This is to allow passing the EventType to the Buffer, using a
consistent {[Time], Type, size, data} API, that is equivalent
for all classes.
This is particularly useful for Lua scripts and plugin UIs
than can call `write_immediate_event()` while being ignorant
where the data is routed to (MIDI tracks, plugins, processors).
The motivation for this is to determine if a given event
originates from a user-controlled live input controller or
from playback from disk or a MIDI file.
This distinction is required for VST3 MIDI learn.
This is required. From the "RestartFlags" documentation:
> kLatencyChanged:
> Latency has changed The plug informs the host that its latency
> has changed, getLatencySamples should return the new latency after
> setActive (true) was called The host has to deactivate and reactivate
> the plug-in, then afterwards the host could ask for the current
> latency (getLatencySamples) see IAudioProcessor::getLatencySamples
This can happen during pre-roll when buffers are filled
to start audible playback at zero.
While the position argument is signed for all plugin-standards,
it seems that some do not support negative timestamps before
00:00:00:00. (e.g. https://github.com/falkTX/Carla/issues/1236)
Furthermore TempoMap::bbt_at_sample() returns 0 for all negative
timestamps, but it was possible tthat tempo-map transmission,
as well as beat-position returned negative values.
When the engine is restarted, ports are re-established,
and previously queued port-connections need to be cleared.
This caused a bug:
* when the engine is stopped all ports are disconnected.
_port_connection_queue contains all disconnections
* engine is stopped so _port_connection_queue is not processed
* engine-restart re-etablishes ports and appends those connections
to _port_connection_queue
* process-callback processes the list in **reverse** order
```
while (!_port_connection_queue.empty ()) {
_port_connection_queue.pop_back ();
}
```
* ARDOUR::PortManager::connect_callback() is first called
with connected() and the disconnected()
* All ports are assumed to not be connected
Port::_externally_connected == 0 for all ports
Result:
* vari-speed playback resampling does not work (only external
I/O is reampled), split cycles processing (looping) fails
since AudioPort::get_audio_buffer() does not apply the
_global_port_buffer_offset
Previously when locating process_can_proceed() was set to true,
and routes were not processed while transport states are cleared.
As a result live input was also not processed.
This is no longer needed because the DiskReader handles seeking
directly.
