Prevent snap_frame_to_frame returning -ve offset from the region start (fixes #3925).

git-svn-id: svn://localhost/ardour2/branches/3.0@9396 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 22 insertions, 6 deletions

diff --git a/gtk2_ardour/midi_region_view.cc b/gtk2_ardour/midi_region_view.cc
index 9be06cb1b7..7b9bb4ae30 100644
--- a/gtk2_ardour/midi_region_view.cc
+++ b/gtk2_ardour/midi_region_view.cc
@@ -2238,14 +2238,30 @@ MidiRegionView::snap_pixel_to_frame(double x)
 	return frame - _region->position(); // convert back to region relative
 }
 
-framepos_t
-MidiRegionView::snap_frame_to_frame(framepos_t x)
+/** Snap a frame offset within our region using the current snap settings.
+ *  @param x Frame offset from this region's position.
+ *  @return Snapped frame offset from this region's position.
+ */
+frameoffset_t
+MidiRegionView::snap_frame_to_frame (frameoffset_t x)
 {
 	PublicEditor& editor = trackview.editor();
-	// x is region relative, convert it to global absolute frames
-	framepos_t frame = x + _region->position();
-	editor.snap_to(frame);
-	return frame - _region->position(); // convert back to region relative
+
+	/* x is region relative, convert it to global absolute frames */
+	framepos_t const session_frame = x + _region->position();
+
+	/* try a snap in either direction */
+	framepos_t frame = session_frame;
+	editor.snap_to (frame, 0);
+
+	/* if we went off the beginning of the region, snap forwards */
+	if (frame < _region->position ()) {
+		frame = session_frame;
+		editor.snap_to (frame, 1);
+	}
+
+	/* back to region relative */
+	return frame - _region->position();
 }
 
 double