
That property must:
+o Be of type STRING
+o Be of format 8
+o Contain the client-ID as a string of XPCS characters
encoded using ISO 8859-1
All top-level, nontransient windows created by a client on
the same display as the client leader must have a
WM_CLIENT_LEADER property. This property contains a window
ID that identifies the client leader window. The client
leader window must have a WM_CLIENT_LEADER property contain-
ing its own window ID (i.e., the client leader window is
pointing to itself). Transient windows need not have a
WM_CLIENT_LEADER property if the client leader can be deter-
mined using the information in the WM_TRANSIENT_FOR prop-
erty. The WM_CLIENT_LEADER property must:
+o Be of type WINDOW
+o Be of format 32
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+o Contain the window ID of the client leader window
A client must withdraw all of its top-level windows on the
same display before modifiying either the WM_CLIENT_LEADER
or the SM_CLIENT_ID property of its client leader window.
It is necessary that other clients be able to uniquely iden-
tify a window (across sessions) among all windows related to
the same client-ID. For example, a window manager can
require this unique ID to restore geometry information from
a previous session, or a workspace manager could use it to
restore information about which windows are in which
workspace. A client may optionally provide a WM_WINDOW_ROLE
property to uniquely identify a window within the scope
specified above. The combination of SM_CLIENT_ID and
WM_WINDOW_ROLE can be used by other clients to uniquely
identify a window across sessions.
If the WM_WINDOW_ROLE property is not specified on a top-
level window, a client that needs to uniquely identify that
window will try to use instead the values of WM_CLASS and
WM_NAME. If a client has multiple windows with identical
WM_CLASS and WM_NAME properties, then it should provide a
WM_WINDOW_ROLE property.
The client must set the WM_WINDOW_ROLE property to a string
that uniquely identifies that window among all windows that
have the same client leader window. The property must:
+o Be of type STRING
+o Be of format 8
+o Contain a string restricted to the XPCS characters,
encoded in ISO 8859-1
A window manager supporting session management must register
with the session manager and obtain its own client-ID. The
window manager should save and restore information such as
the WM_STATE, the layout of windows on the screen, and their
stacking order for every client window that has a valid
SM_CLIENT_ID property (on itself, or on the window named by
WM_CLIENT_LEADER) and that can be uniquely identified.
Clients are allowed to change this state during the first
phase of the session checkpoint process. Therefore, window
managers should request a second checkpoint phase and save
clients' state only during that phase.
The Inter-Client Exchange protocol (ICE) defined as of X11R6
specifies a generic communication framework, independent of
the X server, for data exchange between arbitrary clients.
ICE also defines a protocol for any two ICE clients who also
have X connections to the same X server to locate (ren-
dezvous with) each other.
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This protocol, called the "ICE X Rendezvous" protocol, is
defined in the ICE specification, Appendix B, and uses the
property ICE_PROTOCOLS plus events. Refer to that specifi-
cation for complete details.
X Version 11 permits clients to manipulate a number of
shared resources, for example, the input focus, the pointer,
and colormaps. Conventions are required so that clients
share resources in an orderly fashion.
Clients that explicitly set the input focus must observe one
of two modes:
+o Locally active mode
+o Globally active mode
1. Locally active clients should set the input focus to
one of their windows only when it is already in one of
their windows or when they receive a WM_TAKE_FOCUS mes-
sage. They should set the input field of the WM_HINTS
structure to
2. Globally active clients should set the input focus to
one of their windows only when they receive a button
event and a passive-grabbed key event, or when they
receive a WM_TAKE_FOCUS message. They should set the
input field of the WM_HINTS structure to
3. In addition, clients should use the timestamp of the
event that caused them to attempt to set the input
focus as the time field on the request, not
In general, clients should not warp the pointer. Window
managers, however, may do so (for example, to maintain the
invariant that the pointer is always in the window with the
input focus). Other window managers may want to preserve
the illusion that the user is in sole control of the
pointer.
1. Clients should not warp the pointer.
2. Clients that insist on warping the pointer should do so
only with the src-window argument of the request set to
one of their windows.
A client's attempt to establish a button or a key grab on a
window will fail if some other client has already estab-
lished a conflicting grab on the same window. The grabs,
therefore, are shared resources, and their use requires con-
ventions.
In conformance with the principle that clients should
behave, as far as possible, when a window manager is running
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as they would when it is not, a client that has the input
focus may assume that it can receive all the available keys
and buttons. Window managers should ensure that they pro-
vide some mechanism for their clients to receive events from
all keys and all buttons, except for events involving keys
whose KeySyms are registered as being for window management
functions (for example, a hypothetical WINDOW KeySym).
