Hrvoje Niksic writes:
Whether you use a bg pixmap or not, try comparing scrolling speed with
and without a bg pixmap. For me, scrolling is much slower without a
bg pixmap, even though the pixmap itself doesn't scroll.
I assume you meant that scrolling is slower WITH a background pixmap.
It is definitely repeatable for me.
Repainting an X window with a pixmap is slower than clearing the
same window to a single color. Repainting a window to a single
color can probably be done with a single instruction sent to the
video card. Repainting a pixmap region is going to require data
to be copied from main memory to VRAM on the card. That alone is
enough to really slow down the display of images on my PC. I can
easily see it when running X with an 8bbp vs. 24bbp display using
the same video card.