new pianoroll note range enum, denoting "user selected range"

gtk2_ardour/midi_view_background.cc

@@ -190,7 +190,9 @@ MidiViewBackground::setup_note_lines()
 void
 MidiViewBackground::set_note_visibility_range_style (VisibleNoteRange r)
 {
-	if (r == ContentsRange) {
+	if (r == UserRange) {
+		_visibility_note_range = UserRange;
+	} else if (r == ContentsRange) {
 		if (apply_note_range (_data_note_min, _data_note_max, true)) {
 			_visibility_note_range = ContentsRange;
 		}

gtk2_ardour/midi_view_background.h

@@ -75,7 +75,8 @@ class MidiViewBackground : public virtual ViewBackground
 
 	enum VisibleNoteRange {
 		FullRange,
-		ContentsRange
+		ContentsRange,
+		UserRange
 	};
 
 	ARDOUR::NoteMode  note_mode() const { return _note_mode; }

gtk2_ardour/prh_base.cc

@@ -665,6 +665,7 @@ void
 PianoRollHeaderBase::end_scroomer_drag ()
 {
 	_scroomer_drag = false;
+	_midi_context.set_note_visibility_range_style (MidiViewBackground::UserRange);
 }
 
 bool