In other words, window managers must provide some mechanism
by which a client can receive events from every key and but-
ton (regardless of modifiers) unless and until the X Consor-
tium registers some KeySyms as being reserved for window
management functions. Currently, no KeySyms are registered
for window management functions.
Even so, clients are advised to allow the key and button
combinations used to elicit program actions to be modified,
because some window managers may choose not to observe this
convention or may not provide a convenient method for the
user to transmit events from some keys. Clients should
establish button and key grabs only on windows that they
own.
In particular, this convention means that a window manager
that wishes to establish a grab over the client's top-level
window should either establish the grab on the root or
reparent the window and establish the grab on a proper
ancestor. In some cases, a window manager may want to con-
sume the event received, placing the window in a state where
a subsequent such event will go to the client. Examples
are:
+o Clicking in a window to set focus with the click not
being offered to the client
+o Clicking in a buried window to raise it, again, with the
click not offered to the client
More typically, a window manager should add to, rather than
replace, the client's semantics for key+button combinations
by allowing the event to be used by the client after the
window manager is done with it. To ensure this, the window
manager should establish the grab on the parent by using the
following:
pointer/keyboard-mode == Synchronous
Then, the window manager should release the grab by using an
request with the following specified:
mode == ReplayPointer/Keyboard
In this way, the client will receive the events as if they
had not been intercepted.
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Obviously, these conventions place some constraints on pos-
sible user interface policies. There is a trade-off here
between freedom for window managers to implement their user
interface policies and freedom for clients to implement
theirs. The dilemma is resolved by:
+o Allowing window managers to decide if and when a client
will receive an event from any given key or button
+o Placing a requirement on the window manager to provide
some mechanism, perhaps a "Quote" key, by which the user
can send an event from any key or button to the client
Section 4.1.8 prescribes conventions for clients to communi-
cate with the window manager about their colormap needs. If
your clients are type applications, you should consult sec-
tion 14.3 of [4mXlib[24m [4m-[24m [4mC[24m [4mLanguage[24m [4mX[24m [4mInterface[24m for conventions
connected with sharing standard colormaps. They should look
for and create the properties described there on the root
window of the appropriate screen.
The contents of the RGB_COLOR_MAP type property are as fol-
lows:
l l l. _
[1mField Type Comments[0m
[1m_[0m
colormap COLORMAP ID of the colormap described
red_max CARD32 Values for pixel calculations
red_mult CARD32 green_max CARD32 green_mult CARD32
blue_max CARD32 blue_mult CARD32 base_pixel CARD32
visual_id VISUALID Visual to which colormap belongs
kill_id CARD32 ID for destroying the resources
_
When deleting or replacing an RGB_COLOR_MAP, it is not suf-
ficient to delete the property; it is important to free the
associated colormap resources as well. If kill_id is
greater than one, the resources should be freed by issuing a
request with kill_id as the argument. If kill_id is one,
the resources should be freed by issuing a request with col-
ormap as the colormap argument. If kill_id is zero, no
attempt should be made to free the resources. A client that
creates an RGB_COLOR_MAP for which the colormap resource is
created specifically for this purpose should set kill_id to
one (and can create more than one such standard colormap
using a single connection). A client that creates an
RGB_COLOR_MAP for which the colormap resource is shared in
some way (for example, is the default colormap for the root
window) should create an arbitrary resource and use its
resource ID for kill_id (and should create no other standard
colormaps on the connection). If an RGB_COLOR_MAP property
is too short to contain the visual_id field, it can be
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assumed that the visual_id is the root visual of the appro-
priate screen. If an RGB_COLOR_MAP property is too short to
contain the kill_id field, a value of zero can be assumed.
During the connection handshake, the server informs the
client of the default colormap for each screen. This is a
colormap for the root visual, and clients can use it to
improve the extent of colormap sharing if they use the root
visual.
The X server contains a table (which is read by requests)
that describes the set of symbols appearing on the corre-
sponding key for each keycode generated by the server. This
table does not affect the server's operations in any way; it
is simply a database used by clients that attempt to under-
stand the keycodes they receive. Nevertheless, it is a
shared resource and requires conventions.
It is possible for clients to modify this table by using a
request. In general, clients should not do this. In par-
ticular, this is not the way in which clients should imple-
ment key bindings or key remapping. The conversion between
a sequence of keycodes received from the server and a string
in a particular encoding is a private matter for each client
(as it must be in a world where applications may be using
different encodings to support different languages and
fonts). See the Xlib reference manual for converting key-
board events to text.
The only valid reason for using a request is when the sym-
bols written on the keys have changed as, for example, when
a Dvorak key conversion kit or a set of APL keycaps has been
installed. Of course, a client may have to take the change
to the keycap on trust.
