GL_ARB_debug_output provides a logging callback, which can be used to
diagnose problems etc. in case the driver supports it. It's enabled only
if the vo_opengl "debug" suboption is set.
Now it accepts the same renderer arguments as vo_opengl. This also
disables debug checks by default, and reverts the background color
override. Both can now be controlled by the host application.
Commit d38bc531 is incorrect: the 50ms queue-ahead value and the flip
queue offset have different functions. The latter is about calling
flip_page in advance, so the change attempted to show video frames 50ms
in advance on all VOs.
The change was for vo_opengl_cb, but that can be handled differently.
I think that's expected; mpv shouldn't draw anything while no video is
active. This doesn't blend transparently, though.
Also document the vo_opengl_cb thing.
This adds API to libmpv that lets host applications use the mpv opengl
renderer. This is a more flexible (and possibly more portable) option to
foreign window embedding (via --wid).
This assumes that methods like context sharing and multithreaded OpenGL
rendering are infeasible, and that a way is needed to integrate it with
an application that uses a single thread to render everything.
Add an example that does this with QtQuick/qml. The example is
relatively lazy, but still shows how relatively simple the integration
is. The FBO indirection could probably be avoided, but would require
more work (and would probably lead to worse QtQuick integration, because
it would have to ignore transformations like rotation).
Because this makes mpv directly use the host application's OpenGL
context, there is no platform specific code involved in mpv, except
for hw decoding interop.
main.qml is derived from some Qt example.
The following things are still missing:
- a way to do better video timing
- expose GL renderer options, allow changing them at runtime
- support for color equalizer controls
- support for screenshots
