loginManager: Move UnlockDialog.isSupported() here

With fallback mode dropped, we can no longer rely on gnome-screensaver
to be installed, so we'll have cases where we are unable to lock the
screen. The user menu should not show the "Lock" item in this case,
but as UnlockDialog includes UserMenu, we cannot use the existing check
without creating a circular dependency; move the function to a more
generic place to fix.

https://bugzilla.gnome.org/show_bug.cgi?id=693403

js/misc/loginManager.js

@@ -75,6 +75,35 @@ function haveSystemd() {
     return GLib.access("/sys/fs/cgroup/systemd", 0) >= 0;
 }
 
+function versionCompare(required, reference) {
+    required = required.split('.');
+    reference = reference.split('.');
+
+    for (let i = 0; i < required.length; i++) {
+        if (required[i] != reference[i])
+            return required[i] < reference[i];
+    }
+
+    return true;
+}
+
+function canLock() {
+    try {
+        let params = GLib.Variant.new('(ss)', ['org.gnome.DisplayManager.Manager', 'Version']);
+        let result = Gio.DBus.system.call_sync('org.gnome.DisplayManager',
+                                               '/org/gnome/DisplayManager/Manager',
+                                               'org.freedesktop.DBus.Properties',
+                                               'Get', params, null,
+                                               Gio.DBusCallFlags.NONE,
+                                               -1, null);
+
+        let version = result.deep_unpack()[0].deep_unpack();
+        return versionCompare('3.5.91', version);
+    } catch(e) {
+        return false;
+    }
+}
+
 let _loginManager = null;
 
 /**

js/ui/main.js

@@ -24,6 +24,7 @@ const Panel = imports.ui.panel;
 const Params = imports.misc.params;
 const RunDialog = imports.ui.runDialog;
 const Layout = imports.ui.layout;
+const LoginManager = imports.misc.loginManager;
 const LookingGlass = imports.ui.lookingGlass;
 const NotificationDaemon = imports.ui.notificationDaemon;
 const WindowAttentionHandler = imports.ui.windowAttentionHandler;
@@ -32,7 +33,6 @@ const Scripting = imports.ui.scripting;
 const SessionMode = imports.ui.sessionMode;
 const ShellDBus = imports.ui.shellDBus;
 const ShellMountOperation = imports.ui.shellMountOperation;
-const UnlockDialog = imports.ui.unlockDialog;
 const WindowManager = imports.ui.windowManager;
 const Magnifier = imports.ui.magnifier;
 const XdndHandler = imports.ui.xdndHandler;
@@ -140,7 +140,7 @@ function startSession() {
     overview = new Overview.Overview();
     wm = new WindowManager.WindowManager();
     magnifier = new Magnifier.Magnifier();
-    if (UnlockDialog.isSupported())
+    if (LoginManager.canLock())
         screenShield = new ScreenShield.ScreenShield();
     else
         screenShield = new ScreenShield.ScreenShieldFallback();

js/ui/unlockDialog.js

@@ -27,35 +27,6 @@ const LoginDialog = imports.gdm.loginDialog;
 // The timeout before going back automatically to the lock screen (in seconds)
 const IDLE_TIMEOUT = 2 * 60;
 
-function versionCompare(required, reference) {
-    required = required.split('.');
-    reference = reference.split('.');
-
-    for (let i = 0; i < required.length; i++) {
-        if (required[i] != reference[i])
-            return required[i] < reference[i];
-    }
-
-    return true;
-}
-
-function isSupported() {
-    try {
-        let params = GLib.Variant.new('(ss)', ['org.gnome.DisplayManager.Manager', 'Version']);
-        let result = Gio.DBus.system.call_sync('org.gnome.DisplayManager',
-                                               '/org/gnome/DisplayManager/Manager',
-                                               'org.freedesktop.DBus.Properties',
-                                               'Get', params, null,
-                                               Gio.DBusCallFlags.NONE,
-                                               -1, null);
-
-        let version = result.deep_unpack()[0].deep_unpack();
-        return versionCompare('3.5.91', version);
-    } catch(e) {
-        return false;
-    }
-}
-
 const UnlockDialog = new Lang.Class({
     Name: 'UnlockDialog',
     Extends: ModalDialog.ModalDialog,