C++ RenderLayer类代码示例

RenderObject* RenderObjectChildList::removeChildNode(RenderObject* owner, RenderObject* oldChild, bool fullRemove)
{
    ASSERT(oldChild->parent() == owner);

    // So that we'll get the appropriate dirty bit set (either that a normal flow child got yanked or
    // that a positioned child got yanked).  We also repaint, so that the area exposed when the child
    // disappears gets repainted properly.
    if (!owner->documentBeingDestroyed() && fullRemove && oldChild->everHadLayout()) {
        oldChild->setNeedsLayoutAndPrefWidthsRecalc();
        if (oldChild->isBody())
            owner->view()->repaint();
        else
            oldChild->repaint();
    }

    // If we have a line box wrapper, delete it.
    if (oldChild->isBox())
        toRenderBox(oldChild)->deleteLineBoxWrapper();

    if (!owner->documentBeingDestroyed() && fullRemove) {
        // if we remove visible child from an invisible parent, we don't know the layer visibility any more
        RenderLayer* layer = 0;
        if (owner->style()->visibility() != VISIBLE && oldChild->style()->visibility() == VISIBLE && !oldChild->hasLayer()) {
            if ((layer = owner->enclosingLayer()))
                layer->dirtyVisibleContentStatus();
        }

         // Keep our layer hierarchy updated.
        if (oldChild->firstChild() || oldChild->hasLayer()) {
            if (!layer)
                layer = owner->enclosingLayer();
            oldChild->removeLayers(layer);
        }

        if (oldChild->isListItem())
            toRenderListItem(oldChild)->updateListMarkerNumbers();

        if (oldChild->isPositioned() && owner->childrenInline())
            owner->dirtyLinesFromChangedChild(oldChild);

        if (oldChild->isRenderRegion())
            toRenderRegion(oldChild)->detachRegion();

        if (oldChild->inRenderFlowThread() && oldChild->isBox()) {
            oldChild->enclosingRenderFlowThread()->removeRenderBoxRegionInfo(toRenderBox(oldChild));
            if (oldChild->canHaveRegionStyle())
                oldChild->enclosingRenderFlowThread()->clearRenderBoxCustomStyle(toRenderBox(oldChild));
        }

        if (RenderFlowThread* containerFlowThread = renderFlowThreadContainer(owner))
            containerFlowThread->removeFlowChild(oldChild);

#if ENABLE(SVG)
        // Update cached boundaries in SVG renderers, if a child is removed.
        owner->setNeedsBoundariesUpdate();
#endif
    }
    
    // If oldChild is the start or end of the selection, then clear the selection to
    // avoid problems of invalid pointers.
    // FIXME: The FrameSelection should be responsible for this when it
    // is notified of DOM mutations.
    if (!owner->documentBeingDestroyed() && oldChild->isSelectionBorder())
        owner->view()->clearSelection();

    // remove the child
    if (oldChild->previousSibling())
        oldChild->previousSibling()->setNextSibling(oldChild->nextSibling());
    if (oldChild->nextSibling())
        oldChild->nextSibling()->setPreviousSibling(oldChild->previousSibling());

    if (firstChild() == oldChild)
        setFirstChild(oldChild->nextSibling());
    if (lastChild() == oldChild)
        setLastChild(oldChild->previousSibling());

    oldChild->setPreviousSibling(0);
    oldChild->setNextSibling(0);
    oldChild->setParent(0);

    RenderCounter::rendererRemovedFromTree(oldChild);
    RenderQuote::rendererRemovedFromTree(oldChild);

    if (AXObjectCache::accessibilityEnabled())
        owner->document()->axObjectCache()->childrenChanged(owner);

    return oldChild;
}

RenderObject* RenderContainer::removeChildNode(RenderObject* oldChild, bool fullRemove)
{
    ASSERT(oldChild->parent() == this);

    // So that we'll get the appropriate dirty bit set (either that a normal flow child got yanked or
    // that a positioned child got yanked).  We also repaint, so that the area exposed when the child
    // disappears gets repainted properly.
    if (!documentBeingDestroyed() && fullRemove && oldChild->m_everHadLayout) {
        oldChild->setNeedsLayoutAndPrefWidthsRecalc();
        oldChild->repaint();
    }

