Re: Backing Store (was Re: Desktop Kernel Stuff)

[Owen Taylor <otaylor redhat com>]

On Fri, 2003-07-11 at 17:25, Ettore Perazzoli wrote:
> > Some of the results on low memory boxes go back to the X server behaviour
> > and whether you should always keep display buffers (moving a window tends
> > to bring each app into RAM to scribble rectangles). 
> 
> On a slighty unrelated note, I was actually wondering about this. 
> Shouldn't GTK set BackingStore to WhenMapped in all windows these days? 
> Besides the swapping that Alan is mentioning, it would also prevent the
> ugliness that happens when applications are not redrawing themselves
> because they are busy doing something.
> 
> Of course this is assuming that the X servers honors the setting, which
> is not always the case (but maybe that can be changed too, at least for
> local displays?)...

The main reason is that for technical reasons, backing store as
implemented in X is conceptually broken. One major problem is that 
for a guffawed scrolled window (like a GtkTextView with an embedded
widget), X will happily backing store the entire contents of the
window, not just the visible part.

Also, I think it's wrong for GTK+ to tell the X server that it is 
especially interesting to backing store. GTK+ is no more interesting
to backing store than any other app, and if backing store make
sense for GTK+, the server should be doing it for all apps.

Regards,
					Owen