C++ FrameView::contentsSize方法代码示例

bool RenderIFrame::flattenFrame()
{
    if (!node() || !node()->hasTagName(iframeTag))
        return false;

    // CAPPFIX_WEB_HTML5: SECURITY
    if (isSeamless())
         return false; // Seamless iframes are already "flat", don't try to flatten them.
    // CAPPFIX_WEB_HTML5_END

    HTMLIFrameElement* element = static_cast<HTMLIFrameElement*>(node());
    bool isScrollable = element->scrollingMode() != ScrollbarAlwaysOff;

    if (!isScrollable && style()->width().isFixed()
        && style()->height().isFixed())
        return false;

    Frame* frame = element->document()->frame();
    bool enabled = frame && frame->settings()->frameFlatteningEnabled();

    if (!enabled || !frame->page())
        return false;

    FrameView* view = frame->page()->mainFrame()->view();
    if (!view)
        return false;

    // Do not flatten offscreen inner frames during frame flattening.
    return absoluteBoundingBoxRect().intersects(IntRect(IntPoint(0, 0), view->contentsSize()));
}

bool RenderIFrame::flattenFrame()
{
    if (!node() || !node()->hasTagName(iframeTag))
        return false;

    HTMLIFrameElement* element = static_cast<HTMLIFrameElement*>(node());
    bool isScrollable = element->scrollingMode() != ScrollbarAlwaysOff;

    if (style()->width().isFixed() && style()->height().isFixed()) {
        if (!isScrollable)
            return false;
        if (style()->width().value() <= 0 || style()->height().value() <= 0)
            return false;
    }

    Frame* frame = element->document()->frame();
    bool enabled = frame && frame->settings()->frameFlatteningEnabled();

    if (!enabled || !frame->page())
        return false;

    FrameView* view = frame->page()->mainFrame()->view();
    if (!view)
        return false;

    // Do not flatten offscreen inner frames during frame flattening.
    return absoluteBoundingBoxRect().intersects(IntRect(IntPoint(0, 0), view->contentsSize()));
}

void TouchEventHandler::drawTapHighlight()
{
    Element* elementUnderFatFinger = m_lastFatFingersResult.nodeAsElementIfApplicable();
    if (!elementUnderFatFinger)
        return;

    Element* element = elementForTapHighlight(elementUnderFatFinger);
    if (!element)
        return;

    // Get the element bounding rect in transformed coordinates so we can extract
    // the focus ring relative position each rect.
    RenderObject* renderer = element->renderer();
    ASSERT(renderer);

    Frame* elementFrame = element->document()->frame();
    ASSERT(elementFrame);

    FrameView* elementFrameView = elementFrame->view();
    if (!elementFrameView)
        return;

    // Tell the client if the element is either in a scrollable container or in a fixed positioned container.
    // On the client side, this info is being used to hide the tap highlight window on scroll.
    RenderLayer* layer = m_webPage->enclosingFixedPositionedAncestorOrSelfIfFixedPositioned(renderer->enclosingLayer());
    bool shouldHideTapHighlightRightAfterScrolling = !layer->renderer()->isRenderView();
    shouldHideTapHighlightRightAfterScrolling |= !!m_webPage->m_inRegionScroller->d->node();

    IntPoint framePos(m_webPage->frameOffset(elementFrame));

    // FIXME: We can get more precise on the <map> case by calculating the rect with HTMLAreaElement::computeRect().
    IntRect absoluteRect(renderer->absoluteClippedOverflowRect());
    absoluteRect.move(framePos.x(), framePos.y());

    IntRect clippingRect;
    if (elementFrame == m_webPage->mainFrame())
        clippingRect = IntRect(IntPoint(0, 0), elementFrameView->contentsSize());
    else
        clippingRect = m_webPage->mainFrame()->view()->windowToContents(m_webPage->getRecursiveVisibleWindowRect(elementFrameView, true /*noClipToMainFrame*/));
    clippingRect = intersection(absoluteRect, clippingRect);