    // If we have a line box wrapper, delete it.
    oldChild->deleteLineBoxWrapper();

    if (!documentBeingDestroyed() && fullRemove) {
        // if we remove visible child from an invisible parent, we don't know the layer visibility any more
        RenderLayer* layer = 0;
        if (m_style->visibility() != VISIBLE && oldChild->style()->visibility() == VISIBLE && !oldChild->hasLayer()) {
            layer = enclosingLayer();
            layer->dirtyVisibleContentStatus();
        }

        // Keep our layer hierarchy updated.
        if (oldChild->firstChild() || oldChild->hasLayer()) {
            if (!layer) layer = enclosingLayer();
            oldChild->removeLayers(layer);
        }

        // renumber ordered lists
        if (oldChild->isListItem())
            updateListMarkerNumbers(oldChild->nextSibling());

        if (oldChild->isPositioned() && childrenInline())
            dirtyLinesFromChangedChild(oldChild);
    }

    // If oldChild is the start or end of the selection, then clear the selection to
    // avoid problems of invalid pointers.
    // FIXME: The SelectionController should be responsible for this when it
    // is notified of DOM mutations.
    if (!documentBeingDestroyed() && oldChild->isSelectionBorder())
        view()->clearSelection();

    // remove the child
    if (oldChild->previousSibling())
        oldChild->previousSibling()->setNextSibling(oldChild->nextSibling());
    if (oldChild->nextSibling())
        oldChild->nextSibling()->setPreviousSibling(oldChild->previousSibling());

    if (m_firstChild == oldChild)
        m_firstChild = oldChild->nextSibling();
    if (m_lastChild == oldChild)
        m_lastChild = oldChild->previousSibling();

    oldChild->setPreviousSibling(0);
    oldChild->setNextSibling(0);
    oldChild->setParent(0);

    if (AXObjectCache::accessibilityEnabled())
        document()->axObjectCache()->childrenChanged(this);

    return oldChild;
}

void RenderObjectChildList::insertChildNode(RenderObject* owner, RenderObject* child, RenderObject* beforeChild, bool fullInsert)
{
    if (!beforeChild) {
        appendChildNode(owner, child, fullInsert);
        return;
    }

    ASSERT(!child->parent());
    while (beforeChild->parent() != owner && beforeChild->parent()->isAnonymousBlock())
        beforeChild = beforeChild->parent();
    ASSERT(beforeChild->parent() == owner);

    ASSERT(!owner->isBlockFlow() || (!child->isTableSection() && !child->isTableRow() && !child->isTableCell()));

    if (beforeChild == firstChild())
        setFirstChild(child);

    RenderObject* prev = beforeChild->previousSibling();
    child->setNextSibling(beforeChild);
    beforeChild->setPreviousSibling(child);
    if (prev)
        prev->setNextSibling(child);
    child->setPreviousSibling(prev);

    child->setParent(owner);
    
    if (fullInsert) {
        // Keep our layer hierarchy updated.  Optimize for the common case where we don't have any children
        // and don't have a layer attached to ourselves.
        RenderLayer* layer = 0;
        if (child->firstChild() || child->hasLayer()) {
            layer = owner->enclosingLayer();
            child->addLayers(layer);
        }

        // if the new child is visible but this object was not, tell the layer it has some visible content
        // that needs to be drawn and layer visibility optimization can't be used
        if (owner->style()->visibility() != VISIBLE && child->style()->visibility() == VISIBLE && !child->hasLayer()) {
            if (!layer)
                layer = owner->enclosingLayer();
            if (layer)
                layer->setHasVisibleContent(true);
        }

        if (child->isListItem())
            toRenderListItem(child)->updateListMarkerNumbers();

        if (!child->isFloating() && owner->childrenInline())
            owner->dirtyLinesFromChangedChild(child);

        if (child->isRenderRegion())
            toRenderRegion(child)->attachRegion();

        if (RenderFlowThread* containerFlowThread = renderFlowThreadContainer(owner))
            containerFlowThread->addFlowChild(child, beforeChild);
    }

    RenderCounter::rendererSubtreeAttached(child);
    RenderQuote::rendererSubtreeAttached(child);
    child->setNeedsLayoutAndPrefWidthsRecalc();
    if (!owner->normalChildNeedsLayout())
        owner->setChildNeedsLayout(true); // We may supply the static position for an absolute positioned child.
    
    if (AXObjectCache::accessibilityEnabled())
        owner->document()->axObjectCache()->childrenChanged(owner);
}

bool RenderEmbeddedObject::isReplacementObscured() const
{
    // Return whether or not the replacement content for blocked plugins is accessible to the user.

