Refactors the sprite matrix handling to do most calculations in Dart,...

Refactors the sprite matrix handling to do most calculations in Dart, minimizes the number of calls down to Skia

packages/flutter/example/game/lib/node.dart

@@ -409,20 +409,20 @@ class Node {
 
   // Rendering
 
-  void _visit(PaintingCanvas canvas) {
+  void _visit(PaintingCanvas canvas, Matrix4 totalMatrix) {
     assert(canvas != null);
     if (!visible) return;
 
-    _prePaint(canvas);
-    _visitChildren(canvas);
-    _postPaint(canvas);
+    _prePaint(canvas, totalMatrix);
+    _visitChildren(canvas, totalMatrix);
+    _postPaint(canvas, totalMatrix);
   }
 
-  void _prePaint(PaintingCanvas canvas) {
-    _savedTotalMatrix = new Matrix4.fromFloat32List(canvas.getTotalMatrix());;
+  void _prePaint(PaintingCanvas canvas, Matrix4 matrix) {
+    _savedTotalMatrix = new Matrix4.copy(matrix);
 
     // Get the transformation matrix and apply transform
-    canvas.concat(transformMatrix.storage);
+    matrix.multiply(transformMatrix);
   }
 
   /// Paints this node to the canvas.
@@ -444,7 +444,7 @@ class Node {
   void paint(PaintingCanvas canvas) {
   }
 
-  void _visitChildren(PaintingCanvas canvas) {
+  void _visitChildren(PaintingCanvas canvas, Matrix4 totalMatrix) {
     // Sort children if needed
     _sortChildren();
 
@@ -454,23 +454,24 @@ class Node {
     while (i < _children.length) {
       Node child = _children[i];
       if (child.zPosition >= 0.0) break;
-      child._visit(canvas);
+      child._visit(canvas, totalMatrix);
       i++;
     }
 
     // Paint this node
+    canvas.setMatrix(totalMatrix.storage);
     paint(canvas);
 
     // Visit children in front of this node
     while (i < _children.length) {
       Node child = _children[i];
-      child._visit(canvas);
+      child._visit(canvas, totalMatrix);
       i++;
     }
   }
 
-  void _postPaint(PaintingCanvas canvas) {
-    canvas.setMatrix(_savedTotalMatrix.storage);
+  void _postPaint(PaintingCanvas canvas, Matrix4 totalMatrix) {
+    totalMatrix.setFrom(_savedTotalMatrix);
   }
 
   // Receiving update calls

packages/flutter/example/game/lib/sprite.dart

@@ -67,9 +67,6 @@ class Sprite extends NodeWithSize {
   }
 
   void paint(PaintingCanvas canvas) {
-    // Store old matrix
-    Matrix4 savedMatrix = new Matrix4.fromFloat32List(canvas.getTotalMatrix());
-
     // Account for pivot point
     applyTransformForPivot(canvas);
 
@@ -111,8 +108,5 @@ class Sprite extends NodeWithSize {
       canvas.drawRect(new Rect.fromLTRB(0.0, 0.0, size.width, size.height),
       new Paint()..color = new Color.fromARGB(255, 255, 0, 0));
     }
-
-    // Restore matrix
-    canvas.setMatrix(savedMatrix.storage);
   }
 }

packages/flutter/example/game/lib/sprite_box.dart

@@ -328,7 +328,8 @@ class SpriteBox extends RenderBox {
     canvas.concat(transformMatrix.storage);
 
     // Draw the sprite tree
-    _rootNode._visit(canvas);
+    Matrix4 totalMatrix = new Matrix4.fromFloat32List(canvas.getTotalMatrix());
+    _rootNode._visit(canvas, totalMatrix);
 
     canvas.restore();
   }