The following illustrates a permissible interaction between
a client and a user:
Client: "You just started me on a server without a Pause
key. Please choose a key to be the Pause key and
press it now."
User: Presses the Scroll Lock key
Client: "Adding Pause to the symbols on the Scroll Lock
key: Confirm or Abort."
User: Confirms
Client: Uses a request to add Pause to the keycode that
already contains Scroll Lock and issues this
request, "Please paint Pause on the Scroll Lock
key." Clients should not use requests.
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If a client succeeds in changing the keyboard mapping table,
all clients will receive events. There is no mechanism to
avoid receiving these events. Clients receiving events
should update any internal keycode translation tables they
are using.
X Version 11 supports 8 modifier bits of which 3 are preas-
signed to Shift, Lock, and Control. Each modifier bit is
controlled by the state of a set of keys, and these sets are
specified in a table accessed by and requests. This table
is a shared resource and requires conventions.
A client that needs to use one of the preassigned modifiers
should assume that the modifier table has been set up cor-
rectly to control these modifiers. The Lock modifier should
be interpreted as Caps Lock or Shift Lock according as the
keycodes in its controlling set include XK_Caps_Lock or
XK_Shift_Lock. Clients should determine the meaning of a
modifier bit from the KeySyms being used to control it.
A client that needs to use an extra modifier (for example,
META) should do the following:
+o Scan the existing modifier mappings. If it finds a mod-
ifier that contains a keycode whose set of KeySyms
includes XK_Meta_L or XK_Meta_R, it should use that mod-
ifier bit.
+o If there is no existing modifier controlled by
XK_Meta_L or XK_Meta_R, it should select an unused modi-
fier bit (one with an empty controlling set) and do the
following:
- If there is a keycode with XL_Meta_L in its set of
KeySyms, add that keycode to the set for the chosen
modifier.
- If there is a keycode with XL_Meta_R in its set of
KeySyms, add that keycode to the set for the chosen
modifier.
- If the controlling set is still empty, interact
with the user to select one or more keys to be
META.
+o If there are no unused modifier bits, ask the user to
take corrective action.
1. Clients needing a modifier not currently in use should
assign keycodes carrying suitable KeySyms to an unused
modifier bit.
2. Clients assigning their own modifier bits should ask
the user politely to remove his or her hands from the
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key in question if their request returns a status.
There is no good solution to the problem of reclaiming
assignments to the five nonpreassigned modifiers when they
are no longer being used. The user must use or some other
utility to deassign obsolete modifier mappings by hand.
When a client succeeds in performing a request, all clients
will receive events. There is no mechanism for preventing
these events from being received. A client that uses one of
the nonpreassigned modifiers that receives one of these
events should do a request to discover the new mapping, and
if the modifier it is using has been cleared, it should
reinstall the modifier.
Note that a request must be used to make the and pair in
these transactions atomic.
delim @@
define oc % "\fR{\fP" %
define cc % "\fR}\fP" %
The X protocol provides explicit Red, Green, and Blue (RGB)
values, which are used to directly drive a monitor, and
color names. RGB values provide a mechanism for accessing
the full capabilities of the display device, but at the
expense of having the color perceived by the user remain
unknowable through the protocol. Color names were origi-
nally designed to provide access to a device-independent
color database by having the server vendor tune the defini-
tions of the colors in that textual database. Unfortu-
nately, this still does not provide the client any way of
using an existing device-independent color, nor for the
client to get device-independent color information back
about colors that it has selected.
Furthermore, the client must be able to discover which set
of colors are displayable by the device (the device gamut),
both to allow colors to be intelligently modified to fit
within the device capabilities (gamut compression) and to
enable the user interface to display a representation of the
reachable color space to the user (gamut display).
Therefore, a system is needed that will provide full access
to device-independent color spaces for X clients. This sys-
tem should use a standard mechanism for naming the colors,
be able to provide names for existing colors, and provide
means by which unreachable colors can be modified to fall
within the device gamut.
We are fortunate in this area to have a seminal work, the
1931 CIE color standard, which is nearly universally agreed
upon as adequate for describing colors on CRT devices. This
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standard uses a tri-stimulus model called CIE XYZ in which
each perceivable color is specified as a triplet of numbers.
Other appropriate device-independent color models do exist,
but most of them are directly traceable back to this origi-
nal work.
X device color characterization provides device-independent
color spaces to X clients. It does this by providing the
barest possible amount of information to the client that
allows the client to construct a mapping between CIE XYZ and
the regular X RGB color descriptions.
