View Full Version : Clearing only part of a window

02-28-2005, 08:46 PM
If I want a viewport to take up half of a window, naturally I might want to only have that half of the window cleared. However glClear() clears my entire window. How do I clear only part of the window while leaving everything in the 'uncleared' portion untouched?

02-28-2005, 09:49 PM
You can use glScissor for that purposes.

03-01-2005, 09:08 PM
Thanks, that worked, but it's still clearing the rest of the window to white no matter what my clear color is. It also clears the entire window with white when I don't call glClear().

03-01-2005, 10:30 PM
That's probably the Windows GDI background clear.
You need to override the WM_ERASEBKGND message.
In pure Win32 API message handling just add
case WM_ERASEBKGND: return 1;
to keep windows from clearing your client area.
In MFC generate a message handler function for it and do the same.

03-02-2005, 02:21 PM
Actually this is on a Mac. I'd love to test my Windows and Linux code, but for the time being that's not an option. Anyway it seems to be something in an agl routine. Any ideas?