This file contains a brief description of Poedit's architecture.

As for GUI part, wxWidgets 2.2 is used, together with XML resources
that describe dialogs, menu and toolbar.



- Settings -

Global preferences are saved in registry (win32) or ~/.poedit (unix).
Catalog specific information is put into .po file (if it is part of
standard gettext header, e.g. translator's name) or into .po.poedit file
which is created only if there is a need to store additional information
(the language used, directories & keywords lists needed for update 
feature).



- Data storage -

The core class is Catalog. It stores all catalog data including header
information and provides interface to save/load the catalog, retrieve
and modify strings and their respective translations. It also keeps
track of all references to given string in source code. The most important
feature of this class is it's ability to parse (and save) gettext .po 
catalog files.

The Catalog class provides Update method that merges currently loaded
catalog with source code (i.e. add new strings and remove obsolete 
translations). For this, it uses SourceDigger class. 



- Parsing source code -

SourceDigger class searches given paths for all files Poedit can parse
and runs parser(s) on them. As the result, SourceDigger returns new
catalog with empty translations (so it contains only strings and 
source code references). This catalog is merged with currently edited
one by Catalog::Update (which is the only method that uses SourceDigger)
-- it executes msgmerge program from gettext package to accomplish that.

The digger has ability of executing different parsers based on file's
extension, as specified in File/Preferences. Source digging works as
follows:

  1) list of all files is built
  2) for each parser, list of files matching file types supported 
     by given parser is built
  3) for each parser, do:
     i) divide files list into chunks of no more than 16 files
        (because of OS' command line length limitation). For each
	chunk, do
	a) create command line based on File/Preferences/Parsers:
	   Expand %f, %k, %F, %K as described in parser setting
	   dialog
        b) execute the command which will produce `mini' catalog
	c) append returned `mini' catalog to these produced by
	   previous iterations of i)



- Executing programs -

Poedit uses external programs to do `the real work', namely
msgmerge, msgfmt and xgettext. gexecute.cpp contains process execution 
routine that captures child process' stdout and stderr. (It takes big
advantage of wxWindow's wxProcess class.) stderr output (if any) is
then displayed in errors dialog. 



- User interface -

EditorFrame class. Uses Catalog class for all processing (loading, saving,
updating). The only significant thing is it's special way of handling 
list control: when an item is selected, focus is given to `translation'
text control. The effect is that the user can use up/down arrows to 
navigate in the list and immediately type in translations without need
to press Tab or use mouse. List's content is updated when selection
changes or when command event such as save or open is fired. Technically,
KeysHandler event handler is plugged both into the list control and 
text control so that it can make them cooperate (in list, it handles
typing text, in textctrl it takes care of up/down/pgup/pgdown keys).


- Settings dialogs -

Both catalog settings and preferences dialogs use same technique:
data are transfered to it from catalog or wxConfig immediately upon 
creation (i.e. before showing the dialog) transfered from it if the 
user presses "Ok". If the dialog is cancelled, no data need to be restored 
to its original state.