Linux Aura accessibility is enabled only on GNOME desktops

ui/accessibility/platform/atk_util_auralinux.cc

Index: ui/accessibility/platform/atk_util_auralinux.cc
diff --git a/ui/accessibility/platform/atk_util_auralinux.cc b/ui/accessibility/platform/atk_util_auralinux.cc
index 7fcaf219351289fe7eba1f670d7a6743a8b40ddc..a8d16ed3f113fd93d2cbe700e08d07c52ad56d4e 100644
--- a/ui/accessibility/platform/atk_util_auralinux.cc
+++ b/ui/accessibility/platform/atk_util_auralinux.cc
@@ -8,9 +8,17 @@
 #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"
 
@@ -21,7 +29,7 @@ namespace {
 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";
@@ -45,12 +53,31 @@ bool ShouldEnableAccessibility() {
 
 #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)
 
-#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)();
+  }
+}
 
 }  // namespace
 
@@ -142,33 +169,76 @@ AtkUtilAuraLinux* AtkUtilAuraLinux::GetInstance() {
 AtkUtilAuraLinux::AtkUtilAuraLinux() {
   // Register our util class.
   g_type_class_unref(g_type_class_ref(ATK_UTIL_AURALINUX_TYPE));
+  ShouldAccessibilityBeEnabled();

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

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

+}
 
-  if (!ShouldEnableAccessibility()) {
-    VLOG(1) << "Will not enable ATK accessibility support.";
+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
+}
 
-  // 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();
+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;
   }
 
-  // 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)();
+  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;
   }
-}
 
-AtkUtilAuraLinux::~AtkUtilAuraLinux() {
+  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