Made top controls work with virtual viewport pinch-to-zoom. (Blink)

Source/core/frame/PinchViewport.cpp

Index: Source/core/frame/PinchViewport.cpp
diff --git a/Source/core/frame/PinchViewport.cpp b/Source/core/frame/PinchViewport.cpp
index 3c877332714d5e26b104395b96ea3ed1bfde8e5f..2f6a7d9068ca1e713aff7f31f6b7f78c880b60cf 100644
--- a/Source/core/frame/PinchViewport.cpp
+++ b/Source/core/frame/PinchViewport.cpp
@@ -67,6 +67,7 @@ namespace blink {
 PinchViewport::PinchViewport(FrameHost& owner)
     : m_frameHost(owner)
     , m_scale(1)
+    , m_topControlsAdjustment(0)
 {
     reset();
 }
@@ -81,8 +82,6 @@ void PinchViewport::setSize(const IntSize& size)
     TRACE_EVENT2("blink", "PinchViewport::setSize", "width", size.width(), "height", size.height());
     m_size = size;
 
-    clampToBoundaries();
-
     if (m_innerViewportContainerLayer) {
         m_innerViewportContainerLayer->setSize(m_size);
 
@@ -111,6 +110,7 @@ void PinchViewport::mainFrameDidChangeSize()
 FloatRect PinchViewport::visibleRect() const
 {
     FloatSize scaledSize(m_size);
+    scaledSize.expand(0, m_topControlsAdjustment);
     scaledSize.scale(1 / m_scale);
     return FloatRect(m_offset, scaledSize);
 }
@@ -356,7 +356,24 @@ IntPoint PinchViewport::minimumScrollPosition() const
 
 IntPoint PinchViewport::maximumScrollPosition() const
 {
-    return flooredIntPoint(FloatSize(contentsSize()) - visibleRect().size());
+    FloatSize frameViewSize(contentsSize());

[Rick Byers, 2014/10/10 00:06:09]

not necessarily for this CL (if it's non-trivial to correct here), but note that
we've elsewhere decided that float doesn't have enough precision to properly
represent the size of a document.  Eg. it could result in off-by-one errors in
long documents (eg. with height+1==height).  Elsewhere (miletus@'s fractional
scroll offset work) we're using doubles, you may want to consider changing
PinchViewport to match (or at least testing on a page with height >1,000,000px -
I just got a real-world bug for a page nearly this long the other day).

[bokan, 2014/10/10 14:39:56]

Yes, I've been following the discussion. I'll keep this here for now since it
should match the calculation in LayerImpl::MaxScrollOffset in CC which uses
SizeF. Filed crbug.com/422331 and referenced it with a FIXME.

+
+    // The adjustment should only be non-zero in the case of a top controls offset.
+    // It is made to keep the aspect ratio of the two viewports the same.
+    float aspectRatio = visibleRect().width() / visibleRect().height();
+    float adjustment = frameViewSize.width() / aspectRatio - frameViewSize.height();
+    frameViewSize.expand(0, adjustment);
+
+    frameViewSize.scale(m_scale);
+    frameViewSize = flooredIntSize(frameViewSize);
+
+    FloatSize viewportSize(m_size);
+    viewportSize.expand(0, m_topControlsAdjustment);
+
+    FloatSize maxPosition = frameViewSize - viewportSize;
+    maxPosition.scale(1 / m_scale);
+
+    return flooredIntPoint(maxPosition);
 }
 
 IntPoint PinchViewport::clampDocumentOffsetAtScale(const IntPoint& offset, float scale)
@@ -379,6 +396,11 @@ IntPoint PinchViewport::clampDocumentOffsetAtScale(const IntPoint& offset, float
     return clamped;
 }
 
+void PinchViewport::setTopControlsAdjustment(float adjustment)
+{
+    m_topControlsAdjustment = adjustment;
+}
+
 IntRect PinchViewport::scrollableAreaBoundingBox() const
 {
     // This method should return the bounding box in the parent view's coordinate