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

chrome/browser/gtk/accessibility_event_router_gtk.cc

+// 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.
+
+#include "chrome/browser/gtk/accessibility_event_router_gtk.h"
+
+#include "base/basictypes.h"
+#include "base/stl_util-inl.h"
+#include "chrome/browser/extensions/extension_accessibility_api.h"
+#include "chrome/browser/gtk/gtk_chrome_link_button.h"
+#include "chrome/browser/profile.h"
+#include "chrome/common/notification_type.h"
+
+namespace {
+
+//
+// Callbacks triggered by signals on gtk widgets.
+//
+
+gboolean OnWidgetFocused(GSignalInvocationHint *ihint,
+                         guint n_param_values,
+                         const GValue* param_values,
+                         gpointer user_data) {
+  GtkWidget* widget = GTK_WIDGET(g_value_get_object(param_values));
+  reinterpret_cast<AccessibilityEventRouter *>(user_data)
+      ->DispatchAccessibilityNotification(
+          widget, NotificationType::ACCESSIBILITY_CONTROL_FOCUSED);
+  return true;
+}
+
+gboolean OnButtonClicked(GSignalInvocationHint *ihint,
+                         guint n_param_values,
+                         const GValue* param_values,
+                         gpointer user_data) {
+  GtkWidget* widget = GTK_WIDGET(g_value_get_object(param_values));
+  // Skip toggle buttons because we're also listening on "toggle" events.
+  if (GTK_IS_TOGGLE_BUTTON(widget))
+    return true;
+  reinterpret_cast<AccessibilityEventRouter *>(user_data)
+      ->DispatchAccessibilityNotification(
+          widget, NotificationType::ACCESSIBILITY_CONTROL_ACTION);
+  return true;
+}
+
+gboolean OnButtonToggled(GSignalInvocationHint *ihint,
+                         guint n_param_values,
+                         const GValue* param_values,
+                         gpointer user_data) {
+  GtkWidget* widget = GTK_WIDGET(g_value_get_object(param_values));
+  bool checked = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(widget));
+  // Skip propagating an "uncheck" event for a radio button because it's
+  // redundant; there will always be a corresponding "check" event for
+  // a different radio button the group.
+  if (GTK_IS_RADIO_BUTTON(widget) && !checked)
+    return true;
+  reinterpret_cast<AccessibilityEventRouter *>(user_data)
+      ->DispatchAccessibilityNotification(
+          widget, NotificationType::ACCESSIBILITY_CONTROL_ACTION);
+  return true;
+}
+
+gboolean OnSwitchPage(GSignalInvocationHint *ihint,
+                      guint n_param_values,
+                      const GValue* param_values,
+                      gpointer user_data) {
+  GtkWidget* widget = GTK_WIDGET(g_value_get_object(param_values));
+  reinterpret_cast<AccessibilityEventRouter *>(user_data)
+      ->DispatchAccessibilityNotification(
+          widget, NotificationType::ACCESSIBILITY_CONTROL_ACTION);
+  return true;
+}
+
+}  // anonymous namespace
+
+AccessibilityEventRouter::AccessibilityEventRouter() {
+  // We don't want our event listeners to be installed if accessibility is
+  // disabled. Install listeners so we can install and uninstall them as
+  // needed, then install them now if it's currently enabled.
+  ExtensionAccessibilityEventRouter *accessibility_event_router =
+      ExtensionAccessibilityEventRouter::GetInstance();
+  accessibility_event_router->AddOnEnabledListener(
+      NewCallback(this,
+                  &AccessibilityEventRouter::InstallEventListeners));
+  accessibility_event_router->AddOnDisabledListener(
+      NewCallback(this,
+                  &AccessibilityEventRouter::RemoveEventListeners));
+  if (accessibility_event_router->IsAccessibilityEnabled()) {
+    InstallEventListeners();
+  }
+}
+
+// static
+AccessibilityEventRouter* AccessibilityEventRouter::GetInstance() {
+  return Singleton<AccessibilityEventRouter>::get();
+}
+
+void AccessibilityEventRouter::InstallEventListeners() {
+  // Create and destroy a GtkNotebook to ensure this module is loaded,
+  // otherwise we can't lookup its signals.  All of the other modules we
+  // need will already be loaded by the time we get here.