    // Check the opacity of each layer containing the element or its ancestors.
    float opacity = 1.0;
    for (RenderLayer* layer = enclosingLayer(); layer; layer = layer->parent()) {
        opacity *= layer->renderer().style().opacity();
        if (opacity < 0.1)
            return true;
    }

    // Calculate the absolute rect for the blocked plugin replacement text.
    IntRect absoluteBoundingBox = absoluteBoundingBoxRect();
    LayoutPoint absoluteLocation(absoluteBoundingBox.location());
    LayoutRect rect = unavailablePluginIndicatorBounds(absoluteLocation);
    if (rect.isEmpty())
        return true;

    RenderView* rootRenderView = document().topDocument().renderView();
    ASSERT(rootRenderView);
    if (!rootRenderView)
        return true;

    IntRect rootViewRect = view().frameView().convertToRootView(pixelSnappedIntRect(rect));
    
    HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active | HitTestRequest::IgnoreClipping | HitTestRequest::DisallowShadowContent | HitTestRequest::AllowChildFrameContent);
    HitTestResult result;
    HitTestLocation location;
    
    LayoutUnit x = rootViewRect.x();
    LayoutUnit y = rootViewRect.y();
    LayoutUnit width = rootViewRect.width();
    LayoutUnit height = rootViewRect.height();
    
    // Hit test the center and near the corners of the replacement text to ensure
    // it is visible and is not masked by other elements.
    bool hit = false;
    location = LayoutPoint(x + width / 2, y + height / 2);
    hit = rootRenderView->hitTest(request, location, result);
    if (!hit || result.innerNode() != &frameOwnerElement())
        return true;
    
    location = LayoutPoint(x, y);
    hit = rootRenderView->hitTest(request, location, result);
    if (!hit || result.innerNode() != &frameOwnerElement())
        return true;
    
    location = LayoutPoint(x + width, y);
    hit = rootRenderView->hitTest(request, location, result);
    if (!hit || result.innerNode() != &frameOwnerElement())
        return true;
    
    location = LayoutPoint(x + width, y + height);
    hit = rootRenderView->hitTest(request, location, result);
    if (!hit || result.innerNode() != &frameOwnerElement())
        return true;
    
    location = LayoutPoint(x, y + height);
    hit = rootRenderView->hitTest(request, location, result);
    if (!hit || result.innerNode() != &frameOwnerElement())
        return true;

    return false;
}

static void write(QTextStream &ts, RenderLayer &l,
                  const QRect& layerBounds, const QRect& backgroundClipRect, const QRect& clipRect,
                  int layerType = 0, int indent = 0)
{
    writeIndent(ts, indent);
    
    ts << "layer";
    ts << " " << layerBounds;

    if (layerBounds != layerBounds.intersect(backgroundClipRect))
        ts << " backgroundClip " << backgroundClipRect;
    if (layerBounds != layerBounds.intersect(clipRect))
        ts << " clip " << clipRect;

    if (l.renderer()->hasOverflowClip()) {
        if (l.scrollXOffset())
            ts << " scrollX " << l.scrollXOffset();
        if (l.scrollYOffset())
            ts << " scrollY " << l.scrollYOffset();
        if (l.renderer()->clientWidth() != l.scrollWidth())
            ts << " scrollWidth " << l.scrollWidth();
        if (l.renderer()->clientHeight() != l.scrollHeight())
            ts << " scrollHeight " << l.scrollHeight();
    }

    if (layerType == -1)
        ts << " layerType: background only";
    else if (layerType == 1)
        ts << " layerType: foreground only";
    
    ts << "\n";

    if (layerType != -1)
        write(ts, *l.renderer(), indent + 1);
}

void RenderLayerClipper::calculateClipRects(const ClipRectsContext& clipRectsContext, ClipRects& clipRects) const
{
    if (!m_renderer->layer()->parent()) {
        // The root layer's clip rect is always infinite.
        clipRects.reset(PaintInfo::infiniteRect());
        return;
    }

    ClipRectsType clipRectsType = clipRectsContext.clipRectsType;
    bool useCached = clipRectsType != TemporaryClipRects;

    // For transformed layers, the root layer was shifted to be us, so there is no need to
    // examine the parent. We want to cache clip rects with us as the root.
    RenderLayer* parentLayer = clipRectsContext.rootLayer != m_renderer->layer() ? m_renderer->layer()->parent() : 0;

