Adds MSAA/IAccessible exposure of web content.

chrome/browser/browser_accessibility.h

+// Copyright (c) 2006-2008 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 CHROME_BROWSER_BROWSER_ACCESSIBILITY_H_
+#define CHROME_BROWSER_BROWSER_ACCESSIBILITY_H_
+
+#include <atlbase.h>
+#include <atlcom.h>
+
+#include <oleacc.h>
+
+#include "chrome/common/render_messages.h"
+
+////////////////////////////////////////////////////////////////////////////////
+//
+// BrowserAccessibility
+//
+// Class implementing the MSAA IAccessible COM interface for the
+// Browser-Renderer communication of MSAA information, providing accessibility
+// to be used by screen readers and other assistive technology (AT).
+//
+////////////////////////////////////////////////////////////////////////////////
+class ATL_NO_VTABLE BrowserAccessibility
+  : public CComObjectRootEx<CComMultiThreadModel>,
+    public IDispatchImpl<IAccessible, &IID_IAccessible, &LIBID_Accessibility> {
+ public:
+  BEGIN_COM_MAP(BrowserAccessibility)
+    COM_INTERFACE_ENTRY2(IDispatch, IAccessible)
+    COM_INTERFACE_ENTRY(IAccessible)
+  END_COM_MAP()
+
+  BrowserAccessibility();
+  ~BrowserAccessibility() {}
+
+  // Supported IAccessible methods.
+
+  // Performs the default action on a given object.
+  STDMETHODIMP accDoDefaultAction(VARIANT var_id);
+
+  // Retrieves the child element or child object at a given point on the screen.
+  STDMETHODIMP accHitTest(LONG x_left, LONG y_top, VARIANT* child);
+
+  // Retrieves the specified object's current screen location.
+  STDMETHODIMP accLocation(LONG* x_left,
+                           LONG* y_top,
+                           LONG* width,
+                           LONG* height,
+                           VARIANT var_id);
+
+  // Traverses to another UI element and retrieves the object.
+  STDMETHODIMP accNavigate(LONG nav_dir, VARIANT start, VARIANT* end);
+
+  // Retrieves an IDispatch interface pointer for the specified child.
+  STDMETHODIMP get_accChild(VARIANT var_child, IDispatch** disp_child);
+
+  // Retrieves the number of accessible children.
+  STDMETHODIMP get_accChildCount(LONG* child_count);
+
+  // Retrieves a string that describes the object's default action.
+  STDMETHODIMP get_accDefaultAction(VARIANT var_id, BSTR* default_action);
+
+  // Retrieves the object's description.
+  STDMETHODIMP get_accDescription(VARIANT var_id, BSTR* desc);
+
+  // Retrieves the object that has the keyboard focus.
+  STDMETHODIMP get_accFocus(VARIANT* focus_child);
+
+  // Retrieves the help information associated with the object.
+  STDMETHODIMP get_accHelp(VARIANT var_id, BSTR* help);
+
+  // Retrieves the specified object's shortcut.
+  STDMETHODIMP get_accKeyboardShortcut(VARIANT var_id, BSTR* access_key);
+
+  // Retrieves the name of the specified object.
+  STDMETHODIMP get_accName(VARIANT var_id, BSTR* name);
+
+  // Retrieves the IDispatch interface of the object's parent.
+  STDMETHODIMP get_accParent(IDispatch** disp_parent);
+
+  // Retrieves information describing the role of the specified object.
+  STDMETHODIMP get_accRole(VARIANT var_id, VARIANT* role);
+
+  // Retrieves the current state of the specified object.
+  STDMETHODIMP get_accState(VARIANT var_id, VARIANT* state);
+
+  // Returns the value associated with the object.
+  STDMETHODIMP get_accValue(VARIANT var_id, BSTR* value);
+
+  // Non-supported (by WebKit) IAccessible methods.
+  STDMETHODIMP accSelect(LONG flags_sel, VARIANT var_id);
+
+  STDMETHODIMP get_accHelpTopic(BSTR* help_file,
+                                VARIANT var_id,
+                                LONG* topic_id);
+
+  STDMETHODIMP get_accSelection(VARIANT* selected);
+
+  // Deprecated functions, not implemented here.
+  STDMETHODIMP put_accName(VARIANT var_id, BSTR put_name);
+  STDMETHODIMP put_accValue(VARIANT var_id, BSTR put_val);
+
+  // Modify/retrieve the unique id of this IAccessible instance.
+  void set_iaccessible_id(int iaccessible_id) {
+    iaccessible_id_ = iaccessible_id;
+  }
+  int iaccessible_id() const { return iaccessible_id_; }
+
+  // Modify/retrieve the unique id of this IAccessible's routing variables.
+  void set_instance_id(int instance_id) {
+    instance_id_ = instance_id;
+  }
+  int instance_id() const { return instance_id_; }
+
+  // Modify/retrieve the state (active/inactive) of this instance.
+  void set_instance_active(bool instance_active) {
+    instance_active_ = instance_active;
+  }
+  int instance_active() const { return instance_active_; }
+
+ private:
+  // Creates an empty VARIANT. Used as the equivalent of a NULL (unused) input
+  // parameter.
+  VARIANT EmptyVariant() const {
+    VARIANT empty;
+    empty.vt = VT_EMPTY;
+    return empty;
+  }
+
+  // Wrapper functions, calling through to singleton instance of
+  // BrowserAccessibilityManager.
+
+  // Creates an instance of BrowserAccessibility, initializes it and sets the
+  // |iaccessible_id| and |parent_id|.
+  STDMETHODIMP CreateInstance(REFIID iid,
+                              int iaccessible_id,
+                              void** interface_ptr);
+
+  // Composes and sends a message for requesting needed accessibility
+  // information. Unused LONG input parameters should be NULL, and the VARIANT
+  // an empty, valid instance.
+  bool RequestAccessibilityInfo(int iaccessible_func_id,
+                                VARIANT var_id,
+                                LONG input1, LONG input2);
+
+  // Accessors.
+  ViewHostMsg_Accessibility_Out_Params response();
+  HWND parent_hwnd();
+
+  // Id to uniquely distinguish this instance in the render-side caching,
+  // mapping it to the correct IAccessible on that side. Initialized to -1.
+  int iaccessible_id_;
+
+  // The unique id of this IAccessible instance. Used to help
+  // BrowserAccessibilityManager instance retrieve the correct member
+  // variables for this process.
+  int instance_id_;
+
+  // The instance should only be active if there is a non-terminated
+  // RenderProcessHost associated with it. The BrowserAccessibilityManager keeps
+  // track of this state, and sets it to false to disable all calls into the
+  // renderer from this instance of BroweserAccessibility, and have all
+  // IAccessible functions return E_FAIL.
+  bool instance_active_;
+
+  DISALLOW_COPY_AND_ASSIGN(BrowserAccessibility);
+};
+#endif  // CHROME_BROWSER_BROWSER_ACCESSIBILITY_H_
+