Re: Solving the repaint problem?
First off, it is incorrect to say they don't "touch" the screen. If you skip
the operation of BitBlt'ing the bitmap to the screen, nothing will appear.
Second, you are correct that this approach will eliminate all flicker.
However, if you read my comments again, you'll see that I wasn't focused
only on whether or not flicker would be eliminted. I was also addressing the
issue of which approach would solve the issue most efficiently and using the
least amount of system resources. To me, that matters too.
--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com
"Peter Olcott" <NoSpam@SeeScreen.com> wrote in message
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"Jonathan Wood" <jwood@softcircuits.com> wrote in message
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I would recommend first eliminating any painting done in OnEraseBkgnd.
Second, I would carefully consider how you paint your window. For example,
clearing the background of a rectangle and then drawing text in
TRANSPARENT mode is probably faster than simply drawing the text in OPAQUE
mode, but the first approach will cause more flicker.
It would seem that if every operation to the screen is only done by
updating an offscreen memory bitmap, that no matter how slow these
operations are, they could cause no possible flicker because these
operations themselves do not actually touch the screen.
Only after those issues have been thoroughly addressed would I looking
into drawing first to a bitmap, which uses more resources and can be
slower overall.
--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com
"Peter Olcott" <NoSpam@SeeScreen.com> wrote in message
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"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp> wrote in message
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"Peter Olcott" <NoSpam@SeeScreen.com> wrote in message
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I know that the basic process of eliminating the flash when the screen
updates is to paint everything to an offscreen memory bitmap, and then
to BitBlt() this memory bitmap to the screen in the OnPaint event. Is
the only other reason why I may still have a screen flash is that I did
not yet over-ride the OnEraseBkgnd(CDC* pDC) function?
Yes, overriding OnEraseBkgnd is fundamental to eliminating the flash.
The flash is caused by painting twice: once in OnEraseBkgnd, again in
OnPaint. The eye can see both steps.
This is the only other possible requirement besides painting everything
to an offscreen memory bitmap?