#447 Flashing artefacts with opengl in the window border

[AaronP]

see: https://bugzilla.freedesktop.org/show_bug.cgi?id=98993

This is a dosbox bug, please report it to the dosbox developers:

Making an apitrace of the problem and analyzing it in qapitrace, one can see that as of the third frame, dosbox no longer calls glClear and only draws to the area covered by the DOS shell, not to the borders left and right of it. Clearly, dosbox assumes that there are at most two buffers and that their contents are preserved after glXSwapBuffers, but there are no such guarantees (not even with DRI2, e.g. xf86-video-intel supports triple buffering with that as well).

What dosbox could do is use e.g. the GLX_EXT_buffer_age extension to find out which parts of the current back buffer don't need to be redrawn.

Ultimately this results in flashing artefacts in the window border when using opengl under certain drivers.