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<H1><A NAME="SECTION009100000000000000000">8.10 Updating the Terminal</A></H1>
<P>
As written in the overview, ncurses windows are images in memory. This
means that any change to a window is not printed to the physical screen until
a refresh is done. This optimizes the output to the screen because you
can do a lot of manipulations and then, once, call refresh to print it
to screen. Otherwise, every change would be printed to the terminal and
decrease the performance of your programs.
<P>
<UL><LI> <TT>int refresh()</TT> <A NAME="fun_refresh"> </A><BR>
<TT>int wrefresh(win)</TT> <A NAME="fun_wrefresh"> </A><BR>
<B>refresh()</B> copies to the terminal and
<B>wrefresh(win)</B> copies the window image to and
then makes
looks like .<LI> <TT>int wnoutrefresh(win)</TT> <A NAME="fun_wnoutrefresh"> </A><BR>
<TT>int doupdate()</TT> <A NAME="fun_doupdate"> </A><BR>
<B>wnoutrefresh(win)</B> copies the window <TT>win</TT> to only.
This means that no output to the terminal is done but the virtual
screen actually looks like the programmer wanted.
<B>doupdate()</B> will do the output to the terminal. A program can
change various windows, call <B>wnoutrefresh(win)</B> for every window
and then call <B>doupdate()</B> to update the physical screen only once.
<P>
For instance, we have the following program with two windows.
We change both windows by altering some lines of text.
We can write <I>changewin(win)</I> with <B>wrefresh(win)</B>.
<P>
<P><P>
<P>
This will cause ncurses to update the terminal twice and slow down our
execution. With <B>doupdate()</B> we change <I>changewin(win)</I> and
our main function and will get better a performance.
<P>
<P><P><LI> <TT>int redrawwin(win)</TT> <A NAME="fun_redrawwin"> </A><BR>
<TT>int wredrawln(win, bline, nlines)</TT> <A NAME="fun_wredrawln"> </A><BR>
Use these functions when some lines or the entire screen should
thrown away before writing anything new in it (may be when the
lines are trashed or so).<LI> <TT>int touchwin(win)</TT> <A NAME="fun_touchwin"> </A><BR>
<TT>int touchline(win, start, count)</TT> <A NAME="fun_touchline"> </A><BR>
<TT>int wtouchln(win, y, n, changed)</TT> <A NAME="fun_wtouchln"> </A><BR>
<TT>int untouchwin(win)</TT> <A NAME="fun_untouchwin"> </A><BR>
Tells ncurses that the whole window <TT>win</TT> or the lines from
<TT>start</TT> up to <TT>start+count</TT>
have been manipulated. For instance, when you have some overlapping
windows (as in the example .c) a change to one
window will not affect the image from the other.
<P>
<B>wtouchln(...)</B> will touch <TT>n</TT> lines starting at <TT>y</TT>.
If <TT>change</TT> is TRUE the lines are touched, otherwise untouched
(changed or unchanged).
<P>
<B>untouchwin(win)</B> will mark the window <TT>win</TT> as unchanged
since the last call to <B>refresh()</B>.<LI> <TT>int is_linetouched(win, line)</TT> <A NAME="fun_is_linetouched"> </A><BR>
<TT>int is_wintouched(win)</TT> <A NAME="fun_is_wintouched"> </A><BR>
With these functions you can check if the line <TT>line</TT> or the
window <TT>win</TT> has been touched since the last call to
<B>refresh()</B>.
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