Use automation line's frame of reference for y position.

- removes the need for 'pixel hunting' wrt NAME_HIGHLIGHT_SIZE.
	- new control points generated by clicking on a line are placed
	  where the verbose canvas cursor says they are.

gtk2_ardour/audio_region_view.cc

@@ -1309,18 +1309,32 @@ AudioRegionView::add_gain_point_event (ArdourCanvas::Item *item, GdkEvent *ev, b
 		return;
 	}
 
-	double x, y;
+	uint32_t before_p, after_p;
+	double mx = ev->button.x;
+	double my = ev->button.y;
+
+	item->canvas_to_item (mx, my);
+
+	framecnt_t const frame_within_region = (framecnt_t) floor (mx * samples_per_pixel);
+
+	if (!gain_line->control_points_adjacent (frame_within_region, before_p, after_p)) {
+		/* no adjacent points */
+		return;
+	}
+
+	/*y is in item frame */
+	double const bx = gain_line->nth (before_p)->get_x();
+	double const ax = gain_line->nth (after_p)->get_x();
+	double const click_ratio = (ax - mx) / (ax - bx);
+
+	double y = ((gain_line->nth (before_p)->get_y() * click_ratio) + (gain_line->nth (after_p)->get_y() * (1 - click_ratio)));
 
 	/* don't create points that can't be seen */
 
 	update_envelope_visibility ();
 
-	x = ev->button.x;
-	y = ev->button.y;
-
-	item->canvas_to_item (x, y);
 	framepos_t rpos = region ()->position ();
-	framepos_t fx = trackview.editor().pixel_to_sample (x) + rpos;
+	framepos_t fx = trackview.editor().pixel_to_sample (mx) + rpos;
 	trackview.editor ().snap_to_with_modifier (fx, ev);
 	fx -= rpos;
 
@@ -1330,11 +1344,11 @@ AudioRegionView::add_gain_point_event (ArdourCanvas::Item *item, GdkEvent *ev, b
 
 	/* compute vertical fractional position */
 
-	y = 1.0 - (y / (_height - NAME_HIGHLIGHT_SIZE));
+	y = 1.0 - (y / (gain_line->height()));
 
 	/* map using gain line */
 
-	gain_line->view_to_model_coord (x, y);
+	gain_line->view_to_model_coord (mx, y);
 
 	/* XXX STATEFUL: can't convert to stateful diff until we
 	   can represent automation data with it.

gtk2_ardour/automation_time_axis.cc

@@ -628,11 +628,11 @@ AutomationTimeAxisView::add_automation_event (GdkEvent* event, framepos_t when,
 
 	double x = 0;
 
-	_canvas_display->canvas_to_item (x, y);
+	_line->grab_item().canvas_to_item (x, y);
 
 	/* compute vertical fractional position */
 
-	y = 1.0 - (y / height);
+	y = 1.0 - (y / _line->height());
 
 	/* map using line */
 

gtk2_ardour/editor_drag.cc

@@ -4319,7 +4319,7 @@ LineDrag::start_grab (GdkEvent* event, Gdk::Cursor* /*cursor*/)
 	double mx = event->button.x;
 	double my = event->button.y;
 
-	_line->parent_group().canvas_to_item (mx, my);
+	_line->grab_item().canvas_to_item (mx, my);
 
 	framecnt_t const frame_within_region = (framecnt_t) floor (mx * _editor->samples_per_pixel);
 
@@ -4330,7 +4330,7 @@ LineDrag::start_grab (GdkEvent* event, Gdk::Cursor* /*cursor*/)
 
 	Drag::start_grab (event, _editor->cursors()->fader);
 
-	/* store grab start in parent frame */
+	/* store grab start in item frame */
 	double const bx = _line->nth (_before)->get_x();
 	double const ax = _line->nth (_after)->get_x();
 	double const click_ratio = (ax - mx) / (ax - bx);
@@ -4391,14 +4391,19 @@ LineDrag::finished (GdkEvent* event, bool movement_occured)
 		AutomationTimeAxisView* atv;
 
 		if ((atv = dynamic_cast<AutomationTimeAxisView*>(_editor->clicked_axisview)) != 0) {
-			framepos_t where = _editor->canvas_event_sample (event, 0, 0);
+			framepos_t where = grab_frame ();
 
-			atv->add_automation_event (event, where, event->button.y, false);
+			double cx = 0;
+			double cy = _fixed_grab_y;
+
+			_line->grab_item().item_to_canvas (cx, cy);
+
+			atv->add_automation_event (event, where, cy, false);
 		} else if (dynamic_cast<AudioTimeAxisView*>(_editor->clicked_axisview) != 0) {
 			AudioRegionView* arv;
 
 			if ((arv = dynamic_cast<AudioRegionView*>(_editor->clicked_regionview)) != 0) {
-				arv->add_gain_point_event (arv->get_canvas_group (), event, false);
+				arv->add_gain_point_event (&arv->get_gain_line()->grab_item(), event, false);
 			}
 		}
 	}