From 36d0a6e908cb9fe6aaf495e52ade6a0bac527fc9 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Tue, 4 Jun 2024 13:21:55 -0600
Subject: [PATCH] fix dangling references to a MidiRegion and MidiTrack in a
 MidiView

---
 gtk2_ardour/midi_view.cc | 21 +++++++++++++++++++--
 gtk2_ardour/midi_view.h  |  4 ++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/gtk2_ardour/midi_view.cc b/gtk2_ardour/midi_view.cc
index 0b70ab03d1..812f3507b0 100644
--- a/gtk2_ardour/midi_view.cc
+++ b/gtk2_ardour/midi_view.cc
@@ -174,6 +174,7 @@ MidiView::MidiView (MidiView const & other)
 void
 MidiView::init ()
 {
+	_midi_track->DropReferences.connect (track_going_away_connection, invalidator (*this), boost::bind (&MidiView::track_going_away, this), gui_context());
 	_patch_change_outline = UIConfiguration::instance().color ("midi patch change outline");
 	_patch_change_fill = UIConfiguration::instance().color_mod ("midi patch change fill", "midi patch change fill");
 
@@ -181,15 +182,31 @@ MidiView::init ()
 	EditingContext::DropDownKeys.connect (sigc::mem_fun (*this, &MidiView::drop_down_keys));
 }
 
+void
+MidiView::track_going_away ()
+{
+	_midi_track.reset ();
+}
+
+void
+MidiView::region_going_away ()
+{
+	_midi_region.reset ();
+	_model.reset ();
+	connections_requiring_model.drop_connections();
+}
+
 void
 MidiView::set_region (std::shared_ptr<MidiRegion> mr)
 {
 	_midi_region = mr;
 	if (!_midi_region) {
-		_model.reset ();
-		connections_requiring_model.drop_connections();
+		region_going_away ();
 		return;
 	}
+
+	_midi_region->DropReferences.connect (region_going_away_connection, invalidator (*this), boost::bind (&MidiView::region_going_away, this), gui_context());
+
 	set_model (_midi_region->midi_source (0)->model());
 }
 
diff --git a/gtk2_ardour/midi_view.h b/gtk2_ardour/midi_view.h
index 71a9615821..763467825a 100644
--- a/gtk2_ardour/midi_view.h
+++ b/gtk2_ardour/midi_view.h
@@ -444,6 +444,10 @@ class MidiView : public virtual sigc::trackable
 	bool note_canvas_event(GdkEvent* ev);
 
 	PBD::ScopedConnectionList connections_requiring_model;
+	PBD::ScopedConnection track_going_away_connection;
+	PBD::ScopedConnection region_going_away_connection;
+	void track_going_away ();
+	void region_going_away ();
 
 	void midi_channel_mode_changed ();
 	void instrument_settings_changed ();