change Canvas heirarchy and constructors

Items no longer need a parent group (they require a Canvas pointer instead), so all constructors have been rationalized
and have two variants, one with a parent and one with a canvas.

All Items now inherit from Fill and Outline, to banish diagonal inheritance and virtual base classes and all that.

There were zero changes to the Ardour GUI arising from these changes.

48 files changed, 409 insertions, 178 deletions

diff --git a/libs/canvas/arc.cc b/libs/canvas/arc.cc
index 229097b85a..80141d4c66 100644
--- a/libs/canvas/arc.cc
+++ b/libs/canvas/arc.cc
@@ -31,15 +31,20 @@
 using namespace std;
 using namespace ArdourCanvas;
 
-Arc::Arc (Group* parent)
-	: Item (parent)
-	, Outline (parent)
-	, Fill (parent)
+Arc::Arc (Canvas* c)
+	: Item (c)
 	, _radius (0.0)
 	, _arc_degrees (0.0)
 	, _start_degrees (0.0)
 {
+}
 
+Arc::Arc (Group* g)
+	: Item (g)
+	, _radius (0.0)
+	, _arc_degrees (0.0)
+	, _start_degrees (0.0)
+{
 }
 
 void
diff --git a/libs/canvas/arrow.cc b/libs/canvas/arrow.cc
index 2e9557e179..86d4e33ca9 100644
--- a/libs/canvas/arrow.cc
+++ b/libs/canvas/arrow.cc
@@ -34,11 +34,21 @@ using namespace ArdourCanvas;
 /** Construct an Arrow.
  *  @param parent Parent canvas group.
  */
-Arrow::Arrow (Group* parent)
-	: Group (parent)
+Arrow::Arrow (Canvas* c)
+	: Group (c)
 {
-	assert (parent);
+	setup ();
+}
+
+Arrow::Arrow (Group* g)
+	: Group (g)
+{
+	setup ();
+}
 
+void
+Arrow::setup ()
+{
 	/* set up default arrow heads at each end */
 	for (int i = 0; i < 2; ++i) {
 		_heads[i].polygon = new Polygon (this);
@@ -53,6 +63,7 @@ Arrow::Arrow (Group* parent)
 	CANVAS_DEBUG_NAME (_line, "arrow line");
 }
 
+
 /** Set whether to show an arrow head at one end or other
  *  of the line.
  *  @param which 0 or 1 to specify the arrow head to set up.
diff --git a/libs/canvas/canvas/arc.h b/libs/canvas/canvas/arc.h
index 306a1acb7b..5eaa4a0ab9 100644
--- a/libs/canvas/canvas/arc.h
+++ b/libs/canvas/canvas/arc.h
@@ -26,10 +26,13 @@
 
 namespace ArdourCanvas {
 
-class LIBCANVAS_API Arc : virtual public Item, public Outline, public Fill
+class Canvas;
+
+class LIBCANVAS_API Arc : public Item
 {
 public:
-	Arc (Group *);
+	Arc (Canvas*);
+	Arc (Group*);
 
 	void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
 	void compute_bounding_box () const;
diff --git a/libs/canvas/canvas/arrow.h b/libs/canvas/canvas/arrow.h
index 9d9fe0d700..75c21da07c 100644
--- a/libs/canvas/canvas/arrow.h
+++ b/libs/canvas/canvas/arrow.h
@@ -31,6 +31,7 @@
 
 namespace ArdourCanvas {
 
+class Canvas;
 class Line;
 class Polygon;
 
@@ -48,7 +49,8 @@ class Polygon;
 class LIBCANVAS_API Arrow : public Group
 {
 public:
-	Arrow (Group *);
+	Arrow (Canvas*);
+	Arrow (Group*);
 
 	void set_show_head (int, bool);
 	void set_head_outward (int, bool);
@@ -68,6 +70,7 @@ public:
 
 private:
 	void setup_polygon (int);
+	void setup ();
 
 	/** Representation of a single arrow head */
 	struct Head {
diff --git a/libs/canvas/canvas/circle.h b/libs/canvas/canvas/circle.h
index ee17208a1f..1ca376a7a2 100644
--- a/libs/canvas/canvas/circle.h
+++ b/libs/canvas/canvas/circle.h
@@ -27,8 +27,9 @@ namespace ArdourCanvas {
 
 class LIBCANVAS_API Circle : public Arc
 {
-public:
-	Circle (Group *);
+  public:
+	Circle (Canvas*);
+	Circle (Group*);
 };
 	
 }
diff --git a/libs/canvas/canvas/curve.h b/libs/canvas/canvas/curve.h
index 234956763b..1bcab58e32 100644
--- a/libs/canvas/canvas/curve.h
+++ b/libs/canvas/canvas/curve.h
@@ -29,10 +29,11 @@ namespace ArdourCanvas {
 
 class XFadeCurve;
 
-class LIBCANVAS_API Curve : public PolyItem, public Fill, public InterpolatedCurve
+class LIBCANVAS_API Curve : public PolyItem, public InterpolatedCurve
 {
-public:
-    Curve (Group *);
+  public:
+    Curve (Canvas*);
+    Curve (Group*);
 
     enum CurveFill {
 	    None,
diff --git a/libs/canvas/canvas/fill.h b/libs/canvas/canvas/fill.h
index 56044de4bd..a4a36eb345 100644
--- a/libs/canvas/canvas/fill.h
+++ b/libs/canvas/canvas/fill.h
@@ -23,15 +23,20 @@
 #include <vector>
 #include <stdint.h>
 
