Linux Aura accessibility is enabled only on GNOME desktops

ui/accessibility/platform/atk_util_auralinux.cc

 // Copyright 2015 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 <atk/atk.h>
 #if defined(USE_GCONF)
 #include <gconf/gconf-client.h>
+#elif defined(USE_DBUS)
+#include "dbus/bus.h"
+#include "dbus/message.h"
+#include "dbus/object_path.h"
+#include "dbus/object_proxy.h"
 #endif
 #include <glib-2.0/gmodule.h>
 
+#include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/memory/singleton.h"
+#include "base/message_loop/message_loop.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/threading/thread.h"
 #include "ui/accessibility/platform/atk_util_auralinux.h"
 #include "ui/accessibility/platform/ax_platform_node_auralinux.h"
 
 namespace {
 
+const char kAccessibilityEnabled[] = "ACCESSIBILITY_ENABLED";
+
 #if defined(USE_GCONF)
 
 const char kGnomeAccessibilityEnabledKey[] =
     "/desktop/gnome/interface/accessibility";
 
-bool ShouldEnableAccessibility() {
-  GConfClient* client = gconf_client_get_default();
-  if (!client) {
-    LOG(ERROR) << "gconf_client_get_default failed";
-    return false;
+#elif defined(USE_DBUS)
+
+const char kServiceName[] = "org.a11y.Bus";
+const char kObjectPath[] = "/org/a11y/bus";
+const char kInterfaceName[] = "org.a11y.Status";
+const char kPropertyName[] = "IsEnabled";
+
+#endif
+
+void AccessibilityModuleInit() {
+  // Try to load libatk-bridge.so.
+  base::FilePath atk_bridge_path(ATK_LIB_DIR);
+  atk_bridge_path = atk_bridge_path.Append("gtk-2.0/modules/libatk-bridge.so");
+  GModule* bridge = g_module_open(atk_bridge_path.value().c_str(),
+                                  static_cast<GModuleFlags>(0));
+  if (!bridge) {
+    VLOG(1) << "Unable to open module " << atk_bridge_path.value();
+    return;
   }
 
-  GError* error = nullptr;
-  gboolean value = gconf_client_get_bool(client,
-                                         kGnomeAccessibilityEnabledKey,
-                                         &error);
-  if (error) {
-    VLOG(1) << "gconf_client_get_bool failed";
-    g_error_free(error);
-    g_object_unref(client);
-    return false;
+  // Try to call gnome_accessibility_module_init from libatk-bridge.so.
+  void (*gnome_accessibility_module_init)();
+  if (g_module_symbol(bridge, "gnome_accessibility_module_init",
+                      (gpointer *)&gnome_accessibility_module_init)) {
+    (*gnome_accessibility_module_init)();
   }
-
-  g_object_unref(client);
-  return value;
 }
 
-#else  // !defined(USE_GCONF)
-
-bool ShouldEnableAccessibility() {
-  // TODO(k.czech): implement this for non-GNOME desktops.
-  return false;
-}
-
-#endif  // defined(USE_GCONF)
-
 }  // namespace
 
 G_BEGIN_DECLS
 
 //
 // atk_util_auralinux AtkObject definition and implementation.
 //
 
 #define ATK_UTIL_AURALINUX_TYPE (atk_util_auralinux_get_type())
 #define ATK_UTIL_AURALINUX(obj) \
@@ skipping 67 matching lines @@
 // AtkUtilAuraLinuxClass implementation.
 //
 
 namespace ui {
 
 // static
 AtkUtilAuraLinux* AtkUtilAuraLinux::GetInstance() {
   return Singleton<AtkUtilAuraLinux>::get();
 }
 
 AtkUtilAuraLinux::AtkUtilAuraLinux() {

[dmazzoni, 2015/04/21 22:32:42]

I would initialize is_enabled_ to false here to be safe:

AtkUtilAuraLinux::AtkUtilAuraLinux()
    : is_enabled_(false) {
  // Register our util class.
  ...
}

   // Register our util class.
   g_type_class_unref(g_type_class_ref(ATK_UTIL_AURALINUX_TYPE));
 
-  if (!ShouldEnableAccessibility()) {
+  char* enableAccessibility = getenv(kAccessibilityEnabled);

