cc:: Use clip tree instead of layer tree during hit testing

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 3519f293b6256ada4302075487c1362c8fd818da..d03863138795558b66a21f5b66f79a9f8752604e 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -40,6 +40,7 @@
 #include "cc/trees/property_tree_builder.h"
 #include "ui/gfx/geometry/box_f.h"
 #include "ui/gfx/geometry/point_conversions.h"
+#include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/geometry/vector2d_conversions.h"
 
@@ -1434,25 +1435,68 @@ static const gfx::Transform SurfaceScreenSpaceTransform(
                    layer->render_surface(), transform_tree);
 }
 
+static bool PointIsClippedByAncestorClipNode(
+    const gfx::PointF& screen_space_point,
+    const LayerImpl* layer,
+    const ClipTree& clip_tree,
+    const TransformTree& transform_tree) {
+  // We need to visit all ancestor clip nodes that apply local clip to check
+  // this. Checking with just the combined clip stored at a clip node is not
+  // enough because parent combined clip can sometimes be smaller than current
+  // combined clip. This can happen when we have transforms like rotation that
+  // inflate the combined clip's bounds.
+
+  // We first check if the point is clipped by viewport.
+  const ClipNode* clip_node = clip_tree.Node(1);
+  gfx::Rect combined_clip_in_target_space =
+      gfx::ToEnclosingRect(clip_node->data.combined_clip_in_target_space);
+  if (!PointHitsRect(screen_space_point, gfx::Transform(),
+                     combined_clip_in_target_space, NULL))
+    return true;
+
+  for (const ClipNode* clip_node = clip_tree.Node(layer->clip_tree_index());
+       clip_node->id > 1; clip_node = clip_tree.parent(clip_node)) {
+    if (!clip_node->data.applies_local_clip)
+      continue;
+    const TransformNode* transform_node =
+        transform_tree.Node(clip_node->data.transform_id);
+    gfx::Rect combined_clip_in_target_space =
+        gfx::ToEnclosingRect(clip_node->data.combined_clip_in_target_space);
+
+    if (!PointHitsRect(screen_space_point, transform_node->data.to_screen,
+                       combined_clip_in_target_space, NULL))
+      return true;
+  }
+  return false;
+}
+
 static bool PointIsClippedBySurfaceOrClipRect(
     const gfx::PointF& screen_space_point,
     const LayerImpl* layer,
     const TransformTree& transform_tree,
+    const ClipTree& clip_tree,
     const bool use_property_trees) {
   // Walk up the layer tree and hit-test any render_surfaces and any layer
   // clip rects that are active.
+  if (use_property_trees) {
+    return PointIsClippedByAncestorClipNode(screen_space_point, layer,
+                                            clip_tree, transform_tree);
+  }
+
   for (; layer; layer = GetNextClippingLayer(layer)) {
     if (layer->render_surface() &&
         !PointHitsRect(screen_space_point,
                        SurfaceScreenSpaceTransform(layer, transform_tree,
                                                    use_property_trees),
-                       layer->render_surface()->content_rect(), NULL))
+                       layer->render_surface()->content_rect(), NULL)) {
       return true;
+    }
 
     if (LayerClipsSubtree(layer) &&
         !PointHitsRect(screen_space_point, layer->ScreenSpaceTransform(),
-                       gfx::Rect(layer->bounds()), NULL))
+                       gfx::Rect(layer->bounds()), NULL)) {
       return true;
+    }
   }
 