    // Ensure that our parent's clip has been calculated so that we can examine the values.
    if (parentLayer) {
        if (useCached && parentLayer->clipper().clipRects(clipRectsContext)) {
            clipRects = *parentLayer->clipper().clipRects(clipRectsContext);
        } else {
            ClipRectsContext parentContext(clipRectsContext);
            parentContext.overlayScrollbarSizeRelevancy = IgnoreOverlayScrollbarSize; // FIXME: why?
            parentLayer->clipper().calculateClipRects(parentContext, clipRects);
        }
    } else {
        clipRects.reset(PaintInfo::infiniteRect());
    }

    // A fixed object is essentially the root of its containing block hierarchy, so when
    // we encounter such an object, we reset our clip rects to the fixedClipRect.
    if (m_renderer->style()->position() == FixedPosition) {
        clipRects.setPosClipRect(clipRects.fixedClipRect());
        clipRects.setOverflowClipRect(clipRects.fixedClipRect());
        clipRects.setFixed(true);
    } else if (m_renderer->style()->hasInFlowPosition()) {
        clipRects.setPosClipRect(clipRects.overflowClipRect());
    } else if (m_renderer->style()->position() == AbsolutePosition) {
        clipRects.setOverflowClipRect(clipRects.posClipRect());
    }

    // Update the clip rects that will be passed to child layers.
    if ((m_renderer->hasOverflowClip() && (clipRectsContext.respectOverflowClip == RespectOverflowClip || m_renderer->layer() != clipRectsContext.rootLayer)) || m_renderer->hasClip()) {
        // This layer establishes a clip of some kind.

        // This offset cannot use convertToLayerCoords, because sometimes our rootLayer may be across
        // some transformed layer boundary, for example, in the RenderLayerCompositor overlapMap, where
        // clipRects are needed in view space.
        LayoutPoint offset;
        offset = roundedLayoutPoint(m_renderer->localToContainerPoint(FloatPoint(), clipRectsContext.rootLayer->renderer()));
        RenderView* view = m_renderer->view();
        ASSERT(view);
        if (view && clipRects.fixed() && clipRectsContext.rootLayer->renderer() == view) {
            offset -= view->frameView()->scrollOffsetForFixedPosition();
        }

        if (m_renderer->hasOverflowClip()) {
            ClipRect newOverflowClip = toRenderBox(m_renderer)->overflowClipRect(offset, clipRectsContext.overlayScrollbarSizeRelevancy);
            if (m_renderer->style()->hasBorderRadius())
                newOverflowClip.setHasRadius(true);
            clipRects.setOverflowClipRect(intersection(newOverflowClip, clipRects.overflowClipRect()));
            if (m_renderer->isPositioned())
                clipRects.setPosClipRect(intersection(newOverflowClip, clipRects.posClipRect()));
        }
        if (m_renderer->hasClip()) {
            LayoutRect newPosClip = toRenderBox(m_renderer)->clipRect(offset);
            clipRects.setPosClipRect(intersection(newPosClip, clipRects.posClipRect()));
            clipRects.setOverflowClipRect(intersection(newPosClip, clipRects.overflowClipRect()));
            clipRects.setFixedClipRect(intersection(newPosClip, clipRects.fixedClipRect()));
        }
    }
}

static void write(TextStream& ts, RenderLayer& l,
                  const LayoutRect& layerBounds, const LayoutRect& backgroundClipRect, const LayoutRect& clipRect, const LayoutRect& outlineClipRect,
                  LayerPaintPhase paintPhase = LayerPaintPhaseAll, int indent = 0, RenderAsTextBehavior behavior = RenderAsTextBehaviorNormal)
{
    IntRect adjustedLayoutBounds = pixelSnappedIntRect(layerBounds);
    IntRect adjustedBackgroundClipRect = pixelSnappedIntRect(backgroundClipRect);
    IntRect adjustedClipRect = pixelSnappedIntRect(clipRect);
    IntRect adjustedOutlineClipRect = pixelSnappedIntRect(outlineClipRect);

    writeIndent(ts, indent);

    ts << "layer ";
    
    if (behavior & RenderAsTextShowAddresses)
        ts << static_cast<const void*>(&l) << " ";
      
    ts << adjustedLayoutBounds;

