text: // Copyright 2014 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef CONTENT_BROWSER_FRAME_HOST_FRAME_ACCESSIBILITY_H_
  #define CONTENT_BROWSER_FRAME_HOST_FRAME_ACCESSIBILITY_H_
  
  #include <vector>
  
  #include "base/basictypes.h"
  #include "base/memory/singleton.h"
  #include "content/common/content_export.h"
  
  namespace content {
  
  class RenderFrameHostImpl;
  
  // This singleton class maintains the mappings necessary to link child frames
  // and guest frames into a single tree for accessibility. This class is only
  // used if accessibility is enabled.
  class CONTENT_EXPORT FrameAccessibility {
   public:
    static FrameAccessibility* GetInstance();
  
    // Add a mapping between an accessibility node of |parent_frame_host|
    // and the child frame with the given frame tree node id, in the same
    // frame tree.
    void AddChildFrame(RenderFrameHostImpl* parent_frame_host,
                       int accessibility_node_id,
                       int64 child_frame_tree_node_id);
  
    // Add a mapping between an accessibility node of |parent_frame_host|
    // and the main frame of the guest Webcontents with the given
    // browser plugin instance id.
    void AddGuestWebContents(RenderFrameHostImpl* parent_frame_host,
                             int accessibility_node_id,
                             int browser_plugin_instance_id);
  
    // This is called when a RenderFrameHostImpl is deleted, so invalid
    // mappings can be removed from this data structure.
    void OnRenderFrameHostDestroyed(RenderFrameHostImpl* render_frame_host);
  
    // Given a parent RenderFrameHostImpl and an accessibility node id, look up
    // a child frame or guest frame that was previously associated with this
    // frame and node id. If a mapping exists, return the resulting frame if
    // it's valid. If it doesn't resolve to a valid RenderFrameHostImpl,
    // returns NULL.
    RenderFrameHostImpl* GetChild(RenderFrameHostImpl* parent_frame_host,
                                  int accessibility_node_id);
  
    // Given a parent RenderFrameHostImpl and an accessibility node id, look up
    // all child frames or guest frames that were previously associated with this
    // frame, and populate |child_frame_hosts| with all of them that resolve
    // to a valid RenderFrameHostImpl.
    void GetAllChildFrames(RenderFrameHostImpl* parent_frame_host,
                           std::vector<RenderFrameHostImpl*>* child_frame_hosts);
  
    // Given a RenderFrameHostImpl, check the mapping table to see if it's
    // the child of a node in some other frame. If so, return true and
    // set the parent frame and accessibility node id in the parent frame,
    // otherwise return false.
    bool GetParent(RenderFrameHostImpl* child_frame_host,
                   RenderFrameHostImpl** out_parent_frame_host,
                   int* out_accessibility_node_id);
  
   private:
    FrameAccessibility();
    virtual ~FrameAccessibility();
  
    RenderFrameHostImpl* GetRFHIFromFrameTreeNodeId(
        RenderFrameHostImpl* parent_frame_host,
        int64 child_frame_tree_node_id);
  
    // This structure stores the parent-child relationship between an
    // accessibility node in a parent frame and its child frame, where the
    // child frame may be an iframe or the main frame of a guest browser
    // plugin. It allows the accessibility code to walk both down and up
    // the "composed" accessibility tree.
    struct ChildFrameMapping {
      ChildFrameMapping();
  
      // The parent frame host. Required.
      RenderFrameHostImpl* parent_frame_host;
  
      // The id of the accessibility node that's the host of the child frame,
      // for example the accessibility node for the <iframe> element or the
      // <embed> element.
      int accessibility_node_id;
  
      // If the child frame is an iframe, this is the iframe's FrameTreeNode id,
      // otherwise 0.
      int64 child_frame_tree_node_id;
  
      // If the child frame is a browser plugin, this is its instance id,
      // otherwise 0.
      int browser_plugin_instance_id;
    };
  
    std::vector<ChildFrameMapping> mappings_;
  
    friend struct DefaultSingletonTraits<FrameAccessibility>;
  };
  
  }  // namespace content
  
  #endif  // CONTENT_BROWSER_FRAME_HOST_FRAME_ACCESSIBILITY_H_
  