prevent note-range change signals for every added note in a MidiView

gtk2_ardour/midi_view.cc

@@ -1076,6 +1076,8 @@ MidiView::model_changed()
 		return;
 	}
 
+	MidiViewBackground::NoteRangeSuspender nrs (_midi_context);
+
 	if (_active_notes) {
 		// Currently recording
 		const samplecnt_t zoom = _editing_context.get_current_zoom();

gtk2_ardour/midi_view_background.h

@@ -54,6 +54,19 @@ class MidiViewBackground : public virtual ViewBackground
 
 	Gtk::Adjustment note_range_adjustment;
 
+	struct NoteRangeSuspender {
+		NoteRangeSuspender (MidiViewBackground& mv) : mvb (mv) {
+			mvb.NoteRangeChanged.block ();
+		}
+
+		~NoteRangeSuspender() {
+			mvb.NoteRangeChanged.unblock ();
+			mvb.NoteRangeChanged(); /* EMIT SIGNAL */
+		}
+
+		MidiViewBackground& mvb;
+	};
+
 	enum VisibleNoteRange {
 		FullRange,
 		ContentsRange