   // If we have finished walking all ancestors without having already exited,
@@ -1464,6 +1508,7 @@ static bool PointHitsLayer(const LayerImpl* layer,
                            const gfx::PointF& screen_space_point,
                            float* distance_to_intersection,
                            const TransformTree& transform_tree,
+                           const ClipTree& clip_tree,
                            const bool use_property_trees) {
   gfx::Rect content_rect(layer->bounds());
   if (!PointHitsRect(screen_space_point, layer->ScreenSpaceTransform(),
@@ -1474,7 +1519,8 @@ static bool PointHitsLayer(const LayerImpl* layer,
   // up the parents to ensure that the layer was not clipped in such a way
   // that the hit point actually should not hit the layer.
   if (PointIsClippedBySurfaceOrClipRect(screen_space_point, layer,
-                                        transform_tree, use_property_trees))
+                                        transform_tree, clip_tree,
+                                        use_property_trees))
     return false;
 
   // Skip the HUD layer.
@@ -1500,14 +1546,15 @@ static void FindClosestMatchingLayer(
     LayerImpl* layer,
     const Functor& func,
     const TransformTree& transform_tree,
+    const ClipTree& clip_tree,
     const bool use_property_trees,
     FindClosestMatchingLayerDataForRecursion* data_for_recursion) {
   size_t children_size = layer->children().size();
   for (size_t i = 0; i < children_size; ++i) {
     size_t index = children_size - 1 - i;
     FindClosestMatchingLayer(screen_space_point, layer->children()[index].get(),
-                             func, transform_tree, use_property_trees,
-                             data_for_recursion);
+                             func, transform_tree, clip_tree,
+                             use_property_trees, data_for_recursion);
   }
 
   if (!func(layer))
@@ -1517,10 +1564,10 @@ static void FindClosestMatchingLayer(
   bool hit = false;
   if (layer->Is3dSorted())
     hit = PointHitsLayer(layer, screen_space_point, &distance_to_intersection,
-                         transform_tree, use_property_trees);
+                         transform_tree, clip_tree, use_property_trees);
   else
     hit = PointHitsLayer(layer, screen_space_point, nullptr, transform_tree,
-                         use_property_trees);
+                         clip_tree, use_property_trees);
 
   if (!hit)
     return;
@@ -1569,7 +1616,8 @@ LayerImpl* LayerTreeImpl::FindFirstScrollingLayerThatIsHitByPoint(
       settings().use_property_trees || settings().verify_property_trees;
   FindClosestMatchingLayer(
       screen_space_point, root_layer(), FindScrollingLayerFunctor(),
-      property_trees_.transform_tree, use_property_trees, &data_for_recursion);
+      property_trees_.transform_tree, property_trees_.clip_tree,
+      use_property_trees, &data_for_recursion);
   return data_for_recursion.closest_match;
 }
 
@@ -1594,7 +1642,8 @@ LayerImpl* LayerTreeImpl::FindLayerThatIsHitByPoint(
   FindClosestMatchingLayerDataForRecursion data_for_recursion;
   FindClosestMatchingLayer(screen_space_point, root_layer(),
                            HitTestVisibleScrollableOrTouchableFunctor(),
-                           property_trees_.transform_tree, use_property_trees,
+                           property_trees_.transform_tree,
+                           property_trees_.clip_tree, use_property_trees,
                            &data_for_recursion);
   return data_for_recursion.closest_match;
 }
@@ -1602,6 +1651,7 @@ LayerImpl* LayerTreeImpl::FindLayerThatIsHitByPoint(
 static bool LayerHasTouchEventHandlersAt(const gfx::PointF& screen_space_point,
                                          LayerImpl* layer_impl,
                                          const TransformTree& transform_tree,
+                                         const ClipTree& clip_tree,
                                          const bool use_property_trees) {
   if (layer_impl->touch_event_handler_region().IsEmpty())
     return false;
@@ -1615,7 +1665,8 @@ static bool LayerHasTouchEventHandlersAt(const gfx::PointF& screen_space_point,
   // was not clipped in such a way that the hit point actually should not hit
   // the layer.
   if (PointIsClippedBySurfaceOrClipRect(screen_space_point, layer_impl,
-                                        transform_tree, use_property_trees))
+                                        transform_tree, clip_tree,
+                                        use_property_trees))
     return false;
 
