Add API for hit testing layer_impl touchEventHandlerRegions from the host

cc/layer_tree_host_common.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layer_tree_host_common.h"
 
 #include "cc/layer.h"
 #include "cc/layer_impl.h"
 #include "cc/layer_iterator.h"
 #include "cc/layer_sorter.h"
 #include "cc/math_util.h"
 #include "cc/render_surface.h"
 #include "cc/render_surface_impl.h"
+#include "ui/gfx/point_conversions.h"
 #include "ui/gfx/rect_conversions.h"
 #include <algorithm>
 #include <public/WebTransformationMatrix.h>
 
 using WebKit::WebTransformationMatrix;
 
 namespace cc {
 
 ScrollAndScaleSet::ScrollAndScaleSet()
 {
@@ skipping 847 matching lines @@
     bool clipped = false;
     gfx::PointF hitTestPointInLocalSpace = MathUtil::projectPoint(localSpaceToScreenSpaceTransform.inverse(), screenSpacePoint, clipped);
 
     // If projectPoint could not project to a valid value, then we assume that this point doesn't hit this rect.
     if (clipped)
         return false;
 
     return localSpaceRect.Contains(hitTestPointInLocalSpace);
 }
 
+static bool pointHitsRegion(gfx::PointF screenSpacePoint, const WebTransformationMatrix& screenSpaceTransform, const Region& layerSpaceRegion, float layerContentScaleX, float layerContentScaleY)
+{
+    // If the transform is not invertible, then assume that this point doesn't hit this region.
+    if (!screenSpaceTransform.isInvertible())
+        return false;
+
+    // Transform the hit test point from screen space to the local space of the given region.
+    bool clipped = false;
+    gfx::PointF hitTestPointInContentSpace = MathUtil::projectPoint(screenSpaceTransform.inverse(), screenSpacePoint, clipped);
+    gfx::PointF hitTestPointInLayerSpace = gfx::ScalePoint(hitTestPointInContentSpace, 1 / layerContentScaleX, 1 / layerContentScaleY);
+
+    // If projectPoint could not project to a valid value, then we assume that this point doesn't hit this region.
+    if (clipped)
+        return false;
+
+    return layerSpaceRegion.Contains(gfx::ToRoundedPoint(hitTestPointInLayerSpace));
+}
+
 static bool pointIsClippedBySurfaceOrClipRect(const gfx::PointF& screenSpacePoint, LayerImpl* layer)
 {
     LayerImpl* currentLayer = layer;
 
     // Walk up the layer tree and hit-test any renderSurfaces and any layer clipRects that are active.
     while (currentLayer) {
         if (currentLayer->renderSurface() && !pointHitsRect(screenSpacePoint, currentLayer->renderSurface()->screenSpaceTransform(), currentLayer->renderSurface()->contentRect()))
             return true;
 
         // Note that drawableContentRects are actually in targetSurface space, so the transform we
@@ skipping 34 matching lines @@
             continue;
 
         foundLayer = currentLayer;
         break;
     }
 
     // This can potentially return 0, which means the screenSpacePoint did not successfully hit test any layers, not even the root layer.
     return foundLayer;
 }
 
+LayerImpl* LayerTreeHostCommon::findLayerThatIsHitByPointInTouchHandlerRegion(const gfx::PointF& screenSpacePoint, std::vector<LayerImpl*>& renderSurfaceLayerList)
+{
+    LayerImpl* foundLayer = 0;
+
+    typedef LayerIterator<LayerImpl, std::vector<LayerImpl*>, RenderSurfaceImpl, LayerIteratorActions::FrontToBack> LayerIteratorType;
+    LayerIteratorType end = LayerIteratorType::end(&renderSurfaceLayerList);
+
+    for (LayerIteratorType it = LayerIteratorType::begin(&renderSurfaceLayerList); it != end; ++it) {
+        // We don't want to consider renderSurfaces for hit testing.
+        if (!it.representsItself())
+            continue;
+
+        LayerImpl* currentLayer = (*it);
+
+        if (currentLayer->touchEventHandlerRegion().IsEmpty())
+            continue;
+
+        if (!pointHitsRegion(screenSpacePoint, currentLayer->screenSpaceTransform(), currentLayer->touchEventHandlerRegion(), currentLayer->contentsScaleX(), currentLayer->contentsScaleY()))
+            continue;
+
+        // At this point, we think the point does hit the touch event handler region on the layer, but we need to walk 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(screenSpacePoint, currentLayer))
+            continue;
+
+        foundLayer = currentLayer;
+        break;
+    }
+
+    // This can potentially return 0, which means the screenSpacePoint did not successfully hit test any layers, not even the root layer.
+    return foundLayer;
+}
+
 }  // namespace cc