Add an accessibility API for events raised outside of the web content.

chrome/browser/extensions/extension_accessibility_api.h

+// Copyright (c) 2010 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_EXTENSIONS_EXTENSION_ACCESSIBILITY_API_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTENSION_ACCESSIBILITY_API_H_
+
+#include <string>
+#include <vector>
+
+#include "base/singleton.h"
+#include "chrome/browser/extensions/extension_function.h"
+#include "chrome/common/accessibility_events.h"
+#include "chrome/common/notification_service.h"
+#include "chrome/common/notification_registrar.h"
+
+// Observes the profile and routes accessibility notifications as events
+// to the extension system.
+class ExtensionAccessibilityEventRouter : public NotificationObserver {
+ public:
+  // Single instance of the event router.
+  static ExtensionAccessibilityEventRouter* GetInstance();
+
+  // Safe to call multiple times.
+  void ObserveProfile(Profile* profile);
+
+  // Get the dict representing the last control that received an
+  // OnControlFocus event.
+  DictionaryValue* last_focused_control_dict() {
+    return &last_focused_control_dict_;
+  }
+
+  // Accessibility support is disabled until an extension expicitly enables
+  // it, so that this extension api has no impact on Chrome's performance
+  // otherwise.  These methods handle enabling, disabling, querying the
+  // status, and installing callbacks to execute when accessibility support
+  // is enabled or disabled.
+  void SetAccessibilityEnabled(bool enabled);
+  bool IsAccessibilityEnabled() const;
+  typedef Callback0::Type Callback;
+  void AddOnEnabledListener(Callback* callback);
+  void AddOnDisabledListener(Callback* callback);
+
+ private:
+  friend struct DefaultSingletonTraits<ExtensionAccessibilityEventRouter>;
+
+  ExtensionAccessibilityEventRouter()
+      : enabled_(false) {}
+  virtual ~ExtensionAccessibilityEventRouter() {}
+
+  // NotificationObserver::Observe.
+  virtual void Observe(NotificationType type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details);
+
+  void OnWindowOpened(const AccessibilityWindowInfo* details);
+  void OnWindowClosed(const AccessibilityWindowInfo* details);
+  void OnControlFocused(const AccessibilityControlInfo* details);
+  void OnControlAction(const AccessibilityControlInfo* details);
+  void OnTextChanged(const AccessibilityControlInfo* details);
+
+  void DispatchEvent(Profile* profile,
+                     const char* event_name,
+                     const std::string& json_args);
+
+  // Used for tracking registrations to history service notifications.
+  NotificationRegistrar registrar_;
+
+  DictionaryValue last_focused_control_dict_;
+
+  bool enabled_;
+  std::vector<Callback*> on_enabled_listeners_;
+  std::vector<Callback*> on_disabled_listeners_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExtensionAccessibilityEventRouter);
+};
+
+// API function that enables or disables accessibility support.  Event
+// listeners are only installed when accessibility support is enabled, to
+// minimize the impact.
+class SetAccessibilityEnabledFunction : public SyncExtensionFunction {
+  virtual ~SetAccessibilityEnabledFunction() {}
+  virtual bool RunImpl();
+  DECLARE_EXTENSION_FUNCTION_NAME(
+      "experimental.accessibility.setAccessibilityEnabled")
+};
+
+// API function that returns the most recent focused control.
+class GetFocusedControlFunction : public SyncExtensionFunction {
+  virtual ~GetFocusedControlFunction() {}
+  virtual bool RunImpl();
+  DECLARE_EXTENSION_FUNCTION_NAME(
+      "experimental.accessibility.getFocusedControl")
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_ACCESSIBILITY_API_H_