We added GL_CFLAGS in autotools because we unconditionally included OpenGL
headers. We do not do that anymore for a standard #include <gst/gl/gl.h>.
OpenGL headers are only included for the platform specific files
e.g. #include <gst/gl/x11/gstgldisplay_x11.h> which must always be hidden
behind a #if GST_GL_HAVE_WINDOW_X11, or #include <gst/gl/gstglfuncs.h> to
gain access to the contents of the GstGLFuncs object.
Users of our headers must include the necessary include paths for the
platforms they are intending to support.
We might introduce extra .pc files for what GstGL was built against though.
Fixes https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/issues/735
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/741>
Tests and documentation will follow separately.
The mixer elements in the opengl plugin need to stay
in -bad for now since they use GstVideoAggregator.
https://bugzilla.gnome.org/show_bug.cgi?id=754094
Don't put relative paths in pkg-config files, including uninstalled
ones. For those, use @abs_topbuilddir@ and @abs_topsrcdir@ as we
do elsewhere.
Remove libraries= directives, which doesn't seem to be a pkg-config
variable that actually exists, but has been in all our pkg-config
files for as long as they've existed.
It's architecture dependent and should not be placed into the include
directory as the assumption is that all those headers are architecture
independent.
https://bugzilla.gnome.org/show_bug.cgi?id=739767
