When a session-range coincides with a loop-range location, moving
the session-range also updates the loop-range.
Keeping session and loop-range in sync can be useful if the whole
session is looped. However markers are treated individually, so
we need prevent invalid ranges.
If session-start and loop-start coincide, but loop-end is before the
end-marker, it is possible to move session-start beyond the loop-end.
Automation Controls (and controls in general) are now
only updated in realtime context. Either via automation-playback,
or via SessioEvent. This directly sets the Control:_user_value
(before emitting the Changed signal).
The GUI does not need to evaluate the control at a given point
in time, so the API call can be removed and unified.
This commit first removes all calls to "get_double" to ensure
that no special cases exist.
::automation_run() evaluates the value, possibly ahead of time
depending on latency-compensation. The actual value is set in
realtime-context via set_value_unchecked() -> actually_set_value()
which emits the Changed signal.
At this point in time Control::user_value is already set correctly.
There is no need to evaluate and interpolate again, at a potentially
incorrect (uncompensated) time: `_session.transport_sample()`.
This fixes an issue with the GUI Automation control showing an
outdated value when there is an "immediate jump" in the signal:
eg. add a latent plugin post-fader, then automate the Fader to jump
from 0dB to -inf dB (snap to grid) and play though that transition.
(Plugin controls were not affected by this bug, the process
cycle is split for those, but Mixbus internal AC were affected).
When the loop-range is defined in BeatTime, the disk-reader encounters
rounding issues due to time-domain mismatches.
With a simple session fixed BPM at 120, 48kHz.
looping 1 bar exactly 2 sec at the start of the session:
```
Range::squish start: b0 end: b7680 squish: a113554560
Range::squish using modulo: b45 = a661500
Range::squish using modulo in TD: a5760
Range::squish using earlier(): a658560
```
The correct answer is a113554560 - 2 * 56448000 [SC/sec] = a658560
Calculating the modulo iteratively is not great, however usually
only one iteration is required.
PBD::Transmitter is neither thread-safe nor rt-safe. This likely
fixes a crash on macOS when process-threads are started.
Many threads simultaneously enter coreaudio_process_thread() and
log a message calling `PBD::info << .. << endmsg` simultaneously.
