loginDialog: Allow timed login with disabled user list

At the moment the timed login feature is implemented in the user list.
If there's no user list, we don't show the indicator anywhere and
don't proceed with timed login.

This commit allows timed login to work when the user list is disabled.
It accomplishes this by putting the timed login indicator on the
auth prompt in that scenario.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1809>

data/theme/gnome-shell-sass/widgets/_login-dialog.scss

@@ -151,6 +151,11 @@
   padding-top: 16px;
 }
 
+.login-dialog-timed-login-indicator {
+    height: 2px;
+    background-color: darken($fg_color,40%);
+}
+
 .login-dialog-prompt-layout {
   padding-top: 24px;
   padding-bottom: 12px;

js/gdm/authPrompt.js

@@ -1,7 +1,7 @@
 // -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
 /* exported AuthPrompt */
 
-const { Clutter, GObject, Pango, Shell, St } = imports.gi;
+const { Clutter, GLib, GObject, Pango, Shell, St } = imports.gi;
 
 const Animation = imports.ui.animation;
 const Batch = imports.gdm.batch;
@@ -170,6 +170,13 @@ var AuthPrompt = GObject.registerClass({
         this._mainBox.add_child(this._entry);
         this._entry.grab_key_focus();
 
+        this._timedLoginIndicator = new St.Bin({
+            style_class: 'login-dialog-timed-login-indicator',
+            scale_x: 0,
+        });
+
+        this.add_child(this._timedLoginIndicator);
+
         [this._textEntry, this._passwordEntry].forEach(entry => {
             entry.clutter_text.connect('text-changed', () => {
                 if (!this._userVerifier.hasPendingMessages)
@@ -198,6 +205,40 @@ var AuthPrompt = GObject.registerClass({
         this._defaultButtonWell.add_child(this._spinner);
     }
 
+    showTimedLoginIndicator(time) {
+        let hold = new Batch.Hold();
+
+        this.hideTimedLoginIndicator();
+
+        const startTime = GLib.get_monotonic_time();
+
+        this._timedLoginTimeoutId = GLib.timeout_add(GLib.PRIORITY_DEFAULT, 33,
+            () => {
+                const currentTime = GLib.get_monotonic_time();
+                const elapsedTime = (currentTime - startTime) / GLib.USEC_PER_SEC;
+                this._timedLoginIndicator.scale_x = elapsedTime / time;
+                if (elapsedTime >= time) {
+                    this._timedLoginTimeoutId = 0;
+                    hold.release();
+                    return GLib.SOURCE_REMOVE;
+                }
+
+                return GLib.SOURCE_CONTINUE;
+            });
+
+        GLib.Source.set_name_by_id(this._timedLoginTimeoutId, '[gnome-shell] this._timedLoginTimeoutId');
+
+        return hold;
+    }
+
+    hideTimedLoginIndicator() {
+        if (this._timedLoginTimeoutId) {
+            GLib.source_remove(this._timedLoginTimeoutId);
+            this._timedLoginTimeoutId = 0;
+        }
+        this._timedLoginIndicator.scale_x = 0.;
+    }
+
     _activateNext(shouldSpin) {
         this.verificationStatus = AuthPromptStatus.VERIFICATION_IN_PROGRESS;
         this.updateSensitivity(false);

js/gdm/loginDialog.js

@@ -762,6 +762,9 @@ var LoginDialog = GObject.registerClass({
 
             if (this._authPrompt.verificationStatus == AuthPrompt.AuthPromptStatus.NOT_VERIFYING)
                 this._authPrompt.reset();
+
+            if (this._disableUserList && this._timedLoginUserListHold)
+                this._timedLoginUserListHold.release();
         }
     }
 
@@ -1049,16 +1052,29 @@ var LoginDialog = GObject.registerClass({
         let animationTime;
 
         let tasks = [
-            () => this._waitForItemForUser(userName),
+            () => {
+                if (this._disableUserList)
+                    return;
+
+                this._timedLoginUserListHold = this._waitForItemForUser(userName);
+            },
 
             () => {
-                loginItem = this._userList.getItemFromUserName(userName);
+                this._timedLoginUserListHold = null;
+
+                if (this._disableUserList)
+                    loginItem = this._authPrompt;
+                else
+                    loginItem = this._userList.getItemFromUserName(userName);
 
                 // If there is an animation running on the item, reset it.
                 loginItem.hideTimedLoginIndicator();
             },
 
             () => {
+                if (this._disableUserList)
+                    return;
+
                 // If we're just starting out, start on the right item.
                 if (!this._userManager.is_loaded)
                     this._userList.jumpToItem(loginItem);
@@ -1080,6 +1096,9 @@ var LoginDialog = GObject.registerClass({
             },
 
             () => {
+                if (this._disableUserList)
+                    return;
+
                 // If idle timeout is done, make sure the timed login indicator is shown
                 if (delay > _TIMED_LOGIN_IDLE_THRESHOLD &&
                     this._authPrompt.visible)