Ensure a create note drag rectangle starts with both ends snapped,

otherwise it is possible to drag a note with a size large enough to
be considered valid and smaller than half the grid distance.  These
get snapped to zero length and thus appear infinitely long in the view.
A second try at fixing #3159.


git-svn-id: svn://localhost/ardour2/branches/3.0@7151 d708f5d6-7413-0410-9779-e7cbd77b26cf

gtk2_ardour/midi_region_view.cc

@@ -424,7 +424,7 @@ MidiRegionView::canvas_event(GdkEvent* ev)
 
 				drag_rect->property_y1() = midi_stream_view()->note_to_y(
 						midi_stream_view()->y_to_note(event_y));
-				drag_rect->property_x2() = event_x;
+				drag_rect->property_x2() = trackview.editor().frame_to_pixel(event_frame);
 				drag_rect->property_y2() = drag_rect->property_y1()
 				                         + floor(midi_stream_view()->note_height());
 				drag_rect->property_outline_what() = 0xFF;
@@ -565,13 +565,15 @@ MidiRegionView::create_note_at(double x, double y, double length)
 	assert(note <= 127.0);
 
 	// Start of note in frames relative to region start
-	nframes64_t start_frames = snap_frame_to_frame(trackview.editor().pixel_to_frame(x));
+	nframes64_t const start_frames = snap_frame_to_frame(trackview.editor().pixel_to_frame(x));
 	assert(start_frames >= 0);
 
 	// Snap length
 	length = frames_to_beats(
 			snap_frame_to_frame(start_frames + beats_to_frames(length)) - start_frames);
 
+	assert (length != 0);
+
 	const boost::shared_ptr<NoteType> new_note(new NoteType(0,
 			frames_to_beats(start_frames + _region->start()), length,
 			(uint8_t)note, 0x40));

gtk2_ardour/midi_region_view.h

@@ -281,7 +281,7 @@ class MidiRegionView : public RegionView
 	nframes64_t beats_to_frames(double beats) const;
 
 	/** Convert a timestamp in frames to beats (both relative to region start) */
-	double frames_to_beats(nframes64_t beats) const;
+	double frames_to_beats(nframes64_t) const;
 
 	void goto_previous_note ();
 	void goto_next_note ();