Bug 538266. Part 2: add transform API to layer system. r=jrmuizel,sr=dbaron

gfx/layers/Layers.h

@@ -42,6 +42,7 @@
 #include "nsRegion.h"
 #include "nsPoint.h"
 #include "nsRect.h"
+#include "gfx3DMatrix.h"
 
 class gfxContext;
 class nsPaintEvent;
@@ -228,6 +229,15 @@ public:
     }
   }
 
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Tell this layer what its transform should be. The transformation
+   * is applied when compositing the layer into its parent container.
+   * XXX Currently only transformations corresponding to 2D affine transforms
+   * are supported.
+   */
+  void SetTransform(const gfx3DMatrix& aMatrix) { mTransform = aMatrix; }
+
   // These getters can be used anytime.
   float GetOpacity() { return mOpacity; }
   const nsIntRect* GetClipRect() { return mUseClipRect ? &mClipRect : nsnull; }
@@ -236,6 +246,7 @@ public:
   Layer* GetNextSibling() { return mNextSibling; }
   Layer* GetPrevSibling() { return mPrevSibling; }
   virtual Layer* GetFirstChild() { return nsnull; }
+  const gfx3DMatrix& GetTransform() { return mTransform; }
 
   /**
    * Only the implementation should call this. This is per-implementation
@@ -268,6 +279,7 @@ protected:
   Layer* mNextSibling;
   Layer* mPrevSibling;
   void* mImplData;
+  gfx3DMatrix mTransform;
   float mOpacity;
   nsIntRect mClipRect;
   PRPackedBool mUseClipRect;

gfx/layers/basic/BasicLayers.cpp

@@ -349,7 +349,8 @@ NeedsGroup(Layer* aLayer)
 static PRBool
 NeedsState(Layer* aLayer)
 {
-  return aLayer->GetClipRect() != nsnull;
+  return aLayer->GetClipRect() != nsnull ||
+         !aLayer->GetTransform().IsIdentity();
 }
 
 // Returns true if it's OK to save the contents of aLayer in an
@@ -379,19 +380,38 @@ BasicLayerManager::BeginPaintingLayer(Layer* aLayer)
 {
   PRBool needsGroup = NeedsGroup(aLayer);
   if ((needsGroup || NeedsState(aLayer)) && mTarget) {
-    // If we need to call PushGroup, we should clip to the smallest possible
-    // area first to minimize the size of the temporary surface.
-    nsIntRect bbox = ToData(aLayer)->GetVisibleRegion().GetBounds();
+    mTarget->Save();
+
     if (aLayer->GetClipRect()) {
-      bbox.IntersectRect(bbox, *aLayer->GetClipRect());
+      const nsIntRect& r = *aLayer->GetClipRect();
+      mTarget->NewPath();
+      mTarget->Rectangle(gfxRect(r.x, r.y, r.width, r.height));
+      mTarget->Clip();
     }
 
-    mTarget->Save();
-    mTarget->NewPath();
-    mTarget->Rectangle(gfxRect(bbox.x, bbox.y, bbox.width, bbox.height));
-    mTarget->Clip();
+    gfxMatrix transform;
+    // XXX we need to add some kind of 3D transform support, possibly
+    // using pixman?
+    NS_ASSERTION(aLayer->GetTransform().Is2D(),
+                 "Only 2D transforms supported currently");
+    aLayer->GetTransform().Is2D(&transform);
+    mTarget->Multiply(transform);
 
     if (needsGroup) {
+      // If we need to call PushGroup, we should clip to the smallest possible
+      // area first to minimize the size of the temporary surface.
+      nsIntRect bbox = ToData(aLayer)->GetVisibleRegion().GetBounds();
+      gfxRect deviceRect =
+        mTarget->UserToDevice(gfxRect(bbox.x, bbox.y, bbox.width, bbox.height));
+      deviceRect.RoundOut();
+
+      gfxMatrix currentMatrix = mTarget->CurrentMatrix();
+      mTarget->IdentityMatrix();
+      mTarget->NewPath();
+      mTarget->Rectangle(deviceRect);
+      mTarget->Clip();
+      mTarget->SetMatrix(currentMatrix);
+
       gfxASurface::gfxContentType type = UseOpaqueSurface(aLayer)
           ? gfxASurface::CONTENT_COLOR : gfxASurface::CONTENT_COLOR_ALPHA;
       mTarget->PushGroup(type);