This covers over that audio will fail query position while a seek is in
progress. It also means that instead of returning zero we at least return
something which is much closer to the time that we will soon end up playing
from.
Gapless broke this, so this change makes sure that next/prev/play and gapless
track changes all correctly emit events.
Note that this only ensures we get PLAYING -> PLAYING events. Not the old
STOPPED -> PLAYING and then PLAYING -> STOPPED.
Trigger playback ended on:
- stream changed
- EOS
- stop via stream changed events
Old behavior was to manually trigger on:
- next
- prev
- play with other track and old state != STOPPED
- stop
When about to finish gets called we are running in some GStreamer thread. Our
audio code then calls the shim core callback which is responsible for
transferring our execution to the core actor thread and waiting for the
response. From this point we do normal actor calls to the backend(s) which in
turn call into the audio actor. Since the initial audio code that was called is
outside the actor this should never deadlock due to this loop.
This change has us checking the return value of change_track when deciding if
the play call was a success or if the track is unplayable. Which ensures that
the following can no longer happen: 1) play stream 2) play stream that fails
change_track 3) stream 1) continues playing. Correct behavior being the next
stream playing instead.
While trying to remove traces of stop calls in core to get gapless working I
found we had no way to switch to switch tracks without triggering a play. This
change fixes this by changing the backends playback provider API.
- play() now _only_ starts playback and does not take any arguments.
- prepare_change() has been added, this could have been avoided with a kwarg to
change_track(track), but that would break more backends.
- core has been updated to call prepare_change+change_track+play as needed.
- tests have been updated to handle this change.
Longer term I hope to completely rework the playback API in backends, as 99% of
our backends only use change_track(track) to translate URIs. So we should make
simple case simple, and handle mopidy-spotify / appsrc in some other way.
Cherry picked from the WIP gapless branch.
- Pending track should only be triggered by stream_changed if there is one.
- Tracklist changed was incorrectly calling stop breaking tests and gapless
- Tests have been updated to capture and replay audio events. This should avoid
test deadlocks while still using the audio fakes.