+#include <boost/noncopyable.hpp>
+
 #include "canvas/visibility.h"
-#include "canvas/item.h"
+#include "canvas/types.h"
 
 namespace ArdourCanvas {
 
-class LIBCANVAS_API Fill : virtual public Item
+class Item;
+
+class LIBCANVAS_API Fill : public boost::noncopyable
 {
 public:
-	Fill (Group *);
+	Fill (Item& self);
+	virtual ~Fill() {}
 
 	virtual void set_fill_color (Color);
 	virtual void set_fill (bool);
@@ -51,7 +56,8 @@ public:
 protected:
 	void setup_fill_context (Cairo::RefPtr<Cairo::Context>) const;
         void setup_gradient_context (Cairo::RefPtr<Cairo::Context>, Rect const &, Duple const &) const;
-       	
+
+       	Item& _self;
 	Color _fill_color;
 	bool _fill;
 	bool _transparent;
diff --git a/libs/canvas/canvas/flag.h b/libs/canvas/canvas/flag.h
index 2a15f83921..2429e1775e 100644
--- a/libs/canvas/canvas/flag.h
+++ b/libs/canvas/canvas/flag.h
@@ -30,7 +30,8 @@ class Rectangle;
 class LIBCANVAS_API Flag : public Group
 {
 public:
-	Flag (Group *, Distance, Color, Color, Duple);
+	Flag (Canvas *, Distance, Color, Color, Duple);
+	Flag (Group*, Distance, Color, Color, Duple);
 
 	void set_text (std::string const &);
 	void set_height (Distance);
@@ -38,6 +39,8 @@ public:
         bool covers (Duple const &) const;
 	
 private:
+	void setup (Distance height, Duple position);
+
 	Color _outline_color;
 	Color _fill_color;
 	Text* _text;
diff --git a/libs/canvas/canvas/group.h b/libs/canvas/canvas/group.h
index a9150e7d09..6bfc40ba28 100644
--- a/libs/canvas/canvas/group.h
+++ b/libs/canvas/canvas/group.h
@@ -33,9 +33,10 @@ namespace ArdourCanvas {
 class LIBCANVAS_API Group : public Item
 {
 public:
-	explicit Group (Group *);
-	explicit Group (Group *, Duple);
-	~Group ();
+	Group (Canvas*);
+	Group (Group*);
+	Group (Group*, Duple const& positon);
+	virtual ~Group ();
 
 	void render (Rect const &, Cairo::RefPtr<Cairo::Context>) const;
 	virtual void compute_bounding_box () const;
@@ -60,14 +61,9 @@ public:
 
 	static int default_items_per_cell;
 
-protected:
-	
-	explicit Group (Canvas *);
-	
 private:
 	friend class ::OptimizingLookupTableTest;
 	
-	Group (Group const &);
 	void ensure_lut () const;
 	void invalidate_lut () const;
 	void clear_items (bool with_delete);
diff --git a/libs/canvas/canvas/image.h b/libs/canvas/canvas/image.h
index d54edd3827..fd86818c21 100644
--- a/libs/canvas/canvas/image.h
+++ b/libs/canvas/canvas/image.h
@@ -34,7 +34,8 @@ namespace ArdourCanvas {
 class LIBCANVAS_API Image : public Item
 {
 public:
-    Image (Group *, Cairo::Format, int width, int height);
+    Image (Canvas *, Cairo::Format, int width, int height);
+    Image (Group*, Cairo::Format, int width, int height);
     
     struct Data {
 	Data (uint8_t *d, int w, int h, int s, Cairo::Format fmt)
diff --git a/libs/canvas/canvas/item.h b/libs/canvas/canvas/item.h
index ff3095d1ff..bf752f66db 100644
--- a/libs/canvas/canvas/item.h
+++ b/libs/canvas/canvas/item.h
@@ -30,6 +30,8 @@
 
 #include "canvas/visibility.h"
 #include "canvas/types.h"
+#include "canvas/fill.h"
+#include "canvas/outline.h"
 
 namespace ArdourCanvas
 {
@@ -50,12 +52,12 @@ class ScrollGroup;
  *  and all except the `root group' have a pointer to their parent group.
  */
 	
-class LIBCANVAS_API Item
+class LIBCANVAS_API Item : public Fill, public Outline
 {
 public:
 	Item (Canvas *);
 	Item (Group *);
-	Item (Group *, Duple);
+	Item (Group *, Duple const& p);
 	virtual ~Item ();
 
         void redraw () const;
@@ -219,6 +221,8 @@ public:
         std::string whatami() const;
 
 protected:
+	friend class Fill;
+	friend class Outline;
 
         /** To be called at the beginning of any property change that
 	 *  may alter the bounding box of this item
diff --git a/libs/canvas/canvas/line.h b/libs/canvas/canvas/line.h
index 85b1d41e15..e8f57a00ba 100644
--- a/libs/canvas/canvas/line.h
+++ b/libs/canvas/canvas/line.h
@@ -27,10 +27,11 @@
 
 namespace ArdourCanvas {
 
-class LIBCANVAS_API Line : virtual public Item, public Outline
+class LIBCANVAS_API Line : public Item
 {
-public:
-	Line (Group *);
+  public:
+	Line (Canvas*);
+	Line (Group*);
 
 	void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
 	void compute_bounding_box () const;
diff --git a/libs/canvas/canvas/line_set.h b/libs/canvas/canvas/line_set.h
index 69f2b96907..38f97250ce 100644
--- a/libs/canvas/canvas/line_set.h
+++ b/libs/canvas/canvas/line_set.h
@@ -35,7 +35,8 @@ public:
 		Horizontal
 	};
 
-	LineSet (Group *, Orientation o = Vertical);
+	LineSet (Canvas*, Orientation o = Vertical);
+	LineSet (Group*, Orientation o = Vertical);
 
 	void compute_bounding_box () const;
 	void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
diff --git a/libs/canvas/canvas/outline.h b/libs/canvas/canvas/outline.h
index 972c07b11c..474501c8c7 100644
--- a/libs/canvas/canvas/outline.h
+++ b/libs/canvas/canvas/outline.h
@@ -22,17 +22,20 @@
 
 #include <stdint.h>
 
+#include <boost/noncopyable.hpp>
+
 #include "canvas/visibility.h"
 #include "canvas/types.h"
-#include "canvas/item.h"
 
 namespace ArdourCanvas {
 
-class LIBCANVAS_API Outline : virtual public Item
+class Item;
+
+class LIBCANVAS_API Outline : public boost::noncopyable
 {
 public:
-	Outline (Group *);
-	virtual ~Outline () {}
+	Outline (Item& self);
+	virtual ~Outline() {}
 
