In the earlier days of graphics on Linux this was a common right of passage. As far back as 2003 I can remember running an i915 graphics driver, which Intel has always had pretty good open drivers. When you would open a video in VLC and take a screenshot of the desktop, you would be left with a hole as it would grab the overlay compositing color (blue, green, etc.). However, if X11 was doing a video thing it would be filling these areas with whatever video is happening.