CompositingReasons CompositingReasonFinder::nonStyleDeterminedDirectReasons(const PaintLayer* layer) const
{
    CompositingReasons directReasons = CompositingReasonNone;
    LayoutObject* layoutObject = layer->layoutObject();

    if (hasOverflowScrollTrigger()) {
        if (layer->clipParent())
            directReasons |= CompositingReasonOutOfFlowClipping;

        if (layer->needsCompositedScrolling())
            directReasons |= CompositingReasonOverflowScrollingTouch;
    }

    // Composite |layer| if it is inside of an ancestor scrolling layer, but that
    // scrolling layer is not not on the stacking context ancestor chain of |layer|.
    // See the definition of the scrollParent property in Layer for more detail.
    if (const PaintLayer* scrollingAncestor = layer->ancestorScrollingLayer()) {
        if (scrollingAncestor->needsCompositedScrolling() && layer->scrollParent())
            directReasons |= CompositingReasonOverflowScrollingParent;
    }

    if (requiresCompositingForPositionFixed(layer))
        directReasons |= CompositingReasonPositionFixed;

    directReasons |= layoutObject->additionalCompositingReasons();

    ASSERT(!(directReasons & CompositingReasonComboAllStyleDeterminedReasons));
    return directReasons;
}
Exemplo n.º 2
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CompositingReasons CompositingReasonFinder::nonStyleDeterminedDirectReasons(
    const PaintLayer* layer) const {
  CompositingReasons directReasons = CompositingReasonNone;
  LayoutObject* layoutObject = layer->layoutObject();

  if (m_compositingTriggers & OverflowScrollTrigger && layer->clipParent())
    directReasons |= CompositingReasonOutOfFlowClipping;

  if (layer->needsCompositedScrolling())
    directReasons |= CompositingReasonOverflowScrollingTouch;

  // Composite |layer| if it is inside of an ancestor scrolling layer, but that
  // scrolling layer is not on the stacking context ancestor chain of |layer|.
  // See the definition of the scrollParent property in Layer for more detail.
  if (const PaintLayer* scrollingAncestor = layer->ancestorScrollingLayer()) {
    if (scrollingAncestor->needsCompositedScrolling() && layer->scrollParent())
      directReasons |= CompositingReasonOverflowScrollingParent;
  }

  // TODO(flackr): Rename functions and variables to include sticky position
  // (i.e. ScrollDependentPosition rather than PositionFixed).
  if (requiresCompositingForScrollDependentPosition(layer))
    directReasons |= CompositingReasonScrollDependentPosition;

  directReasons |= layoutObject->additionalCompositingReasons();

  DCHECK(!(directReasons & CompositingReasonComboAllStyleDeterminedReasons));
  return directReasons;
}