x11 and wayland VOs + backends all have logic that skips drawing frames
when the mpv isn't visible for efficiency reasons. This is implemented
in each individual VO, but it is useful for the core to be aware of this
as well. Currently, the display-sync modes on x11 do not try to be
efficient and always render anyways because there is no blocking on the
graphics API level if you skip rendering a frame (wayland works here by
accident). This means mpv would otherwise blaze through frames which is
not what anyone wants. We can instead improve this by implementing the
blocking mechanism in the core and using that when appropriate. This
commit does not implement that yet, but simply switches the draw_frame
to a boolean. Receiving false means that the VO is not drawing frames
and it should be treated as if the surface was hidden.
It turns out that it's generally more useful to look up hwdecs by image
format, rather than device type. In the situations where we need to
find one, we generally know the image format we're dealing with. Doing
this avoids us having to create mappings from image format to device
type.
The most significant part of this change is filling in the image format
for the various hw interops. There is a hw_imgfmt field today today, but
only a couple of the interops fill it in, and that seems to be because
we've never actually used this piece of metadata before. Well, now we
have a good use for it.
Dudemanguy