diff --git a/gtk2_ardour/editing_context.cc b/gtk2_ardour/editing_context.cc
index abe531ab0e..5a42ade4c6 100644
--- a/gtk2_ardour/editing_context.cc
+++ b/gtk2_ardour/editing_context.cc
@@ -104,6 +104,7 @@ EditingContext::EditingContext (std::string const & name)
 	, _draw_length (GridTypeNone)
 	, _draw_velocity (DRAW_VEL_AUTO)
 	, _draw_channel (DRAW_CHAN_AUTO)
+	, _timeline_origin (0.)
 	, _drags (new DragManager (this))
 	, _leftmost_sample (0)
 	, _playhead_cursor (nullptr)
diff --git a/gtk2_ardour/editing_context.h b/gtk2_ardour/editing_context.h
index b1b4484f3b..21917e6ac7 100644
--- a/gtk2_ardour/editing_context.h
+++ b/gtk2_ardour/editing_context.h
@@ -176,6 +176,8 @@ public:
 
 	samplecnt_t get_current_zoom () const { return samples_per_pixel; }
 
+	double timeline_origin() const { return _timeline_origin; }
+
 	/* NOTE: these functions assume that the "pixel" coordinate is
 	   in canvas coordinates. These coordinates already take into
 	   account any scrolling offsets.
@@ -191,13 +193,18 @@ public:
 		   is "before the start".
 		*/
 
-		if (pixel >= 0) {
-			return pixel * samples_per_pixel;
+		if (pixel >= _timeline_origin) {
+			return (pixel - _timeline_origin) * samples_per_pixel;
 		} else {
 			return 0;
 		}
 	}
 
+	/* It makes no sense to ever call these functions to convert to or from a
+	 * non-timeline relative pixel position, so they all assume that is
+	 * what they are being asked to do.
+	 */
+
 	samplepos_t pixel_to_sample (double pixel) const {
 		return pixel * samples_per_pixel;
 	}
@@ -207,13 +214,24 @@ public:
 	}
 
 	double sample_to_pixel_unrounded (samplepos_t sample) const {
-		return sample / (double) samples_per_pixel;
+		return (sample / (double) samples_per_pixel);
 	}
 
 	double time_to_pixel (Temporal::timepos_t const & pos) const;
 	double time_to_pixel_unrounded (Temporal::timepos_t const & pos) const;
+
 	double duration_to_pixels (Temporal::timecnt_t const & pos) const;
 	double duration_to_pixels_unrounded (Temporal::timecnt_t const & pos) const;
+	samplecnt_t pixel_duration_to_samples (double pixels) const {
+		return pixels * samples_per_pixel;
+	}
+
+	/* These two convert between timeline-relative x-axis pixel positions and
+	 * global canvas ones.
+	 */
+
+	double timeline_to_canvas (double p) const { return p + _timeline_origin; }
+	double canvas_to_timeline (double p) const { return p - _timeline_origin; }
 
 	/** computes the timeline position for an event whose coordinates
 	 * are in canvas units (pixels, scroll offset included). The time
@@ -390,6 +408,8 @@ public:
 	int _draw_velocity;
 	int _draw_channel;
 
+	double _timeline_origin;
+
 	ArdourWidgets::ArdourDropdown grid_type_selector;
 	void build_grid_type_menu ();