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>
 #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 "dbus/bus.h"
+#include "dbus/message.h"
+#include "dbus/object_path.h"
+#include "dbus/object_proxy.h"
 #include "ui/accessibility/platform/atk_util_auralinux.h"
 #include "ui/accessibility/platform/ax_platform_node_auralinux.h"
 
 namespace {
 
 #if defined(USE_GCONF)
 
 const char kGnomeAccessibilityEnabledKey[] =
     "/desktop/gnome/interface/accessibility";
 
-bool ShouldEnableAccessibility() {
+bool CheckGnomeAccessibilityKey() {
   GConfClient* client = gconf_client_get_default();
   if (!client) {
     LOG(ERROR) << "gconf_client_get_default failed";
     return false;
   }
 
   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;
   }
 
   g_object_unref(client);
   return value;
 }
 
 #else  // !defined(USE_GCONF)
 
-bool ShouldEnableAccessibility() {
-  // TODO(k.czech): implement this for non-GNOME desktops.
-  return false;
+const char kServiceName[] = "org.a11y.Bus";
+const char kObjectPath[] = "/org/a11y/bus";
+const char kInterfaceName[] = "org.a11y.Status";
+const char kPropertyName[] = "IsEnabled";
+
+#endif // defined(USE_GCONF)
+
+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;
+  }
+
+  // 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)();
+  }
 }
 
-#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 70 matching lines @@
 namespace ui {
 
 // static
 AtkUtilAuraLinux* AtkUtilAuraLinux::GetInstance() {
   return Singleton<AtkUtilAuraLinux>::get();
 }
 
 AtkUtilAuraLinux::AtkUtilAuraLinux() {
   // Register our util class.
   g_type_class_unref(g_type_class_ref(ATK_UTIL_AURALINUX_TYPE));
-
-  if (!ShouldEnableAccessibility()) {
-    VLOG(1) << "Will not enable ATK accessibility support.";
-    return;
-  }
-
-  VLOG(1) << "Enabling ATK accessibility support.";
-
-  // 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;
-  }
-
-  // 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)();
-  }
+  ShouldAccessibilityBeEnabled();

[dmazzoni, 2015/04/15 16:48:35]

I'd rename this to CheckIfAccessibilityIsEnabled since it doesn't return a bool
now

 }
 
 AtkUtilAuraLinux::~AtkUtilAuraLinux() {
 }
 
+void AtkUtilAuraLinux::ShouldAccessibilityBeEnabled() {
+#if defined(USE_GCONF)
+  if (CheckGnomeAccessibilityKey()) {

[dmazzoni, 2015/04/15 16:48:35]

I think we should run this in a separate thread too. It also slows down startup.

Would you mind changing it so that the thread is called
accessibility_init_thread_ or something like that, and we either post a task to
check dbus or to check gconf?

+    VLOG(1) << "Will not enable ATK accessibility support."
+    return;
+  }
+
+  VLOG(1) << "Enabling ATK accessibility support.";
+  accessibilityModuleInit();
+#else

[dmazzoni, 2015/04/15 16:48:35]

Should this check USE_DBUS like the gyp file does?

+  dbusThread_.reset(new base::Thread("AtSpi D-Bus Thread"));
+  base::Thread::Options threadOptions(base::MessageLoop::Type::TYPE_IO, 0);
+  dbusThread_->StartWithOptions(threadOptions);
+  dbusThread_->task_runner()->PostTask(
+    FROM_HERE,
+    base::Bind(&AtkUtilAuraLinux::CheckAtSpiIsEnabledProperty,
+    base::Unretained(this)));
+#endif
+}
+
+void AtkUtilAuraLinux::CheckAtSpiIsEnabledProperty() {
+  DCHECK(dbusThread_->task_runner()->RunsTasksOnCurrentThread());
+
+  dbus::Bus::Options options;
+  options.connection_type = dbus::Bus::PRIVATE;
+  options.dbus_task_runner = dbusThread_->task_runner();
+
+  scoped_refptr<dbus::Bus> dbus(new dbus::Bus(options));
+  dbus::ObjectProxy* objectProxy = dbus->GetObjectProxy(
+    kServiceName, dbus::ObjectPath(kObjectPath));

[dmazzoni, 2015/04/15 16:48:35]

nit: indent 4 spaces for line continuation

+
+  if (!objectProxy) {
+    LOG(ERROR) << "Does not support " << kServiceName << " over DBUS";
+    return;
+  }
+
+  dbus::MethodCall methodCall(DBUS_INTERFACE_PROPERTIES, "Get");
+  dbus::MessageWriter messageWriter(&methodCall);
+  messageWriter.AppendString(kInterfaceName);
+  messageWriter.AppendString(kPropertyName);
+
+  scoped_ptr<dbus::Response> response(
+    objectProxy->CallMethodAndBlock(&methodCall,

[dmazzoni, 2015/04/15 16:48:35]

nit: same (4 spaces)

+    dbus::ObjectProxy::TIMEOUT_USE_DEFAULT));
+
+  if (!response) {
+    LOG(ERROR) << "AtSpi: failed to get " << kPropertyName;
+    return;
+  }
+
+  dbus::MessageReader reader(response.get());
+  bool IsEnabled = false;
+  if (!reader.PopVariantOfBool(&IsEnabled)) {
+    LOG(ERROR) << "AtSpi: unexpected response";
+    return;
+  }
+
+  if (!IsEnabled) {
+    VLOG(1) << "Will not enable ATK accessibility support.";
+    return;
+  }
+
+  accessibilityModuleInit();
+  dbus->ShutdownAndBlock();
+}
+
 }  // namespace ui