Force flattening for elements with non-initial value of opacity

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 439 matching lines @@
     }
     LayoutRectOutsets borderImageOutsets() const
     {
         return imageOutsets(borderImage());
     }
 
     // Returns |true| if any property that renders using filter operations is
     // used (including, but not limited to, 'filter').
     bool hasFilterInducingProperty() const { return hasFilter() || (RuntimeEnabledFeatures::cssBoxReflectFilterEnabled() && hasBoxReflect()); }
 
+    // Returns |true| if opacity should be considered to have non-initial value for the purpose
+    // of creating stacking contexts.
+    bool hasNonInitialOpacity() const { return opacity() != 1.0f || hasWillChangeOpacityHint() || hasCurrentOpacityAnimation(); }

[chrishtr, 2016/06/15 16:06:41]

hasOpacity() is the way to check for inequality with 1.0.

Also, do hasWillChangeOpacityHint() or hasCurrentOpacityAnimation() cause
stacking contexts in the code right now?

[trchen, 2016/06/18 00:27:09]

Done.
Yes for will-change:opacity.

No for opacity animation (on the frame that opacity happens to be 1.0). I think
it is a bug but isn't really important.

+
+    // Returns whether this style contains any grouping property as defined by [css-transforms].
+    // The main purpose of this is to adjust the used value of transform-style property.
+    // Note: We currently don't include every grouping property on the spec to maintain
+    //       backward compatibility.
+    // [css-transforms] https://drafts.csswg.org/css-transforms/#grouping-property-values
+    bool hasGroupingProperty() const { return !isOverflowVisible() || hasFilterInducingProperty() || hasNonInitialOpacity(); }
+
     Order rtlOrdering() const { return static_cast<Order>(inherited_flags.m_rtlOrdering); }
     void setRTLOrdering(Order o) { inherited_flags.m_rtlOrdering = o; }
 
     bool isStyleAvailable() const;
 
     bool hasAnyPublicPseudoStyles() const;
     bool hasPseudoStyle(PseudoId) const;
     void setHasPseudoStyle(PseudoId);
     bool hasUniquePseudoStyle() const;
     bool hasPseudoElementStyle() const;
@@ skipping 482 matching lines @@
 
     // Apple-specific property getter methods
     EPointerEvents pointerEvents() const { return static_cast<EPointerEvents>(inherited_flags._pointerEvents); }
     const CSSAnimationData* animations() const { return rareNonInheritedData->m_animations.get(); }
     const CSSTransitionData* transitions() const { return rareNonInheritedData->m_transitions.get(); }
 
     CSSAnimationData& accessAnimations();
     CSSTransitionData& accessTransitions();
 
     ETransformStyle3D transformStyle3D() const { return static_cast<ETransformStyle3D>(rareNonInheritedData->m_transformStyle3D); }
-    bool preserves3D() const { return rareNonInheritedData->m_transformStyle3D == TransformStyle3DPreserve3D; }
+    ETransformStyle3D usedTransformStyle3D() const;
+    bool preserves3D() const { return usedTransformStyle3D() != TransformStyle3DFlat; }
 
     EBackfaceVisibility backfaceVisibility() const { return static_cast<EBackfaceVisibility>(rareNonInheritedData->m_backfaceVisibility); }
     float perspective() const { return rareNonInheritedData->m_perspective; }
     bool hasPerspective() const { return rareNonInheritedData->m_perspective > 0; }
     const LengthPoint& perspectiveOrigin() const { return rareNonInheritedData->m_perspectiveOrigin; }
     const Length& perspectiveOriginX() const { return perspectiveOrigin().x(); }
     const Length& perspectiveOriginY() const { return perspectiveOrigin().y(); }
     const FloatSize& pageSize() const { return rareNonInheritedData->m_pageSize; }
     PageSizeType getPageSizeType() const { return static_cast<PageSizeType>(rareNonInheritedData->m_pageSizeType); }
 
@@ skipping 47 matching lines @@
     ScrollSnapType getScrollSnapType() const { return static_cast<ScrollSnapType>(rareNonInheritedData->m_scrollSnapType); }
     const ScrollSnapPoints& scrollSnapPointsX() const { return rareNonInheritedData->m_scrollSnap->m_xPoints; }
     const ScrollSnapPoints& scrollSnapPointsY() const { return rareNonInheritedData->m_scrollSnap->m_yPoints; }
     const Vector<LengthPoint>& scrollSnapCoordinate() const { return rareNonInheritedData->m_scrollSnap->m_coordinates; }
     const LengthPoint& scrollSnapDestination() const { return rareNonInheritedData->m_scrollSnap->m_destination; }
 
     const Vector<CSSPropertyID>& willChangeProperties() const { return rareNonInheritedData->m_willChange->m_properties; }
     bool willChangeContents() const { return rareNonInheritedData->m_willChange->m_contents; }
     bool willChangeScrollPosition() const { return rareNonInheritedData->m_willChange->m_scrollPosition; }
     bool hasWillChangeCompositingHint() const;
+    bool hasWillChangeOpacityHint() const { return willChangeProperties().contains(CSSPropertyOpacity); }
     bool hasWillChangeTransformHint() const;
     bool subtreeWillChangeContents() const { return rareInheritedData->m_subtreeWillChangeContents; }
 
 // attribute setter methods
 
     void setDisplay(EDisplay v) { noninherited_flags.effectiveDisplay = v; }
     void setOriginalDisplay(EDisplay v) { noninherited_flags.originalDisplay = v; }
     void setPosition(EPosition v) { noninherited_flags.position = v; }
     void setFloating(EFloat v) { noninherited_flags.floating = v; }
 
@@ skipping 985 matching lines @@
 }
 
 inline bool ComputedStyle::hasPseudoElementStyle() const
 {
     return noninherited_flags.pseudoBits & ElementPseudoIdMask;
 }
 
 } // namespace blink
 
 #endif // ComputedStyle_h