This is mostly so BGMApp won't leave BGMDevice as the default if BGMApp
crashes, which would stop audio from playing until the user changed the
default device themselves. Also handles SIGINT, SIGTERM and SIGQUIT.
For crashes where the BGMApp process may be in an unknown state, e.g.
segfaults, BGMXPCHelper handles changing the default device.
Should fix the Travis Xcode 9 build, which is currently failing because
the AppleScript we use to quit BGMApp in .travis.yml gets "user
cancelled" for some reason.
Also makes some minor improvements to the reports generated by
CrashReporter. The way CrashReporter works with Background Music should
otherwise be unchanged.
On macOS, apps are supposed to play UI-related sounds using the "system
default" device. This commit creates a new instance of BGM_Driver, which
BGMApp sets as the system default device. BGMApp ignores audio played to
that device when deciding whether to pause/unpause the user's music
player.
Since UI sounds are short, this helps avoid pausing the music player and
unpausing it shortly after.
It turns out that the HAL will sometimes call BGM_Driver::StartIO before
sending kAudioDevicePropertyDeviceIsRunning to BGMPlayThrough. In that
case, BGMApp would start playthrough and tell BGMDriver to return from
StartIO immediately, which meant we would drop the initial frames while
the output device started up.
So now BGMApp waits for the output device in that case as well.
Fixes#7.
The BGMApp project now builds an XPC service bundle called BGMXPCHelper,
which vends a Mach service that BGMApp and BGMDriver can use to
communicate. This will hopefully be useful for some of the tasks HAL
notifications aren't suited to.
In this commit, BGMDriver uses the XPC helper when starting IO, to wait
until BGMApp is ready for playthrough. BGMApp can only start playthrough
when the output hardware is ready for IO. BGMDriver can now tell the HAL
when we're ready for IO, which means we don't have to keep the output
hardware running all the time (or drop frames or increase latency).
The end result is that playthrough doesn't waste CPU time while idle any
more. This also means that now playthrough won't prevent the system from
sleeping when idle.
