Initial draft - modify ViewportAnchor to know about both inner and outer viewports.

Source/web/ViewportAnchor.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 38 matching lines @@
 // and an anchor point (in view coordinates, e.g., (0, 0) == viewport origin,
 // (0.5, 0) == viewport top center). The anchor point tracks the underlying DOM
 // node; as the node moves or the view is resized, the viewport anchor maintains
 // its orientation relative to the node, and the viewport origin maintains its
 // orientation relative to the anchor.
 class ViewportAnchor {
     STACK_ALLOCATED();
 public:
     explicit ViewportAnchor(EventHandler*);
 
-    void setAnchor(const IntRect& viewRect, const FloatSize& anchorInViewCoords);
+    void setAnchor(const IntRect& innerViewRect, const IntRect& outerViewRect, const FloatSize& anchorInViewCoords);
 
-    IntPoint computeOrigin(const IntSize& currentViewSize) const;
+    IntPoint computeInnerViewportOrigin(const IntSize& innerSize) const;
+
+    IntPoint computeOuterViewportOrigin(const IntPoint& innerOrigin, const IntSize& outerSize) const;

[aelias_OOO_until_Jul13, 2014/09/10 01:46:24]

How about merging these two functions into:

void computeOrigins(const IntSize& innerSize, const IntSize& outerSize, IntSize*
outerScrollOffset, FloatSize pinchViewportOffset);

(pinchViewportOffset would be the vector from outer -> inner, i.e. exactly the
value needed in the PinchViewport class.)

[timav, 2014/09/10 18:22:40]

Will do.

 
 private:
     RawPtrWillBeMember<EventHandler> m_eventHandler;
 
     IntRect m_viewRect;
 
     RefPtrWillBeMember<Node> m_anchorNode;
     LayoutRect m_anchorNodeBounds;
 
     FloatSize m_anchorInViewCoords;
     FloatSize m_anchorInNodeCoords;
+    FloatSize m_outerInInnerCoords;

[aelias_OOO_until_Jul13, 2014/09/10 01:46:24]

Please rename this to m_normalizedPinchViewportOffset and invert the sign
(currently it's always negative or zero which seems weird, please make it always
nonnegative instead).

[timav, 2014/09/10 18:22:40]

Yes. The sign was positive in the beginning, but I decided to avoid multiplying
by -1.0. Was not thinking straight.

 };
 
 } // namespace blink
 
  #endif