Implement elementsFromPoint

Source/core/rendering/HitTestRequest.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  * Copyright (C) 2009 Torch Mobile Inc. http://www.torchmobile.com/
  * Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 20 matching lines @@
         ReadOnly = 1 << 1,
         Active = 1 << 2,
         Move = 1 << 3,
         Release = 1 << 4,
         IgnoreClipping = 1 << 5,
         SVGClipContent = 1 << 6,
         TouchEvent = 1 << 7,
         AllowChildFrameContent = 1 << 8,
         ChildFrameHitTest = 1 << 9,
         IgnorePointerEventsNone = 1 << 10,
+        // Collect a list of nodes instead of just one.
+        // (e.g., for elementsFromPoint or rect-based tests).

[Rick Byers, 2015/02/04 10:34:03]

Is it legal to ask for a list-based hit-test without supplying either an area or
the penetrating flag?

[pdr., 2015/02/17 04:10:13]

It's not, I've updated the comment to be a bit more clear here.

I've also added an assert in HitTestRequest's constructor to enforce this.

[Rick Byers, 2015/02/20 20:02:23]

That enforces the penetrating part, but does anything enforce that you can't ask
for simple list-based with an area of 0?  Either we should enforce that, or just
make it work and return a single-element list.  The latter would avoid adding
new complexity to a few of your callsites  (the hit type could return to being
non-conditional - always list based, area may or may not be zero).

+        ListBased = 1 << 11,
+        // Continues hit testing even after a hit has been found. This is useful
+        // with list-based testing for finding all nodes in an area.
+        Penetrating = 1 << 12,

[Rick Byers, 2015/02/04 10:34:03]

What does it mean to have a penetrating hit test that's not list-based?

[pdr., 2015/02/17 04:10:13]

It doesn't make sense. I've renamed this PenetratingList to make this clearer.

     };
 
     typedef unsigned HitTestRequestType;
 
     HitTestRequest(HitTestRequestType requestType)
         : m_requestType(requestType)
     {
     }
 
     bool readOnly() const { return m_requestType & ReadOnly; }
     bool active() const { return m_requestType & Active; }
     bool move() const { return m_requestType & Move; }
     bool release() const { return m_requestType & Release; }
     bool ignoreClipping() const { return m_requestType & IgnoreClipping; }
     bool svgClipContent() const { return m_requestType & SVGClipContent; }
     bool touchEvent() const { return m_requestType & TouchEvent; }
     bool allowsChildFrameContent() const { return m_requestType & AllowChildFrameContent; }
     bool isChildFrameHitTest() const { return m_requestType & ChildFrameHitTest; }
     bool ignorePointerEventsNone() const { return m_requestType & IgnorePointerEventsNone; }
+    bool listBased() const { return m_requestType & ListBased; }
+    bool penetrating() const { return m_requestType & Penetrating; }
 
     // Convenience functions
     bool touchMove() const { return move() && touchEvent(); }
 
     HitTestRequestType type() const { return m_requestType; }
 
 private:
     HitTestRequestType m_requestType;
 };
 
 } // namespace blink
 
 #endif // HitTestRequest_h