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 6c0ff5a74f9afec86ed38e8a0b3235ae0537cfbc..68a1cdf903a1fa24968c40137fe593fa60e79228 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"
 
@@ -1430,25 +1431,79 @@ 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 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. Also, the point can be clipped by the contect rect of an

[ajuma, 2016/01/06 19:53:44]

s/contect/content

[jaydasika, 2016/01/06 22:44:46]

Done.

+  // ancestor render surface.
+
+  // 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) {
+      const TransformNode* transform_node =
+          transform_tree.Node(clip_node->data.transform_id);

[ajuma, 2016/01/06 19:53:44]

Should this be target_id (given that the clip we're using below is in target
space)? Do we have unit tests for the case that the clip node's own transform id
is different from its target id?

[jaydasika, 2016/01/06 22:44:45]

It should be target id. Did not find any unit test with that case. So added one.

+      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;
+    }
+    const LayerImpl* clip_node_owner =
+        layer->layer_tree_impl()->LayerById(clip_node->owner_id);
+    if (clip_node_owner->render_surface() &&
+        !PointHitsRect(
+            screen_space_point,
+            SurfaceScreenSpaceTransform(clip_node_owner, transform_tree,
+                                        true /*use_property_trees*/),
+            clip_node_owner->render_surface()->content_rect(), 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,
@@ -1460,6 +1515,7 @@ 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(),
@@ -1470,7 +1526,8 @@ 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.
@@ -1496,14 +1553,15 @@ 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))
@@ -1513,10 +1571,10 @@ 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;
@@ -1565,7 +1623,8 @@ 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;
 }
 
@@ -1590,7 +1649,8 @@ 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;
 }
@@ -1598,6 +1658,7 @@ 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;
@@ -1611,7 +1672,8 @@ 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;
@@ -1634,19 +1696,21 @@ 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;
 };
 
@@ -1660,11 +1724,12 @@ 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;
 }
 
@@ -1677,6 +1742,7 @@ 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;
@@ -1722,7 +1788,7 @@ 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;
 }
@@ -1736,7 +1802,7 @@ 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 ||
@@ -1747,7 +1813,7 @@ 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);
   }
 }