"Nils �gren" <[EMAIL PROTECTED]> wrote in message
news:3650@palm-dev-forum...
> I'm using simple double buffering when drawing; first I draw everything in
a
> offscreen WinHandle and then I copy the offscreen into the screenBuffer.
> It works well, almost. It's still flickering! I believe this is because of
> the time it takes for my Palm V to copy the offscreen to the screen...
If you're willing to require OS 3.5 or later for your application, you can
use the new WinScreenLock and WinScreenUnlock API to effectively switch the
screen hardware to point to a different chunk of memory, giving a very fast
switch from the old state to the new state. By passing winLockDontCare, it
is possible to avoid the cost of copying the entire screen each time, but
you'll have to add code to keep track of three different states in the
animation rather than just two. If you want to support older OS versions,
you could build your own wrapper functions that would use the new API when
it is available and would copy from an offscreen window when it isn't. Note
that copying bitmaps is slower on color devices because of the greater
screen depth, so if you're having trouble with a Palm V, it'll likely be
even worse on a IIIc. You should avoid copying the entire offscreen window
to the screen, and only copy the area(s) that changed. Coalescing many small
areas into one large one will improve performance in some cases, but not if
the unchanged area is large. You can use POSE to profile your displaying to
find an approach that works for your application on all the devices you want
to support.
-
Peter Epstein
--
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