Device color characterization is defined by the name and
contents of two window properties that, together, permit
converting between CIE XYZ space and linear RGB device space
(such as standard CRTs). Linear RGB devices require just
two pieces of information to completely characterize them:
+o A @3 times 3@ matrix @M@ and its inverse @M sup -1@,
which convert between XYZ and RGB intensity (@RGB sub
intensity@):
RGB sub intensity ~ = ~ M ~ times ~ XYZ
XYZ ~ = ~ M sup -1 ~ times ~ RGB sub intensity
+o A way of mapping between RGB intensity and RGB protocol
value. XDCCC supports three mechanisms which will be
outlined later.
If other device types are eventually necessary, additional
properties will be required to describe them.
Because of the limited dynamic range of both XYZ and RGB
intensity, these matrices will be encoded using a fixed-
point representation of a 32-bit two's complement number
scaled by @2 sup 27@, giving a range of @-16@ to @16 -
epsilon@, where @epsilon ~ = ~ 2 sup -27@.
These matrices will be packed into an 18-element list of
32-bit values, XYZ -> RGB matrix first, in row major order
and stored in the XDCCC_LINEAR_RGB_MATRICES properties (for-
mat = 32) on the root window of each screen, using values
appropriate for that screen.
This will be encoded as shown in the following table:
center; c s s c c c l l l. XDCCC_LINEAR_RGB_MATRICES prop-
erty contents
_
[1mField Type Comments[0m
_
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@M sub 0,0@ INT32 Interpreted as a fixed-point number
@-16~<=~x~<~16@ @M sub 0,1@ INT32 ... @M sub
3,3@ INT32 @{M sup -1} sub 0,0@ INT32 @{M
sup -1} sub 0,1@ INT32 ... @{M sup -1} sub
3,3@ INT32
_
XDCCC provides two representations for describing the con-
version between RGB intensity and the actual X protocol RGB
values:
0 RGB value/RGB intensity level pairs
1 RGB intensity ramp
In both cases, the relevant data will be stored in the
XDCCC_LINEAR_RGB_CORRECTION properties on the root window of
each screen, using values appropriate for that screen, in
whatever format provides adequate resolution. Each property
can consist of multiple entries concatenated together, if
different visuals for the screen require different conver-
sion data. An entry with a VisualID of 0 specifies data for
all visuals of the screen that are not otherwise explicitly
listed.
The first representation is an array of RGB value/intensity
level pairs, with the RGB values in strictly increasing
order. When converting, the client must linearly interpo-
late between adjacent entries in the table to compute the
desired value. This allows the server to perform gamma cor-
rection itself and encode that fact in a short two-element
correction table. The intensity will be encoded as an
unsigned number to be interpreted as a value between 0 and 1
(inclusive). The precision of this value will depend on the
format of the property in which it is stored (8, 16, or 32
bits). For 16-bit and 32-bit formats, the RGB value will
simply be the value stored in the property. When stored in
8-bit format, the RGB value can be computed from the value
in the property by:
RGB sub value ~ = ~ { Property ~ Value ~ times ~ 65535 } over 255
Because the three electron guns in the device may not be
exactly alike in response characteristics, it is necessary
to allow for three separate tables, one each for red, green,
and blue. Therefore, each table will be preceded by the
number of entries in that table, and the set of tables will
be preceded by the number of tables. When three tables are
provided, they will be in red, green, blue order.
This will be encoded as shown in the following table:
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center; c s s c c c l l l. XDCCC_LINEAR_RGB_CORRECTION
Property Contents for Type 0 Correction
_
[1mField Type Comments[0m
_
VisualID0 CARD Most significant portion of VisualID Visu-
alID1 CARD Exists if and only if the property format is 8
VisualID2 CARD Exists if and only if the property format is
8 VisualID3 CARD T{ Least significant portion, exists if and
only if the property format is 8 or 16 T} type CARD 0 for
this type of correction count CARD Number of tables fol-
lowing (either 1 or 3) length CARD Number of pairs - 1
following in this table value CARD X Protocol RGB value
intensity CARD Interpret as a number @0~<=~intensity~<=~1@
... ... Total of [4mlength+1[24m pairs of value/intensity values
lengthg CARD T{ Number of pairs - 1 following in this ta-
ble (if and only if [4mcount[24m is 3) T} value CARD X Protocol
RGB value intensity CARD Interpret as a number @0~<=~inten-
sity~<=~1@ ... ... Total of [4mlengthg+1[24m pairs of
value/intensity values lengthb CARD T{ Number of pairs - 1
following in this table (if and only if [4mcount[24m is 3) T}
value CARD X Protocol RGB value intensity CARD Interpret
as a number @0~<=~intensity~<=~1@ ... ... Total of
[4mlengthb+1[24m pairs of value/intensity values
_
The VisualID is stored in 4, 2, or 1 pieces, depending on
whether the property format is 8, 16, or 32, respectively.
