[gnome-shell] unlockDialog: Transition switch-user button with prompt

[Florian Müllner <fmuellner src gnome org>]

commit ff2a736193a02aa4971da52a1de7f876f23612a2
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Feb 19 14:30:05 2020 +0100

    unlockDialog: Transition switch-user button with prompt
    
    We ended up always showing the switch-user button on the lock screen,
    as showing and hiding it with the prompt was too visually distracting.
    
    But now that we have a fancy transition in place, we can easily extend
    it to the switch-user button as well.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/1029

 js/ui/unlockDialog.js | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)
---
diff --git a/js/ui/unlockDialog.js b/js/ui/unlockDialog.js
index 43d3bdbdb0..33635fdd03 100644
--- a/js/ui/unlockDialog.js
+++ b/js/ui/unlockDialog.js
@@ -556,12 +556,13 @@ var UnlockDialog = GObject.registerClass({
         this._otherUserButton = new St.Button({
             style_class: 'modal-dialog-button button switch-user-button',
             accessible_name: _('Log in as another user'),
-            can_focus: true,
-            reactive: true,
+            reactive: false,
+            opacity: 0,
             x_align: Clutter.ActorAlign.END,
             y_align: Clutter.ActorAlign.END,
             child: new St.Icon({ icon_name: 'system-users-symbolic' }),
         });
+        this._otherUserButton.set_pivot_point(0.5, 0.5);
         this._otherUserButton.connect('clicked', this._otherUserClicked.bind(this));
 
         let screenSaverSettings = new Gio.Settings({ schema_id: 'org.gnome.desktop.screensaver' });
@@ -713,6 +714,11 @@ var UnlockDialog = GObject.registerClass({
         this._promptBox.visible = progress > 0;
         this._clock.visible = progress < 1;
 
+        this._otherUserButton.set({
+            reactive: progress > 0,
+            can_focus: progress > 0,
+        });
+
         const { scaleFactor } = St.ThemeContext.get_for_stage(global.stage);
 
         this._promptBox.set({
@@ -728,6 +734,12 @@ var UnlockDialog = GObject.registerClass({
             scale_y: FADE_OUT_SCALE + (1 - FADE_OUT_SCALE) * (1 - progress),
             translation_y: -FADE_OUT_TRANSLATION * progress * scaleFactor,
         });
+
+        this._otherUserButton.set({
+            opacity: 255 * progress,
+            scale_x: FADE_OUT_SCALE + (1 - FADE_OUT_SCALE) * progress,
+            scale_y: FADE_OUT_SCALE + (1 - FADE_OUT_SCALE) * progress,
+        });
     }
 
     _fail() {