ScreenShield: use session mode to handle the GDM login dialog

Have main.js call .showDialog() when going back from the lock-screen, instead
of using the return value of createUnlockDialog to know if the dialog
was persistent.
_keepDialog is still used as LoginDialog cannot really be destroyed,
and cancelling it does not destroy it.

https://bugzilla.gnome.org/show_bug.cgi?id=683156

js/ui/main.js

@@ -69,22 +69,9 @@ let _overridesSettings = null;
 
 let background = null;
 
-function createGDMLoginDialog(parentActor) {
-    // We do this this here instead of at the top to prevent GDM
-    // related code from getting loaded in normal user sessions
-    const LoginDialog = imports.gdm.loginDialog;
-
-    let loginDialog = new LoginDialog.LoginDialog(parentActor);
-    return [loginDialog, true];
-}
-
-function createSessionUnlockDialog(parentActor) {
-    let dialog = new UnlockDialog.UnlockDialog(parentActor);
-    return [dialog, false];
-}
-
 function _sessionUpdated() {
-    Meta.keybindings_set_custom_handler('panel-run-dialog', sessionMode.hasRunDialog ? openRunDialog : null);
+    if (sessionMode.isGreeter)
+        screenShield.showDialog();
 }
 
 function start() {

js/ui/screenShield.js

@@ -606,7 +606,9 @@ const ScreenShield = new Lang.Class({
 
     _ensureUnlockDialog: function() {
         if (!this._dialog) {
-            [this._dialog, this._keepDialog] = Main.sessionMode.createUnlockDialog(this._lockDialogGroup);
+            let constructor = Main.sessionMode.unlockDialog;
+            this._dialog = new constructor(this._lockDialogGroup);
+            this._keepDialog = Main.sessionMode.isGreeter;
             if (!this._dialog) {
                 // This session mode has no locking capabilities
                 this.unlock();
@@ -624,7 +626,7 @@ const ScreenShield = new Lang.Class({
             this._dialog.connect('unlocked', Lang.bind(this, this._onUnlockSucceded));
         }
 
-        if (this._keepDialog) {
+        if (Main.sessionMode.isGreeter) {
             // Notify the other components that even though we are showing the
             // screenshield, we're not in a locked state
             // (this happens for the gdm greeter)
@@ -764,12 +766,9 @@ const ScreenShield = new Lang.Class({
         if (this._hasLockScreen)
             this._clearLockScreen();
 
-        if (this._keepDialog) {
+        if (this._dialog && !this._keepDialog) {
-            // The dialog must be kept alive,
+            this._dialog.destroy();
-            // so immediately go back to it
+            this._dialog = null;
-            // This will also reset _isLocked
-            this._ensureUnlockDialog();
-            return;
         }
 
         this._lightbox.hide();

js/ui/sessionMode.js

@@ -19,7 +19,8 @@ const _modes = {
         hasWorkspaces: false,
         hasWindows: false,
         isLocked: false,
-        createUnlockDialog: null,
+        isGreeter: false,
+        unlockDialog: null,
         components: [],
         panel: {
             left: [],
@@ -30,7 +31,8 @@ const _modes = {
 
     'gdm': {
         allowKeybindingsWhenModal: true,
-        createUnlockDialog: Main.createGDMLoginDialog,
+        isGreeter: true,
+        unlockDialog: imports.gdm.loginDialog.LoginDialog,
         panel: {
             left: [],
             center: ['dateMenu'],
@@ -41,8 +43,9 @@ const _modes = {
 
     'lock-screen': {
         isLocked: true,
+        isGreeter: undefined,
+        unlockDialog: undefined,
         components: ['networkAgent', 'polkitAgent', 'telepathyClient'],
-        createUnlockDialog: Main.createSessionUnlockDialog,
         panel: {
             left: ['userMenu'],
             center: [],
@@ -67,6 +70,8 @@ const _modes = {
         hasRunDialog: true,
         hasWorkspaces: true,
         hasWindows: true,
+        unlockDialog: imports.ui.unlockDialog.UnlockDialog,
+        isLocked: false,
         components: ['networkAgent', 'polkitAgent', 'telepathyClient',
                      'keyring', 'recorder', 'autorunManager', 'automountManager'],
         panel: {
@@ -113,18 +118,14 @@ const SessionMode = new Lang.Class({
         let params = _modes[this.currentMode];
         params = Params.parse(params, _modes[DEFAULT_MODE]);
 
-        this._createUnlockDialog = params.createUnlockDialog;
+        // A simplified version of Lang.copyProperties, handles
-        delete params.createUnlockDialog;
+        // undefined as a special case for "no change / inherit from previous mode"
+        for (let prop in params) {
+            if (params[prop] !== undefined)
+                this[prop] = params[prop];
+        }
 
-        Lang.copyProperties(params, this);
         this.emit('updated');
-    },
+    }
-
-    createUnlockDialog: function() {
-        if (this._createUnlockDialog)
-            return this._createUnlockDialog.apply(this, arguments);
-        else
-            return null;
-    },
 });
 Signals.addSignalMethods(SessionMode.prototype);