- xcb is supposedly thread-safe!
videotestsrc ! glimagesink now doesn't spuriously result in a
'call XInitThreads()' error however if anybody else is using X11,
then XInitThreads() still needs to be called and multiple glimagesink's
still need XInitThreads().
Everything still takes libX11 handles as they are compatible with the xcb
variants. Unfortunately we cannot move fully over to xcb due to GLX being
entirely based on Xlib. It's also impossible to transform a xcb_connection
to a Display which means we require X11 handles.
GstGLDisplayX11 holds the display connection and name. Each thread requires
it's own X11 Display connection (initialised from name) due to the fact that
we do not want to call XInitThreads(). Doing so would result in segfaults
when integrating with GUI toolkits Gtk, Qt, etc.
The Display connection is for OpenGL platforms where a constant display is
required in order to share contexts (egl). In the case of a wrapped context
(added later), we do not have GstGLWindow to retreive the display from so a
'master' connection is used instead.
