[hyena/canvas] [Hyena.Gui] Avoid generating tons Rects in CanvasItem

[Gabriel Burt <gburt src gnome org>]

commit bcf7df422177bb63a3e5aca75f56d24a69b42223
Author: Gabriel Burt <gabriel burt gmail com>
Date:   Tue Oct 26 17:45:04 2010 -0500

    [Hyena.Gui] Avoid generating tons Rects in CanvasItem

 Hyena.Gui/Hyena.Gui.Canvas/CanvasItem.cs |   38 +++++++++++++++++++-----------
 1 files changed, 24 insertions(+), 14 deletions(-)
---
diff --git a/Hyena.Gui/Hyena.Gui.Canvas/CanvasItem.cs b/Hyena.Gui/Hyena.Gui.Canvas/CanvasItem.cs
index beaf0ff..6758385 100644
--- a/Hyena.Gui/Hyena.Gui.Canvas/CanvasItem.cs
+++ b/Hyena.Gui/Hyena.Gui.Canvas/CanvasItem.cs
@@ -193,11 +193,9 @@ namespace Hyena.Gui.Canvas
         public Brush Background { get; set; }
 
         public Thickness Padding { get; set; }
-        public Thickness Margin { get; set; }
         public MarginStyle MarginStyle { get; set; }
 
         public Size DesiredSize { get; protected set; }
-        public Rect Allocation { get; set; }
         // FIXME need this?
         public Rect VirtualAllocation { get; set; }
 
@@ -225,29 +223,41 @@ namespace Hyena.Gui.Canvas
         public double Width { get; set; }
         public double Height { get; set; }
 
-        public Rect ContentAllocation {
-            get {
-                return new Rect (
+        private Thickness margin;
+        public Thickness Margin {
+            get { return margin; }
+            set {
+                margin = value;
+                // Refresh the ContentAllocation etc values
+                Allocation = allocation;
+            }
+        }
+
+        private Rect allocation;
+        public Rect Allocation {
+            get { return allocation; }
+            set {
+                allocation = value;
+                ContentAllocation = new Rect (
                     Allocation.X + Margin.Left,
                     Allocation.Y + Margin.Top,
-                    Math.Max (0, Allocation.Width - Margin.Left - Margin.Right),
-                    Math.Max (0, Allocation.Height - Margin.Top - Margin.Bottom)
+                    Math.Max (0, Allocation.Width - Margin.X),
+                    Math.Max (0, Allocation.Height - Margin.Y)
                 );
+                ContentSize = new Size (ContentAllocation.Width, ContentAllocation.Height);
+                RenderSize = new Size (Math.Round (ContentAllocation.Width), Math.Round (ContentAllocation.Height));
             }
         }
 
+        public Rect ContentAllocation { get; private set; }
+        public Size ContentSize { get; private set; }
+        protected Size RenderSize { get; private set; }
+
         protected virtual Rect InvalidationRect {
             //get { return Rect.Empty; }
             get { return Allocation; }
         }
 
-        public Size ContentSize {
-            get { return new Size (ContentAllocation.Width, ContentAllocation.Height); }
-        }
-
-        protected Size RenderSize {
-            get { return new Size (Math.Round (ContentAllocation.Width), Math.Round (ContentAllocation.Height)); }
-        }
 
         #endregion