Double buffer widget drawing

[Alexander Piskunov <sd90034 lanet lv>]

Today widget drawing in GTK is very complicated and eye straining.
Every time widget appearance should be changed, entire widget's
window (sometimes part of it) is cleared and widget is redrawed(it is
required to lay backgroundpixmap).
Those XClearArea (or it's GDK wrapper) calls cause flicker.

So i have one idea: following drawing algorithm should be implemented
 * allocate chunk of memory
 * draw entire widget to this memory
 * copy memory area to X window
 * free memory
You see, only one X call is used here. It is much faster than current
algorithm and it is completely flicker free.(err.. perhaps memory
requirements will change)
Implementation of this algorithm will require *major* GTK(and GDK) change.
We can also give user a choice. One theme will draw straight to the
screen, another to memory.

How do you like this idea?