    if (!adjustedLayoutBounds.isEmpty()) {
        if (!adjustedBackgroundClipRect.contains(adjustedLayoutBounds))
            ts << " backgroundClip " << adjustedBackgroundClipRect;
        if (!adjustedClipRect.contains(adjustedLayoutBounds))
            ts << " clip " << adjustedClipRect;
        if (!adjustedOutlineClipRect.contains(adjustedLayoutBounds))
            ts << " outlineClip " << adjustedOutlineClipRect;
    }

    if (l.renderer()->hasOverflowClip()) {
        if (l.scrollXOffset())
            ts << " scrollX " << l.scrollXOffset();
        if (l.scrollYOffset())
            ts << " scrollY " << l.scrollYOffset();
        if (l.renderBox() && l.renderBox()->pixelSnappedClientWidth() != l.scrollWidth())
            ts << " scrollWidth " << l.scrollWidth();
        if (l.renderBox() && l.renderBox()->pixelSnappedClientHeight() != l.scrollHeight())
            ts << " scrollHeight " << l.scrollHeight();
    }

    if (paintPhase == LayerPaintPhaseBackground)
        ts << " layerType: background only";
    else if (paintPhase == LayerPaintPhaseForeground)
        ts << " layerType: foreground only";
    
#if USE(ACCELERATED_COMPOSITING)
    if (behavior & RenderAsTextShowCompositedLayers) {
        if (l.isComposited())
            ts << " (composited, bounds=" << l.backing()->compositedBounds() << ", drawsContent=" << l.backing()->graphicsLayer()->drawsContent() << ", paints into ancestor=" << l.backing()->paintsIntoCompositedAncestor() << ")";
    }
#else
    UNUSED_PARAM(behavior);
#endif
    
    ts << "\n";

    if (paintPhase != LayerPaintPhaseBackground)
        write(ts, *l.renderer(), indent + 1, behavior);
}

// The bounds of the GraphicsLayer created for a compositing layer is the union of the bounds of all the descendant
// RenderLayers that are rendered by the composited RenderLayer.
IntRect RenderLayerCompositor::calculateCompositedBounds(const RenderLayer* layer, const RenderLayer* ancestorLayer)
{
    if (!layer->isSelfPaintingLayer())
        return IntRect();

    IntRect boundingBoxRect, unionBounds;
    boundingBoxRect = unionBounds = layer->localBoundingBox();
    
    if (layer->renderer()->hasOverflowClip() || layer->renderer()->hasMask()) {
        int ancestorRelX = 0, ancestorRelY = 0;
        layer->convertToLayerCoords(ancestorLayer, ancestorRelX, ancestorRelY);
        boundingBoxRect.move(ancestorRelX, ancestorRelY);
        return boundingBoxRect;
    }

    if (RenderLayer* reflection = layer->reflectionLayer()) {
        if (!reflection->isComposited()) {
            IntRect childUnionBounds = calculateCompositedBounds(reflection, layer);
            unionBounds.unite(childUnionBounds);
        }
    }
    
    ASSERT(layer->isStackingContext() || (!layer->m_posZOrderList || layer->m_posZOrderList->size() == 0));

    if (Vector<RenderLayer*>* negZOrderList = layer->negZOrderList()) {
        size_t listSize = negZOrderList->size();
        for (size_t i = 0; i < listSize; ++i) {
            RenderLayer* curLayer = negZOrderList->at(i);
            if (!curLayer->isComposited()) {
                IntRect childUnionBounds = calculateCompositedBounds(curLayer, layer);
                unionBounds.unite(childUnionBounds);
            }
        }
    }

    if (Vector<RenderLayer*>* posZOrderList = layer->posZOrderList()) {
        size_t listSize = posZOrderList->size();
        for (size_t i = 0; i < listSize; ++i) {
            RenderLayer* curLayer = posZOrderList->at(i);
            if (!curLayer->isComposited()) {
                IntRect childUnionBounds = calculateCompositedBounds(curLayer, layer);
                unionBounds.unite(childUnionBounds);
            }
        }
    }

    if (Vector<RenderLayer*>* normalFlowList = layer->normalFlowList()) {
        size_t listSize = normalFlowList->size();
        for (size_t i = 0; i < listSize; ++i) {
            RenderLayer* curLayer = normalFlowList->at(i);
            if (!curLayer->isComposited()) {
                IntRect curAbsBounds = calculateCompositedBounds(curLayer, layer);
                unionBounds.unite(curAbsBounds);
            }
        }
    }

