Bug 1057578 - Change the overscroll transform exposed by APZC from a ViewTransform to a Matrix4x4. r=kats

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -2184,7 +2184,7 @@ bool AsyncPanZoomController::UpdateAnimation(const TimeStamp& aSampleTime,
   return false;
 }
 
-void AsyncPanZoomController::GetOverscrollTransform(ViewTransform* aTransform) const {
+void AsyncPanZoomController::GetOverscrollTransform(Matrix4x4* aTransform) const {
   // The overscroll effect is a combination of a translation in
   // the direction of overscroll, and shrinking in both directions.
   // With the effect applied, we can think of the composited region as being
@@ -2265,9 +2265,10 @@ void AsyncPanZoomController::GetOverscrollTransform(ViewTransform* aTransform) c
 
   float scale = 1 - (kZEffect * spaceProp);
 
-  // Finally, apply the transformations.
-  aTransform->mScale.scale *= scale;
-  aTransform->mTranslation += translation * mFrameMetrics.GetZoom();
+  // Finally, create a matrix representing the transformations.
+  ScreenPoint screenTranslation = translation * mFrameMetrics.GetZoom();
+  *aTransform = Matrix4x4().Scale(scale, scale, 1)
+                           .PostTranslate(screenTranslation.x, screenTranslation.y, 0);
 }
 
 bool AsyncPanZoomController::AdvanceAnimations(const TimeStamp& aSampleTime)
@@ -2336,7 +2337,7 @@ bool AsyncPanZoomController::AdvanceAnimations(const TimeStamp& aSampleTime)
 
 void AsyncPanZoomController::SampleContentTransformForFrame(ViewTransform* aOutTransform,
                                                             ScreenPoint& aScrollOffset,
-                                                            ViewTransform* aOutOverscrollTransform)
+                                                            Matrix4x4* aOutOverscrollTransform)
 {
   ReentrantMonitorAutoEnter lock(mMonitor);
 

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -175,7 +175,7 @@ public:
    */
   void SampleContentTransformForFrame(ViewTransform* aOutTransform,
                                       ScreenPoint& aScrollOffset,
-                                      ViewTransform* aOutOverscrollTransform);
+                                      Matrix4x4* aOutOverscrollTransform);
 
   /**
    * A shadow layer update has arrived. |aLayerMetrics| is the new FrameMetrics
@@ -576,7 +576,7 @@ private:
    * Return in |aTransform| a visual effect that reflects this apzc's
    * overscrolled state, if any.
    */
-  void GetOverscrollTransform(ViewTransform* aTransform) const;
+  void GetOverscrollTransform(Matrix4x4* aTransform) const;
 
   enum AxisLockMode {
     FREE,     /* No locking at all */

gfx/layers/composite/AsyncCompositionManager.cpp

@@ -567,7 +567,8 @@ AsyncCompositionManager::ApplyAsyncContentTransformToTree(Layer *aLayer)
 
     hasAsyncTransform = true;
 
-    ViewTransform asyncTransformWithoutOverscroll, overscrollTransform;
+    ViewTransform asyncTransformWithoutOverscroll;
+    Matrix4x4 overscrollTransform;
     ScreenPoint scrollOffset;
     controller->SampleContentTransformForFrame(&asyncTransformWithoutOverscroll,
                                                scrollOffset,
@@ -591,7 +592,7 @@ AsyncCompositionManager::ApplyAsyncContentTransformToTree(Layer *aLayer)
     mLayerManager->GetCompositor()->SetScreenRenderOffset(offset);
 
     combinedAsyncTransformWithoutOverscroll *= asyncTransformWithoutOverscroll;
-    combinedAsyncTransform *= (asyncTransformWithoutOverscroll * overscrollTransform);
+    combinedAsyncTransform *= (Matrix4x4(asyncTransformWithoutOverscroll) * overscrollTransform);
   }
 
   if (hasAsyncTransform) {

gfx/tests/gtest/TestAsyncPanZoomController.cpp

@@ -160,11 +160,11 @@ public:
 
   bool SampleContentTransformForFrame(const TimeStamp& aSampleTime,
                                       ViewTransform* aOutTransform,
-                                      ScreenPoint& aScrollOffset,
-                                      ViewTransform* aOutOverscrollTransform = nullptr) {
+                                      ScreenPoint& aScrollOffset) {
+    Matrix4x4 aOverscrollTransform;  // ignored
     bool ret = AdvanceAnimations(aSampleTime);
     AsyncPanZoomController::SampleContentTransformForFrame(
-      aOutTransform, aScrollOffset, aOutOverscrollTransform);
+      aOutTransform, aScrollOffset, &aOverscrollTransform);
     return ret;
   }
 };