    Vector<FloatQuad> focusRingQuads;
    renderer->absoluteFocusRingQuads(focusRingQuads);

    Platform::IntRectRegion region;
    for (size_t i = 0; i < focusRingQuads.size(); ++i) {
        IntRect rect = focusRingQuads[i].enclosingBoundingBox();
        rect.move(framePos.x(), framePos.y());
        IntRect clippedRect = intersection(clippingRect, rect);
        clippedRect.inflate(2);
        region = unionRegions(region, Platform::IntRect(clippedRect));
    }

    Color highlightColor = element->renderStyle()->tapHighlightColor();

    m_webPage->m_tapHighlight->draw(region,
                                    highlightColor.red(), highlightColor.green(), highlightColor.blue(), highlightColor.alpha(),
                                    shouldHideTapHighlightRightAfterScrolling);
}

InRegionScrollableArea::InRegionScrollableArea(WebPagePrivate* webPage, RenderLayer* layer)
    : m_webPage(webPage)
    , m_layer(layer)
{
    ASSERT(webPage);
    ASSERT(layer);
    m_isNull = false;

    // FIXME: Add an ASSERT here as the 'layer' must be scrollable.

    RenderObject* layerRenderer = layer->renderer();
    ASSERT(layerRenderer);

    if (layerRenderer->isRenderView()) { // #document case

        FrameView* view = toRenderView(layerRenderer)->frameView();
        ASSERT(view);

        Frame* frame = view->frame();
        ASSERT_UNUSED(frame, frame);

        m_scrollPosition = m_webPage->mapToTransformed(view->scrollPosition());
        m_contentsSize = m_webPage->mapToTransformed(view->contentsSize());
        m_viewportSize = m_webPage->mapToTransformed(view->visibleContentRect(false /*includeScrollbars*/)).size();

        m_visibleWindowRect = m_webPage->mapToTransformed(m_webPage->getRecursiveVisibleWindowRect(view));
        IntRect transformedWindowRect = IntRect(IntPoint::zero(), m_webPage->transformedViewportSize());
        m_visibleWindowRect.intersect(transformedWindowRect);

        m_scrollsHorizontally = view->contentsWidth() > view->visibleWidth();
        m_scrollsVertically = view->contentsHeight() > view->visibleHeight();

        m_overscrollLimitFactor = 0.0; // FIXME eventually support overscroll
    } else { // RenderBox-based elements case (scrollable boxes (div's, p's, textarea's, etc)).

        RenderBox* box = m_layer->renderBox();
        ASSERT(box);
        ASSERT(box->canBeScrolledAndHasScrollableArea());

        ScrollableArea* scrollableArea = static_cast<ScrollableArea*>(m_layer);
        m_scrollPosition = m_webPage->mapToTransformed(scrollableArea->scrollPosition());
        m_contentsSize = m_webPage->mapToTransformed(scrollableArea->contentsSize());
        m_viewportSize = m_webPage->mapToTransformed(scrollableArea->visibleContentRect(false /*includeScrollbars*/)).size();

        m_visibleWindowRect = m_layer->renderer()->absoluteClippedOverflowRect();
        m_visibleWindowRect = m_layer->renderer()->frame()->view()->contentsToWindow(m_visibleWindowRect);
        IntRect visibleFrameWindowRect = m_webPage->getRecursiveVisibleWindowRect(m_layer->renderer()->frame()->view());
        m_visibleWindowRect.intersect(visibleFrameWindowRect);
        m_visibleWindowRect = m_webPage->mapToTransformed(m_visibleWindowRect);
        IntRect transformedWindowRect = IntRect(IntPoint::zero(), m_webPage->transformedViewportSize());
        m_visibleWindowRect.intersect(transformedWindowRect);

        m_scrollsHorizontally = box->scrollWidth() != box->clientWidth() && box->scrollsOverflowX();
        m_scrollsVertically = box->scrollHeight() != box->clientHeight() && box->scrollsOverflowY();

        m_overscrollLimitFactor = 0.0; // FIXME eventually support overscroll
    }
}

IntSize WebFrame::size() const
{
    if (!m_coreFrame)
        return IntSize();