 	Color outline_color () const {
 		return _outline_color;
@@ -55,10 +58,11 @@ public:
 protected:
 
 	void setup_outline_context (Cairo::RefPtr<Cairo::Context>) const;
-	
-	Color _outline_color;
+
+	Item&    _self;
+	Color    _outline_color;
 	Distance _outline_width;
-	bool _outline;
+	bool     _outline;
 };
 
 }
diff --git a/libs/canvas/canvas/pixbuf.h b/libs/canvas/canvas/pixbuf.h
index 3974b560a9..eba73e57bf 100644
--- a/libs/canvas/canvas/pixbuf.h
+++ b/libs/canvas/canvas/pixbuf.h
@@ -34,7 +34,8 @@ namespace ArdourCanvas {
 class LIBCANVAS_API Pixbuf : public Item
 {
 public:
-	Pixbuf (Group *);
+	Pixbuf (Canvas*);
+	Pixbuf (Group*);
 
 	void render (Rect const &, Cairo::RefPtr<Cairo::Context>) const;
 	void compute_bounding_box () const;
diff --git a/libs/canvas/canvas/poly_item.h b/libs/canvas/canvas/poly_item.h
index 4745d24ab9..ab68204ff0 100644
--- a/libs/canvas/canvas/poly_item.h
+++ b/libs/canvas/canvas/poly_item.h
@@ -26,10 +26,11 @@
 
 namespace ArdourCanvas {
 
-class LIBCANVAS_API PolyItem : virtual public Item, public Outline
+class LIBCANVAS_API PolyItem : public Item
 {
 public:
-	PolyItem (Group *);
+	PolyItem (Canvas*);
+	PolyItem (Group*);
 
 	void compute_bounding_box () const;
 
diff --git a/libs/canvas/canvas/poly_line.h b/libs/canvas/canvas/poly_line.h
index 4f1b2b0157..5476711e97 100644
--- a/libs/canvas/canvas/poly_line.h
+++ b/libs/canvas/canvas/poly_line.h
@@ -29,7 +29,8 @@ namespace ArdourCanvas {
 class LIBCANVAS_API PolyLine : public PolyItem
 {
   public:
-	PolyLine (Group *);
+	PolyLine (Canvas*);
+	PolyLine (Group*);
 	
 	void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
 	
diff --git a/libs/canvas/canvas/polygon.h b/libs/canvas/canvas/polygon.h
index 917122a9a2..a3eed37cdc 100644
--- a/libs/canvas/canvas/polygon.h
+++ b/libs/canvas/canvas/polygon.h
@@ -27,10 +27,11 @@
 
 namespace ArdourCanvas {
 
-class LIBCANVAS_API Polygon : public PolyItem, public Fill
+class LIBCANVAS_API Polygon : public PolyItem
 {
 public:
-	Polygon (Group *);
+	Polygon (Canvas*);
+	Polygon (Group*);
         virtual ~Polygon();
 
 	void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
diff --git a/libs/canvas/canvas/rectangle.h b/libs/canvas/canvas/rectangle.h
index 91f23f9336..ff6eca3cd9 100644
--- a/libs/canvas/canvas/rectangle.h
+++ b/libs/canvas/canvas/rectangle.h
@@ -29,11 +29,13 @@
 namespace ArdourCanvas
 {
 
-class LIBCANVAS_API Rectangle : virtual public Item, public Outline, public Fill
+class LIBCANVAS_API Rectangle : public Item
 {
 public:
-	Rectangle (Group *);
-	Rectangle (Group *, Rect const &);
+	Rectangle (Canvas*);
+	Rectangle (Canvas*, Rect const &);
+	Rectangle (Group*);
+	Rectangle (Group*, Rect const &);
 	
 	void render (Rect const &, Cairo::RefPtr<Cairo::Context>) const;
 	void compute_bounding_box () const;
diff --git a/libs/canvas/canvas/ruler.h b/libs/canvas/canvas/ruler.h
index 72e38b56f9..633a1d569e 100644
--- a/libs/canvas/canvas/ruler.h
+++ b/libs/canvas/canvas/ruler.h
@@ -55,8 +55,10 @@ public:
 		virtual void get_marks (std::vector<Mark>&, double lower, double upper, int maxchars) const = 0;
 	};
 	
-	Ruler (Group *, const Metric& m);
-	Ruler (Group *, const Metric& m, Rect const&);
+	Ruler (Canvas*, const Metric& m);
+	Ruler (Canvas*, const Metric& m, Rect const&);
+	Ruler (Group*, const Metric& m);
+	Ruler (Group*, const Metric& m, Rect const&);
 	
 	void set_range (double lower, double upper);
 	void set_font_description (Pango::FontDescription);
diff --git a/libs/canvas/canvas/scroll_group.h b/libs/canvas/canvas/scroll_group.h
index 7652ae2e9b..552538eb21 100644
--- a/libs/canvas/canvas/scroll_group.h
+++ b/libs/canvas/canvas/scroll_group.h
@@ -31,8 +31,8 @@ class LIBCANVAS_API ScrollGroup : public Group
 		ScrollsHorizontally = 0x2
 	};
 	
-	explicit ScrollGroup (Group *, ScrollSensitivity);
-	explicit ScrollGroup (Group *, Duple, ScrollSensitivity);
+	ScrollGroup (Canvas*, ScrollSensitivity);
+	ScrollGroup (Group*, ScrollSensitivity);
 
 	void scroll_to (Duple const& d);
 	Duple scroll_offset() const { return _scroll_offset; }
diff --git a/libs/canvas/canvas/stateful_image.h b/libs/canvas/canvas/stateful_image.h
index 80687c5113..5952752e71 100644
--- a/libs/canvas/canvas/stateful_image.h
+++ b/libs/canvas/canvas/stateful_image.h
@@ -49,6 +49,7 @@ class StatefulImage : public Item
 
   public:
 