The VisualID is always stored most significant piece first.
Note that the length fields are stored as one less than the
actual length, so 256 entries can be stored in format 8.
The second representation is a simple array of intensities
for a linear subset of RGB values. The expected size of
this table is the bits-per-rgb-value of the screen, but it
can be any length. This is similar to the first mechanism,
except that the RGB value numbers are implicitly defined by
the index in the array (indices start at 0):
RGB sub value ~ = ~ { Array ~ Index ~ times ~ 65535 } over
{ Array ~ Size ~ - ~ 1 }
When converting, the client may linearly interpolate between
entries in this table. The intensity values will be encoded
just as in the first representation.
This will be encoded as shown in the following table:
center; c s s c c c l l l. XDCCC_LINEAR_RGB_CORRECTION
Property Contents for Type 1 Correction
_
[1mField Type Comments[0m
_
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VisualID0 CARD Most significant portion of VisualID Visu-
alID1 CARD Exists if and only if the property format is 8
VisualID2 CARD Exists if and only if the property format is
8 VisualID3 CARD T{ Least significant portion, exists if and
only if the property format is 8 or 16 T} type CARD 1 for
this type of correction count CARD Number of tables fol-
lowing (either 1 or 3) length CARD Number of elements - 1
following in this table intensity CARD Interpret as a number
@0~<=~intensity~<=~1@ ... ... Total of [4mlength+1[24m intensity
elements lengthg CARD T{ Number of elements - 1 following
in this table (if and only if [4mcount[24m is 3) T} inten-
sity CARD Interpret as a number @0~<=~intensity~<=~1@
... ... Total of [4mlengthg+1[24m intensity elements
lengthb CARD T{ Number of elements - 1 following in this
table (if and only if [4mcount[24m is 3) T} intensity CARD Inter-
pret as a number @0~<=~intensity~<=~1@ ... ... Total of
[4mlengthb+1[24m intensity elements
_
This document provides the protocol-level specification of
the minimal conventions needed to ensure that X Version 11
clients can interoperate properly. This document specifies
interoperability conventions only for the X Version 11 pro-
tocol. Clients should be aware of other protocols that
should be used for better interoperation in the X environ-
ment. The reader is referred to [4mX[24m [4mSession[24m [4mManagement[24m [4mProto-[0m
[4mcol[24m for information on session management, and to [4mInter-[0m
[4mClient[24m [4mExchange[24m [4mProtocol[24m for information on general-purpose
communication among clients.
The X Consortium maintains a registry of certain X-related
items, to aid in avoiding conflicts and in sharing of such
items. Readers are encouraged to use the registry. The
classes of items kept in the registry that are relevant to
the ICCCM include property names, property types, selection
names, selection targets, WM_PROTOCOLS protocols, types, and
application classes. Requests to register items, or ques-
tions about registration, should be addressed to
delim off
xregistry@x.org
or to
Registry
X Consortium
201 Broadway
Cambridge, MA 02139-1955
USA
Electronic mail will be acknowledged upon receipt. Please
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allow up to 4 weeks for a formal response to registration
and inquiries.
The registry is published as part of the X software distri-
bution from the X Consortium. All registered items must
have the postal address of someone responsible for the item
or a reference to a document describing the item and the
postal address of where to write to obtain the document.
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[1mAppendix A[0m
This appendix describes the revision history of this docu-
ment and summarizes the incompatibilities between this and
earlier versions.
The February 25, 1988, draft that was distributed as part of
X Version 11, Release 2, was clearly labeled as such, and
many areas were explicitly labeled as liable to change.
Nevertheless, in the revision work done since then, we have
been very careful not to introduce gratuitous incompatibil-
ity. As far as possible, we have tried to ensure that
clients obeying the conventions in the X11R2 draft would
still work.
The Consortium review was based on a draft dated July 27,
1988. This draft included several areas in which incompati-
bilities with the X11R2 draft were necessary:
+o The use of property in requests is no longer allowed.
Owners that receive them are free to use the target atom
as the property to respond with, which will work in most
cases.
+o The protocol for INCREMENTAL type properties as selec-
tion replies has changed, and the name has been changed
to INCR. Selection requestors are free to implement the
earlier protocol if they receive properties of type
INCREMENTAL.
+o The protocol for INDIRECT type properties as selection
replies has changed, and the name has been changed to
MULTIPLE. Selection requestors are free to implement
the earlier protocol if they receive properties of type
INDIRECT.
