content/browser/frame_host/frame_accessibility.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CONTENT_BROWSER_FRAME_HOST_FRAME_ACCESSIBILITY_H_
   6 #define CONTENT_BROWSER_FRAME_HOST_FRAME_ACCESSIBILITY_H_
   7
   8 #include <vector>
   9
  10 #include "base/basictypes.h"
  11 #include "base/memory/singleton.h"
  12 #include "content/common/content_export.h"
  13
  14 namespace content {
  15
  16 class RenderFrameHostImpl;
  17
  18 // This singleton class maintains the mappings necessary to link child frames
  19 // and guest frames into a single tree for accessibility. This class is only
  20 // used if accessibility is enabled.
  21 class CONTENT_EXPORT FrameAccessibility {
  22  public:
  23   static FrameAccessibility* GetInstance();
  24
  25   // Add a mapping between an accessibility node of |parent_frame_host|
  26   // and the child frame with the given frame tree node id, in the same
  27   // frame tree.
  28   void AddChildFrame(RenderFrameHostImpl* parent_frame_host,
  29                      int accessibility_node_id,
  30                      int64 child_frame_tree_node_id);
  31
  32   // Add a mapping between an accessibility node of |parent_frame_host|
  33   // and the main frame of the guest Webcontents with the given
  34   // browser plugin instance id.
  35   void AddGuestWebContents(RenderFrameHostImpl* parent_frame_host,
  36                            int accessibility_node_id,
  37                            int browser_plugin_instance_id);
  38
  39   // This is called when a RenderFrameHostImpl is deleted, so invalid
  40   // mappings can be removed from this data structure.
  41   void OnRenderFrameHostDestroyed(RenderFrameHostImpl* render_frame_host);
  42
  43   // Given a parent RenderFrameHostImpl and an accessibility node id, look up
  44   // a child frame or guest frame that was previously associated with this
  45   // frame and node id. If a mapping exists, return the resulting frame if
  46   // it's valid. If it doesn't resolve to a valid RenderFrameHostImpl,
  47   // returns NULL.
  48   RenderFrameHostImpl* GetChild(RenderFrameHostImpl* parent_frame_host,
  49                                 int accessibility_node_id);
  50
  51   // Given a parent RenderFrameHostImpl and an accessibility node id, look up
  52   // all child frames or guest frames that were previously associated with this
  53   // frame, and populate |child_frame_hosts| with all of them that resolve
  54   // to a valid RenderFrameHostImpl.
  55   void GetAllChildFrames(RenderFrameHostImpl* parent_frame_host,
  56                          std::vector<RenderFrameHostImpl*>* child_frame_hosts);
  57
  58   // Given a RenderFrameHostImpl, check the mapping table to see if it's
  59   // the child of a node in some other frame. If so, return true and
  60   // set the parent frame and accessibility node id in the parent frame,
  61   // otherwise return false.
  62   bool GetParent(RenderFrameHostImpl* child_frame_host,
  63                  RenderFrameHostImpl** out_parent_frame_host,
  64                  int* out_accessibility_node_id);
  65
  66  private:
  67   FrameAccessibility();
  68   virtual ~FrameAccessibility();
  69
  70   RenderFrameHostImpl* GetRFHIFromFrameTreeNodeId(
  71       RenderFrameHostImpl* parent_frame_host,
  72       int64 child_frame_tree_node_id);
  73
  74   // This structure stores the parent-child relationship between an
  75   // accessibility node in a parent frame and its child frame, where the
  76   // child frame may be an iframe or the main frame of a guest browser
  77   // plugin. It allows the accessibility code to walk both down and up
  78   // the "composed" accessibility tree.
  79   struct ChildFrameMapping {
  80     ChildFrameMapping();
  81
  82     // The parent frame host. Required.
  83     RenderFrameHostImpl* parent_frame_host;
  84
  85     // The id of the accessibility node that's the host of the child frame,
  86     // for example the accessibility node for the <iframe> element or the
  87     // <embed> element.
  88     int accessibility_node_id;
  89
  90     // If the child frame is an iframe, this is the iframe's FrameTreeNode id,
  91     // otherwise 0.
  92     int64 child_frame_tree_node_id;
  93
  94     // If the child frame is a browser plugin, this is its instance id,
  95     // otherwise 0.
  96     int browser_plugin_instance_id;
  97   };
  98
  99   std::vector<ChildFrameMapping> mappings_;
 100
 101   friend struct DefaultSingletonTraits<FrameAccessibility>;
 102 };
 103
 104 }  // namespace content
 105
 106 #endif  // CONTENT_BROWSER_FRAME_HOST_FRAME_ACCESSIBILITY_H_