+    StatefulImage (Canvas*, const XMLNode&);
     StatefulImage (Group*, const XMLNode&);
     ~StatefulImage ();
 
diff --git a/libs/canvas/canvas/text.h b/libs/canvas/canvas/text.h
index 59d2007ceb..cc6d5c815d 100644
--- a/libs/canvas/canvas/text.h
+++ b/libs/canvas/canvas/text.h
@@ -31,7 +31,8 @@ namespace ArdourCanvas {
 class LIBCANVAS_API Text : public Item
 {
 public:
-	Text (Group *);
+	Text (Canvas*);
+	Text (Group*);
        ~Text();
 
 	void render (Rect const &, Cairo::RefPtr<Cairo::Context>) const;
diff --git a/libs/canvas/canvas/wave_view.h b/libs/canvas/canvas/wave_view.h
index 6327277ef4..674df969a5 100644
--- a/libs/canvas/canvas/wave_view.h
+++ b/libs/canvas/canvas/wave_view.h
@@ -45,7 +45,7 @@ class WaveViewTest;
 	
 namespace ArdourCanvas {
 
-class LIBCANVAS_API WaveView : virtual public Item, public Outline, public Fill
+class LIBCANVAS_API WaveView : public Item
 {
 public:
 
@@ -86,7 +86,8 @@ public:
     */
 
 
-	WaveView (Group *, boost::shared_ptr<ARDOUR::AudioRegion>);
+	WaveView (Canvas *, boost::shared_ptr<ARDOUR::AudioRegion>);
+	WaveView (Group*, boost::shared_ptr<ARDOUR::AudioRegion>);
        ~WaveView ();
 
 	void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
diff --git a/libs/canvas/canvas/widget.h b/libs/canvas/canvas/widget.h
index 18822ef185..842f336a51 100644
--- a/libs/canvas/canvas/widget.h
+++ b/libs/canvas/canvas/widget.h
@@ -28,10 +28,11 @@
 namespace ArdourCanvas
 {
 
-class LIBCANVAS_API Widget : virtual public Item
+class LIBCANVAS_API Widget : public Item
 {
 public:
-	Widget (Group *, CairoWidget&);
+	Widget (Canvas*, CairoWidget&);
+	Widget (Group*, CairoWidget&);
 	
 	void render (Rect const &, Cairo::RefPtr<Cairo::Context>) const;
 	void compute_bounding_box () const;
diff --git a/libs/canvas/canvas/xfade_curve.h b/libs/canvas/canvas/xfade_curve.h
index a1151817e2..d6a10d1f86 100644
--- a/libs/canvas/canvas/xfade_curve.h
+++ b/libs/canvas/canvas/xfade_curve.h
@@ -34,8 +34,10 @@ public:
 		End,
 	};
 
-	XFadeCurve (Group *);
-	XFadeCurve (Group *, XFadePosition);
+	XFadeCurve (Canvas *);
+	XFadeCurve (Canvas *, XFadePosition);
+	XFadeCurve (Group*);
+	XFadeCurve (Group*, XFadePosition);
 
 	void set_fade_position (XFadePosition xfp) { _xfadeposition = xfp; }
 	
diff --git a/libs/canvas/circle.cc b/libs/canvas/circle.cc
index 15a1679f74..3799bf60ac 100644
--- a/libs/canvas/circle.cc
+++ b/libs/canvas/circle.cc
@@ -20,10 +20,16 @@
 
 using namespace ArdourCanvas;
 
-Circle::Circle (Group* parent)
-	: Item (parent)
-	, Arc (parent)
+Circle::Circle (Canvas* c)
+	: Arc (c)
 {
 	set_arc (360.0);
 }
 
+Circle::Circle (Group* g)
+	: Arc (g)
+{
+	set_arc (360.0);
+}
+
+
diff --git a/libs/canvas/curve.cc b/libs/canvas/curve.cc
index ce7f163d10..547783ae08 100644
--- a/libs/canvas/curve.cc
+++ b/libs/canvas/curve.cc
@@ -27,10 +27,17 @@ using namespace ArdourCanvas;
 using std::min;
 using std::max;
 
-Curve::Curve (Group* parent)
-	: Item (parent)
-	, PolyItem (parent)
-	, Fill (parent)
+Curve::Curve (Canvas* c)
+	: PolyItem (c)
+	, n_samples (0)
+	, points_per_segment (16)
+	, curve_type (CatmullRomCentripetal)
+	, curve_fill (None)
+{
+}
+
+Curve::Curve (Group* g)
+	: PolyItem (g)
 	, n_samples (0)
 	, points_per_segment (16)
 	, curve_type (CatmullRomCentripetal)
diff --git a/libs/canvas/fill.cc b/libs/canvas/fill.cc
index 41c616a0f9..42bcbfff3c 100644
--- a/libs/canvas/fill.cc
+++ b/libs/canvas/fill.cc
@@ -17,31 +17,34 @@
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
+#include <cairomm/cairomm.h>
+
 #include "ardour/utils.h"
 
 #include "pbd/compose.h"
 #include "pbd/convert.h"
 
 #include "canvas/fill.h"
+#include "canvas/item.h"
+#include "canvas/types.h"
 #include "canvas/utils.h"
 
 using namespace std;
 using namespace ArdourCanvas;
 
-Fill::Fill (Group* parent)
-	: Item (parent)
+Fill::Fill (Item& self)
+	: _self (self)
 	, _fill_color (0x000000ff)
 	, _fill (true)
 	, _transparent (false)
 {
-
 }
 
 void
 Fill::set_fill_color (Color color)
 {
 	if (_fill_color != color) {
-		begin_visual_change ();
+		_self.begin_visual_change ();
 		_fill_color = color;
 
 		double r, g, b, a;
@@ -52,7 +55,7 @@ Fill::set_fill_color (Color color)
 			_transparent = false;
 		}
 
-		end_visual_change ();
+		_self.end_visual_change ();
 	}
 }
 
@@ -60,9 +63,9 @@ void
 Fill::set_fill (bool fill)
 {
 	if (_fill != fill) {
-		begin_visual_change ();
+		_self.begin_visual_change ();
 		_fill = fill;
-		end_visual_change ();
+		_self.end_visual_change ();
 	}
 }
 
