cocoa-cb: initial implementation via opengl-cb API

this is meant to replace the old and not properly working vo_gpu/opengl
cocoa backend in the future. the problems are various shortcomings of
Apple's opengl implementation and buggy behaviour in certain
circumstances that couldn't be properly worked around. there are also
certain regressions on newer macOS versions from 10.11 onwards.

- awful opengl performance with a none layer backed context
- huge amount of dropped frames with an early context flush
- flickering of system elements like the dock or volume indicator
- double buffering not properly working with a none layer backed context
- bad performance in fullscreen because of system optimisations

all the problems were caused by using a normal opengl context, that
seems somewhat abandoned by apple, and are fixed by using a layer backed
opengl context instead. problems that couldn't be fixed could be
properly worked around.

this has all features our old backend has sans the wid embedding,
the possibility to disable the automatic GPU switching and taking
screenshots of the window content. the first was deemed unnecessary by
me for now, since i just use the libmpv API that others can use anyway.
second is technically not possible atm because we have to pre-allocate
our opengl context at a time the config isn't read yet, so we can't get
the needed property. third one is a bit tricky because of deadlocking
and it needed to be in sync, hopefully i can work around that in the
future.

this also has at least one additional feature or eye-candy. a properly
working fullscreen animation with the native fs. also since this is a
direct port of the old backend of the parts that could be used, though
with adaptions and improvements, this looks a lot cleaner and easier to
understand.

some credit goes to @pigoz for the initial swift build support which
i could improve upon.

Fixes: #5478, #5393, #5152, #5151, #4615, #4476, #3978, #3746, #3739,
#2392, #2217

2 files changed, 4 insertions, 2 deletions

diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst
index 9f0c672919..c12453ae5f 100644
--- a/DOCS/man/options.rst
+++ b/DOCS/man/options.rst
@@ -4876,7 +4876,7 @@ The following video options are currently all specific to ``--vo=gpu`` and
     auto
         auto-select (default)
     cocoa
-        Cocoa/OS X
+        Cocoa/OS X (deprecated, use --vo=opengl-cb instead)
     win
         Win32/WGL
     winvk
diff --git a/DOCS/man/vo.rst b/DOCS/man/vo.rst
index 20e406dd4e..d5a4ef9b26 100644
--- a/DOCS/man/vo.rst
+++ b/DOCS/man/vo.rst
@@ -429,7 +429,9 @@ Available video output drivers are:
         Specify the directory to save the image files to (default: ``./``).
 
 ``opengl-cb``
-    For use with libmpv direct OpenGL embedding; useless in any other contexts.
+    For use with libmpv direct OpenGL embedding. As a special case, on OS X it
+    is used like a normal VO within mpv (cocoa-cb). Otherwise useless in any
+    other contexts.
     (See ``<mpv/opengl_cb.h>``.)
 
     This also supports many of the options the ``gpu`` VO has.