   return true;
@@ -1638,19 +1689,21 @@ LayerImpl* LayerTreeImpl::FindLayerWithWheelHandlerThatIsHitByPoint(
       settings().use_property_trees || settings().verify_property_trees;
   FindWheelEventLayerFunctor func;
   FindClosestMatchingLayerDataForRecursion data_for_recursion;
-  FindClosestMatchingLayer(screen_space_point, root_layer(), func,
-                           property_trees_.transform_tree, use_property_trees,
-                           &data_for_recursion);
+  FindClosestMatchingLayer(
+      screen_space_point, root_layer(), func, property_trees_.transform_tree,
+      property_trees_.clip_tree, use_property_trees, &data_for_recursion);
   return data_for_recursion.closest_match;
 }
 
 struct FindTouchEventLayerFunctor {
   bool operator()(LayerImpl* layer) const {
     return LayerHasTouchEventHandlersAt(screen_space_point, layer,
-                                        transform_tree, use_property_trees);
+                                        transform_tree, clip_tree,
+                                        use_property_trees);
   }
   const gfx::PointF screen_space_point;
   const TransformTree& transform_tree;
+  const ClipTree& clip_tree;
   const bool use_property_trees;
 };
 
@@ -1664,11 +1717,12 @@ LayerImpl* LayerTreeImpl::FindLayerThatIsHitByPointInTouchHandlerRegion(
   bool use_property_trees =
       settings().use_property_trees || settings().verify_property_trees;
   FindTouchEventLayerFunctor func = {
-      screen_space_point, property_trees_.transform_tree, use_property_trees};
+      screen_space_point, property_trees_.transform_tree,
+      property_trees_.clip_tree, use_property_trees};
   FindClosestMatchingLayerDataForRecursion data_for_recursion;
-  FindClosestMatchingLayer(screen_space_point, root_layer(), func,
-                           property_trees_.transform_tree, use_property_trees,
-                           &data_for_recursion);
+  FindClosestMatchingLayer(
+      screen_space_point, root_layer(), func, property_trees_.transform_tree,
+      property_trees_.clip_tree, use_property_trees, &data_for_recursion);
   return data_for_recursion.closest_match;
 }
 
@@ -1681,6 +1735,7 @@ static ViewportSelectionBound ComputeViewportSelectionBound(
     LayerImpl* layer,
     float device_scale_factor,
     const TransformTree& transform_tree,
+    const ClipTree& clip_tree,
     const bool use_property_trees) {
   ViewportSelectionBound viewport_bound;
   viewport_bound.type = layer_bound.type;
@@ -1726,7 +1781,7 @@ static ViewportSelectionBound ComputeViewportSelectionBound(
   float intersect_distance = 0.f;
   viewport_bound.visible =
       PointHitsLayer(layer, visibility_point, &intersect_distance,
-                     transform_tree, use_property_trees);
+                     transform_tree, clip_tree, use_property_trees);
 
   return viewport_bound;
 }
@@ -1740,7 +1795,7 @@ void LayerTreeImpl::GetViewportSelection(ViewportSelection* selection) {
       selection_.start,
       selection_.start.layer_id ? LayerById(selection_.start.layer_id) : NULL,
       device_scale_factor(), property_trees_.transform_tree,
-      use_property_trees);
+      property_trees_.clip_tree, use_property_trees);
   selection->is_editable = selection_.is_editable;
   selection->is_empty_text_form_control = selection_.is_empty_text_form_control;
   if (selection->start.type == SELECTION_BOUND_CENTER ||
@@ -1751,7 +1806,7 @@ void LayerTreeImpl::GetViewportSelection(ViewportSelection* selection) {
         selection_.end,
         selection_.end.layer_id ? LayerById(selection_.end.layer_id) : NULL,
         device_scale_factor(), property_trees_.transform_tree,
-        use_property_trees);
+        property_trees_.clip_tree, use_property_trees);
   }
 }