+o The protocol for the special CLIPBOARD client has
changed. The earlier protocol is subject to race condi-
tions and should not be used.
+o The set of state values in WM_HINTS.initial_state has
been reduced, but the values that are still valid are
unchanged. Window managers should treat the other val-
ues sensibly.
+o The methods an application uses to change the state of
its top-level window have changed but in such a way that
cases that used to work will still work.
+o The x, y, width, and height fields have been removed
from the WM_NORMAL_HINTS property and replaced by pad
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fields. Values set into these fields will be ignored.
The position and size of the window should be set by
setting the appropriate window attributes.
+o A pair of base fields and a win_gravity field have been
added to the WM_NORMAL_HINTS property. Window managers
will assume values for these fields if the client sets a
short property.
The Consortium review resulted in several incompatible
changes. These changes were included in drafts that were
distributed for public review during the first half of 1989.
+o The messages field of the WM_HINTS property was found to
be unwieldy and difficult to evolve. It has been
replaced by the WM_PROTOCOLS property, but clients that
use the earlier mechanism can be detected because they
set the messages bit in the flags field of the WM_HINTS
property, and window managers can provide a backwards
compatibility mode.
+o The mechanism described in the earlier draft by which
clients installed their own subwindow colormaps could
not be made to work reliably and mandated some features
of the look and feel. It has been replaced by the
WM_COLORMAP_WINDOWS property. Clients that use the ear-
lier mechanism can be detected by the WM_COLORMAPS prop-
erty they set on their top-level window, but providing a
reliable backwards compatibility mode is not possible.
+o The recommendations for window manager treatment of top-
level window borders have been changed as those in the
earlier draft produced problems with Visibility events.
For nonwindow manager clients, there is no incompatibil-
ity.
+o The pseudoroot facility in the earlier draft has been
removed. Although it has been successfully implemented,
it turns out to be inadequate to support the uses envis-
aged. An extension will be required to support these
uses fully, and it was felt that the maximum freedom
should be left to the designers of the extension. In
general, the previous mechanism was invisible to clients
and no incompatibility should result.
+o The addition of the WM_DELETE_WINDOW protocol (which
prevents the danger that multi-window clients may be
terminated unexpectedly) has meant some changes in the
WM_SAVE_YOURSELF protocol, to ensure that the two proto-
cols are orthogonal. Clients using the earlier protocol
can be detected (see WM_PROTOCOLS above) and supported
in a backwards compatibility mode.
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+o The conventions in Section 14.3.1. of [4mXlib[24m [4m-[24m [4mC[24m [4mLanguage[0m
[4mX[24m [4mInterface[24m regarding properties of type RGB_COLOR_MAP
have been changed, but clients that use the earlier con-
ventions can be detected because their properties are 4
bytes shorter. These clients will work correctly if the
server supports only a single Visual or if they use only
the Visual of the root. These are the only cases in
which they would have worked, anyway.
The public review resulted in a set of mostly editorial
changes. The changes in version 1.0 that introduced some
degree of incompatibility with the earlier drafts are:
+o A new section (6.3) was added covering the window man-
ager's use of Grabs. The restrictions it imposes should
affect only window managers.
+o The TARGETS selection target has been clarified, and it
may be necessary for clients to add some entries to
their replies.
+o A selection owner using INCR transfer should no longer
replace targets in a MULTIPLE property with the atom
INCR.
+o The contents of the event sent by a client to iconify
itself has been clarified, but there should be no incom-
patibility because the earlier contents would not in
fact have worked.
+o The border-width in synthetic events is now specified,
but this should not cause any incompatibility.
+o Clients are now asked to set a border-width on all
requests.
+o Window manager properties on icon windows now will be
ignored, but there should be no incompatibility because
there was no specification that they be obeyed previ-
ously.
+o The ordering of real and synthetic events is now speci-
fied, but any incompatibility should affect only window
managers.
+o The semantics of WM_SAVE_YOURSELF have been clarified
and restricted to be a checkpoint operation only.
Clients that were using it as part of a shutdown
sequence may need to be modified, especially if they
were interacting with the user during the shutdown.
+o A kill_id field has been added to RGB_COLOR_MAP proper-
ties. Clients using earlier conventions can be detected
by the size of their RGB_COLOR_MAP properties, and the
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cases that would have worked will still work.
Version 1.1 was released with X11R5 in September 1991. In
addition to some minor editorial changes, there were a few
semantic changes since Version 1.0:
+o The section on Device Color Characterization was added.
+o The meaning of the NULL property type was clarified.
+o Appropriate references to Compound Text were added.
