Implement the overflow-anchor CSS property as an opt-out for ScrollAnchoring

third_party/WebKit/Source/core/style/ComputedStyle.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 200 matching lines @@
         // 42 bits
     } m_inheritedData;
 
 // don't inherit
     struct NonInheritedData {
         // Compare computed styles, differences in other flags should not cause an inequality.
         bool operator==(const NonInheritedData& other) const
         {
             return m_effectiveDisplay == other.m_effectiveDisplay
                 && m_originalDisplay == other.m_originalDisplay
+                && m_overflowAnchor == other.m_overflowAnchor
                 && m_overflowX == other.m_overflowX
                 && m_overflowY == other.m_overflowY
                 && m_verticalAlign == other.m_verticalAlign
                 && m_clear == other.m_clear
                 && m_position == other.m_position
                 && m_floating == other.m_floating
                 && m_tableLayout == other.m_tableLayout
                 && m_unicodeBidi == other.m_unicodeBidi
                 // hasViewportUnits
                 && m_breakBefore == other.m_breakBefore
                 && m_breakAfter == other.m_breakAfter
                 && m_breakInside == other.m_breakInside;
                 // styleType
                 // pseudoBits
                 // explicitInheritance
                 // unique
                 // emptyState
                 // affectedByFocus
                 // affectedByHover
                 // affectedByActive
                 // affectedByDrag
                 // isLink
         }
 
         bool operator!=(const NonInheritedData& other) const { return !(*this == other); }
 
         unsigned m_effectiveDisplay : 5; // EDisplay
         unsigned m_originalDisplay : 5; // EDisplay
+        unsigned m_overflowAnchor : 2; // EOverflowAnchor
         unsigned m_overflowX : 3; // EOverflow
         unsigned m_overflowY : 3; // EOverflow
         unsigned m_verticalAlign : 4; // EVerticalAlign
         unsigned m_clear : 2; // EClear
         unsigned m_position : 3; // EPosition
         unsigned m_floating : 2; // EFloat
         unsigned m_tableLayout : 1; // ETableLayout
         unsigned m_unicodeBidi : 3; // EUnicodeBidi
 
         // This is set if we used viewport units when resolving a length.
@@ skipping 46 matching lines @@
         m_inheritedData.m_whiteSpace = initialWhiteSpace();
         m_inheritedData.m_borderCollapse = initialBorderCollapse();
         m_inheritedData.m_rtlOrdering = initialRTLOrdering();
         m_inheritedData.m_boxDirection = initialBoxDirection();
         m_inheritedData.m_printColorAdjust = initialPrintColorAdjust();
         m_inheritedData.m_pointerEvents = initialPointerEvents();
         m_inheritedData.m_insideLink = NotInsideLink;
         m_inheritedData.m_writingMode = initialWritingMode();
 
         m_nonInheritedData.m_effectiveDisplay = m_nonInheritedData.m_originalDisplay = initialDisplay();
+        m_nonInheritedData.m_overflowAnchor = initialOverflowAnchor();
         m_nonInheritedData.m_overflowX = initialOverflowX();
         m_nonInheritedData.m_overflowY = initialOverflowY();
         m_nonInheritedData.m_verticalAlign = initialVerticalAlign();
         m_nonInheritedData.m_clear = initialClear();
         m_nonInheritedData.m_position = initialPosition();
         m_nonInheritedData.m_floating = initialFloating();
         m_nonInheritedData.m_tableLayout = initialTableLayout();
         m_nonInheritedData.m_unicodeBidi = initialUnicodeBidi();
         m_nonInheritedData.m_breakBefore = initialBreakBefore();
         m_nonInheritedData.m_breakAfter = initialBreakAfter();
@@ skipping 244 matching lines @@
     {
         if (m_background->outline().style() == BorderStyleNone)
             return 0;
         return m_background->outline().width();
     }
     bool hasOutline() const { return outlineWidth() > 0 && outlineStyle() > BorderStyleHidden; }
     EBorderStyle outlineStyle() const { return m_background->outline().style(); }
     OutlineIsAuto outlineStyleIsAuto() const { return static_cast<OutlineIsAuto>(m_background->outline().isAuto()); }
     int outlineOutsetExtent() const;
 