    FrameView* frameView = m_coreFrame->view();
    if (!frameView)
        return IntSize();

    return frameView->contentsSize();
}

void WebViewBenchmarkSupportImpl::softwarePaint(PaintClient* paintClient, PaintMode paintMode)
{
    WebSize size = m_webViewImpl->size();
    WebRect paintSize;
    switch (paintMode) {
    case PaintModeEverything:
        if (m_webViewImpl->page() && m_webViewImpl->page()->mainFrame()) {
            FrameView* view = m_webViewImpl->page()->mainFrame()->view();
            IntSize contentsSize = view->contentsSize();
            paintSize = WebRect(0, 0, contentsSize.width(), contentsSize.height());
        } else
            paintSize = WebRect(0, 0, size.width, size.height);
        break;
    }

    WebSize canvasSize(paintSize.width, paintSize.height);
    WebCanvas* canvas = paintClient->willPaint(canvasSize);
    m_webViewImpl->paint(canvas, paintSize);
    paintClient->didPaint(canvas);
}

void InspectorEmulationAgent::viewportChanged()
{
    if (!m_webViewImpl->devToolsEmulator()->deviceEmulationEnabled() || !frontend())
        return;

    FrameView* view = m_webViewImpl->mainFrameImpl()->frameView();
    IntSize contentsSize = view->contentsSize();
    FloatPoint scrollOffset;
    scrollOffset = FloatPoint(view->scrollableArea()->visibleContentRectDouble().location());

    RefPtr<TypeBuilder::Emulation::Viewport> viewport = TypeBuilder::Emulation::Viewport::create()
        .setScrollX(scrollOffset.x())
        .setScrollY(scrollOffset.y())
        .setContentsWidth(contentsSize.width())
        .setContentsHeight(contentsSize.height())
        .setPageScaleFactor(m_webViewImpl->page()->pageScaleFactor())
        .setMinimumPageScaleFactor(m_webViewImpl->minimumPageScaleFactor())
        .setMaximumPageScaleFactor(m_webViewImpl->maximumPageScaleFactor());
    frontend()->viewportChanged(viewport);
}

void PaintPropertyTreeBuilder::buildTreeNodes(
    FrameView& frameView,
    PaintPropertyTreeBuilderContext& context) {
  if (RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
    LayoutView* layoutView = frameView.layoutView();
    if (!layoutView)
      return;

    TransformationMatrix frameTranslate;
    frameTranslate.translate(frameView.x() + layoutView->location().x() +
                                 context.current.paintOffset.x(),
                             frameView.y() + layoutView->location().y() +
                                 context.current.paintOffset.y());
    context.current.transform =
        layoutView->getMutableForPainting()
            .ensurePaintProperties()
            .updatePaintOffsetTranslation(context.current.transform,
                                          frameTranslate, FloatPoint3D());
    context.current.paintOffset = LayoutPoint();
    context.current.renderingContextID = 0;
    context.current.shouldFlattenInheritedTransform = true;
    context.absolutePosition = context.current;
    context.containerForAbsolutePosition =
        nullptr;  // This will get set in updateOutOfFlowContext().
    context.fixedPosition = context.current;
    return;
  }

  TransformationMatrix frameTranslate;
  frameTranslate.translate(frameView.x() + context.current.paintOffset.x(),
                           frameView.y() + context.current.paintOffset.y());
  context.current.transform = updateFrameViewPreTranslation(
      frameView, context.current.transform, frameTranslate, FloatPoint3D());