The following changes have been made in preparing the public
review draft for Version 2.0.
+o [P01] Addition of advice to clients on how to keep track
of a top-level window's absolute position on the screen.
+o [P03] A technique for clients to detect when it is safe
to reuse a top-level window has been added.
+o [P06] Section 4.1.8, on colormaps, has been rewritten.
A new feature that allows clients to install their own
colormaps has also been added.
+o [P08] The LENGTH target has been deprecated.
+o [P11] The manager selections facility was added.
+o [P17] The definition of the aspect ratio fields of the
WM_NORMAL_HINTS property has been changed to include the
base size.
+o [P19] has been added to the list of values allowed for
the win_gravity field of the WM_HINTS property. The
meaning of the value has been clarified.
+o [P20] A means for clients to query the ICCCM compliance
level of the window manager has been added.
+o [P22] The definition of the MULTIPLE selection target
has been clarified.
+o [P25] A definition of "top-level window" has been added.
The WM_STATE property has been defined and exposed to
clients.
+o [P26] The definition of window states has been clarified
and the wording regarding window state changes has been
made more consistent.
+o [P27] Clarified the rules governing when window managers
are required to send synthetic events.
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+o [P28] Added a recommended technique for setting the
input focus to a window as soon as it is mapped.
+o [P29] The required lifetime of resource IDs named in
window manager properties has been specified.
+o [P30] Advice for dealing with keystrokes and override-
redirect windows has been added.
+o [P31] A statement on the ownership of resources trans-
ferred through the selection mechanism has been added.
+o [P32] The definition of the CLIENT_WINDOW target has
been clarified.
+o [P33] A rule about requiring the selection owner to
reacquire the selection under certain circumstances has
been added.
+o [P42] Added several new selection targets.
+o [P44] Ambiguous wording regarding the withdrawal of top-
level windows has been removed.
+o [P45] A facility for requestors to pass parameters dur-
ing a selection request has been added.
+o [P49] A convention on discrimated names has been added.
+o [P57] The C_STRING property type was added.
+o [P62] An ordering requirement on processing selection
requests was added.
+o [P63] The flag was added.
+o [P64] The session management section has been updated to
align with the new session management protocol. The old
session management conventions have been moved to Appen-
dix C.
+o References to the never-forthcoming [4mWindow[24m [4mand[24m [4mSession[0m
[4mManager[24m [4mConventions[24m [4mManual[24m have been removed.
+o Information on the X Registry and references to the ses-
sion management and ICE documents have been added.
+o Numerous editorial and typographical improvements have
been made.
The following changes have been made in preparation for
releasing the final edition of Version 2.0 with X11R6.
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+o The PIXMAP selection target has been revised to return a
property of type PIXMAP instead of type DRAWABLE.
+o The session management section has been revised slightly
to correspond with the changes to the [4mX[24m [4mSession[24m [4mManage-[0m
[4mment[24m [4mProtocol[24m.
+o Window managers are now prohibited from placing in the
timestamp field of WM_TAKE_FOCUS messages.
+o In the WM_HINTS property, the flag has been renamed to
Its semantics have also been defined more thoroughly.
+o Additional editorial and typographical changes have been
made.
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[1mAppendix B[0m
During the development of these conventions, a number of
inadequacies have been discovered in the core X11 protocol.
They are summarized here as input to an eventual protocol
revision design process:
+o There is no way for anyone to find out the last-change
time of a selection. The request should be changed to
return the last-change time as well as the owner.
+o There is no way for a client to find out which selection
atoms are valid.
+o There would be no need for WM_TAKE_FOCUS if the event
contained a timestamp and a previous-focus field. This
could avoid the potential race condition. There is
space in the event for this information; it should be
added at the next protocol revision.
+o There is a race condition in the request. It does not
take a timestamp and may be executed after the top-level
colormap has been uninstalled. The next protocol revi-
sion should provide the timestamp in the requests and in
the event. The timestamp should be used in a similar
way to the last-focus-change time for the input focus.
The lack of timestamps in these packets is the reason
for restricting colormap installation to the window man-
ager.
+o The protocol needs to be changed to provide some way of
identifying the Visual and the Screen of a colormap.
+o There should be some way to reclaim assignments to the
five nonpreassigned modifiers when they are no longer
needed. The manual method is unpleasantly low-tech.
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[1mAppendix C[0m
This appendix contains obsolete conventions for session man-
agement using X properties and messages. The conventions
described here are deprecated and are described only for
historical interest. For further information on session
management, see [4mX[24m [4mSession[24m [4mManagement[24m [4mProtocol.[0m
The client communicates with the session manager by placing
two properties (WM_COMMAND and WM_CLIENT_MACHINE) on its
top-level window. If the client has a group of top-level
windows, these properties should be placed on the group
leader window.
