chrome/browser/browser_accessibility.h

   1 // Copyright (c) 2006-2008 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 CHROME_BROWSER_BROWSER_ACCESSIBILITY_H_
   6 #define CHROME_BROWSER_BROWSER_ACCESSIBILITY_H_
   7
   8 #include <atlbase.h>
   9 #include <atlcom.h>
  10
  11 #include <oleacc.h>
  12
  13 #include "chrome/common/render_messages.h"
  14
  15 ////////////////////////////////////////////////////////////////////////////////
  16 //
  17 // BrowserAccessibility
  18 //
  19 // Class implementing the MSAA IAccessible COM interface for the
  20 // Browser-Renderer communication of MSAA information, providing accessibility
  21 // to be used by screen readers and other assistive technology (AT).
  22 //
  23 ////////////////////////////////////////////////////////////////////////////////
  24 class ATL_NO_VTABLE BrowserAccessibility
  25   : public CComObjectRootEx<CComMultiThreadModel>,
  26     public IDispatchImpl<IAccessible, &IID_IAccessible, &LIBID_Accessibility> {
  27  public:
  28   BEGIN_COM_MAP(BrowserAccessibility)
  29     COM_INTERFACE_ENTRY2(IDispatch, IAccessible)
  30     COM_INTERFACE_ENTRY(IAccessible)
  31   END_COM_MAP()
  32
  33   BrowserAccessibility();
  34   ~BrowserAccessibility() {}
  35
  36   // Supported IAccessible methods.
  37
  38   // Performs the default action on a given object.
  39   STDMETHODIMP accDoDefaultAction(VARIANT var_id);
  40
  41   // Retrieves the child element or child object at a given point on the screen.
  42   STDMETHODIMP accHitTest(LONG x_left, LONG y_top, VARIANT* child);
  43
  44   // Retrieves the specified object's current screen location.
  45   STDMETHODIMP accLocation(LONG* x_left,
  46                            LONG* y_top,
  47                            LONG* width,
  48                            LONG* height,
  49                            VARIANT var_id);
  50
  51   // Traverses to another UI element and retrieves the object.
  52   STDMETHODIMP accNavigate(LONG nav_dir, VARIANT start, VARIANT* end);
  53
  54   // Retrieves an IDispatch interface pointer for the specified child.
  55   STDMETHODIMP get_accChild(VARIANT var_child, IDispatch** disp_child);
  56
  57   // Retrieves the number of accessible children.
  58   STDMETHODIMP get_accChildCount(LONG* child_count);
  59
  60   // Retrieves a string that describes the object's default action.
  61   STDMETHODIMP get_accDefaultAction(VARIANT var_id, BSTR* default_action);
  62
  63   // Retrieves the object's description.
  64   STDMETHODIMP get_accDescription(VARIANT var_id, BSTR* desc);
  65
  66   // Retrieves the object that has the keyboard focus.
  67   STDMETHODIMP get_accFocus(VARIANT* focus_child);
  68
  69   // Retrieves the help information associated with the object.
  70   STDMETHODIMP get_accHelp(VARIANT var_id, BSTR* help);
  71
  72   // Retrieves the specified object's shortcut.
  73   STDMETHODIMP get_accKeyboardShortcut(VARIANT var_id, BSTR* access_key);
  74
  75   // Retrieves the name of the specified object.
  76   STDMETHODIMP get_accName(VARIANT var_id, BSTR* name);
  77
  78   // Retrieves the IDispatch interface of the object's parent.
  79   STDMETHODIMP get_accParent(IDispatch** disp_parent);
  80
  81   // Retrieves information describing the role of the specified object.
  82   STDMETHODIMP get_accRole(VARIANT var_id, VARIANT* role);
  83
  84   // Retrieves the current state of the specified object.
  85   STDMETHODIMP get_accState(VARIANT var_id, VARIANT* state);
  86
  87   // Returns the value associated with the object.
  88   STDMETHODIMP get_accValue(VARIANT var_id, BSTR* value);
  89
  90   // Non-supported (by WebKit) IAccessible methods.
  91   STDMETHODIMP accSelect(LONG flags_sel, VARIANT var_id);
  92
  93   STDMETHODIMP get_accHelpTopic(BSTR* help_file,
  94                                 VARIANT var_id,
  95                                 LONG* topic_id);
  96
  97   STDMETHODIMP get_accSelection(VARIANT* selected);
  98
  99   // Deprecated functions, not implemented here.
 100   STDMETHODIMP put_accName(VARIANT var_id, BSTR put_name);
 101   STDMETHODIMP put_accValue(VARIANT var_id, BSTR put_val);
 102
 103   // Modify/retrieve the unique id of this IAccessible instance.
 104   void set_iaccessible_id(int iaccessible_id) {
 105     iaccessible_id_ = iaccessible_id;
 106   }
 107   int iaccessible_id() const { return iaccessible_id_; }
 108
 109   // Modify/retrieve the unique id of this IAccessible's routing variables.
 110   void set_instance_id(int instance_id) {
 111     instance_id_ = instance_id;
 112   }
 113   int instance_id() const { return instance_id_; }
 114
 115   // Modify/retrieve the state (active/inactive) of this instance.
 116   void set_instance_active(bool instance_active) {
 117     instance_active_ = instance_active;
 118   }
 119   int instance_active() const { return instance_active_; }
 120
 121  private:
 122   // Creates an empty VARIANT. Used as the equivalent of a NULL (unused) input
 123   // parameter.
 124   VARIANT EmptyVariant() const {
 125     VARIANT empty;
 126     empty.vt = VT_EMPTY;
 127     return empty;
 128   }
 129
 130   // Wrapper functions, calling through to singleton instance of
 131   // BrowserAccessibilityManager.
 132
 133   // Creates an instance of BrowserAccessibility, initializes it and sets the
 134   // |iaccessible_id| and |parent_id|.
 135   STDMETHODIMP CreateInstance(REFIID iid,
 136                               int iaccessible_id,
 137                               void** interface_ptr);
 138
 139   // Composes and sends a message for requesting needed accessibility
 140   // information. Unused LONG input parameters should be NULL, and the VARIANT
 141   // an empty, valid instance.
 142   bool RequestAccessibilityInfo(int iaccessible_func_id,
 143                                 VARIANT var_id,
 144                                 LONG input1, LONG input2);
 145
 146   // Accessors.
 147   ViewHostMsg_Accessibility_Out_Params response();
 148   HWND parent_hwnd();
 149
 150   // Id to uniquely distinguish this instance in the render-side caching,
 151   // mapping it to the correct IAccessible on that side. Initialized to -1.
 152   int iaccessible_id_;
 153
 154   // The unique id of this IAccessible instance. Used to help
 155   // BrowserAccessibilityManager instance retrieve the correct member
 156   // variables for this process.
 157   int instance_id_;
 158
 159   // The instance should only be active if there is a non-terminated
 160   // RenderProcessHost associated with it. The BrowserAccessibilityManager keeps
 161   // track of this state, and sets it to false to disable all calls into the
 162   // renderer from this instance of BroweserAccessibility, and have all
 163   // IAccessible functions return E_FAIL.
 164   bool instance_active_;
 165
 166   DISALLOW_COPY_AND_ASSIGN(BrowserAccessibility);
 167 };
 168 #endif  // CHROME_BROWSER_BROWSER_ACCESSIBILITY_H_
 169