Adds scroll position/scale emulation to DevTools.

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 132 matching lines @@
     , m_needsUpdateWidgetGeometries(false)
     , m_needsUpdateViewportIntersection(true)
     , m_needsUpdateViewportIntersectionInSubtree(true)
 #if ENABLE(ASSERT)
     , m_hasBeenDisposed(false)
 #endif
     , m_horizontalScrollbarMode(ScrollbarAuto)
     , m_verticalScrollbarMode(ScrollbarAuto)
     , m_horizontalScrollbarLock(false)
     , m_verticalScrollbarLock(false)
+    , m_scrollOverrideEnabled(false)
     , m_scrollbarsAvoidingResizer(0)
     , m_scrollbarsSuppressed(false)
     , m_inUpdateScrollbars(false)
     , m_frameTimingRequestsDirty(true)
     , m_viewportIntersectionValid(false)
     , m_hiddenForThrottling(false)
     , m_crossOriginForThrottling(false)
     , m_subtreeThrottled(false)
     , m_isUpdatingAllLifecyclePhases(false)
     , m_scrollAnchor(this)
@@ skipping 1394 matching lines @@
         scrollToFragmentAnchor();
 }
 
 void FrameView::clearFragmentAnchor()
 {
     m_fragmentAnchor = nullptr;
 }
 
 void FrameView::setScrollPosition(const DoublePoint& scrollPoint, ScrollType scrollType, ScrollBehavior scrollBehavior)
 {
-    DoublePoint newScrollPosition = clampScrollPosition(scrollPoint);
+    DoublePoint newScrollPosition = clampScrollPosition(applyScrollOverrideToPosition(newScrollPosition));
     if (newScrollPosition == scrollPositionDouble())
         return;
 
     if (scrollBehavior == ScrollBehaviorAuto)
         scrollBehavior = scrollBehaviorStyle();
 
     ScrollableArea::setScrollPosition(newScrollPosition, scrollType, scrollBehavior);
 }
 
+void FrameView::setScrollOverride(const DoublePoint& position)
+{
+    m_scrollOverrideEnabled = true;
+    m_scrollOverridePosition = position;
+    setScrollPosition(scrollPosition(), ProgrammaticScroll, ScrollBehaviorInstant);
+}
+
+void FrameView::clearScrollOverride()
+{
+    m_scrollOverrideEnabled = false;
+}
+
 void FrameView::didUpdateElasticOverscroll()
 {
     Page* page = frame().page();
     if (!page)
         return;
     FloatSize elasticOverscroll = page->chromeClient().elasticOverscroll();
     if (m_horizontalScrollbar) {
         float delta = elasticOverscroll.width() - m_horizontalScrollbar->elasticOverscroll();
         if (delta != 0) {
             m_horizontalScrollbar->setElasticOverscroll(elasticOverscroll.width());
@@ skipping 1639 matching lines @@
         return orientation == HorizontalScrollbar ? scrollSize.width() : scrollSize.height();
     }
 
     return scrollbar->totalSize() - scrollbar->visibleSize();
 }
 
 void FrameView::setScrollOffset(const DoublePoint& offset, ScrollType scrollType)
 {
     // TODO(skobes): We shouldn't have to clamp here; instead we should update callers
     // ScrollableArea::scrollPositionChanged to only pass clamped offsets.
-    DoublePoint newPosition = clampScrollPosition(offset);
+    DoublePoint newPosition = clampScrollPosition(applyScrollOverrideToPosition(offset));
 
     DoublePoint oldPosition = m_scrollPosition;
     DoubleSize scrollDelta = newPosition - oldPosition;
     if (scrollDelta.isZero())
         return;
 
     if (m_frame->settings() && m_frame->settings()->rootLayerScrolls()) {
         // Don't scroll the FrameView!
         ASSERT_NOT_REACHED();
     }
@@ skipping 28 matching lines @@
     if (AXObjectCache* cache = m_frame->document()->existingAXObjectCache())
         cache->handleScrollPositionChanged(this);
 
     frame().loader().saveScrollState();
     frame().loader().client()->didChangeScrollOffset();
 
     if (RuntimeEnabledFeatures::scrollAnchoringEnabled() && scrollType != AnchoringScroll)
         m_scrollAnchor.clear();
 }
 
+DoublePoint FrameView::applyScrollOverrideToPosition(const DoublePoint& position)
+{
+    DoublePoint newPosition = position;
+    if (m_scrollOverrideEnabled) {
+        if (m_scrollOverridePosition.x() >= 0)

[Sami, 2016/06/23 17:34:03]

Do we need to validate the coordinates again here?

[Eric Seckler, 2016/06/23 18:12:43]

At the moment, I'm using a value <0 to signal "no override for this coordinate".
Does that make sense? If so, I will add a comment to that effect.

[Sami, 2016/06/24 14:48:26]

Oh I see, I didn't notice we can override just one axis. Hopefully this will be
more obvious in the new centralized class.

+            newPosition.setX(m_scrollOverridePosition.x());
+        if (m_scrollOverridePosition.y() >= 0)
+            newPosition.setY(m_scrollOverridePosition.y());
+    }
+    return newPosition;
+}
+
 void FrameView::windowResizerRectChanged()
 {
     updateScrollbars();
 }
 
 bool FrameView::hasOverlayScrollbars() const
 {
     return (m_horizontalScrollbar && m_horizontalScrollbar->isOverlayScrollbar())
         || (m_verticalScrollbar && m_verticalScrollbar->isOverlayScrollbar());
 }
@@ skipping 847 matching lines @@
     return m_subtreeThrottled || (m_hiddenForThrottling && m_crossOriginForThrottling);
 }
 
 LayoutBox& FrameView::boxForScrollControlPaintInvalidation() const
 {
     ASSERT(!layoutViewItem().isNull());
     return *layoutView();
 }
 
 } // namespace blink