  FloatRoundedRect contentClip(
      IntRect(IntPoint(), frameView.visibleContentSize()));
  context.current.clip = updateFrameViewContentClip(
      frameView, context.current.clip, frameView.preTranslation(), contentClip);

  // Record the fixed properties before any scrolling occurs.
  const auto* fixedTransformNode = context.current.transform;
  auto* fixedScrollNode = context.current.scroll;

  ScrollOffset scrollOffset = frameView.scrollOffset();
  if (frameView.isScrollable() || !scrollOffset.isZero()) {
    TransformationMatrix frameScroll;
    frameScroll.translate(-scrollOffset.width(), -scrollOffset.height());
    context.current.transform = updateFrameViewScrollTranslation(
        frameView, frameView.preTranslation(), frameScroll, FloatPoint3D());

    IntSize scrollClip = frameView.visibleContentSize();
    IntSize scrollBounds = frameView.contentsSize();
    bool userScrollableHorizontal =
        frameView.userInputScrollable(HorizontalScrollbar);
    bool userScrollableVertical =
        frameView.userInputScrollable(VerticalScrollbar);
    context.current.scroll = updateFrameViewScroll(
        frameView, context.current.scroll, frameView.scrollTranslation(),
        scrollClip, scrollBounds, userScrollableHorizontal,
        userScrollableVertical);
  } else {
    // Ensure pre-existing properties are cleared when there is no scrolling.
    frameView.setScrollTranslation(nullptr);
    frameView.setScroll(nullptr);
  }

  // Initialize the context for current, absolute and fixed position cases.
  // They are the same, except that scroll translation does not apply to
  // fixed position descendants.
  context.current.paintOffset = LayoutPoint();
  context.current.renderingContextID = 0;
  context.current.shouldFlattenInheritedTransform = true;
  context.absolutePosition = context.current;
  context.containerForAbsolutePosition = nullptr;
  context.fixedPosition = context.current;
  context.fixedPosition.transform = fixedTransformNode;
  context.fixedPosition.scroll = fixedScrollNode;

  std::unique_ptr<PropertyTreeState> contentsState(
      new PropertyTreeState(context.current.transform, context.current.clip,
                            context.currentEffect, context.current.scroll));
  frameView.setTotalPropertyTreeStateForContents(std::move(contentsState));
}

void PaintPropertyTreeBuilder::updateFramePropertiesAndContext(
    FrameView& frameView,
    PaintPropertyTreeBuilderContext& context) {
  if (RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
    // With root layer scrolling, the LayoutView (a LayoutObject) properties are
    // updated like other objects (see updatePropertiesAndContextForSelf and
    // updatePropertiesAndContextForChildren) instead of needing LayoutView-
    // specific property updates here.
    context.current.paintOffset.moveBy(frameView.location());
    context.current.renderingContextID = 0;
    context.current.shouldFlattenInheritedTransform = true;
    context.absolutePosition = context.current;
    context.containerForAbsolutePosition = nullptr;
    context.fixedPosition = context.current;
    return;
  }

  TransformationMatrix frameTranslate;
  frameTranslate.translate(frameView.x() + context.current.paintOffset.x(),
                           frameView.y() + context.current.paintOffset.y());
  updateFrameViewPreTranslation(frameView, context.current.transform,
                                frameTranslate, FloatPoint3D());

  FloatRoundedRect contentClip(
      IntRect(IntPoint(), frameView.visibleContentSize()));
  updateFrameViewContentClip(frameView, context.current.clip,
                             frameView.preTranslation(), contentClip);

  ScrollOffset scrollOffset = frameView.scrollOffset();
  if (frameView.isScrollable() || !scrollOffset.isZero()) {
    TransformationMatrix frameScroll;
    frameScroll.translate(-scrollOffset.width(), -scrollOffset.height());
    updateFrameViewScrollTranslation(frameView, frameView.preTranslation(),
                                     frameScroll, FloatPoint3D());

