C++ LayoutBoxModelObject::viewRect方法代码示例

void BackgroundImageGeometry::calculate(
    const LayoutBoxModelObject& obj,
    const LayoutBoxModelObject* paintContainer,
    const GlobalPaintFlags globalPaintFlags,
    const FillLayer& fillLayer,
    const LayoutRect& paintRect) {
  LayoutUnit left;
  LayoutUnit top;
  LayoutSize positioningAreaSize;
  bool isLayoutView = obj.isLayoutView();
  const LayoutBox* rootBox = nullptr;
  if (isLayoutView) {
    // It is only possible reach here when root element has a box.
    Element* documentElement = obj.document().documentElement();
    DCHECK(documentElement);
    DCHECK(documentElement->layoutObject());
    DCHECK(documentElement->layoutObject()->isBox());
    rootBox = toLayoutBox(documentElement->layoutObject());
  }
  const LayoutBoxModelObject& positioningBox =
      isLayoutView ? static_cast<const LayoutBoxModelObject&>(*rootBox) : obj;

  // Determine the background positioning area and set destRect to the
  // background painting area.  destRect will be adjusted later if the
  // background is non-repeating.
  // FIXME: transforms spec says that fixed backgrounds behave like scroll
  // inside transforms.
  bool fixedAttachment = fillLayer.attachment() == FixedBackgroundAttachment;

  if (RuntimeEnabledFeatures::fastMobileScrollingEnabled()) {
    // As a side effect of an optimization to blit on scroll, we do not honor
    // the CSS property "background-attachment: fixed" because it may result in
    // rendering artifacts. Note, these artifacts only appear if we are blitting
    // on scroll of a page that has fixed background images.
    fixedAttachment = false;
  }

  if (!fixedAttachment) {
    setDestRect(paintRect);

    LayoutUnit right;
    LayoutUnit bottom;
    // Scroll and Local.
    if (fillLayer.origin() != BorderFillBox) {
      left = LayoutUnit(positioningBox.borderLeft());
      right = LayoutUnit(positioningBox.borderRight());
      top = LayoutUnit(positioningBox.borderTop());
      bottom = LayoutUnit(positioningBox.borderBottom());
      if (fillLayer.origin() == ContentFillBox) {
        left += positioningBox.paddingLeft();
        right += positioningBox.paddingRight();
        top += positioningBox.paddingTop();
        bottom += positioningBox.paddingBottom();
      }
    }

    if (isLayoutView) {
      // The background of the box generated by the root element covers the
      // entire canvas and will be painted by the view object, but the we should
      // still use the root element box for positioning.
      positioningAreaSize =
          rootBox->size() - LayoutSize(left + right, top + bottom),
      rootBox->location();
      // The input paint rect is specified in root element local coordinate
      // (i.e. a transform is applied on the context for painting), and is
      // expanded to cover the whole canvas.  Since left/top is relative to the
      // paint rect, we need to offset them back.
      left -= paintRect.x();
      top -= paintRect.y();
    } else {
      positioningAreaSize =
          paintRect.size() - LayoutSize(left + right, top + bottom);
    }
  } else {
    setHasNonLocalGeometry();

    LayoutRect viewportRect = obj.viewRect();
    if (fixedBackgroundPaintsInLocalCoordinates(obj, globalPaintFlags)) {
      viewportRect.setLocation(LayoutPoint());
    } else {
      if (FrameView* frameView = obj.view()->frameView())
        viewportRect.setLocation(IntPoint(frameView->scrollOffsetInt()));
      // Compensate the translations created by ScrollRecorders.
      // TODO(trchen): Fix this for SP phase 2. crbug.com/529963.
      viewportRect.moveBy(
          accumulatedScrollOffsetForFixedBackground(obj, paintContainer));
    }

    if (paintContainer)
      viewportRect.moveBy(
          LayoutPoint(-paintContainer->localToAbsolute(FloatPoint())));

    setDestRect(viewportRect);
    positioningAreaSize = destRect().size();
  }

  LayoutSize fillTileSize(
      calculateFillTileSize(positioningBox, fillLayer, positioningAreaSize));
  // It's necessary to apply the heuristic here prior to any further
  // calculations to avoid incorrectly using sub-pixel values that won't be
//.........这里部分代码省略.........