OpenGL child windows (bug 2398, fixed!)

Chris Robinson chris.kcat at
Wed Oct 3 09:47:17 CDT 2007

On Wednesday 03 October 2007 06:59:15 am Florian Köberle wrote:
> Hi
> I tried the Window with Button Demo from:
> The main window still overdraw the button.
> Used wine version:
> 57a67ebcceb08639736f218f0f545aa41737ad96
> graphic card:
> GeForce 7800 GTX
> driver:
> NVIDIA UNIX x86 Kernel Module  100.14.11
> Thanks for the try to fix it anyway.

This seems to be due to a couple factors. First, since the GL window is the 
top-level window, it draws to it directly so it doesn't get clipped. Second, 
CreateWindow for the GL window is missing the WS_CLIPCHILDREN flag. If I 
force offscreen rendering and add the flag, the demo works.

What can probably be done is to check if the window has the flags set to clip 
from children, and don't allow onscreen rendering with that. Then the only 
question is why Windows is assuming WS_CLIPCHILDREN for the window (maybe 
CreateWindow implies it while CreateWindowEx doesn't?).

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