    IntSize scrollClip = frameView.visibleContentSize();
    IntSize scrollBounds = frameView.contentsSize();
    bool userScrollableHorizontal =
        frameView.userInputScrollable(HorizontalScrollbar);
    bool userScrollableVertical =
        frameView.userInputScrollable(VerticalScrollbar);
    updateFrameViewScroll(frameView, context.current.scroll,
                          frameView.scrollTranslation(), scrollClip,
                          scrollBounds, userScrollableHorizontal,
                          userScrollableVertical);
  } else {
    // Ensure pre-existing properties are cleared when there is no scrolling.
    frameView.setScrollTranslation(nullptr);
    frameView.setScroll(nullptr);
  }

  // Initialize the context for current, absolute and fixed position cases.
  // They are the same, except that scroll translation does not apply to
  // fixed position descendants.
  const auto* fixedTransformNode = frameView.preTranslation()
                                       ? frameView.preTranslation()
                                       : context.current.transform;
  auto* fixedScrollNode = context.current.scroll;
  DCHECK(frameView.preTranslation());
  context.current.transform = frameView.preTranslation();
  DCHECK(frameView.contentClip());
  context.current.clip = frameView.contentClip();
  if (const auto* scrollTranslation = frameView.scrollTranslation())
    context.current.transform = scrollTranslation;
  if (auto* scroll = frameView.scroll())
    context.current.scroll = scroll;
  context.current.paintOffset = LayoutPoint();
  context.current.renderingContextID = 0;
  context.current.shouldFlattenInheritedTransform = true;
  context.absolutePosition = context.current;
  context.containerForAbsolutePosition = nullptr;
  context.fixedPosition = context.current;
  context.fixedPosition.transform = fixedTransformNode;
  context.fixedPosition.scroll = fixedScrollNode;

  std::unique_ptr<PropertyTreeState> contentsState(
      new PropertyTreeState(context.current.transform, context.current.clip,
                            context.currentEffect, context.current.scroll));
  frameView.setTotalPropertyTreeStateForContents(std::move(contentsState));
}

InRegionScrollableArea::InRegionScrollableArea(WebPagePrivate* webPage, RenderLayer* layer)
    : m_webPage(webPage)
    , m_layer(layer)
    , m_document(0)
    , m_hasWindowVisibleRectCalculated(false)
{
    ASSERT(webPage);
    ASSERT(layer);
    m_isNull = false;

    // Add a pointer to the enclosing document as the pointer to layer or node along the way may become invalid.
    if (m_layer->enclosingElement())
        m_document = m_layer->enclosingElement()->document();

    // FIXME: Add an ASSERT here as the 'layer' must be scrollable.

    RenderObject* layerRenderer = layer->renderer();
    ASSERT(layerRenderer);

    if (layerRenderer->isRenderView()) { // #document case

        RenderView* renderView = toRenderView(layerRenderer);
        ASSERT(renderView);

        FrameView* view = toRenderView(layerRenderer)->frameView();
        ASSERT(view);

        Frame* frame = view->frame();
        ASSERT_UNUSED(frame, frame);

        const Platform::ViewportAccessor* viewportAccessor = m_webPage->m_webkitThreadViewportAccessor;
        m_scrollPosition = viewportAccessor->roundToPixelFromDocumentContents(WebCore::FloatPoint(view->scrollPosition()));
        m_contentsSize = viewportAccessor->roundToPixelFromDocumentContents(Platform::FloatRect(Platform::FloatPoint::zero(), WebCore::FloatSize(view->contentsSize()))).size();
        m_viewportSize = viewportAccessor->roundToPixelFromDocumentContents(WebCore::FloatRect(view->visibleContentRect(ScrollableArea::ExcludeScrollbars))).size();
        m_documentViewportRect = view->frameRect();

        m_scrollsHorizontally = view->contentsWidth() > view->visibleWidth();
        m_scrollsVertically = view->contentsHeight() > view->visibleHeight();

        m_supportsCompositedScrolling = true;

        m_scrollTarget = InnerFrame;

        ASSERT(!m_cachedNonCompositedScrollableNode);

        m_camouflagedCompositedScrollableLayer = reinterpret_cast<unsigned>(renderView->compositor()->scrollLayer()->platformLayer());
        m_cachedCompositedScrollableLayer = renderView->compositor()->scrollLayer()->platformLayer();

    } else { // RenderBox-based elements case (scrollable boxes (div's, p's, textarea's, etc)).

