Hi,

I thought window video was all continuous in memory, such that a MemSet
could clear a window of any dimentions?  Why would successive scan lines
reside contiguously in memory?  (from your post "needs to compute the
start and end addresses for each scan line...")

I refer to the WindowType.displayAddr attribute (now displayAddrV20 in
SDK3.5), which we are advised not to use.  This implies that the video
memory for a window starts at a known address (*displayAddr) and is a
solid lump of data in memory, whose size is easily computable given the
window size and colour depth.

I ask because I use a backbuffer larger than the actual screen size (by
about 16 pixels at each edge) so that my drawing calls can exceed the
screen's dimentions by a little and not cause a problem.  My
WinEraseWindow therefore is done on my large backbuffer, only 160x160 of
which is blitted to the screen each frame.  Your comments worry me :)

I feel sure that any answer to my question will refer to system changes
between different PalmOS versions.

Neek :)

Bob Ebert wrote:
> WinEraseWindow is already optimized for full-screen-width cases.   It
> (eventually) just calls MemSet, which is about as fast as you can get.  Of
> course, if your window is not fully as wide as the screen, this won't be
> quite as fast because it needs to compute the start and end addresses for
> each scan line...

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