From bfa5eb982d174ccdfe855023c4c3119f6df3a585 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Thu, 19 Dec 2019 13:11:43 -0700
Subject: handle MIDI rendering correctly when there are no regions

---
 libs/ardour/midi_playlist.cc | 55 ++++++++++++++++++++++++--------------------
 1 file changed, 30 insertions(+), 25 deletions(-)

diff --git a/libs/ardour/midi_playlist.cc b/libs/ardour/midi_playlist.cc
index 3b24232626..b79a90fde6 100644
--- a/libs/ardour/midi_playlist.cc
+++ b/libs/ardour/midi_playlist.cc
@@ -339,46 +339,51 @@ MidiPlaylist::render (MidiChannelFilter* filter)
 	/* RAII */
 	RTMidiBuffer::WriteProtectRender wpr (_rendered);
 
-	if (regs.size() == 1) {
-		tgt = &_rendered;
+	if (regs.empty()) {
 		wpr.acquire ();
 		_rendered.clear ();
 	} else {
-		tgt = &evlist;
-	}
 
-	DEBUG_TRACE (DEBUG::MidiPlaylistIO, string_compose ("\t%1 regions to read, direct: %2\n", regs.size(), (regs.size() == 1)));
+		if (regs.size() == 1) {
+			tgt = &_rendered;
+			wpr.acquire ();
+			_rendered.clear ();
+		} else {
+			tgt = &evlist;
+		}
 
-	for (vector<boost::shared_ptr<Region> >::iterator i = regs.begin(); i != regs.end(); ++i) {
+		DEBUG_TRACE (DEBUG::MidiPlaylistIO, string_compose ("\t%1 regions to read, direct: %2\n", regs.size(), (regs.size() == 1)));
 
-		boost::shared_ptr<MidiRegion> mr = boost::dynamic_pointer_cast<MidiRegion>(*i);
+		for (vector<boost::shared_ptr<Region> >::iterator i = regs.begin(); i != regs.end(); ++i) {
 
-		if (!mr) {
-			continue;
-		}
+			boost::shared_ptr<MidiRegion> mr = boost::dynamic_pointer_cast<MidiRegion>(*i);
 
-		DEBUG_TRACE (DEBUG::MidiPlaylistIO, string_compose ("render from %1\n", mr->name()));
-		mr->render (*tgt, 0, _note_mode, filter);
-	}
+			if (!mr) {
+				continue;
+			}
 
-	if (!evlist.empty()) {
-		/* We've read from multiple regions into evlist, sort the event list by time. */
-		EventsSortByTimeAndType<samplepos_t> cmp;
-		evlist.sort (cmp);
+			DEBUG_TRACE (DEBUG::MidiPlaylistIO, string_compose ("render from %1\n", mr->name()));
+			mr->render (*tgt, 0, _note_mode, filter);
+		}
 
-		/* Copy ordered events from event list to _rendered. */
+		if (!evlist.empty()) {
+			/* We've read from multiple regions into evlist, sort the event list by time. */
+			EventsSortByTimeAndType<samplepos_t> cmp;
+			evlist.sort (cmp);
 
-		wpr.acquire ();
-		_rendered.clear ();
+			/* Copy ordered events from event list to _rendered. */
 
-		for (Evoral::EventList<samplepos_t>::iterator e = evlist.begin(); e != evlist.end(); ++e) {
-			Evoral::Event<samplepos_t>* ev (*e);
-			_rendered.write (ev->time(), ev->event_type(), ev->size(), ev->buffer());
-			delete ev;
+			wpr.acquire ();
+			_rendered.clear ();
+
+			for (Evoral::EventList<samplepos_t>::iterator e = evlist.begin(); e != evlist.end(); ++e) {
+				Evoral::Event<samplepos_t>* ev (*e);
+				_rendered.write (ev->time(), ev->event_type(), ev->size(), ev->buffer());
+				delete ev;
+			}
 		}
 	}
 
-
 	/* no need to release - RAII with WriteProtectRender takes care of it */
 
 	DEBUG_TRACE (DEBUG::MidiPlaylistIO, string_compose ("---- End MidiPlaylist::render, events: %1\n", _rendered.size()));
-- 
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