        RenderBox* box = m_layer->renderBox();
        ASSERT(box);
        ASSERT(InRegionScrollerPrivate::canScrollRenderBox(box));

        const Platform::ViewportAccessor* viewportAccessor = m_webPage->m_webkitThreadViewportAccessor;
        ScrollableArea* scrollableArea = static_cast<ScrollableArea*>(m_layer);

        m_scrollPosition = viewportAccessor->roundToPixelFromDocumentContents(WebCore::FloatPoint(scrollableArea->scrollPosition()));
        m_contentsSize = viewportAccessor->roundToPixelFromDocumentContents(Platform::FloatRect(Platform::FloatPoint::zero(), WebCore::FloatSize(scrollableArea->contentsSize()))).size();
        m_viewportSize = viewportAccessor->roundToPixelFromDocumentContents(WebCore::FloatRect(scrollableArea->visibleContentRect(ScrollableArea::ExcludeScrollbars))).size();
        m_documentViewportRect = enclosingIntRect(box->absoluteClippedOverflowRect());

        m_scrollsHorizontally = box->scrollWidth() != box->clientWidth();
        m_scrollsVertically = box->scrollHeight() != box->clientHeight();

        // Check the overflow if its not an input field because overflow can be set to hidden etc. by the content.
        if (!DOMSupport::isShadowHostTextInputElement(box->node())) {
            m_scrollsHorizontally = m_scrollsHorizontally && box->scrollsOverflowX();
            m_scrollsVertically = m_scrollsVertically && box->scrollsOverflowY();
        }

        m_scrollTarget = BlockElement;

        // Both caches below are self-exclusive.
        if (m_layer->usesCompositedScrolling()) {
            m_forceContentToBeHorizontallyScrollable = m_scrollsHorizontally;
            m_forceContentToBeVerticallyScrollable = m_scrollsVertically;
            // Force content to be scrollable even if it doesn't need to scroll in either direction.
            if (!m_scrollsHorizontally && !m_scrollsVertically) {
                if (box->scrollsOverflowY())
                    m_forceContentToBeVerticallyScrollable = true;
                else if (box->scrollsOverflowX()) // If it's already forced scrollable vertically, don't force it to scroll horizontally
                    m_forceContentToBeHorizontallyScrollable = true;
            }
            m_supportsCompositedScrolling = true;
            ASSERT(m_layer->backing()->hasScrollingLayer());
            m_camouflagedCompositedScrollableLayer = reinterpret_cast<unsigned>(m_layer->backing()->scrollingContentsLayer()->platformLayer());
            m_cachedCompositedScrollableLayer = m_layer->backing()->scrollingContentsLayer()->platformLayer();
            ASSERT(!m_cachedNonCompositedScrollableNode);
        } else {
            m_camouflagedCompositedScrollableLayer = reinterpret_cast<unsigned>(m_layer->enclosingElement());
            m_cachedNonCompositedScrollableNode = m_layer->enclosingElement();
            ASSERT(!m_cachedCompositedScrollableLayer);
        }
    }
}

InRegionScrollableArea::InRegionScrollableArea(WebPagePrivate* webPage, RenderLayer* layer)
    : m_webPage(webPage)
    , m_layer(layer)
    , m_document(0)
    , m_hasWindowVisibleRectCalculated(false)
{
    ASSERT(webPage);
    ASSERT(layer);
    m_isNull = false;

    // Add a pointer to the enclosing document as the pointer to layer or node along the way may become invalid.
    if (m_layer->enclosingElement())
        m_document = m_layer->enclosingElement()->document();

    // FIXME: Add an ASSERT here as the 'layer' must be scrollable.

