Re: GTK+ redrawing strategy: backing store, double buffering

["Gustavo J. A. M. Carneiro" <gjc inescporto pt>]

    I see -- and agree with -- your arguments.  But until windowing
systems handle this more efficiently, couldn't gtk+ do this at the
toolkit level, optionally?  Unless, of course, X-Windows will support
that in a not too distant future.

A Ter, 2003-10-07 às 16:19, Owen Taylor escreveu:
> Here's a a mail I sent to  forum xfree86 org on the subject explaining
> of why I think doing it in the toolkit is a bad idea:
> 
> ===
> From: Owen Taylor <otaylor redhat com>
> To: forum XFree86 Org
> Subject: Re: [forum] Snappy GUI response
> Date: 04 Jul 2003 14:35:16 -0400
> 
> On Fri, 2003-07-04 at 14:05, Mark Vojkovich wrote:
> 
> [...]
> >    I advocate backing pixmaps for as many windows as it 
> > makes sense, and no expose events on them.  Not only is this
> > extremely fast even if server is rendering in software, but
> > it looks great (you don't see redrawing).  That is, save all
> > your expensive rendering, don't keep redrawing it.  Put it in
> > a pixmap and set it as the window background.  There's also
> > a good change this pixmap will end up in video ram rather than 
> > system ram.
> 
> Saving the full contents of each toplevel window makes a lot
> of sense these days. Doing it in the toolkit doesn't:
> 
>  * If the windowing system saves the full contents of each
>    toplevel (see below for why that works better), then you
>    double the 50+ megabytes of memory you are using by
>    saving the full contents of each window in the toolkit.
> 
>    The directfb and OS X X servers are current examples of
>    X servers that save the full contents of each window.
> 
>  * The windowing system, if it has the full contents, can
>    do neat things like per-window alpha channels.
> 
>  * The windowing system is generally in a much better position
>    to know when to dump the window contents and ask the app to
>    redraw them. (because you are out of memory, because 
>    the window is fully obscured or on a different desktop, etc.)
> 
> Regards,
>                                         Owen
> 
> 
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-- 
Gustavo João Alves Marques Carneiro
<gjc inescporto pt> <gustavo users sourceforge net>