C++ PaintLayer::stackingNode方法代码示例

static bool shouldCreateSubsequence(const PaintLayer& paintLayer, GraphicsContext& context, const PaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
{
    // Caching is not needed during printing.
    if (context.printing())
        return false;

    // Don't create subsequence for a composited layer because if it can be cached,
    // we can skip the whole painting in GraphicsLayer::paint() with CachedDisplayItemList.
    // This also avoids conflict of PaintLayer::previousXXX() when paintLayer is composited
    // scrolling and is painted twice for GraphicsLayers of container and scrolling contents.
    if (paintLayer.compositingState() == PaintsIntoOwnBacking)
        return false;

    // Don't create subsequence during special painting to avoid cache conflict with normal painting.
    if (paintingInfo.globalPaintFlags() & GlobalPaintFlattenCompositingLayers)
        return false;
    if (paintFlags & (PaintLayerPaintingReflection | PaintLayerPaintingRootBackgroundOnly | PaintLayerPaintingOverlayScrollbars | PaintLayerUncachedClipRects))
        return false;

    // Create subsequence for only stacking contexts whose painting are atomic.
    if (!paintLayer.stackingNode()->isStackingContext())
        return false;

    // The layer doesn't have children. Subsequence caching is not worth because normally the actual painting will be cheap.
    if (!PaintLayerStackingNodeIterator(*paintLayer.stackingNode(), AllChildren).next())
        return false;

    return true;
}

void GraphicsLayerTreeBuilder::rebuild(PaintLayer& layer, AncestorInfo info)
{
    // Make the layer compositing if necessary, and set up clipping and content layers.
    // Note that we can only do work here that is independent of whether the descendant layers
    // have been processed. computeCompositingRequirements() will already have done the paint invalidation if necessary.

    layer.stackingNode()->updateLayerListsIfNeeded();

    const bool hasCompositedLayerMapping = layer.hasCompositedLayerMapping();
    CompositedLayerMapping* currentCompositedLayerMapping = layer.compositedLayerMapping();

    // If this layer has a compositedLayerMapping, then that is where we place subsequent children GraphicsLayers.
    // Otherwise children continue to append to the child list of the enclosing layer.
    GraphicsLayerVector layerChildren;
    AncestorInfo infoForChildren(info);
    if (hasCompositedLayerMapping) {
        infoForChildren.childLayersOfEnclosingCompositedLayer = &layerChildren;
        infoForChildren.enclosingCompositedLayer = &layer;
    }

#if ENABLE(ASSERT)
    LayerListMutationDetector mutationChecker(layer.stackingNode());
#endif

    if (layer.stackingNode()->isStackingContext()) {
        PaintLayerStackingNodeIterator iterator(*layer.stackingNode(), NegativeZOrderChildren);
        while (PaintLayerStackingNode* curNode = iterator.next())
            rebuild(*curNode->layer(), infoForChildren);

        // If a negative z-order child is compositing, we get a foreground layer which needs to get parented.
        if (hasCompositedLayerMapping && currentCompositedLayerMapping->foregroundLayer())
            infoForChildren.childLayersOfEnclosingCompositedLayer->append(currentCompositedLayerMapping->foregroundLayer());
    }

    PaintLayerStackingNodeIterator iterator(*layer.stackingNode(), NormalFlowChildren | PositiveZOrderChildren);
    while (PaintLayerStackingNode* curNode = iterator.next())
        rebuild(*curNode->layer(), infoForChildren);

    if (hasCompositedLayerMapping) {
        bool parented = false;
        if (layer.layoutObject()->isLayoutPart())
            parented = PaintLayerCompositor::attachFrameContentLayersToIframeLayer(toLayoutPart(layer.layoutObject()));

        if (!parented)
            currentCompositedLayerMapping->setSublayers(layerChildren);

        if (shouldAppendLayer(layer))
            info.childLayersOfEnclosingCompositedLayer->append(currentCompositedLayerMapping->childForSuperlayers());
    }

    if (layer.scrollParent()
        && layer.scrollParent()->hasCompositedLayerMapping()
        && layer.scrollParent()->compositedLayerMapping()->needsToReparentOverflowControls()
        && layer.scrollParent()->getScrollableArea()->topmostScrollChild() == &layer)
        info.childLayersOfEnclosingCompositedLayer->append(layer.scrollParent()->compositedLayerMapping()->detachLayerForOverflowControls(*info.enclosingCompositedLayer));
}

static void checkIsClippingStackingContextAndContainer(LayoutBoxModelObject& obj)
{
    EXPECT_TRUE(obj.canContainFixedPositionObjects());
    EXPECT_TRUE(obj.hasClipRelatedProperty());
    EXPECT_TRUE(obj.style()->containsPaint());