@@ -95,7 +98,7 @@ Fill::setup_gradient_context (Cairo::RefPtr<Cairo::Context> context, Rect const
 void
 Fill::set_gradient (StopList const & stops, bool vertical)
 {
-	begin_visual_change ();
+	_self.begin_visual_change ();
 
 	if (stops.empty()) {
 		_stops.clear ();
@@ -104,5 +107,5 @@ Fill::set_gradient (StopList const & stops, bool vertical)
 		_vertical_gradient = vertical;
 	}
 
-	end_visual_change ();
+	_self.end_visual_change ();
 }
diff --git a/libs/canvas/flag.cc b/libs/canvas/flag.cc
index e72aece1f5..f5379791df 100644
--- a/libs/canvas/flag.cc
+++ b/libs/canvas/flag.cc
@@ -25,11 +25,25 @@
 using namespace std;
 using namespace ArdourCanvas;
 
-Flag::Flag (Group* parent, Distance height, Color outline_color, Color fill_color, Duple position)
-	: Group (parent)
+Flag::Flag (Canvas* canvas, Distance height, Color outline_color, Color fill_color, Duple position)
+	: Group (canvas)
 	, _outline_color (outline_color)
 	, _fill_color (fill_color)
 {
+	setup (height, position);
+}
+
+Flag::Flag (Group* group, Distance height, Color outline_color, Color fill_color, Duple position)
+	: Group (group)
+	, _outline_color (outline_color)
+	, _fill_color (fill_color)
+{
+	setup (height, position);
+}
+
+void 
+Flag::setup (Distance height, Duple position)
+{
 	_text = new Text (this);
 	_text->set_alignment (Pango::ALIGN_CENTER);
 	_text->set_color (_outline_color);
diff --git a/libs/canvas/group.cc b/libs/canvas/group.cc
index 2316e4c997..d63b217396 100644
--- a/libs/canvas/group.cc
+++ b/libs/canvas/group.cc
@@ -39,21 +39,18 @@ Group::Group (Canvas* canvas)
 	: Item (canvas)
 	, _lut (0)
 {
-	
 }
 
-Group::Group (Group* parent)
-	: Item (parent)
+Group::Group (Group* group)
+	: Item (group)
 	, _lut (0)
 {
-	
 }
 
-Group::Group (Group* parent, Duple position)
-	: Item (parent, position)
+Group::Group (Group* group, Duple const& p)
+	: Item (group, p)
 	, _lut (0)
 {
-	
 }
 
 Group::~Group ()
@@ -197,10 +194,9 @@ Group::add (Item* i)
 	/* XXX should really notify canvas about this */
 
 	_items.push_back (i);
+	i->reparent (this);
 	invalidate_lut ();
 	_bounding_box_dirty = true;
-
-	
 }
 
 void
diff --git a/libs/canvas/image.cc b/libs/canvas/image.cc
index 32e453dc30..5ab280cbbc 100644
--- a/libs/canvas/image.cc
+++ b/libs/canvas/image.cc
@@ -22,6 +22,16 @@
 
 using namespace ArdourCanvas;
 
+Image::Image (Canvas* canvas, Cairo::Format fmt, int width, int height)
+	: Item (canvas)
+	, _format (fmt)
+	, _width (width)
+	, _height (height)
+	, _need_render (false)
+{
+	DataReady.connect (data_connections, MISSING_INVALIDATOR, boost::bind (&Image::accept_data, this), gui_context());
+}
+
 Image::Image (Group* group, Cairo::Format fmt, int width, int height)
 	: Item (group)
 	, _format (fmt)
diff --git a/libs/canvas/item.cc b/libs/canvas/item.cc
index 2bca2feac2..53dca5d976 100644
--- a/libs/canvas/item.cc
+++ b/libs/canvas/item.cc
@@ -34,41 +34,53 @@ using namespace PBD;
 using namespace ArdourCanvas;
 
 Item::Item (Canvas* canvas)
-	: _canvas (canvas)
+	: Fill (*this)
+	, Outline (*this)
+	,  _canvas (canvas)
 	, _parent (0)
+	, _visible (true)
+	, _bounding_box_dirty (true)
+	, _ignore_events (false)
 {
-	init ();
-}
+	DEBUG_TRACE (DEBUG::CanvasItems, string_compose ("new canvas item %1\n", this));
+}	
 
 Item::Item (Group* parent)
-	: _canvas (parent->canvas ())
+	: Fill (*this)
+	, Outline (*this)
+	,  _canvas (parent->canvas())
 	, _parent (parent)
+	, _visible (true)
+	, _bounding_box_dirty (true)
+	, _ignore_events (false)
 {
-	init ();
-}
+	DEBUG_TRACE (DEBUG::CanvasItems, string_compose ("new canvas item %1\n", this));
+
+	if (parent) {
+		_parent->add (this);
+	}
+
+	find_scroll_parent ();
+}	
 
-Item::Item (Group* parent, Duple position)
-	: _canvas (parent->canvas())
+Item::Item (Group* parent, Duple const& p)
+	: Fill (*this)
+	, Outline (*this)
+	,  _canvas (parent->canvas())
 	, _parent (parent)
-	, _position (position)
+	, _position (p)
+	, _visible (true)
+	, _bounding_box_dirty (true)
+	, _ignore_events (false)
 {
-	init ();
-}
+	DEBUG_TRACE (DEBUG::CanvasItems, string_compose ("new canvas item %1\n", this));
 
-void
-Item::init ()
-{
-	_visible = true;
-	_bounding_box_dirty = true;
-	_ignore_events = false;
-	
-	if (_parent) {
+	if (parent) {
 		_parent->add (this);
 	}
 
 	find_scroll_parent ();
 
-	DEBUG_TRACE (DEBUG::CanvasItems, string_compose ("new canvas item %1\n", this));
 }	
 
 Item::~Item ()
@@ -98,7 +110,7 @@ Item::window_origin () const
 	if (_parent) {
 		return _parent->item_to_window (_position);
 	} else {
-		return _parent->item_to_window (Duple (0,0));
+		return _position;
 	}
 }
 
