diff --git a/libs/canvas/canvas/constraint_packer.h b/libs/canvas/canvas/constraint_packer.h
index b1f36cac48..c7507c5942 100644
--- a/libs/canvas/canvas/constraint_packer.h
+++ b/libs/canvas/canvas/constraint_packer.h
@@ -30,12 +30,13 @@ namespace ArdourCanvas
 
 class Rectangle;
 class ConstrainedItem;
+class BoxConstrainedItem;
 
 class LIBCANVAS_API ConstraintPacker : public Container
 {
 public:
-	ConstraintPacker (Canvas *);
-	ConstraintPacker (Item *);
+	ConstraintPacker (Canvas *, Orientation o = Horizontal);
+	ConstraintPacker (Item *, Orientation o = Horizontal);
 
 	void add (Item *);
 	void add_front (Item *);
@@ -72,6 +73,12 @@ public:
 
 	void non_const_preferred_size (Duple& mininum, Duple& natural);
 	virtual void update_constraints ();
+
+  private:
+	Orientation _orientation;
+	typedef std::list<BoxConstrainedItem*> BoxPackedItems;
+	BoxPackedItems vpacked;
+	BoxPackedItems hpacked;
 };
 
 }
diff --git a/libs/canvas/constraint_packer.cc b/libs/canvas/constraint_packer.cc
index bffa90d434..3a56b7dfc2 100644
--- a/libs/canvas/constraint_packer.cc
+++ b/libs/canvas/constraint_packer.cc
@@ -37,12 +37,13 @@ using std::vector;
 using kiwi::Constraint;
 using namespace kiwi;
 
-ConstraintPacker::ConstraintPacker (Canvas* canvas)
+ConstraintPacker::ConstraintPacker (Canvas* canvas, Orientation o)
 	: Container (canvas)
 	, width (X_("packer width"))
 	, height (X_("packer height"))
 	, in_alloc (false)
 	, _need_constraint_update (false)
+	, _orientation (o)
 {
 	set_fill (false);
 	set_outline (false);
@@ -52,12 +53,13 @@ ConstraintPacker::ConstraintPacker (Canvas* canvas)
 	_solver.addEditVariable (height, kiwi::strength::strong);
 }
 
-ConstraintPacker::ConstraintPacker (Item* parent)
+ConstraintPacker::ConstraintPacker (Item* parent, Orientation o)
 	: Container (parent)
 	, width (X_("packer width"))
 	, height (X_("packer height"))
 	, in_alloc (false)
 	, _need_constraint_update (false)
+	, _orientation (o)
 {
 	set_fill (false);
 	set_outline (false);