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Index > Windows > So... how does ValidateRect/InvalidateRect work, exactly?

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Fred



Joined: 22 Oct 2010
Posts: 39
Fred
I obviously have no idea how these two works... haha!
When I have filled my rendering buffer with pixel data, I invoke InvalidateRect so a WM_PAINT gets run. In there I do some openGL stuff, swapbuffers, and invoke ValidateRect. Now by doing this, I do indeed get expected output in my window. However... every *other* program that is running starts to flicker violently. For the longest time I've let it be because I could never find anything that made a difference. On a whim today, I replaced InvalidateRect with ValidateRect, and voila! Still getting to WM_PAINT and no more flickering!

How does this work? I have a very bad grasp of how WM_PAINT and the likes work, if you couldn't tell already, haha. Does ValidateRect queue up a WM_PAINT?
Post 01 Sep 2013, 16:40
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cod3b453



Joined: 25 Aug 2004
Posts: 619
cod3b453
InvalidateRect tells the window that a region must be redrawn (schedule a WM_PAINT), while ValidateRect tells the window that a region must not be redrawn (de-schedule a WM_PAINT, regardless of whether it was drawn or not).

It sounds like your call to InvalidateRect is forcing a window redraw when it is not needed - in fact I believe this probably conflicts with normal openGL drawing loop. [The only openGL code I have shows a thread doing "while (1) { /*draw objects here*/ glFlush(); /* event handling code */ }" without any mention of window messages.]
Post 01 Sep 2013, 17:08
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Fred



Joined: 22 Oct 2010
Posts: 39
Fred
Hmm, not quite sure what this means. I shouldn't be using InvalidateRect? Do my GL stuff outside of WM_PAINT, somehow get there and only swapbuffers in there? Invalidate after the openGL stuff? I've tried to move the GL code i have in the WM_PAINT (glClear, glTexSubImage2D, glVertexPointer, glTexCoordPointer, glDrawArrays) to where my InvalidateRect is, but that just crashes the program.

But yes - "It sounds like your call to InvalidateRect is forcing a window redraw when it is not needed" is probably what happens... maybe™.


Edit: I'm trying to read up on the subject, and the openGL wiki suggests to not use WM_PAINT. I guess I shall figure out how this works.
Post 01 Sep 2013, 18:20
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Fred



Joined: 22 Oct 2010
Posts: 39
Fred
Looked over NeHe's openGL tutorials and a openGL fps example written by someone here on the forums (forgot who), and it seems to work pretty good so far. It crashes on exit, but that's probably me doing something stupid.

I moved all openGL invokes to right before InvalidateRect in my main loop, and only did ValidateRect in WM_PAINT. I also skipped WM_CREATE, but dunno how much that matters.
Post 04 Sep 2013, 12:13
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edfed



Joined: 20 Feb 2006
Posts: 4242
Location: 2018
edfed
BitRake made the fps demo Smile

BitRake: have you finally used a sphere for the sky box or is it still a cube?
Post 04 Sep 2013, 13:30
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bitRAKE



Joined: 21 Jul 2003
Posts: 3055
Location: vpcmipstrm
bitRAKE
Post 04 Sep 2013, 14:40
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Fred



Joined: 22 Oct 2010
Posts: 39
Fred
Yeah, that's it. Good guy bitshifter!

I noticed now that the call to InvalidateRect was unnecessary, btw. Now that all that works, I'm going to see if I can get this VBO thing to work. The wglGetProcAddress in this one is strong.

Edit: It lives! (the window title is wrong by now, didn't bother to fix)
Image
Post 05 Sep 2013, 07:50
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