The new API has literally no advantages (other than that we can drop
mp_vt_download_image and other things later), but it's sort-of uniform
with the other hwaccels.
"--videotoolbox-format=no" is not supported with the new API, because it
doesn't "fit in". Probably could be added later again.
The iOS code change is untested (no way to test).
Originally, there was probably some sort of intention to restrict it to
formats supported by the interop, or something. But in the end it was
overcomplicated nonsense.
In the future, we could use mp_hwdec_ctx.supported_formats or other
mechanisms to handle this in a better way.
mp_hwdec_ctx.ctx is not set to a dummy pointer - hwdec_devices_load() is
only used to detect whether to vo_opengl interop is present, and the
common hwdec code expects that the .ctx field is not NULL.
This also changes videotoolbox-copy to use --videotoolbox-format,
instead of the FFmpeg-set default.
The code for copying a videotoolbox surface to mp_image was duplicated
(with some minor differences - I picked the hw_videotoolbox.c version,
because it was "better"). mp_imgfmt_from_cvpixelformat() is somewhat
duplicated with the vt_formats[] table, but this will be fixed in a
later commit, and moving the function to shared code is preparation.
wm4