Bug 900742 - Fix APZC hit testing problem introduced by bug 866232. r=BenWa

gfx/layers/composite/APZCTreeManager.cpp

@@ -67,7 +67,7 @@ APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor, Laye
                                 aRoot,
                                 // aCompositor is null in gtest scenarios
                                 aCompositor ? aCompositor->RootLayerTreeId() : 0,
-                                nullptr, nullptr,
+                                gfx3DMatrix(), nullptr, nullptr,
                                 aIsFirstPaint, aFirstPaintLayersId,
                                 &apzcsToDestroy);
   }
@@ -81,11 +81,15 @@ APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor, Laye
 AsyncPanZoomController*
 APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor,
                                              Layer* aLayer, uint64_t aLayersId,
+                                             gfx3DMatrix aTransform,
                                              AsyncPanZoomController* aParent,
                                              AsyncPanZoomController* aNextSibling,
                                              bool aIsFirstPaint, uint64_t aFirstPaintLayersId,
                                              nsTArray< nsRefPtr<AsyncPanZoomController> >* aApzcsToDestroy)
 {
+  // Accumulate the CSS transform between layers that have an APZC
+  aTransform = aTransform * aLayer->GetTransform();
+
   ContainerLayer* container = aLayer->AsContainerLayer();
   AsyncPanZoomController* controller = nullptr;
   if (container) {
@@ -116,12 +120,12 @@ APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor,
         controller->NotifyLayersUpdated(container->GetFrameMetrics(),
                                         aIsFirstPaint && (aLayersId == aFirstPaintLayersId));
 
-        gfx3DMatrix transform = container->GetEffectiveTransform();
         LayerRect visible = container->GetFrameMetrics().mViewport * container->GetFrameMetrics().LayersPixelsPerCSSPixel();
-        gfxRect transformed = transform.TransformBounds(gfxRect(visible.x, visible.y, visible.width, visible.height));
-        controller->SetVisibleRegion(transformed);
-        APZC_LOG("Setting rect(%f %f %f %f) as visible region for %p\n", transformed.x, transformed.y,
-                                                                         transformed.width, transformed.height,
+        controller->SetLayerHitTestData(visible, aTransform);
+        // Reset the accumulated transform once we hit a layer with an APZC
+        aTransform = gfx3DMatrix();
+        APZC_LOG("Setting rect(%f %f %f %f) as visible region for APZC %p\n", visible.x, visible.y,
+                                                                              visible.width, visible.height,
                                                                               controller);
 
         // Bind the APZC instance into the tree of APZCs
@@ -144,7 +148,7 @@ APZCTreeManager::UpdatePanZoomControllerTree(CompositorParent* aCompositor,
   uint64_t childLayersId = (aLayer->AsRefLayer() ? aLayer->AsRefLayer()->GetReferentId() : aLayersId);
   AsyncPanZoomController* next = nullptr;
   for (Layer* child = aLayer->GetLastChild(); child; child = child->GetPrevSibling()) {
-    next = UpdatePanZoomControllerTree(aCompositor, child, childLayersId, aParent, next,
+    next = UpdatePanZoomControllerTree(aCompositor, child, childLayersId, aTransform, aParent, next,
                                        aIsFirstPaint, aFirstPaintLayersId, aApzcsToDestroy);
   }
 
@@ -366,17 +370,19 @@ APZCTreeManager::FindTargetAPZC(AsyncPanZoomController* aApzc, const ScrollableL
 AsyncPanZoomController*
 APZCTreeManager::GetAPZCAtPoint(AsyncPanZoomController* aApzc, gfxPoint aHitTestPoint)
 {
+  gfx3DMatrix transform = gfx3DMatrix(aApzc->GetCurrentAsyncTransform()) * aApzc->GetCSSTransform();
+  gfx3DMatrix untransform = transform.Inverse();
+  gfxPoint untransformed = untransform.ProjectPoint(aHitTestPoint);
+
   // This walks the tree in depth-first, reverse order, so that it encounters
   // APZCs front-to-back on the screen.
-  ViewTransform apzcTransform = aApzc->GetCurrentAsyncTransform();
-  gfxPoint untransformed = gfx3DMatrix(apzcTransform).Inverse().ProjectPoint(aHitTestPoint);
   for (AsyncPanZoomController* child = aApzc->GetLastChild(); child; child = child->GetPrevSibling()) {
     AsyncPanZoomController* match = GetAPZCAtPoint(child, untransformed);
     if (match) {
       return match;
     }
   }
-  if (aApzc->VisibleRegionContains(untransformed)) {
+  if (aApzc->VisibleRegionContains(LayerPoint(untransformed.x, untransformed.y))) {
     return aApzc;
   }
   return nullptr;

gfx/layers/composite/APZCTreeManager.h

@@ -253,6 +253,7 @@ private:
    */
   AsyncPanZoomController* UpdatePanZoomControllerTree(CompositorParent* aCompositor,
                                                       Layer* aLayer, uint64_t aLayersId,
+                                                      gfx3DMatrix aTransform,
                                                       AsyncPanZoomController* aParent,
                                                       AsyncPanZoomController* aNextSibling,
                                                       bool aIsFirstPaint,

gfx/layers/ipc/AsyncPanZoomController.h

@@ -16,6 +16,7 @@
 #include "Axis.h"
 #include "TaskThrottler.h"
 #include "mozilla/layers/APZCTreeManager.h"
+#include "gfx3DMatrix.h"
 
 #include "base/message_loop.h"
 
@@ -641,17 +642,28 @@ private:
    * hit-testing to see which APZC instance should handle touch events.
    */
 public:
-  void SetVisibleRegion(gfxRect rect) { mVisibleRegion = rect; }
+  void SetLayerHitTestData(const LayerRect& aRect, const gfx3DMatrix& aTransform) {
+    mVisibleRect = aRect;
+    mCSSTransform = aTransform;
+  }
 
-  bool VisibleRegionContains(const gfxPoint& aPoint) const {
-    return mVisibleRegion.Contains(aPoint.x, aPoint.y);
+  gfx3DMatrix GetCSSTransform() const {
+    return mCSSTransform;
+  }
+
+  bool VisibleRegionContains(const LayerPoint& aPoint) const {
+    return mVisibleRect.Contains(aPoint);
   }
 
 private:
-  /* This is the viewport of the layer that this APZC corresponds to, but
-   * post-transform. In other words, it is in the coordinate space of its
-   * parent layer. */
-  gfxRect mVisibleRegion;
+  /* This is the viewport of the layer that this APZC corresponds to, in
+   * layer pixels. It position here does not account for any transformations
+   * applied to any layers, whether they are CSS transforms or async
+   * transforms. */
+  LayerRect mVisibleRect;
+  /* This is the cumulative layer transform from the parent APZC down to this
+   * one. */
+  gfx3DMatrix mCSSTransform;
 };
 
 }