New API:
- gst_gl_context_get_config()
- gst_gl_context_request_config()
A GL context configuration is a GstStructure that has some well-known
names for common values that can also be extended in platform-specific
ways if necessary.
Wrapped OpenGL contexts may be able to retrieve the GL context
configuration depending on the platform. If that information is
available, GstGLContext will attempt to create an context that matches
the shared OpenGL context config unless gst_gl_context_request_config()
has been called.
A new environment variable 'GST_GL_CONFIG' will be read to influence the
configuration chosen. The environment variable will only be used as a
fallback if gst_gl_context_request_config() has not been called.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/809>
We need different export decorators for the different libs.
For now no actual change though, just rename before the release,
and add prelude headers to define the new decorator to GST_EXPORT.
Except for gst/gl/gstglfuncs.h
It is up to the client app to include these headers.
It is coherent with the fact that gstreamer-gl.pc does not
require any egl.pc/gles.pc. I.e. it is the responsability
of the app to search these headers within its build setup.
For example gstreamer-vaapi includes explicitly EGL/egl.h
and search for it in its configure.ac.
For example with this patch, if an app includes the headers
gst/gl/egl/gstglcontext_egl.h
gst/gl/egl/gstgldisplay_egl.h
gst/gl/egl/gstglmemoryegl.h
it will *no longer* automatically include EGL/egl.h and GLES2/gl2.h.
Which is good because the app might want to use the gstgl api only
without the need to bother about gl headers.
Also added a test: cd tests/check && make libs/gstglheaders.check
https://bugzilla.gnome.org/show_bug.cgi?id=784779
Intended for use with wrapped contexts that are created shared with gst's
gl contexts in order to manage the internal sharegroup state correctly.
e.g. with caopengllayer (which is used in glimagesink and caopengllayersink
on OS X), we create a CGL context from the gst context and the sharing state
was not being correctly set on either GL context and gst_gl_context_is_shared()
was always returning FALSE.
With 11fb4fff80 only flushing with multiple
shared contexts, the required flush was not occuring causing screen
corruption or stuttering.
Note: this didn't affect GST_GL_API=opengl pipelines
https://bugzilla.gnome.org/show_bug.cgi?id=762620
Some operations are unnecessary when running with only a single GL
context.
e.g. glFlush when setting a fence object as the flush happens on wait.
API: gst_gl_context_is_shared
They require to get_proc_address some functions through the
platform specific {glX,egl}GetProcAddress rather than the default
GL library symbol lookup.
