O2D: Several (unrelated) improvements:...

core/cross/cairo/layer.h

Index: core/cross/cairo/layer.h
===================================================================
--- core/cross/cairo/layer.h	(revision 71191)
+++ core/cross/cairo/layer.h	(working copy)
@@ -50,6 +50,8 @@
  public:
   typedef SmartPointer<Layer> Ref;
 
+  virtual ~Layer();
+
   Pattern* pattern() const {
     return pattern_;
   }
@@ -82,6 +84,14 @@
     y_ = y;
   }
 
+  double z() const {
+    return z_;
+  }
+
+  void set_z(double z) {
+    z_ = z;
+  }
+
   double width() const {
     return width_;
   }
@@ -132,6 +142,9 @@
   // The y coordinate of the top-left corner of this layer.
   double y_;
 
+  // The z coordinate of the layer (used only to determine stacking order).
+  double z_;
+
   // The width of this layer.
   double width_;