Adds scroll position/scale emulation to DevTools.

third_party/WebKit/Source/core/frame/VisualViewport.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 18 matching lines @@
  */
 
 #include "core/frame/VisualViewport.h"
 
 #include "core/dom/DOMNodeIds.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/PageScaleConstraints.h"
 #include "core/frame/PageScaleConstraintsSet.h"
+#include "core/frame/ScrollAndScaleEmulator.h"
 #include "core/frame/Settings.h"
 #include "core/inspector/InspectorInstrumentation.h"
 #include "core/layout/TextAutosizer.h"
 #include "core/layout/compositing/PaintLayerCompositor.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/Page.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
 #include "platform/Histogram.h"
 #include "platform/TraceEvent.h"
@@ skipping 166 matching lines @@
 void VisualViewport::move(const FloatSize& delta)
 {
     setLocation(m_offset + delta);
 }
 
 void VisualViewport::setScale(float scale)
 {
     setScaleAndLocation(scale, m_offset);
 }
 
+void VisualViewport::setScrollAndScaleEmulator(const RefPtr<ScrollAndScaleEmulator>& emulator)
+{
+    m_scrollAndScaleEmulator = emulator;
+    setScaleAndLocation(scale(), location());

[bokan, 2016/07/01 21:05:12]

We should call setScaleAndLocation to clamp the scroll position from the caller
(inside ScrollAndScaleEmulator). Also, visual viewport has a clampToBoundaries
method you could use.

[Eric Seckler, 2016/07/04 14:33:08]

Done, using clampToBoundaries() now. (This boils down to the same
setScaleAndLocation() invocation.)

+}
+
 double VisualViewport::scrollLeft()
 {
     if (!mainFrame())
         return 0;
 
     updateStyleAndLayoutIgnorePendingStylesheets();
 
     return adjustScrollForAbsoluteZoom(visibleRect().x(), mainFrame()->pageZoomFactor());
 }
 
@@ skipping 308 matching lines @@
 }
 
 int VisualViewport::scrollSize(ScrollbarOrientation orientation) const
 {
     IntSize scrollDimensions = maximumScrollPosition() - minimumScrollPosition();
     return (orientation == HorizontalScrollbar) ? scrollDimensions.width() : scrollDimensions.height();
 }
 
 IntPoint VisualViewport::minimumScrollPosition() const
 {
-    return IntPoint();
+    return flooredIntPoint(minimumScrollPositionDouble());
+}
+
+DoublePoint VisualViewport::minimumScrollPositionDouble() const
+{
+    if (m_scrollAndScaleEmulator) {
+        DoublePoint minimum = calculateMinimumScrollPositionDouble();
+        DoublePoint maximum = calculateMaximumScrollPositionDouble();
+        return m_scrollAndScaleEmulator->applyVisualViewportPositionOverride(minimum, minimum, maximum);
+    }
+
+    return calculateMinimumScrollPositionDouble();
+}
+
+DoublePoint VisualViewport::calculateMinimumScrollPositionDouble() const
+{
+    return DoublePoint();
 }
 
 IntPoint VisualViewport::maximumScrollPosition() const
 {
     return flooredIntPoint(maximumScrollPositionDouble());
 }
 
 DoublePoint VisualViewport::maximumScrollPositionDouble() const
 {
+    if (m_scrollAndScaleEmulator) {
+        DoublePoint minimum = calculateMinimumScrollPositionDouble();
+        DoublePoint maximum = calculateMaximumScrollPositionDouble();
+        return m_scrollAndScaleEmulator->applyVisualViewportPositionOverride(maximum, minimum, maximum);
+    }
+
+    return calculateMaximumScrollPositionDouble();
+}
+
+DoublePoint VisualViewport::calculateMaximumScrollPositionDouble() const
+{
     if (!mainFrame())
         return IntPoint();
 
     // TODO(bokan): We probably shouldn't be storing the bounds in a float. crbug.com/470718.
     FloatSize frameViewSize(contentsSize());
 
     if (m_topControlsAdjustment) {
         float minScale = frameHost().pageScaleConstraintsSet().finalConstraints().minimumScale;
         frameViewSize.expand(0, m_topControlsAdjustment / minScale);
     }
@@ skipping 259 matching lines @@
     } else if (graphicsLayer == m_rootTransformLayer.get()) {
         name =  "Root Transform Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink