aBothe
I tried to experiment a bit with SDL2 and OpenGL today and noticed that something caused some weird flickering when resizing my nicely drawn SDL2/OpenGL window:
Just after resizing, the background went black and I had to let my OpenGL code redraw the contents..
However, after some hours spent with googling I found out that in OpenGL examples where this CWBackPixel flag was not used when creating X windows, there was no flickering while resizing the window.
See http://www.sbin.org/doc/Xlib/chapt_04.html @ "The Window Background" for more info.