[dmazzoni, 2015/04/21 22:32:42]

enable_accessibility

+  if (enableAccessibility && atoi(enableAccessibility) == 1) {
+    AccessibilityModuleInit();
+    return;
+  }
+
+  CheckIfAccessibilityIsEnabled();
+}
+
+AtkUtilAuraLinux::~AtkUtilAuraLinux() {
+}
+
+#if defined(USE_GCONF) || defined(USE_DBUS)
+
+void AtkUtilAuraLinux::CheckIfAccessibilityIsEnabled() {
+  is_enabled_ = false;
+
+  accessibility_init_thread_.reset(
+      new base::Thread("Accessibility Init Thread"));
+  base::Thread::Options thread_options(base::MessageLoop::Type::TYPE_IO, 0);
+  accessibility_init_thread_->StartWithOptions(thread_options);
+  accessibility_init_thread_->task_runner()->PostTaskAndReply(
+      FROM_HERE,
+      base::Bind(&AtkUtilAuraLinux::CheckPlatformAccessibilitySupport,
+                 base::Unretained(this)),
+      base::Bind(&AtkUtilAuraLinux::OnStopAccessibilityThread,
+                 base::Unretained(this)));
+}
+
+void AtkUtilAuraLinux::OnStopAccessibilityThread() {
+  accessibility_init_thread_.reset();
+  if (!is_enabled_) {
     VLOG(1) << "Will not enable ATK accessibility support.";
     return;
   }
 
   VLOG(1) << "Enabling ATK accessibility support.";
+  AccessibilityModuleInit();
+}
 
-  // Try to load libatk-bridge.so.
-  base::FilePath atk_bridge_path(ATK_LIB_DIR);
-  atk_bridge_path = atk_bridge_path.Append("gtk-2.0/modules/libatk-bridge.so");
-  GModule* bridge = g_module_open(atk_bridge_path.value().c_str(),
-                                  static_cast<GModuleFlags>(0));
-  if (!bridge) {
-    VLOG(1) << "Unable to open module " << atk_bridge_path.value();
+#else
+
+void AtkUtilAuraLinux::CheckIfAccessibilityIsEnabled() {
+}
+
+void AtkUtilAuraLinux::OnStopAccessibilityThread() {
+}
+
+#endif
+
+#if defined(USE_GCONF)
+void AtkUtilAuraLinux::CheckPlatformAccessibilitySupport() {
+  DCHECK(accessibility_init_thread_->task_runner()->RunsTasksOnCurrentThread());
+
+  GConfClient* client = gconf_client_get_default();
+  if (!client) {
+    LOG(ERROR) << "gconf_client_get_default failed";
     return;
   }
 
-  // Try to call gnome_accessibility_module_init from libatk-bridge.so.
-  void (*gnome_accessibility_module_init)();
-  if (g_module_symbol(bridge, "gnome_accessibility_module_init",
-                      (gpointer *)&gnome_accessibility_module_init)) {
-    (*gnome_accessibility_module_init)();
+  GError* error = nullptr;
+  is_enabled_ = gconf_client_get_bool(client,
+                                      kGnomeAccessibilityEnabledKey,
+                                      &error);
+
+  g_object_unref(client);
+
+  if (error) {
+    VLOG(1) << "gconf_client_get_bool failed";
+    g_error_free(error);
+    return;
   }
 }
 
-AtkUtilAuraLinux::~AtkUtilAuraLinux() {
+#elif defined(USE_DBUS)
+
+void AtkUtilAuraLinux::CheckPlatformAccessibilitySupport() {
+  DCHECK(accessibility_init_thread_->task_runner()->RunsTasksOnCurrentThread());
+
+  dbus::Bus::Options options;
+  options.dbus_task_runner = accessibility_init_thread_->task_runner();
+
+  scoped_refptr<dbus::Bus> dbus(new dbus::Bus(options));
+  dbus::ObjectProxy* object_proxy = dbus->GetObjectProxy(
+      kServiceName, dbus::ObjectPath(kObjectPath));
+
+  DCHECK(object_proxy);
+
+  dbus::MethodCall method_call(DBUS_INTERFACE_PROPERTIES, "Get");
+  dbus::MessageWriter message_writer(&method_call);
+  message_writer.AppendString(kInterfaceName);
+  message_writer.AppendString(kPropertyName);
+
+  scoped_ptr<dbus::Response> response(
+      object_proxy->CallMethodAndBlock(&method_call,
+      dbus::ObjectProxy::TIMEOUT_USE_DEFAULT));
+
+  if (!response) {
+    LOG(ERROR) << "AtSpi: failed to get " << kPropertyName;
+    dbus->ShutdownAndBlock();
+    return;
+  }
+
+  dbus::MessageReader reader(response.get());
+  if (!reader.PopVariantOfBool(&is_enabled_))
+    LOG(ERROR) << "AtSpi: unexpected response";
+
+  dbus->ShutdownAndBlock();
 }
 
+#else
+
+void AtkUtilAuraLinux::CheckPlatformAccessibilitySupport() {
+}
+
+#endif
+
 }  // namespace ui