third_party/WebKit/Source/modules/plugins/PluginOcclusionSupport.cpp

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "modules/plugins/PluginOcclusionSupport.h"

#include "core/HTMLNames.h"
#include "core/dom/Element.h"
#include "core/frame/FrameView.h"
#include "core/frame/LocalFrame.h"
#include "core/html/HTMLElement.h"
#include "core/html/HTMLFrameOwnerElement.h"
#include "core/layout/LayoutBox.h"
#include "core/layout/LayoutObject.h"
#include "platform/Widget.h"
#include "wtf/HashSet.h"

// This file provides a utility function to support rendering certain elements
// above plugins.

namespace blink {

static void getObjectStack(const LayoutObject* ro,
                           Vector<const LayoutObject*>* roStack) {
  roStack->clear();
  while (ro) {
    roStack->append(ro);
    ro = ro->parent();
  }
}

// Returns true if stack1 is at or above stack2
static bool iframeIsAbovePlugin(
    const Vector<const LayoutObject*>& iframeZstack,
    const Vector<const LayoutObject*>& pluginZstack) {
  for (size_t i = 0; i < iframeZstack.size() && i < pluginZstack.size(); i++) {
    // The root is at the end of these stacks. We want to iterate
    // root-downwards so we index backwards from the end.
    const LayoutObject* ro1 = iframeZstack[iframeZstack.size() - 1 - i];
    const LayoutObject* ro2 = pluginZstack[pluginZstack.size() - 1 - i];

    if (ro1 != ro2) {
      // When we find nodes in the stack that are not the same, then
      // we've found the nodes just below the lowest comment ancestor.
      // Determine which should be on top.

      // See if z-index determines an order.
      if (ro1->style() && ro2->style()) {
        int z1 = ro1->style()->zIndex();
        int z2 = ro2->style()->zIndex();
        if (z1 > z2)
          return true;
        if (z1 < z2)
          return false;
      }

      // If the plugin does not have an explicit z-index it stacks behind the
      // iframe.  This is for maintaining compatibility with IE.
      if (!ro2->isPositioned()) {
        // The 0'th elements of these LayoutObject arrays represent the plugin
        // node and the iframe.
        const LayoutObject* pluginLayoutObject = pluginZstack[0];
        const LayoutObject* iframeLayoutObject = iframeZstack[0];

        if (pluginLayoutObject->style() && iframeLayoutObject->style()) {
          if (pluginLayoutObject->style()->zIndex() >
              iframeLayoutObject->style()->zIndex())
            return false;
        }
        return true;
      }

      // Inspect the document order. Later order means higher stacking.
      const LayoutObject* parent = ro1->parent();
      if (!parent)
        return false;
      ASSERT(parent == ro2->parent());

      for (const LayoutObject* ro = parent->slowFirstChild(); ro;
           ro = ro->nextSibling()) {
        if (ro == ro1)
          return false;
        if (ro == ro2)
          return true;
      }
      ASSERT(false);  // We should have seen ro1 and ro2 by now.
      return false;
    }
  }
  return true;
}

static bool intersectsRect(const LayoutObject* renderer, const IntRect& rect) {
  return renderer->absoluteBoundingBoxRectIgnoringTransforms().intersects(
             rect) &&
         (!renderer->style() ||
          renderer->style()->visibility() == EVisibility::Visible);
}

static void addToOcclusions(const LayoutBox* renderer,
                            Vector<IntRect>& occlusions) {
  occlusions.append(IntRect(roundedIntPoint(renderer->localToAbsolute()),
                            flooredIntSize(renderer->size())));
}

static void addTreeToOcclusions(const LayoutObject* renderer,
                                const IntRect& frameRect,
                                Vector<IntRect>& occlusions) {
  if (!renderer)
    return;
  if (renderer->isBox() && intersectsRect(renderer, frameRect))
    addToOcclusions(toLayoutBox(renderer), occlusions);
  for (LayoutObject* child = renderer->slowFirstChild(); child;
       child = child->nextSibling())
    addTreeToOcclusions(child, frameRect, occlusions);
}

static const Element* topLayerAncestor(const Element* element) {
  while (element && !element->isInTopLayer())
    element = element->parentOrShadowHostElement();
  return element;
}

// Return a set of rectangles that should not be overdrawn by the
// plugin ("cutouts"). This helps implement the "iframe shim"
// technique of overlaying a windowed plugin with content from the
// page. In a nutshell, iframe elements should occlude plugins when
// they occur higher in the stacking order.
void getPluginOcclusions(Element* element,
                         Widget* parentWidget,
                         const IntRect& frameRect,
                         Vector<IntRect>& occlusions) {
  LayoutObject* pluginNode = element->layoutObject();
  ASSERT(pluginNode);
  if (!pluginNode->style())
    return;
  Vector<const LayoutObject*> pluginZstack;
  Vector<const LayoutObject*> iframeZstack;
  getObjectStack(pluginNode, &pluginZstack);

  if (!parentWidget->isFrameView())
    return;

  FrameView* parentFrameView = toFrameView(parentWidget);

  // Occlusions by iframes.
  const FrameView::ChildrenWidgetSet* children = parentFrameView->children();
  for (FrameView::ChildrenWidgetSet::const_iterator it = children->begin();
       it != children->end(); ++it) {
    // We only care about FrameView's because iframes show up as FrameViews.
    if (!(*it)->isFrameView())
      continue;

    const FrameView* frameView = toFrameView(it->get());
    // Check to make sure we can get both the element and the LayoutObject
    // for this FrameView, if we can't just move on to the next object.
    // FIXME: Plugin occlusion by remote frames is probably broken.
    HTMLElement* element = frameView->frame().deprecatedLocalOwner();
    if (!element || !element->layoutObject())
      continue;

    LayoutObject* iframeRenderer = element->layoutObject();

    if (isHTMLIFrameElement(*element) &&
        intersectsRect(iframeRenderer, frameRect)) {
      getObjectStack(iframeRenderer, &iframeZstack);
      if (iframeIsAbovePlugin(iframeZstack, pluginZstack))
        addToOcclusions(toLayoutBox(iframeRenderer), occlusions);
    }
  }

  // Occlusions by top layer elements.
  // FIXME: There's no handling yet for the interaction between top layer and
  // iframes. For example, a plugin in the top layer will be occluded by an
  // iframe. And a plugin inside an iframe in the top layer won't be respected
  // as being in the top layer.
  const Element* ancestor = topLayerAncestor(element);
  Document* document = parentFrameView->frame().document();
  const HeapVector<Member<Element>>& elements = document->topLayerElements();
  size_t start = ancestor ? elements.find(ancestor) + 1 : 0;
  for (size_t i = start; i < elements.size(); ++i)
    addTreeToOcclusions(elements[i]->layoutObject(), frameRect, occlusions);
}

}  // namespace blink