@@ -254,22 +266,25 @@ Item::set_y_position (Coord y)
 void
 Item::raise_to_top ()
 {
-	assert (_parent);
-	_parent->raise_child_to_top (this);
+	if (_parent) {
+		_parent->raise_child_to_top (this);
+	}
 }
 
 void
 Item::raise (int levels)
 {
-	assert (_parent);
-	_parent->raise_child (this, levels);
+	if (_parent) {
+		_parent->raise_child (this, levels);
+	}
 }
 
 void
 Item::lower_to_bottom ()
 {
-	assert (_parent);
-	_parent->lower_child_to_bottom (this);
+	if (_parent) {
+		_parent->lower_child_to_bottom (this);
+	}
 }
 
 void
@@ -318,7 +333,11 @@ Item::unparent ()
 void
 Item::reparent (Group* new_parent)
 {
-	assert (_canvas == _parent->canvas());
+	if (new_parent == _parent) {
+		return;
+	}
+
+	assert (_canvas == new_parent->canvas());
 
 	if (_parent) {
 		_parent->remove (this);
@@ -370,10 +389,16 @@ Item::common_ancestor_within (uint32_t limit, const Item& other) const
 
 	while (d1 != d2) {
 		if (d1 > d2) {
+			if (!i1) {
+				return false;
+			}
 			i1 = i1->parent();
 			d1--;
 			limit--;
 		} else {
+			if (!i2) {
+				return false;
+			}
 			i2 = i2->parent();
 			d2--;
 			limit--;
@@ -416,9 +441,15 @@ Item::closest_ancestor_with (const Item& other) const
 
 	while (d1 != d2) {
 		if (d1 > d2) {
+			if (!i1) {
+				return 0;
+			}
 			i1 = i1->parent();
 			d1--;
 		} else {
+			if (!i2) {
+				return 0;
+			}
 			i2 = i2->parent();
 			d2--;
 		}
diff --git a/libs/canvas/line.cc b/libs/canvas/line.cc
index 0528a44c38..844f05522d 100644
--- a/libs/canvas/line.cc
+++ b/libs/canvas/line.cc
@@ -29,11 +29,14 @@
 using namespace std;
 using namespace ArdourCanvas;
 
-Line::Line (Group* parent)
-	: Item (parent)
-	, Outline (parent)
+Line::Line (Canvas* c)
+	: Item (c)
 {
+}
 
+Line::Line (Group* group)
+	: Item (group)
+{
 }
 
 void
diff --git a/libs/canvas/line_set.cc b/libs/canvas/line_set.cc
index 0cc4690f76..3eacadaba2 100644
--- a/libs/canvas/line_set.cc
+++ b/libs/canvas/line_set.cc
@@ -30,8 +30,16 @@ public:
 	}
 };
 
-LineSet::LineSet (Group* parent, Orientation o)
-	: Item (parent)
+LineSet::LineSet (Canvas* c, Orientation o)
+	: Item (c)
+	, _extent (0)
+	, _orientation (o)
+{
+
+}
+
+LineSet::LineSet (Group* group, Orientation o)
+	: Item (group)
 	, _extent (0)
 	, _orientation (o)
 {
diff --git a/libs/canvas/outline.cc b/libs/canvas/outline.cc
index be8b924df2..9416859e59 100644
--- a/libs/canvas/outline.cc
+++ b/libs/canvas/outline.cc
@@ -23,28 +23,29 @@
 #include "pbd/convert.h"
 
 #include "ardour/utils.h"
+
+#include "canvas/item.h"
 #include "canvas/outline.h"
 #include "canvas/utils.h"
 #include "canvas/debug.h"
 
 using namespace ArdourCanvas;
 
-Outline::Outline (Group* parent)
-	: Item (parent)
+Outline::Outline (Item& self)
+	: _self (self)
 	, _outline_color (0x000000ff)
 	, _outline_width (1.0)
 	, _outline (true)
 {
-
 }
 
 void
 Outline::set_outline_color (Color color)
 {
 	if (color != _outline_color) {
-		begin_visual_change ();
+		_self.begin_visual_change ();
 		_outline_color = color;
-		end_visual_change ();
+		_self.end_visual_change ();
 	}
 }
 
@@ -52,10 +53,10 @@ void
 Outline::set_outline_width (Distance width)
 {
 	if (width != _outline_width) {
-		begin_change ();
+		_self.begin_change ();
 		_outline_width = width;
-		_bounding_box_dirty = true;
-		end_change ();
+		_self._bounding_box_dirty = true;
+		_self.end_change ();
 	}
 }
 
@@ -63,10 +64,10 @@ void
 Outline::set_outline (bool outline)
 {
 	if (outline != _outline) {
-		begin_change ();
+		_self.begin_change ();
 		_outline = outline;
-		_bounding_box_dirty = true;
-		end_change ();
+		_self._bounding_box_dirty = true;
+		_self.end_change ();
 	}
 }
 
diff --git a/libs/canvas/pixbuf.cc b/libs/canvas/pixbuf.cc
index 62d9357c61..82eb916397 100644
--- a/libs/canvas/pixbuf.cc
+++ b/libs/canvas/pixbuf.cc
@@ -25,10 +25,14 @@
 using namespace std;
 using namespace ArdourCanvas;
 
+Pixbuf::Pixbuf (Canvas* c)
+	: Item (c)
+{
+}
+
 Pixbuf::Pixbuf (Group* g)
 	: Item (g)
 {
-	
 }
 
 void
diff --git a/libs/canvas/poly_item.cc b/libs/canvas/poly_item.cc
index 0d3369f70b..618983db97 100644
--- a/libs/canvas/poly_item.cc
+++ b/libs/canvas/poly_item.cc
@@ -27,11 +27,14 @@
 using namespace std;
 using namespace ArdourCanvas;
 
-PolyItem::PolyItem (Group* parent)
-	: Item (parent)
-	, Outline (parent)
+PolyItem::PolyItem (Canvas* c)
+	: Item (c)
 {
+}
 