+  g_object_unref(g_object_ref_sink(gtk_notebook_new()));
+
+  // Add signal emission hooks for the events we're interested in.
+  focus_hook_ = g_signal_add_emission_hook(
+      g_signal_lookup("focus-in-event", GTK_TYPE_WIDGET),
+      0, OnWidgetFocused, (gpointer)this, NULL);
+  click_hook_ = g_signal_add_emission_hook(
+      g_signal_lookup("clicked", GTK_TYPE_BUTTON),
+      0, OnButtonClicked, (gpointer)this, NULL);
+  toggle_hook_ = g_signal_add_emission_hook(
+      g_signal_lookup("toggled", GTK_TYPE_TOGGLE_BUTTON),
+      0, OnButtonToggled, (gpointer)this, NULL);
+  switch_page_hook_ = g_signal_add_emission_hook(
+      g_signal_lookup("switch-page", GTK_TYPE_NOTEBOOK),
+      0, OnSwitchPage, (gpointer)this, NULL);
+}
+
+void AccessibilityEventRouter::RemoveEventListeners() {
+  g_signal_remove_emission_hook(
+      g_signal_lookup("focus-in-event", GTK_TYPE_WIDGET), focus_hook_);
+  g_signal_remove_emission_hook(
+      g_signal_lookup("clicked", GTK_TYPE_BUTTON), click_hook_);
+  g_signal_remove_emission_hook(
+      g_signal_lookup("toggled", GTK_TYPE_TOGGLE_BUTTON), toggle_hook_);
+  g_signal_remove_emission_hook(
+      g_signal_lookup("switch-page", GTK_TYPE_NOTEBOOK), switch_page_hook_);
+}
+
+void AccessibilityEventRouter::AddRootWidget(
+    GtkWidget* root_widget, Profile* profile) {
+  root_widget_profile_map_[root_widget] = profile;
+}
+
+void AccessibilityEventRouter::RemoveRootWidget(GtkWidget* root_widget) {
+  DCHECK(root_widget_profile_map_.find(root_widget) !=
+         root_widget_profile_map_.end());
+  root_widget_profile_map_.erase(root_widget);
+}
+
+void AccessibilityEventRouter::IgnoreWidget(GtkWidget* widget) {
+  widget_info_map_[widget].ignore = true;
+}
+
+void AccessibilityEventRouter::SetWidgetName(
+    GtkWidget* widget, std::string name) {
+  widget_info_map_[widget].name = name;
+}
+
+void AccessibilityEventRouter::RemoveWidget(GtkWidget* widget) {
+  DCHECK(widget_info_map_.find(widget) != widget_info_map_.end());
+  widget_info_map_.erase(widget);
+}
+
+bool AccessibilityEventRouter::IsWidgetAccessible(
+    GtkWidget* widget, Profile** profile) {
+  // First see if it's a descendant of a root widget.
+  bool is_accessible = false;
+  for (base::hash_map<GtkWidget*, Profile*>::const_iterator iter =
+           root_widget_profile_map_.begin();
+       iter != root_widget_profile_map_.end();
+       ++iter) {
+    if (gtk_widget_is_ancestor(widget, iter->first)) {
+      is_accessible = true;
+      if (profile)
+        *profile = iter->second;
+      break;
+    }
+  }
+  if (!is_accessible)
+    return false;
+
+  // Now make sure it's not marked as a widget to be ignored.
+  base::hash_map<GtkWidget*, WidgetInfo>::const_iterator iter =
+      widget_info_map_.find(widget);
+  if (iter != widget_info_map_.end() && iter->second.ignore) {
+    is_accessible = false;
+  }
+
+  return is_accessible;
+}
+
+std::string AccessibilityEventRouter::GetWidgetName(GtkWidget* widget) {
+  base::hash_map<GtkWidget*, WidgetInfo>::const_iterator iter =
+      widget_info_map_.find(widget);
+  if (iter != widget_info_map_.end()) {
+    return iter->second.name;
+  } else {
+    return "";
+  }
+}
+
+void AccessibilityEventRouter::DispatchAccessibilityNotification(
+    GtkWidget* widget, NotificationType type) {
+  Profile *profile;
+  if (!IsWidgetAccessible(widget, &profile))
+    return;
+
+  // The order of these checks matters, because, for example, a radio button
+  // is a subclass of button.  We need to catch the most specific type that
+  // we can handle for each object.