    // TODO(leviw): Ideally, we wouldn't require a paint layer to handle the clipping
    // and stacking performed by paint containment.
    ASSERT(obj.layer());
    PaintLayer* layer = obj.layer();
    EXPECT_TRUE(layer->stackingNode() && layer->stackingNode()->isStackingContext());
}

void PaintLayerStackingNode::rebuildZOrderLists() {
#if DCHECK_IS_ON()
  DCHECK(m_layerListMutationAllowed);
#endif
  DCHECK(isDirtyStackingContext());

  for (PaintLayer* child = layer()->firstChild(); child;
       child = child->nextSibling())
    child->stackingNode()->collectLayers(m_posZOrderList, m_negZOrderList);

  // Sort the two lists.
  if (m_posZOrderList)
    std::stable_sort(m_posZOrderList->begin(), m_posZOrderList->end(),
                     compareZIndex);

  if (m_negZOrderList)
    std::stable_sort(m_negZOrderList->begin(), m_negZOrderList->end(),
                     compareZIndex);

  // Append layers for top layer elements after normal layer collection, to
  // ensure they are on top regardless of z-indexes.  The layoutObjects of top
  // layer elements are children of the view, sorted in top layer stacking
  // order.
  if (layer()->isRootLayer()) {
    LayoutBlockFlow* rootBlock = layoutObject()->view();
    // If the viewport is paginated, everything (including "top-layer" elements)
    // gets redirected to the flow thread. So that's where we have to look, in
    // that case.
    if (LayoutBlockFlow* multiColumnFlowThread =
            rootBlock->multiColumnFlowThread())
      rootBlock = multiColumnFlowThread;
    for (LayoutObject* child = rootBlock->firstChild(); child;
         child = child->nextSibling()) {
      Element* childElement = (child->node() && child->node()->isElementNode())
                                  ? toElement(child->node())
                                  : 0;
      if (childElement && childElement->isInTopLayer()) {
        PaintLayer* layer = toLayoutBoxModelObject(child)->layer();
        // Create the buffer if it doesn't exist yet.
        if (!m_posZOrderList)
          m_posZOrderList = wrapUnique(new Vector<PaintLayerStackingNode*>);
        m_posZOrderList->append(layer->stackingNode());
      }
    }
  }

#if ENABLE(ASSERT)
  updateStackingParentForZOrderLists(this);
#endif

  m_zOrderListsDirty = false;
}

PaintLayerStackingNode* PaintLayerStackingNodeReverseIterator::next()
{
    if (m_remainingChildren & NegativeZOrderChildren) {
        Vector<PaintLayerStackingNode*>* negZOrderList = m_root.negZOrderList();
        if (negZOrderList && m_index >= 0)
            return negZOrderList->at(m_index--);

        m_remainingChildren &= ~NegativeZOrderChildren;
        setIndexToLastItem();
    }

    if (m_remainingChildren & NormalFlowChildren) {
        for (; m_currentNormalFlowChild; m_currentNormalFlowChild = m_currentNormalFlowChild->previousSibling()) {
            if (!m_currentNormalFlowChild->stackingNode()->isStacked() && !m_currentNormalFlowChild->isReflection()) {
                PaintLayer* normalFlowChild = m_currentNormalFlowChild;
                m_currentNormalFlowChild = m_currentNormalFlowChild->previousSibling();
                return normalFlowChild->stackingNode();
            }
        }

        m_remainingChildren &= ~NormalFlowChildren;
        setIndexToLastItem();
    }

    if (m_remainingChildren & PositiveZOrderChildren) {
        Vector<PaintLayerStackingNode*>* posZOrderList = m_root.posZOrderList();
        if (posZOrderList && m_index >= 0)
            return posZOrderList->at(m_index--);

        m_remainingChildren &= ~PositiveZOrderChildren;
        setIndexToLastItem();
    }

    return 0;
}

PaintLayerStackingNode* PaintLayerStackingNode::ancestorStackingContextNode()
    const {
  for (PaintLayer* ancestor = layer()->parent(); ancestor;
       ancestor = ancestor->parent()) {
    PaintLayerStackingNode* stackingNode = ancestor->stackingNode();
    if (stackingNode->isStackingContext())
      return stackingNode;
  }
  return 0;
}

void PaintLayerStackingNode::collectLayers(
    std::unique_ptr<Vector<PaintLayerStackingNode*>>& posBuffer,
    std::unique_ptr<Vector<PaintLayerStackingNode*>>& negBuffer) {
  if (layer()->isInTopLayer())
    return;

  if (isStacked()) {
    std::unique_ptr<Vector<PaintLayerStackingNode*>>& buffer =
        (zIndex() >= 0) ? posBuffer : negBuffer;
    if (!buffer)
      buffer = wrapUnique(new Vector<PaintLayerStackingNode*>);
    buffer->append(this);
  }

  if (!isStackingContext()) {
    for (PaintLayer* child = layer()->firstChild(); child;
         child = child->nextSibling())
      child->stackingNode()->collectLayers(posBuffer, negBuffer);
  }
}