+PolyItem::PolyItem (Group* g)
+	: Item (g)
+{
 }
 
 void
diff --git a/libs/canvas/poly_line.cc b/libs/canvas/poly_line.cc
index 08d611117f..bade7d855e 100644
--- a/libs/canvas/poly_line.cc
+++ b/libs/canvas/poly_line.cc
@@ -25,12 +25,16 @@
 
 using namespace ArdourCanvas;
 
-PolyLine::PolyLine (Group* parent)
-	: Item (parent)
-	, PolyItem (parent)
+PolyLine::PolyLine (Canvas* c)
+	: PolyItem (c)
 	, _threshold (1.0)
 {
+}
 
+PolyLine::PolyLine (Group* g)
+	: PolyItem (g)
+	, _threshold (1.0)
+{
 }
 
 void
diff --git a/libs/canvas/polygon.cc b/libs/canvas/polygon.cc
index 56a85c2f47..d84bca4af6 100644
--- a/libs/canvas/polygon.cc
+++ b/libs/canvas/polygon.cc
@@ -21,15 +21,20 @@
 
 using namespace ArdourCanvas;
 
-Polygon::Polygon (Group* parent)
-	: Item (parent)
-	, PolyItem (parent)
-	, Fill (parent)
+Polygon::Polygon (Canvas* c)
+	: PolyItem (c)
 	, multiple (0)
 	, constant (0)
 	, cached_size (0)
 {
+}
 
+Polygon::Polygon (Group* g)
+	: PolyItem (g)
+	, multiple (0)
+	, constant (0)
+	, cached_size (0)
+{
 }
 
 Polygon::~Polygon ()
diff --git a/libs/canvas/rectangle.cc b/libs/canvas/rectangle.cc
index cea5567dcc..ac05003693 100644
--- a/libs/canvas/rectangle.cc
+++ b/libs/canvas/rectangle.cc
@@ -30,22 +30,30 @@
 using namespace std;
 using namespace ArdourCanvas;
 
-Rectangle::Rectangle (Group* parent)
-	: Item (parent)
-	, Outline (parent)
-	, Fill (parent)
+Rectangle::Rectangle (Canvas* c)
+	: Item (c)
 	, _outline_what ((What) (LEFT | RIGHT | TOP | BOTTOM))
 {
 }
 
-Rectangle::Rectangle (Group* parent, Rect const & rect)
-	: Item (parent)
-	, Outline (parent)
-	, Fill (parent)
+Rectangle::Rectangle (Canvas* c, Rect const & rect)
+	: Item (c)
+	, _rect (rect)
+	, _outline_what ((What) (LEFT | RIGHT | TOP | BOTTOM))
+{
+}
+
+Rectangle::Rectangle (Group* g)
+	: Item (g)
+	, _outline_what ((What) (LEFT | RIGHT | TOP | BOTTOM))
+{
+}
+
+Rectangle::Rectangle (Group* g, Rect const & rect)
+	: Item (g)
 	, _rect (rect)
 	, _outline_what ((What) (LEFT | RIGHT | TOP | BOTTOM))
 {
-	
 }
 
 void
diff --git a/libs/canvas/ruler.cc b/libs/canvas/ruler.cc
index aa48b52e92..1e7a731899 100644
--- a/libs/canvas/ruler.cc
+++ b/libs/canvas/ruler.cc
@@ -31,9 +31,8 @@
 using namespace std;
 using namespace ArdourCanvas;
 
-Ruler::Ruler (Group *p, const Metric& m)
-	: Item (p)
-	, Rectangle (p)
+Ruler::Ruler (Canvas* c, const Metric& m)
+	: Rectangle (c)
 	, _metric (m)
 	, _lower (0)
 	, _upper (0)
@@ -41,9 +40,26 @@ Ruler::Ruler (Group *p, const Metric& m)
 {
 }
 
-Ruler::Ruler (Group *p, const Metric& m, Rect const& r)
-	: Item (p)
-	, Rectangle (p, r)
+Ruler::Ruler (Canvas* c, const Metric& m, Rect const& r)
+	: Rectangle (c, r)
+	, _metric (m)
+	, _lower (0)
+	, _upper (0)
+	, _need_marks (true)
+{
+}
+
+Ruler::Ruler (Group* g, const Metric& m)
+	: Rectangle (g)
+	, _metric (m)
+	, _lower (0)
+	, _upper (0)
+	, _need_marks (true)
+{
+}
+
+Ruler::Ruler (Group* g, const Metric& m, Rect const& r)
+	: Rectangle (g, r)
 	, _metric (m)
 	, _lower (0)
 	, _upper (0)
diff --git a/libs/canvas/scroll_group.cc b/libs/canvas/scroll_group.cc
index 0ce612018a..d78caf4ed0 100644
--- a/libs/canvas/scroll_group.cc
+++ b/libs/canvas/scroll_group.cc
@@ -27,15 +27,15 @@
 using namespace std;
 using namespace ArdourCanvas;
 
-ScrollGroup::ScrollGroup (Group* parent, ScrollSensitivity s)
-	: Group (parent)
+ScrollGroup::ScrollGroup (Canvas* c, ScrollSensitivity s)
+	: Group (c)
 	, _scroll_sensitivity (s)	
 {
 }
 
-ScrollGroup::ScrollGroup (Group* parent, Duple position, ScrollSensitivity s)
-	: Group (parent, position)
-	, _scroll_sensitivity (s)
+ScrollGroup::ScrollGroup (Group* g, ScrollSensitivity s)
+	: Group (g)
+	, _scroll_sensitivity (s)	
 {
 }
 
diff --git a/libs/canvas/stateful_image.cc b/libs/canvas/stateful_image.cc
index f2b8e71744..b372ade7b8 100644
--- a/libs/canvas/stateful_image.cc
+++ b/libs/canvas/stateful_image.cc
@@ -19,8 +19,8 @@ using PBD::error;
 PBD::Searchpath StatefulImage::_image_search_path;
 StatefulImage::ImageCache StatefulImage::_image_cache;
 