The window manager is responsible for placing a WM_STATE
property on each top-level client window for use by session
managers and other clients that need to be able to identify
top-level client windows and their state.
The WM_COMMAND property represents the command used to start
or restart the client. By updating this property, clients
should ensure that it always reflects a command that will
restart them in their current state. The content and type
of the property depend on the operating system of the
machine running the client. On POSIX-conformant systems
using ISO Latin-1 characters for their command lines, the
property should:
+o Be of type STRING
+o Contain a list of null-terminated strings
+o Be initialized from argv
Other systems will need to set appropriate conventions
for the type and contents of WM_COMMAND properties.
Window and session managers should not assume that
STRING is the type of WM_COMMAND or that they will be
able to understand or display its contents.
Note that WM_COMMAND strings are null-terminated and differ
from the general conventions that STRING properties are
null-separated. This inconsistency is necessary for back-
wards compatibility.
A client with multiple top-level windows should ensure that
exactly one of them has a WM_COMMAND with nonzero length.
Zero-length WM_COMMAND properties can be used to reply to
WM_SAVE_YOURSELF messages on other top-level windows but
will otherwise be ignored.
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This property is described in section 4.1.2.9.
Because they communicate by means of unreliable network con-
nections, clients must be prepared for their connection to
the server to be terminated at any time without warning.
They cannot depend on getting notification that termination
is imminent or on being able to use the server to negotiate
with the user about their fate. For example, clients cannot
depend on being able to put up a dialog box.
Similarly, clients may terminate at any time without notice
to the session manager. When a client terminates itself
rather than being terminated by the session manager, it is
viewed as having resigned from the session in question, and
it will not be revived if the session is revived.
Clients may need to respond to session manager actions in
two ways:
+o Saving their internal state
+o Deleting a window
Clients that want to be warned when the session manager
feels that they should save their internal state (for exam-
ple, when termination impends) should include the atom
WM_SAVE_YOURSELF in the WM_PROTOCOLS property on their top-
level windows to participate in the WM_SAVE_YOURSELF proto-
col. They will receive a event as described in section
4.2.8 with the atom WM_SAVE_YOURSELF in its data[0] field.
Clients that receive WM_SAVE_YOURSELF should place them-
selves in a state from which they can be restarted and
should update WM_COMMAND to be a command that will restart
them in this state. The session manager will be waiting for
a event on WM_COMMAND as a confirmation that the client has
saved its state. Therefore, WM_COMMAND should be updated
(perhaps with a zero-length append) even if its contents are
correct. No interactions with the user are permitted during
this process.
Once it has received this confirmation, the session manager
will feel free to terminate the client if that is what the
user asked for. Otherwise, if the user asked for the ses-
sion to be put to sleep, the session manager will ensure
that the client does not receive any mouse or keyboard
events.
After receiving a WM_SAVE_YOURSELF, saving its state, and
updating WM_COMMAND, the client should not change its state
(in the sense of doing anything that would require a change
to WM_COMMAND) until it receives a mouse or keyboard event.
Once it does so, it can assume that the danger is over. The
session manager will ensure that these events do not reach
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clients until the danger is over or until the clients have
been killed.
Irrespective of how they are arranged in window groups,
clients with multiple top-level windows should ensure the
following:
+o Only one of their top-level windows has a nonzero-length
WM_COMMAND property.
+o They respond to a WM_SAVE_YOURSELF message by:
- First, updating the nonzero-length WM_COMMAND prop-
erty, if necessary
- Second, updating the WM_COMMAND property on the
window for which they received the WM_SAVE_YOURSELF
message if it was not updated in the first step
Receiving WM_SAVE_YOURSELF on a window is, conceptually, a
command to save the entire client state.16
Windows are deleted using the WM_DELETE_WINDOW protocol,
which is described in section 4.2.8.1.
The session manager properties are listed in the following
table:
l l n c. _
[1mName Type Format See Section[0m
[1m_[0m
WM_CLIENT_MACHINE TEXT 4.1.2.9 WM_COM-
MAND TEXT C.1.1 WM_STATE WM_STATE 32 4.1.3.1
_
-----------
16 This convention has changed since earlier
drafts because of the introduction of the protocol
in the next section. In the public review draft,
there was ambiguity as to whether WM_SAVE_YOURSELF
was a checkpoint or a shutdown facility. It is
now unambiguously a checkpoint facility; if a
shutdown facility is judged to be necessary, a
separate WM_PROTOCOLS protocol will be developed
and registered with the X Consortium.
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