I'm using SFML with opengl and a gui created with CEGUI. When I run my program creating a window doesn't call glViewport (I set a breakpoint to confirm this) so none of my gl calls get displayed. Note that CEGUI does set glViewport internally so it is displayed.
If I use the mouse to resize the window a resize event occurs and glViewport is called, and everything works correctly. Another workaround is to manually call glViewport after creating the window; however, I would like to pinpoint the cause of the problem, rather than hacking in a solution.
Steve.