-StatefulImage::StatefulImage (Group* group, const XMLNode& node)
-	: Item (group)
+StatefulImage::StatefulImage (Canvas* c, const XMLNode& node)
+	: Item (c)
 	, _state (0)
 	, _font (0)
 	, _text_x (0)
diff --git a/libs/canvas/text.cc b/libs/canvas/text.cc
index 438413080a..12fe3eb6cb 100644
--- a/libs/canvas/text.cc
+++ b/libs/canvas/text.cc
@@ -31,8 +31,8 @@
 using namespace std;
 using namespace ArdourCanvas;
 
-Text::Text (Group* parent)
-	: Item (parent)
+Text::Text (Canvas* c)
+	: Item (c)
 	, _color (0x000000ff)
 	, _font_description (0)
 	, _alignment (Pango::ALIGN_LEFT)
@@ -41,7 +41,18 @@ Text::Text (Group* parent)
 	, _need_redraw (false)
 	, _clamped_width (COORD_MAX)
 {
+}
 
+Text::Text (Group* g)
+	: Item (g)
+	, _color (0x000000ff)
+	, _font_description (0)
+	, _alignment (Pango::ALIGN_LEFT)
+	, _width (0)
+	, _height (0)
+	, _need_redraw (false)
+	, _clamped_width (COORD_MAX)
+{
 }
 
 Text::~Text ()
diff --git a/libs/canvas/wave_view.cc b/libs/canvas/wave_view.cc
index 6f626e7010..2d24e38969 100644
--- a/libs/canvas/wave_view.cc
+++ b/libs/canvas/wave_view.cc
@@ -53,10 +53,31 @@ double WaveView::_clip_level = 0.98853;
 PBD::Signal0<void> WaveView::VisualPropertiesChanged;
 PBD::Signal0<void> WaveView::ClipLevelChanged;
 
-WaveView::WaveView (Group* parent, boost::shared_ptr<ARDOUR::AudioRegion> region)
-	: Item (parent)
-	, Outline (parent)
-	, Fill (parent)
+WaveView::WaveView (Canvas* c, boost::shared_ptr<ARDOUR::AudioRegion> region)
+	: Item (c)
+	, _region (region)
+	, _channel (0)
+	, _samples_per_pixel (0)
+	, _height (64)
+	, _show_zero (false)
+	, _zero_color (0xff0000ff)
+	, _clip_color (0xff0000ff)
+	, _logscaled (_global_logscaled)
+	, _shape (_global_shape)
+	, _gradient_depth (_global_gradient_depth)
+	, _shape_independent (false)
+	, _logscaled_independent (false)
+	, _gradient_depth_independent (false)
+	, _amplitude_above_axis (1.0)
+	, _region_amplitude (_region->scale_amplitude ())
+	, _region_start (region->start())
+{
+	VisualPropertiesChanged.connect_same_thread (invalidation_connection, boost::bind (&WaveView::handle_visual_property_change, this));
+	ClipLevelChanged.connect_same_thread (invalidation_connection, boost::bind (&WaveView::handle_clip_level_change, this));
+}
+
+WaveView::WaveView (Group* g, boost::shared_ptr<ARDOUR::AudioRegion> region)
+	: Item (g)
 	, _region (region)
 	, _channel (0)
 	, _samples_per_pixel (0)
diff --git a/libs/canvas/widget.cc b/libs/canvas/widget.cc
index 9206213dbd..0961382128 100644
--- a/libs/canvas/widget.cc
+++ b/libs/canvas/widget.cc
@@ -29,8 +29,15 @@
 using namespace std;
 using namespace ArdourCanvas;
 
-Widget::Widget (Group* parent, CairoWidget& w)
-	: Item (parent)
+Widget::Widget (Canvas* c, CairoWidget& w)
+	: Item (c)
+	, _widget (w)
+{
+	Event.connect (sigc::mem_fun (*this, &Widget::event_proxy));
+}
+
+Widget::Widget (Group* g, CairoWidget& w)
+	: Item (g)
 	, _widget (w)
 {
 	Event.connect (sigc::mem_fun (*this, &Widget::event_proxy));
@@ -39,6 +46,7 @@ Widget::Widget (Group* parent, CairoWidget& w)
 bool
 Widget::event_proxy (GdkEvent* ev)
 {
+	/* XXX need to translate coordinate into widget's own coordinate space */
 	return _widget.event (ev);
 }
 
diff --git a/libs/canvas/xfade_curve.cc b/libs/canvas/xfade_curve.cc
index 5e68dbbb82..9a854cd54e 100644
--- a/libs/canvas/xfade_curve.cc
+++ b/libs/canvas/xfade_curve.cc
@@ -30,8 +30,8 @@ using namespace ArdourCanvas;
 using std::min;
 using std::max;
 
-XFadeCurve::XFadeCurve (Group* parent)
-	: Item (parent)
+XFadeCurve::XFadeCurve (Canvas* c)
+	: Item (c)
 	, points_per_segment (32)
 	, _xfadeposition (Start)
 	, _outline_color (0x000000ff)
@@ -39,8 +39,26 @@ XFadeCurve::XFadeCurve (Group* parent)
 {
 }
 
-XFadeCurve::XFadeCurve (Group* parent, XFadePosition pos)
-	: Item (parent)
+XFadeCurve::XFadeCurve (Canvas* c, XFadePosition pos)
+	: Item (c)
+	, points_per_segment (32)
+	, _xfadeposition (pos)
+	, _outline_color (0x000000ff)
+	, _fill_color (0x22448880)
+{
+}
+
+XFadeCurve::XFadeCurve (Group* g)
+	: Item (g)
+	, points_per_segment (32)
+	, _xfadeposition (Start)
+	, _outline_color (0x000000ff)
+	, _fill_color (0x22448880)
+{
+}
+
+XFadeCurve::XFadeCurve (Group* g, XFadePosition pos)
+	: Item (g)
 	, points_per_segment (32)
 	, _xfadeposition (pos)
 	, _outline_color (0x000000ff)