[gnome-shell] closeDialog: Fix dialog size when using geometry scaling

[Florian Müllner <fmuellner src gnome org>]

commit b6e57a5ae8e3871161e2bdcc44e46af1cc56b2f7
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Tue Oct 15 16:20:09 2019 +0200

    closeDialog: Fix dialog size when using geometry scaling
    
    The close dialog is added as a child to MetaWindowActor, and, in Wayland
    sessions, since commit [1] MetaWindowActor applies a transformation
    matrix which scales all it's children using the geometry scale factor.
    Now because the dialog actor is not a window (i.e. a MetaSurfaceActor),
    but a subclass of StWidget, the scale factor is also applied to the
    properties of the dialog by StThemeNode, so we end up applying the
    geometry scale twice to the close dialog.
    
    Fix this by applying the inverted scale to the dialog, which leaves the
    scaling only to MetaWindowActor. This means we also can't apply a pivot
    point other than 0 to the dialog actor, so apply the 0.5-pivot point to
    the `_dialog` child of the Dialog class (the actual visible dialog box)
    and also perform scaling animations on this child.
    
    [1] https://gitlab.gnome.org/GNOME/mutter/commit/fb9e8768
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/783

 js/ui/closeDialog.js | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)
---
diff --git a/js/ui/closeDialog.js b/js/ui/closeDialog.js
index 6d0519f8e9..5cbeb9c5cb 100644
--- a/js/ui/closeDialog.js
+++ b/js/ui/closeDialog.js
@@ -1,7 +1,7 @@
 // -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
 /* exported CloseDialog */
 
-const { Clutter, Gio, GLib, GObject, Meta, Shell } = imports.gi;
+const { Clutter, Gio, GLib, GObject, Meta, Shell, St } = imports.gi;
 
 const Dialog = imports.ui.dialog;
 const Main = imports.ui.main;
@@ -46,6 +46,18 @@ var CloseDialog = GObject.registerClass({
         return new Dialog.MessageDialogContent({ icon, title, subtitle });
     }
 
+    _updateScale() {
+        // Since this is a child of MetaWindowActor (which, in Wayland sessions,
+        // applies the geometry scale factor to its children itself, see
+        // meta_window_actor_set_geometry_scale()), make sure we don't apply
+        // the factor twice in the end.
+        if (!Meta.is_wayland_compositor())
+            return;
+
+        let { scaleFactor } = St.ThemeContext.get_for_stage(global.stage);
+        this._dialog.set_scale(1 / scaleFactor, 1 / scaleFactor);
+    }
+
     _initDialog() {
         if (this._dialog)
             return;
@@ -64,6 +76,11 @@ var CloseDialog = GObject.registerClass({
                                  key: Clutter.Escape });
 
         global.focus_manager.add_group(this._dialog);
+
+        let themeContext = St.ThemeContext.get_for_stage(global.stage);
+        themeContext.connect('notify::scale-factor', this._updateScale.bind(this));
+
+        this._updateScale();
     }
 
     _addWindowEffect() {
@@ -145,10 +162,10 @@ var CloseDialog = GObject.registerClass({
         this._addWindowEffect();
         this._initDialog();
 
-        this._dialog.scale_y = 0;
-        this._dialog.set_pivot_point(0.5, 0.5);
+        this._dialog._dialog.scale_y = 0;
+        this._dialog._dialog.set_pivot_point(0.5, 0.5);
 
-        this._dialog.ease({
+        this._dialog._dialog.ease({
             scale_y: 1,
             mode: Clutter.AnimationMode.LINEAR,
             duration: DIALOG_TRANSITION_TIME,
@@ -175,7 +192,7 @@ var CloseDialog = GObject.registerClass({
         this._dialog = null;
         this._removeWindowEffect();
 
-        dialog.ease({
+        dialog._dialog.ease({
             scale_y: 0,
             mode: Clutter.AnimationMode.LINEAR,
             duration: DIALOG_TRANSITION_TIME,