Don't toolkits using many (sub-)windows hurt composite?

Clemens Eisserer linuxhippy at
Tue Aug 15 02:45:52 PDT 2006

Hi there,

As far as I know there are 2 different way (maybe even more ;) ) to
design a toolkit from ground up. Only request one top level window and
do all layouting/repainting stuff yourself or use X11' sub-windows, so
X11 handles clipping, event delevery, repainting for your.
As far as I know the second approach is the one X11 was more or less
"designed" for and is used by GTK and some other toolkits. (Well GTk
uses a mixed modell).

I wonder how the "x11 subwindow model" could be mapped efficiently to
an X server which runs a composition manager? I ran gftp with a
modified gtk version (which allocates a pixmap per window instead of
each repaint) and the result where 15mb of pixmaps allocated for a
maximized window (1024x680) and its subwindows. According to "xrestop"
Eclipse itself consists of 315 sub-windows, so I assume about 30-60mb
of pixmaps.

As far as I understand when running a composition manager the content
of each window is stored in pixmaps - however when using sub-windows
most of of these pixmaps are quite likely hidden by other sub-windows.

Are there special techniques to avoid this problem. Are there any
recommandations how toolkits should be designed nowdays?

Thank you in advance, lg Clemens

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