Clip PaintLayerScrollableArea::scrollIntoView return to layer bounds

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 1389 matching lines @@
         LayoutUnit baseHeight = box().size().height() - (isBoxSizingBorder ? LayoutUnit() : box().borderAndPaddingHeight());
         baseHeight = LayoutUnit(baseHeight / zoomFactor);
         element->setInlineStyleProperty(CSSPropertyHeight, roundToInt(baseHeight + difference.height()), CSSPrimitiveValue::UnitType::Pixels);
     }
 
     document.updateStyleAndLayout();
 
     // FIXME (Radar 4118564): We should also autoscroll the window as necessary to keep the point under the cursor in view.
 }
 
 LayoutRect PaintLayerScrollableArea::scrollIntoView(const LayoutRect& rect, const ScrollAlignment& alignX, const ScrollAlignment& alignY, ScrollType scrollType)

[bokan, 2016/08/26 16:12:14]

Please add a comment in the header file for this method explaining it's return
value. e.g.

"Returns the new position, after scrolling, of the given rect in absolute
coordinates, clipped by the parent's client rect."

 {
     LayoutRect localExposeRect(box().absoluteToLocalQuad(FloatQuad(FloatRect(rect)), UseTransforms).boundingBox());
     localExposeRect.move(-box().borderLeft(), -box().borderTop());
     LayoutRect layerBounds(LayoutPoint(), LayoutSize(box().clientWidth(), box().clientHeight()));
     LayoutRect r = ScrollAlignment::getRectToExpose(layerBounds, localExposeRect, alignX, alignY);
 
     DoublePoint clampedScrollPosition = clampScrollPosition(scrollPositionDouble() + roundedIntSize(r.location()));
     if (clampedScrollPosition == scrollPositionDouble())
-        return rect;
+        return LayoutRect(box().localToAbsoluteQuad(FloatQuad(FloatRect(intersection(layerBounds, localExposeRect))), UseTransforms).boundingBox());
 
     DoubleSize oldScrollOffset = adjustedScrollOffset();
     scrollToPosition(clampedScrollPosition, ScrollOffsetUnclamped, ScrollBehaviorInstant, scrollType);
     DoubleSize scrollOffsetDifference = adjustedScrollOffset() - oldScrollOffset;
     localExposeRect.move(-LayoutSize(scrollOffsetDifference));
-    return LayoutRect(box().localToAbsoluteQuad(FloatQuad(FloatRect(localExposeRect)), UseTransforms).boundingBox());
+    return LayoutRect(box().localToAbsoluteQuad(FloatQuad(FloatRect(intersection(layerBounds, localExposeRect))), UseTransforms).boundingBox());
 }
 
 void PaintLayerScrollableArea::updateScrollableAreaSet(bool hasOverflow)
 {
     LocalFrame* frame = box().frame();
     if (!frame)
         return;
 
     FrameView* frameView = frame->view();
     if (!frameView)
@@ skipping 337 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollPositionClampScope::clampScrollableAreas()
 {
     for (auto& scrollableArea : *s_needsClamp)
         scrollableArea->clampScrollPositionsAfterLayout();
     delete s_needsClamp;
     s_needsClamp = nullptr;
 }
 
 } // namespace blink