Clearing only part of a window

[capnbishop]

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?

[CWiC]

You can use glScissor for that purposes.

[capnbishop]

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().

[Relic]

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.

[capnbishop]

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?