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) {
@@ -116,13 +120,13 @@ 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->SetLayerHitTestData(visible, aTransform);
-        controller->SetVisibleRegion(transformed);
+        // Reset the accumulated transform once we hit a layer with an APZC
-        APZC_LOG("Setting rect(%f %f %f %f) as visible region for %p\n", transformed.x, transformed.y,
+        aTransform = gfx3DMatrix();
-                                                                         transformed.width, transformed.height,
+        APZC_LOG("Setting rect(%f %f %f %f) as visible region for APZC %p\n", visible.x, visible.y,
-                                                                         controller);
+                                                                              visible.width, visible.height,
+                                                                              controller);
 
         // Bind the APZC instance into the tree of APZCs
         if (aNextSibling) {
@@ -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 +370,21 @@ 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);
+  APZC_LOG("Untransformed %f %f to %f %f for APZC %p\n", aHitTestPoint.x, aHitTestPoint.y, untransformed.x, untransformed.y, aApzc);
+
   // 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))) {
+    APZC_LOG("Successfully matched untransformed point %f %f to visible region for APZC %p\n", untransformed.x, untransformed.y, aApzc);
     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 {
+  gfx3DMatrix GetCSSTransform() const {
-    return mVisibleRegion.Contains(aPoint.x, aPoint.y);
+    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
+  /* This is the viewport of the layer that this APZC corresponds to, in
-   * post-transform. In other words, it is in the coordinate space of its
+   * layer pixels. It position here does not account for any transformations
-   * parent layer. */
+   * applied to any layers, whether they are CSS transforms or async
-  gfxRect mVisibleRegion;
+   * transforms. */
+  LayerRect mVisibleRect;
+  /* This is the cumulative layer transform from the parent APZC down to this
+   * one. */
+  gfx3DMatrix mCSSTransform;
 };
 
 }

gfx/tests/gtest/TestAsyncPanZoomController.cpp

@@ -421,20 +421,20 @@ TEST(APZCTreeManager, GetAPZCAtPoint) {
   gfx3DMatrix transform;
   transform.ScalePost(0.1, 0.1, 1);
   root->SetBaseTransform(transform);
-  root->ComputeEffectiveTransforms(gfx3DMatrix());
   manager->UpdatePanZoomControllerTree(nullptr, root, 0, false);
   hit = manager->GetTargetAPZC(ScreenPoint(50, 50)); // This point is now outside the root layer
   EXPECT_EQ(nullAPZC, hit.get());
 
+  // This hit test will hit both layers[3] and layers[4]; layers[4] is later in the tree so
+  // it is a better match
   hit = manager->GetTargetAPZC(ScreenPoint(2, 2));
-  EXPECT_EQ(layers[3]->AsContainerLayer()->GetAsyncPanZoomController(), hit.get());
+  EXPECT_EQ(layers[4]->AsContainerLayer()->GetAsyncPanZoomController(), hit.get());
   // expect hit point at LayerPoint(20, 20)
 
   // Scale layer[4] outside the range
   layers[4]->SetBaseTransform(transform);
   // layer 4 effective visible screenrect: (0.05, 0.05, 0.2, 0.2)
   // Does not contain (2, 2)
-  root->ComputeEffectiveTransforms(gfx3DMatrix());
   manager->UpdatePanZoomControllerTree(nullptr, root, 0, false);
   hit = manager->GetTargetAPZC(ScreenPoint(2, 2));
   EXPECT_EQ(layers[3]->AsContainerLayer()->GetAsyncPanZoomController(), hit.get());
@@ -455,7 +455,6 @@ TEST(APZCTreeManager, GetAPZCAtPoint) {
   translateTransform3.ScalePost(1,15,1);
   layers[7]->SetBaseTransform(translateTransform3);
 
-  root->ComputeEffectiveTransforms(gfx3DMatrix());
   manager->UpdatePanZoomControllerTree(nullptr, root, 0, false);
   // layer 7 effective visible screenrect (0,16,4,60) but clipped by parent layers
   hit = manager->GetTargetAPZC(ScreenPoint(1, 45));