Made double-tap zoom work in pinch virtual viewport mode. (Blink-side)

Source/core/frame/PinchViewport.cpp

 /*
  * 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 152 matching lines @@
     coordinator->scrollableAreaScrollLayerDidChange(this);
 
     mainFrame()->loader().saveScrollState();
 }
 
 void PinchViewport::move(const FloatPoint& delta)
 {
     setLocation(m_offset + delta);
 }
 
-void PinchViewport::setScale(float scale)
+void PinchViewport::setScaleWithoutClampingViewportOffset(float scale)
 {
     if (scale == m_scale)
         return;
 
     m_scale = scale;
 
     if (mainFrame())
         mainFrame()->loader().saveScrollState();
 
     // Old-style pinch sets scale here but we shouldn't call into the
     // clamping code below.
     if (!m_innerViewportScrollLayer)
         return;
 
-    // Ensure we clamp so we remain within the bounds.
-    setLocation(visibleRect().location());
-
     // TODO: We should probably be calling scaleDidChange type functions here.
     // see Page::setPageScaleFactor.
 }
 
+void PinchViewport::setScale(float scale)
+{
+    setScaleWithoutClampingViewportOffset(scale);
+
+    // Ensure we clamp so we remain within the bounds.
+    setLocation(visibleRect().location());
+}
+
 // Modifies the top of the graphics layer tree to add layers needed to support
 // the inner/outer viewport fixed-position model for pinch zoom. When finished,
 // the tree will look like this (with * denoting added layers):
 //
 // *rootTransformLayer
 //  +- *innerViewportContainerLayer (fixed pos container)
 //      +- *pageScaleLayer
 //  |       +- *innerViewportScrollLayer
 //  |           +-- overflowControlsHostLayer (root layer)
 //  |               +-- outerViewportContainerLayer (fixed pos container) [frame container layer in RenderLayerCompositor]
@@ skipping 139 matching lines @@
 IntPoint PinchViewport::minimumScrollPosition() const
 {
     return IntPoint();
 }
 
 IntPoint PinchViewport::maximumScrollPosition() const
 {
     return flooredIntPoint(FloatSize(contentsSize()) - visibleRect().size());
 }
 
+IntPoint PinchViewport::clampDocumentOffsetAtScale(const IntPoint& offset, float scale)
+{
+    if (!mainFrame() || !mainFrame()->view())
+        return IntPoint();
+
+    FrameView* view = mainFrame()->view();
+
+    FloatSize scaledSize(m_size);
+    scaledSize.scale(1 / scale);
+
+    IntPoint pinchViewportMax = flooredIntPoint(FloatSize(contentsSize()) - scaledSize);
+    IntPoint max = view->maximumScrollPosition() + pinchViewportMax;
+    IntPoint min = view->minimumScrollPosition(); // PinchViewportMin should be (0, 0)
+
+    IntPoint clamped = offset;
+    clamped = clamped.shrunkTo(max);
+    clamped = clamped.expandedTo(min);
+    return clamped;
+}
+
 IntRect PinchViewport::scrollableAreaBoundingBox() const
 {
     // This method should return the bounding box in the parent view's coordinate
     // space; however, PinchViewport technically isn't a child of any Frames.
     // Nonetheless, the PinchViewport always occupies the entire main frame so just
     // return that.
     LocalFrame* frame = mainFrame();
 
     if (!frame || !frame->view())
         return IntRect();
@@ skipping 78 matching lines @@
     } else if (graphicsLayer == m_overlayScrollbarVertical.get()) {
         name =  "Overlay Scrollbar Vertical Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink