Bug 689416 - Stop using intermediate layers to render 3d transforms. r=roc

gfx/layers/Layers.cpp

@@ -444,6 +444,7 @@ ContainerLayer::DefaultComputeEffectiveTransforms(const gfx3DMatrix& aTransformT
 {
   gfxMatrix residual;
   gfx3DMatrix idealTransform = GetLocalTransform()*aTransformToSurface;
+  idealTransform.ProjectTo2D();
   mEffectiveTransform = SnapTransform(idealTransform, gfxRect(0, 0, 0, 0), &residual);
 
   bool useIntermediateSurface;
@@ -453,9 +454,7 @@ ContainerLayer::DefaultComputeEffectiveTransforms(const gfx3DMatrix& aTransformT
   } else {
     useIntermediateSurface = PR_FALSE;
     gfxMatrix contTransform;
-    if (!mEffectiveTransform.Is2D(&contTransform)) {
-     useIntermediateSurface = PR_TRUE;   
-    } else if (
+    if (!mEffectiveTransform.Is2D(&contTransform) ||
 #ifdef MOZ_GFX_OPTIMIZE_MOBILE
         !contTransform.PreservesAxisAlignedRectangles()) {
 #else

gfx/layers/opengl/ContainerLayerOGL.cpp

@@ -175,7 +175,6 @@ ContainerRender(Container* aContainer,
   float opacity = aContainer->GetEffectiveOpacity();
   const gfx3DMatrix& transform = aContainer->GetEffectiveTransform();
   bool needsFramebuffer = aContainer->UseIntermediateSurface();
-  gfxMatrix contTransform;
   if (needsFramebuffer) {
     LayerManagerOGL::InitMode mode = LayerManagerOGL::InitModeClear;
     nsIntRect framebufferRect = visibleRect;
@@ -213,11 +212,6 @@ ContainerRender(Container* aContainer,
     frameBuffer = aPreviousFrameBuffer;
     aContainer->mSupportsComponentAlphaChildren = (aContainer->GetContentFlags() & Layer::CONTENT_OPAQUE) ||
       (aContainer->GetParent() && aContainer->GetParent()->SupportsComponentAlphaChildren());
-#ifdef DEBUG
-    bool is2d =
-#endif
-    transform.Is2D(&contTransform);
-    NS_ASSERTION(is2d, "Transform must be 2D");
   }
 
   nsAutoTArray<Layer*, 12> children;

gfx/thebes/gfx3DMatrix.cpp

@@ -730,6 +730,19 @@ gfx3DMatrix::CanDraw2D(gfxMatrix* aMatrix) const
   return PR_TRUE;
 }
 
+gfx3DMatrix&
+gfx3DMatrix::ProjectTo2D()
+{
+  _31 = 0.0f;
+  _32 = 0.0f;
+  _13 = 0.0f; 
+  _23 = 0.0f; 
+  _33 = 1.0f; 
+  _43 = 0.0f; 
+  _34 = 0.0f;
+  return *this;
+}
+
 gfxPoint gfx3DMatrix::ProjectPoint(const gfxPoint& aPoint) const
 {
   // Define a ray of the form P + Ut where t is a real number

gfx/thebes/gfx3DMatrix.h

@@ -121,6 +121,12 @@ public:
    */
   bool CanDraw2D(gfxMatrix* aMatrix = nsnull) const;
 
+  /**
+   * Converts the matrix to one that doesn't modify the z coordinate of points,
+   * but leaves the rest of the transformation unchanged.
+   */
+  gfx3DMatrix& ProjectTo2D();
+
   /**
    * Returns true if the matrix is the identity matrix. The most important
    * property we require is that gfx3DMatrix().IsIdentity() returns true.