+  if (GTK_IS_RADIO_BUTTON(widget)) {
+    SendRadioButtonNotification(widget, type, profile);
+  } else if (GTK_IS_TOGGLE_BUTTON(widget)) {
+    SendCheckboxNotification(widget, type, profile);
+  } else if (GTK_IS_BUTTON(widget)) {
+    SendButtonNotification(widget, type, profile);
+  } else if (GTK_IS_ENTRY(widget)) {
+    SendTextBoxNotification(widget, type, profile);
+  } else if (GTK_IS_NOTEBOOK(widget)) {
+    SendTabNotification(widget, type, profile);
+  }
+}
+
+void AccessibilityEventRouter::SendRadioButtonNotification(
+    GtkWidget* widget, NotificationType type, Profile* profile) {
+  // Get the radio button name
+  std::string button_name = GetWidgetName(widget);
+  if (button_name.empty() && gtk_button_get_label(GTK_BUTTON(widget)))
+    button_name = gtk_button_get_label(GTK_BUTTON(widget));
+
+  // Get its state
+  bool checked = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(widget));
+
+  // Get the index of this radio button and the total number of
+  // radio buttons in the group.
+  int item_count = 0;
+  int item_index = -1;
+  for (GSList* group = gtk_radio_button_get_group(GTK_RADIO_BUTTON(widget));
+       group;
+       group = group->next) {
+    if (group->data == widget) {
+      item_index = item_count;
+    }
+    item_count++;
+  }
+  item_index = item_count - 1 - item_index;
+
+  AccessibilityRadioButtonInfo info(
+      profile, button_name, checked, item_index, item_count);
+  SendAccessibilityNotification(type, &info);
+}
+
+void AccessibilityEventRouter::SendCheckboxNotification(
+    GtkWidget* widget, NotificationType type, Profile* profile) {
+  std::string button_name = GetWidgetName(widget);
+  if (button_name.empty() && gtk_button_get_label(GTK_BUTTON(widget)))
+    button_name = gtk_button_get_label(GTK_BUTTON(widget));
+  bool checked = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(widget));
+  AccessibilityCheckboxInfo info(profile, button_name, checked);
+  SendAccessibilityNotification(type, &info);
+}
+
+void AccessibilityEventRouter::SendButtonNotification(
+    GtkWidget* widget, NotificationType type, Profile* profile) {
+  std::string button_name = GetWidgetName(widget);
+  if (button_name.empty() && gtk_button_get_label(GTK_BUTTON(widget)))
+    button_name = gtk_button_get_label(GTK_BUTTON(widget));
+  AccessibilityButtonInfo info(profile, button_name);
+  SendAccessibilityNotification(type, &info);
+}
+
+void AccessibilityEventRouter::SendTextBoxNotification(
+    GtkWidget* widget, NotificationType type, Profile* profile) {
+  std::string name = GetWidgetName(widget);
+  std::string value = gtk_entry_get_text(GTK_ENTRY(widget));
+  gint start_pos;
+  gint end_pos;
+  gtk_editable_get_selection_bounds(GTK_EDITABLE(widget), &start_pos, &end_pos);
+  AccessibilityTextBoxInfo info(profile, name, false);
+  info.SetValue(value, start_pos, end_pos);
+  SendAccessibilityNotification(type, &info);
+}
+
+void AccessibilityEventRouter::SendTabNotification(
+    GtkWidget* widget, NotificationType type, Profile* profile) {
+  int index = gtk_notebook_get_current_page(GTK_NOTEBOOK(widget));
+  int page_count = gtk_notebook_get_n_pages(GTK_NOTEBOOK(widget));
+  GtkWidget* page = gtk_notebook_get_nth_page(GTK_NOTEBOOK(widget), index);
+  GtkWidget* label = gtk_notebook_get_tab_label(GTK_NOTEBOOK(widget), page);
+  std::string name = GetWidgetName(widget);
+  if (name.empty() && gtk_label_get_text(GTK_LABEL(label))) {
+    name = gtk_label_get_text(GTK_LABEL(label));
+  }
+  AccessibilityTabInfo info(profile, name, index, page_count);
+  SendAccessibilityNotification(type, &info);
+}