glimagesink regression: does not render video since using libxcb

Submitted by Mark Nauwelaerts @mnauw

Link to original bug (#774809)

Description

Created attachment 340468
gl: x11 display glx workaround

More precisely, when running (gst-launch-1.0) the example pipeline videotestsrc ! glimagesink, then a window is created and shown, but it remains as an outline and no content is ever filled (so whatever is behind the window remains visible).

This happens as of commit 4f6c226bd24ae3ef66bd8f4c17b001444c9b0bf1 (using libxcb in gl/x11), it rendered ok before that. Some additional observations; forcing GST_GL_PLATFORM=egl renders video fine (problem occurs with GST_GL_PLATFORM=glx). Also, upon applying the attached patch, the video also renders fine with GST_GL_PLATFORM=glx. It is not really a fix though, as it knocks out the event handling.

All that is rather puzzling, possibly somehow system-specific and might be dismissed as "lower level problems", but still if someone has additional insight (and solution?) ...

Patch 340468, "gl: x11 display glx workaround":
0001-gl-x11display-workaround-silence-xcb-event-handling.patch