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 5d25c510e3258a7a990185f625cfc181eb1ad462..0f770c279da58da514638bd7d4d43860096ed801 100644
--- a/ui/accessibility/platform/atk_util_auralinux.cc
+++ b/ui/accessibility/platform/atk_util_auralinux.cc
@@ -5,10 +5,17 @@
 #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/location.h"
 #include "base/logging.h"
 #include "base/memory/singleton.h"
 #include "ui/accessibility/platform/atk_util_auralinux.h"
@@ -16,41 +23,49 @@
 
 namespace {
 
-#if defined(USE_GCONF)
+typedef void (*gnome_accessibility_module_init)();
 
-const char kGnomeAccessibilityEnabledKey[] =
-    "/desktop/gnome/interface/accessibility";
+const char kAccessibilityEnabled[] = "ACCESSIBILITY_ENABLED";
+const char kAtkBridgePath[] = "gtk-2.0/modules/libatk-bridge.so";
+const char kAtkBridgeSymbolName[] = "gnome_accessibility_module_init";
 
-bool ShouldEnableAccessibility() {
-  GConfClient* client = gconf_client_get_default();
-  if (!client) {
-    LOG(ERROR) << "gconf_client_get_default failed";
+gnome_accessibility_module_init g_accessibility_module_init = nullptr;
+
+bool AccessibilityModuleInitOnFileThread() {
+  // Try to load libatk-bridge.so.
+  base::FilePath atk_bridge_path(ATK_LIB_DIR);
+  atk_bridge_path = atk_bridge_path.Append(kAtkBridgePath);
+  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 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);
+  if (!g_module_symbol(bridge, kAtkBridgeSymbolName,
+                       (gpointer *)&g_accessibility_module_init)) {
+    VLOG(1) << "Unable to get symbol pointer from " << atk_bridge_path.value();
+    // Just to make sure it's null;
+    g_accessibility_module_init = nullptr;
     return false;
   }
 
-  g_object_unref(client);
-  return value;
+  return true;
 }
 
-#else  // !defined(USE_GCONF)
+#if defined(USE_GCONF)
 
-bool ShouldEnableAccessibility() {
-  // TODO(k.czech): implement this for non-GNOME desktops.
-  return false;
-}
+const char kGnomeAccessibilityEnabledKey[] =
+    "/desktop/gnome/interface/accessibility";
 
-#endif  // defined(USE_GCONF)
+#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
 
 }  // namespace
 
@@ -139,44 +154,135 @@ AtkUtilAuraLinux* AtkUtilAuraLinux::GetInstance() {
   return Singleton<AtkUtilAuraLinux>::get();
 }
 
+#if defined(USE_GCONF) || defined(USE_DBUS)
+
+AtkUtilAuraLinux::AtkUtilAuraLinux()
+    : is_enabled_(false) {
+}
+
+#else
+
 AtkUtilAuraLinux::AtkUtilAuraLinux() {
 }
 
+#endif
+
 void AtkUtilAuraLinux::Initialize(
     scoped_refptr<base::TaskRunner> init_task_runner) {
-  // TODO(k.czech): use |init_task_runner| to post a task to do the
-  // initialization rather than doing it on this thread.
-  // http://crbug.com/468112
 
   // 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;
+  init_task_runner->PostTaskAndReply(
+      FROM_HERE,
+      base::Bind(
+          &AtkUtilAuraLinux::CheckIfAccessibilityIsEnabledOnFileThread,
+          base::Unretained(this)),
+      base::Bind(
+          &AtkUtilAuraLinux::FinishAccessibilityInitOnUIThread,
+          base::Unretained(this)));
+}
+
+AtkUtilAuraLinux::~AtkUtilAuraLinux() {
+}
+
+void AtkUtilAuraLinux::CheckIfAccessibilityIsEnabledOnFileThread() {
+  char* enable_accessibility = getenv(kAccessibilityEnabled);
+  if ((enable_accessibility && atoi(enable_accessibility) == 1) ||
+      CheckPlatformAccessibilitySupportOnFileThread())
+    is_enabled_ = AccessibilityModuleInitOnFileThread();
+}
+
+#if defined(USE_GCONF)
+
+bool AtkUtilAuraLinux::CheckPlatformAccessibilitySupportOnFileThread() {
+  GConfClient* client = gconf_client_get_default();
+  if (!client) {
+    LOG(ERROR) << "gconf_client_get_default failed";
+    return false;
   }
 
-  VLOG(1) << "Enabling ATK accessibility support.";
+  GError* error = nullptr;
+  bool is_enabled = gconf_client_get_bool(client,
+                                      kGnomeAccessibilityEnabledKey,
+                                      &error);
 
-  // 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();
+  g_object_unref(client);
+
+  if (error) {
+    VLOG(1) << "gconf_client_get_bool failed";
+    g_error_free(error);
+    return false;
+  }
+
+  return is_enabled;
+}
+
+#elif defined(USE_DBUS)
+
+bool AtkUtilAuraLinux::CheckPlatformAccessibilitySupportOnFileThread() {
+  dbus::Bus::Options options;
+  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);
+
+  // TODO(k.czech) replace this with asynchronous call
+  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 false;
+  }
+
+  // TODO(k.czech) handle case for at-spi2-core version 2.2.0/2.2.2
+  // org.a11y.Bus.Enabled returns variant struct with a bool instead of bool
+  bool is_enabled = false;
+  dbus::MessageReader reader(response.get());
+  if (!reader.PopVariantOfBool(&is_enabled))
+    LOG(ERROR) << "AtSpi: unexpected response";
+
+  dbus->ShutdownAndBlock();
+
+  return is_enabled;
+}
+
+#else
+
+bool AtkUtilAuraLinux::CheckPlatformAccessibilitySupportOnFileThread() {
+  return false;
+}
+
+#endif
+
+#if defined(USE_GCONF) || defined(USE_DBUS)
+
+void AtkUtilAuraLinux::FinishAccessibilityInitOnUIThread() {
+  if (!is_enabled_) {
+    VLOG(1) << "Will not enable ATK accessibility support.";
     return;
   }
 
+  VLOG(1) << "Enabling ATK accessibility support.";
   // 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)();
-  }
+  DCHECK(g_accessibility_module_init);
+  g_accessibility_module_init();
 }
 
-AtkUtilAuraLinux::~AtkUtilAuraLinux() {
+#else
+
+void AtkUtilAuraLinux::FinishAccessibilityInitOnUIThread() {
 }
 
+#endif
+
 }  // namespace ui