    if (layer->paintsWithTransform(PaintBehaviorNormal)) {
        TransformationMatrix* affineTrans = layer->transform();
        boundingBoxRect = affineTrans->mapRect(boundingBoxRect);
        unionBounds = affineTrans->mapRect(unionBounds);
    }

    int ancestorRelX = 0, ancestorRelY = 0;
    layer->convertToLayerCoords(ancestorLayer, ancestorRelX, ancestorRelY);
    unionBounds.move(ancestorRelX, ancestorRelY);

    return unionBounds;
}

bool CompositingReasonFinder::requiresCompositingForPositionFixed(RenderObject* renderer, const RenderLayer* layer, RenderLayer::ViewportConstrainedNotCompositedReason* viewportConstrainedNotCompositedReason, bool* needToRecomputeCompositingRequirements) const
{
    if (!(m_compositingTriggers & ViewportConstrainedPositionedTrigger))
        return false;

    if (renderer->style()->position() != FixedPosition)
        return false;

    RenderObject* container = renderer->container();
    // If the renderer is not hooked up yet then we have to wait until it is.
    if (!container) {
        ASSERT(m_renderView.document().lifecycle().state() < DocumentLifecycle::InCompositingUpdate);
        // FIXME: Remove this and ASSERT(container) once we get rid of the incremental
        // allocateOrClearCompositedLayerMapping compositing update. This happens when
        // adding the renderer to the tree because we setStyle before addChild in
        // createRendererForElementIfNeeded.
        *needToRecomputeCompositingRequirements = true;
        return false;
    }

    // Don't promote fixed position elements that are descendants of a non-view container, e.g. transformed elements.
    // They will stay fixed wrt the container rather than the enclosing frame.
    if (container != &m_renderView) {
        if (viewportConstrainedNotCompositedReason)
            *viewportConstrainedNotCompositedReason = RenderLayer::NotCompositedForNonViewContainer;
        return false;
    }

    // If the fixed-position element does not have any scrollable ancestor between it and
    // its container, then we do not need to spend compositor resources for it. Start by
    // assuming we can opt-out (i.e. no scrollable ancestor), and refine the answer below.
    bool hasScrollableAncestor = false;

    // The FrameView has the scrollbars associated with the top level viewport, so we have to
    // check the FrameView in addition to the hierarchy of ancestors.
    FrameView* frameView = m_renderView.frameView();
    if (frameView && frameView->isScrollable())
        hasScrollableAncestor = true;

    RenderLayer* ancestor = layer->parent();
    while (ancestor && !hasScrollableAncestor) {
        if (ancestor->scrollsOverflow())
            hasScrollableAncestor = true;
        if (ancestor->renderer() == &m_renderView)
            break;
        ancestor = ancestor->parent();
    }

    if (!hasScrollableAncestor) {
        if (viewportConstrainedNotCompositedReason)
            *viewportConstrainedNotCompositedReason = RenderLayer::NotCompositedForUnscrollableAncestors;
        return false;
    }

    // Subsequent tests depend on layout. If we can't tell now, just keep things the way they are until layout is done.
    // FIXME: Get rid of this codepath once we get rid of the incremental compositing update in RenderLayer::styleChanged.
    if (m_renderView.document().lifecycle().state() < DocumentLifecycle::LayoutClean) {
        *needToRecomputeCompositingRequirements = true;
        return layer->hasCompositedLayerMapping();
    }

    bool paintsContent = layer->isVisuallyNonEmpty() || layer->hasVisibleDescendant();
    if (!paintsContent) {
        if (viewportConstrainedNotCompositedReason)
            *viewportConstrainedNotCompositedReason = RenderLayer::NotCompositedForNoVisibleContent;
        return false;
    }

    // Fixed position elements that are invisible in the current view don't get their own layer.
    if (FrameView* frameView = m_renderView.frameView()) {
        ASSERT(m_renderView.document().lifecycle().state() == DocumentLifecycle::InCompositingUpdate);
        LayoutRect viewBounds = frameView->viewportConstrainedVisibleContentRect();
        LayoutRect layerBounds = layer->boundingBoxForCompositing(layer->compositor()->rootRenderLayer(), RenderLayer::ApplyBoundsChickenEggHacks);
        if (!viewBounds.intersects(enclosingIntRect(layerBounds))) {
            if (viewportConstrainedNotCompositedReason)
                *viewportConstrainedNotCompositedReason = RenderLayer::NotCompositedForBoundsOutOfView;
            return false;
        }
    }

    return true;
}