    RenderObject* layerRenderer = layer->renderer();
    ASSERT(layerRenderer);

    if (layerRenderer->isRenderView()) { // #document case

        RenderView* renderView = toRenderView(layerRenderer);
        ASSERT(renderView);

        FrameView* view = toRenderView(layerRenderer)->frameView();
        ASSERT(view);

        Frame* frame = view->frame();
        ASSERT_UNUSED(frame, frame);

        m_scrollPosition = m_webPage->mapToTransformed(view->scrollPosition());
        m_contentsSize = m_webPage->mapToTransformed(view->contentsSize());
        m_viewportSize = m_webPage->mapToTransformed(view->visibleContentRect(ScrollableArea::ExcludeScrollbars)).size();
        m_documentViewportRect = view->frameRect();

        m_scrollsHorizontally = view->contentsWidth() > view->visibleWidth();
        m_scrollsVertically = view->contentsHeight() > view->visibleHeight();

        m_supportsCompositedScrolling = true;

        m_scrollTarget = InnerFrame;

        ASSERT(!m_cachedNonCompositedScrollableNode);

        m_camouflagedCompositedScrollableLayer = reinterpret_cast<unsigned>(renderView->compositor()->scrollLayer()->platformLayer());
        m_cachedCompositedScrollableLayer = renderView->compositor()->scrollLayer()->platformLayer();

    } else { // RenderBox-based elements case (scrollable boxes (div's, p's, textarea's, etc)).

        RenderBox* box = m_layer->renderBox();
        ASSERT(box);
        ASSERT(InRegionScrollerPrivate::canScrollRenderBox(box));

        ScrollableArea* scrollableArea = static_cast<ScrollableArea*>(m_layer);
        m_scrollPosition = m_webPage->mapToTransformed(scrollableArea->scrollPosition());
        m_contentsSize = m_webPage->mapToTransformed(scrollableArea->contentsSize());
        m_viewportSize = m_webPage->mapToTransformed(scrollableArea->visibleContentRect(ScrollableArea::ExcludeScrollbars)).size();
        m_documentViewportRect = enclosingIntRect(box->absoluteClippedOverflowRect());

        m_scrollsHorizontally = box->scrollWidth() != box->clientWidth();
        m_scrollsVertically = box->scrollHeight() != box->clientHeight();

        // Check the overflow if its not an input field because overflow can be set to hidden etc. by the content.
        if (!box->node() || !box->node()->rendererIsEditable()) {
            m_scrollsHorizontally = m_scrollsHorizontally && box->scrollsOverflowX();
            m_scrollsVertically = m_scrollsVertically && box->scrollsOverflowY();
        }

        m_scrollTarget = BlockElement;

        // Both caches below are self-exclusive.
        if (m_layer->usesCompositedScrolling()) {
            m_forceContentToBeVerticallyScrollable = true;
            m_supportsCompositedScrolling = true;
            ASSERT(m_layer->backing()->hasScrollingLayer());
            m_camouflagedCompositedScrollableLayer = reinterpret_cast<unsigned>(m_layer->backing()->scrollingContentsLayer()->platformLayer());
            m_cachedCompositedScrollableLayer = m_layer->backing()->scrollingContentsLayer()->platformLayer();
            ASSERT(!m_cachedNonCompositedScrollableNode);
        } else {
            m_camouflagedCompositedScrollableLayer = reinterpret_cast<unsigned>(m_layer->enclosingElement());
            m_cachedNonCompositedScrollableNode = m_layer->enclosingElement();
            ASSERT(!m_cachedCompositedScrollableLayer);
        }
    }
}