It's working!

Author: lenemter

src/BaseItem.vala

@@ -107,6 +107,7 @@ public class Dock.BaseItem : Gtk.Box {
 
         append (bin);
         append (running_revealer);
+        append (new BottomMargin ());
 
         icon_size = dock_settings.get_int ("icon-size");
         dock_settings.changed["icon-size"].connect (() => {

src/BottomMargin.vala

@@ -0,0 +1,30 @@
+/*
+ * SPDX-License-Identifier: GPL-3.0
+ * SPDX-FileCopyrightText: 2025 elementary, Inc. (https://elementary.io)
+ */
+
+public class BottomMargin : Gtk.Widget {
+    private static GLib.List<unowned BottomMargin> instances = new GLib.List<unowned BottomMargin> ();
+
+    class construct {
+        set_css_name ("bottom-margin");
+    }
+
+    construct {
+        instances.append (this);
+    }
+
+    ~BottomMargin () {
+        instances.remove (this);
+    }
+
+    public new static int get_size () {
+        foreach (var instance in instances) {
+            if (instance.get_realized ()) {
+                return instance.get_height ();
+            }
+        }
+
+        return 0;
+    }
+}

src/MainWindow.vala

@@ -5,50 +5,12 @@
 
 public class Dock.MainWindow : Gtk.ApplicationWindow {
     private class Container : Gtk.Widget {
-        private Settings settings = new Settings ("io.elementary.dock");
-
         class construct {
             set_css_name ("dock");
         }
 
         construct {
-            height_request = ItemManager.get_launcher_size ();
-            settings.changed["icon-size"].connect (() => {
-                height_request = ItemManager.get_launcher_size ();
-            });
-        }
-    }
-
-    private class BottomMargin : Gtk.Widget {
-        private static BottomMargin? first_instance;
-
-        class construct {
-            set_css_name ("bottom-margin");
-        }
-
-        construct {
-            if (first_instance == null) {
-                first_instance = this;
-            }
-        }
-
-        public new static int get_size () {
-            if (first_instance == null) {
-                return 0;
-            }
-
-            Graphene.Rect bounds;
-            first_instance.compute_bounds (first_instance, out bounds);
-
-            return (int) bounds.get_height ();
-        }
-    }
-
-    private class DockBox : Gtk.Box {
-        construct {
-            orientation = VERTICAL;
-            append (new Container ());
-            append (new BottomMargin ());
+            vexpand = true;
         }
     }
 
@@ -64,27 +26,32 @@ public class Dock.MainWindow : Gtk.ApplicationWindow {
 
     private WindowDragManager window_drag_manager;
     private bool initialized_blur = false;
-    private DockBox dock_box;
 
     class construct {
         set_css_name ("dock-window");
     }
 
     construct {
-        var launcher_manager = ItemManager.get_default ();
-
         overflow = VISIBLE;
         resizable = false;
         titlebar = new Gtk.Label ("") { visible = false };
 
-        dock_box = new DockBox ();
+        var dock_box = new Gtk.Box (VERTICAL, 0);
+        dock_box.append (new Container ());
+        dock_box.append (new BottomMargin ());
+
+        unowned var launcher_manager = ItemManager.get_default ();
 
         // Don't clip launchers to dock background https://github.com/elementary/dock/issues/275
         var overlay = new Gtk.Overlay () {
             child = dock_box
         };
         overlay.add_overlay (launcher_manager);
 
+        var size_group = new Gtk.SizeGroup (Gtk.SizeGroupMode.BOTH);
+        size_group.add_widget (dock_box);
+        size_group.add_widget (launcher_manager);
+
         child = overlay;
 
         remove_css_class ("background");
@@ -155,9 +122,6 @@ public class Dock.MainWindow : Gtk.ApplicationWindow {
             unowned var item_manager = ItemManager.get_default ();
             var item_manager_width = item_manager.get_width ();
 
-            dock_box.width_request = item_manager_width;
-            item_manager.height_request = dock_box.get_height ();
-
             // manually set input region since container's shadow are is the content of the window
             // and it still gets window events
             var shadow_size = (width - item_manager_width) / 2;

src/meson.build

@@ -2,6 +2,7 @@ sources = [
     'Application.vala',
     'BaseIconGroup.vala',
     'BaseItem.vala',
+    'BottomMargin.vala',
     'ItemManager.vala',
     'MainWindow.vala',
     'AppSystem' / 'App.vala',