New subject: Speed of scrolling with a background pixmap

Monday, 1 November 1999

        Kyle Jones <kyle_jones(a)wonderworks.com&gt; writes:

...
 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. 
Of course; sorry for the confusion.

...
 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. 
Would it help if the X server be made to remember the picture?  For
instance, is it possible to tell X that the letters are a layer over
the background image, which will be removed and replaced with new
ones?  I assume the graphical 2D acceleration hardware has *some*
optimizations for these cases?

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Re: Speed of scrolling with a background pixmap