fix seamless midi-looping - fixes #5438

well, now...
 - Midi-Ports have a midi-buffer.
 - Midi-Tracks have a midi-buffer.
 - Midi-tracks have a diskstream.
 - Midi-diskstream has a midi-ring-buffer.
 - Midi-tracks have a delivery
 - The delivery can get a reference to the actual backend-ports
 - The delivery calls the Midi-Port's flush() buffer to send out queued events
   at the end of a cycle

all clear ? :)

 - when splitting the process-cycle: only the Ports are informed.
   all other objects see a "normal" short process cycle starting at "0".

The offset needs to be applied early on, so that internally routed buffers
push the event at the correct time when combining the buffer with
immediate and async events.

Luckily Port::port_offset() is a static member, available to all, objects,
which allows to bridge the conceptual gap between the diskstream and
the delivery.

There's a snag:
When there's a note-on directly at the beginning of the loop it coincides
with the panic message sent when looping.
The panic comes before note events, so it *should* be good.

Also the final note-offs (state tracker end of loop/region) are sent
1 sample too early (smells like an off-by-one), and are hence dropped.
(no matter we send a panic right after it).
It should really be at the same time, just before the panic.

libs/ardour/midi_buffer.cc

@@ -26,6 +26,7 @@
 
 #include "ardour/debug.h"
 #include "ardour/midi_buffer.h"
+#include "ardour/port.h"
 
 using namespace std;
 using namespace ARDOUR;
@@ -35,6 +36,7 @@ using namespace PBD;
 MidiBuffer::MidiBuffer(size_t capacity)
 	: Buffer (DataType::MIDI)
 	, _data (0)
+	, _size (0)
 {
 	if (capacity) {
 		resize (capacity);
@@ -85,7 +87,7 @@ MidiBuffer::copy(const MidiBuffer& copy)
  * Note that offset and nframes refer to sample time, NOT buffer offsets or event counts.
  */
 void
-MidiBuffer::read_from (const Buffer& src, framecnt_t nframes, framecnt_t dst_offset, framecnt_t src_offset)
+MidiBuffer::read_from (const Buffer& src, framecnt_t nframes, framecnt_t dst_offset, framecnt_t /* src_offset*/)
 {
 	assert (src.type() == DataType::MIDI);
 	assert (&src != this);
@@ -99,15 +101,19 @@ MidiBuffer::read_from (const Buffer& src, framecnt_t nframes, framecnt_t dst_off
 		assert (_size == 0);
 	}
 
-	/* XXX use dst_offset somehow */
+	framecnt_t offset = Port::port_offset();
 
 	for (MidiBuffer::const_iterator i = msrc.begin(); i != msrc.end(); ++i) {
 		const Evoral::MIDIEvent<TimeType> ev(*i, false);
-		if (ev.time() >= src_offset && ev.time() < (nframes+src_offset)) {
+		if (ev.time() >= offset && ev.time() < (nframes + offset)) {
 			push_back (ev);
 		} else {
 			cerr << "MIDI event @ " <<  ev.time() << " skipped, not within range "
-			     << src_offset << " .. " << (nframes + src_offset) << endl;
+			     << offset << " .. " << (nframes + offset) << ":";
+				for (size_t xx = 0; xx < ev.size(); ++xx) {
+					cerr << ' ' << hex << (int) ev.buffer()[xx];
+				}
+				cerr << dec << endl;
 		}
 	}
 

libs/ardour/midi_diskstream.cc

@@ -1437,6 +1437,7 @@ MidiDiskstream::get_playback (MidiBuffer& dst, framecnt_t nframes)
         // cerr << "----------------\n";
 
 	size_t events_read = 0;
+	const size_t split_cycle_offset = Port::port_offset ();
 
 	if (loc) {
 		framepos_t effective_start;
@@ -1454,11 +1455,13 @@ MidiDiskstream::get_playback (MidiBuffer& dst, framecnt_t nframes)
 			   beyond the loop end.
 			*/
 
-			_playback_buf->resolve_tracker (dst, 0);
+			_playback_buf->resolve_tracker (dst, split_cycle_offset);
 		}
 
 		_playback_buf->skip_to (effective_start);
 
+		/* for split-cycles we need to offset the events */
+
 		if (loc->end() >= effective_start && loc->end() < effective_start + nframes) {
 			/* end of loop is within the range we are reading, so
 			   split the read in two, and lie about the location
@@ -1475,23 +1478,23 @@ MidiDiskstream::get_playback (MidiBuffer& dst, framecnt_t nframes)
 			if (first) {
 				DEBUG_TRACE (DEBUG::MidiDiskstreamIO, string_compose ("loop read #1, from %1 for %2\n",
 										      effective_start, first));
-				events_read = _playback_buf->read (dst, effective_start, first);
+				events_read = _playback_buf->read (dst, effective_start, first, split_cycle_offset);
 			}
 
 			if (second) {
 				DEBUG_TRACE (DEBUG::MidiDiskstreamIO, string_compose ("loop read #2, from %1 for %2\n",
 										      loc->start(), second));
-				events_read += _playback_buf->read (dst, loc->start(), second);
+				events_read += _playback_buf->read (dst, loc->start(), second, split_cycle_offset);
 			}
 
 		} else {
 			DEBUG_TRACE (DEBUG::MidiDiskstreamIO, string_compose ("loop read #3, adjusted start as %1 for %2\n",
 									      effective_start, nframes));
-			events_read = _playback_buf->read (dst, effective_start, effective_start + nframes);
+			events_read = _playback_buf->read (dst, effective_start, effective_start + nframes, split_cycle_offset);
 		}
 	} else {
 		_playback_buf->skip_to (playback_sample);
-		events_read = _playback_buf->read (dst, playback_sample, playback_sample + nframes);
+		events_read = _playback_buf->read (dst, playback_sample, playback_sample + nframes, split_cycle_offset);
 	}
 
 	DEBUG_TRACE (DEBUG::MidiDiskstreamIO, string_compose (

libs/ardour/midi_track.cc

@@ -935,7 +935,7 @@ MidiTrack::act_on_mute ()
 		}
 
 		/* Resolve active notes. */
-		midi_diskstream()->resolve_tracker(_immediate_events, 0);
+		midi_diskstream()->resolve_tracker(_immediate_events, Port::port_offset());
 	}
 }
 

libs/ardour/plugin.cc

@@ -50,6 +50,7 @@
 #include "ardour/midi_state_tracker.h"
 #include "ardour/plugin.h"
 #include "ardour/plugin_manager.h"
+#include "ardour/port.h"
 #include "ardour/session.h"
 #include "ardour/types.h"
 
@@ -304,7 +305,7 @@ Plugin::resolve_midi ()
 	*/
 
 	_pending_stop_events.get_midi(0).clear ();
-	_tracker.resolve_notes (_pending_stop_events.get_midi (0), 0);
+	_tracker.resolve_notes (_pending_stop_events.get_midi (0), /* split cycle offset*/ Port::port_offset());
 	_have_pending_stop_events = true;
 }