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WM_PAINT
Author
Ok, so I admit it, I''m new at this.
I am familiar with Windows SDK programming, but noticed in NeHe''s framework there is no repainting explicitly done for a WM_PAINT message. How does OpenGL know that it has to repaint the scene when a GL window is uncovered for example?
swapbuffers(). That functions tells the card to swap the front and back buffers. Once that is done you are just waiting for a new screen refresh to see your things
Edited by - Gorg on August 2, 2000 10:08:02 AM
Edited by - Gorg on August 2, 2000 10:08:02 AM
Author
Thanks!
Ok - but in standard SDK programming, after drawing a window once, nothing automatically redraws the window when it gets corrupted (like when a window is exposed my moving another window out of the way) - it has to be manually redrawn each time.
In the case of ogl, though, it seems to be handling this automatically - where?
For example - draw an ogl window (not full screen) open another app, cover the ogl app window, then expose it again. in standard SDK programming, this would generate a WM_PAINT and I''d have to redraw manually using my sdk code - but in ogl this doesn''t seem necessary - what is handling this WM_PAINT?
Ok - but in standard SDK programming, after drawing a window once, nothing automatically redraws the window when it gets corrupted (like when a window is exposed my moving another window out of the way) - it has to be manually redrawn each time.
In the case of ogl, though, it seems to be handling this automatically - where?
For example - draw an ogl window (not full screen) open another app, cover the ogl app window, then expose it again. in standard SDK programming, this would generate a WM_PAINT and I''d have to redraw manually using my sdk code - but in ogl this doesn''t seem necessary - what is handling this WM_PAINT?
In the tutorials there is no WM_PAINT because it''s drawed every time when swapbuffers() is called.
I also think it would be to slow to handle the WM_PAINT message with OGL (except for editors).
I also think it would be to slow to handle the WM_PAINT message with OGL (except for editors).
Author
OK, I get it now.
On each pass through the message loop, if there is nothing to do, it does a swap buffers. This makes sure the screen stays updated with the last calculated display.
I get it now.
I did some experimenting, and noticed that it even does this when the screen is minimized! It doesn''t recalc, but it swaps buffers like crazy - i''ll do some more experimenting.
On each pass through the message loop, if there is nothing to do, it does a swap buffers. This makes sure the screen stays updated with the last calculated display.
I get it now.
I did some experimenting, and noticed that it even does this when the screen is minimized! It doesn''t recalc, but it swaps buffers like crazy - i''ll do some more experimenting.
i do recommend calling swap buffers in the paint statment if u use a model dialog in your program othjerwise when the user drags a dialog over the screen there will be a black trail after it
I dunno if you noticed but in NeHe''s code, whenever it runs in a window, then WS_EX_TOPMOST is specified, meaning that nothing is ever drawn over it.
OGL windows only ever update when you call SwapBuffers() anyway.
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Smidge
www.smidge-tech.co.uk
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OGL windows only ever update when you call SwapBuffers() anyway.
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Smidge
www.smidge-tech.co.uk
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