+    EOverflowAnchor overflowAnchor() const { return static_cast<EOverflowAnchor>(m_nonInheritedData.m_overflowAnchor); }
     EOverflow overflowX() const { return static_cast<EOverflow>(m_nonInheritedData.m_overflowX); }
     EOverflow overflowY() const { return static_cast<EOverflow>(m_nonInheritedData.m_overflowY); }
     // It's sufficient to just check one direction, since it's illegal to have visible on only one overflow value.
     bool isOverflowVisible() const { ASSERT(overflowX() != OverflowVisible || overflowX() == overflowY()); return overflowX() == OverflowVisible; }
     bool isOverflowPaged() const { return overflowY() == OverflowPagedX || overflowY() == OverflowPagedY; }
 
     EVisibility visibility() const { return static_cast<EVisibility>(m_inheritedData.m_visibility); }
     EVerticalAlign verticalAlign() const { return static_cast<EVerticalAlign>(m_nonInheritedData.m_verticalAlign); }
     const Length& getVerticalAlignLength() const { return m_box->verticalAlign(); }
 
@@ skipping 578 matching lines @@
         if (!otherStyle)
             return !hasOutline();
         return m_background->outline().visuallyEqual(otherStyle->m_background->outline());
     }
     void setOutlineFromStyle(const ComputedStyle& o)
     {
         ASSERT(!isOutlineEquivalent(&o));
         m_background.access()->m_outline = o.m_background->m_outline;
     }
 
+    void setOverflowAnchor(EOverflowAnchor v) { m_nonInheritedData.m_overflowAnchor = v; }
     void setOverflowX(EOverflow v) { m_nonInheritedData.m_overflowX = v; }
     void setOverflowY(EOverflow v) { m_nonInheritedData.m_overflowY = v; }
     void setVisibility(EVisibility v) { m_inheritedData.m_visibility = v; }
     void setVerticalAlign(EVerticalAlign v) { m_nonInheritedData.m_verticalAlign = v; }
     void setVerticalAlignLength(const Length& length) { setVerticalAlign(VerticalAlignLength); SET_VAR(m_box, m_verticalAlign, length); }
 
     void setHasAutoClip() { SET_VAR(m_visual, hasAutoClip, true); SET_VAR(m_visual, clip, ComputedStyle::initialClip()); }
     void setClip(const LengthBox& box) { SET_VAR(m_visual, hasAutoClip, false); SET_VAR(m_visual, clip, box); }
 
     void setUnicodeBidi(EUnicodeBidi b) { m_nonInheritedData.m_unicodeBidi = b; }
@@ skipping 509 matching lines @@
     static WritingMode initialWritingMode() { return TopToBottomWritingMode; }
     static TextCombine initialTextCombine() { return TextCombineNone; }
     static TextOrientation initialTextOrientation() { return TextOrientationMixed; }
     static ObjectFit initialObjectFit() { return ObjectFitFill; }
     static LengthPoint initialObjectPosition() { return LengthPoint(Length(50.0, Percent), Length(50.0, Percent)); }
     static EDisplay initialDisplay() { return INLINE; }
     static EEmptyCells initialEmptyCells() { return EmptyCellsShow; }
     static EFloat initialFloating() { return NoFloat; }
     static EListStylePosition initialListStylePosition() { return ListStylePositionOutside; }
     static EListStyleType initialListStyleType() { return Disc; }
+    static EOverflowAnchor initialOverflowAnchor() { return AnchorAuto; }
     static EOverflow initialOverflowX() { return OverflowVisible; }
     static EOverflow initialOverflowY() { return OverflowVisible; }
     static EBreak initialBreakAfter() { return BreakAuto; }
     static EBreak initialBreakBefore() { return BreakAuto; }
     static EBreak initialBreakInside() { return BreakAuto; }
     static EPosition initialPosition() { return StaticPosition; }
     static ETableLayout initialTableLayout() { return TableLayoutAuto; }
     static EUnicodeBidi initialUnicodeBidi() { return UBNormal; }
     static ETextTransform initialTextTransform() { return TTNONE; }
     static EVisibility initialVisibility() { return VISIBLE; }
@@ skipping 339 matching lines @@
 }
 
 inline bool ComputedStyle::hasPseudoElementStyle() const
 {
     return m_nonInheritedData.m_pseudoBits & ElementPseudoIdMask;
 }
 
 } // namespace blink
 
 #endif // ComputedStyle_h