Expose the window in a static variable

The reason is that it can't be accessed during initialization otherwise.

AvaloniaExtensions/CanvasComponentBase.cs

@@ -51,6 +51,11 @@ public void SetupThemeColours() {
     }
   }
 
+  internal T SetInitialControlToFocus<T>(T control) where T : Control {
+    InitialControlToFocus = control;
+    return control;
+  }
+
   public static T RegisterOnResizeAction<T>(T control, Action resizeAction) where T : Control {
     var canvasComponent = FindCanvasComponent(control);
     canvasComponent.RegisterOnResizeAction(resizeAction);

AvaloniaExtensions/CanvasControlExtensions.cs

@@ -21,6 +21,11 @@ public static T Ref<T>(this T control) where T : Control {
     return control;
   }
 
+  // --- Misc ---
+  public static T WithInitialFocus<T>(this T control) where T : Control {
+    return CanvasComponentBase.FindCanvasComponent(control).SetInitialControlToFocus(control);
+  }
+
   // --- Basic position and size ---
   public static double GetX(this Control control) => Canvas.GetLeft(control);
   public static double GetY(this Control control) => Canvas.GetTop(control);

AvaloniaExtensions/ExtendedWindow.cs

@@ -9,11 +9,16 @@
 namespace AvaloniaExtensions;
 
 public sealed class ExtendedWindow : Window {
+  // Unfortunately CanvasComponentBase.Parent is null during initialization, so we have to find another way
+  private static ExtendedWindow? _windowObject;
+  public static ExtendedWindow Get => _windowObject ?? throw new InvalidOperationException("No window created yet.");
+
   private readonly Dictionary<Type, ViewBase> _components;
   private readonly Dictionary<Type, Func<ViewBase>> _lazyComponents;
   private readonly Dictionary<Type, SettingsFile> _settingsFiles;
 
   private ExtendedWindow() {
+    _windowObject = this;
     _components = new Dictionary<Type, ViewBase>();
     _lazyComponents = new Dictionary<Type, Func<ViewBase>>();
     _settingsFiles = new Dictionary<Type, SettingsFile>();

ExampleApp/SettingsComponent.cs

@@ -17,15 +17,13 @@ protected override void InitializeControls() {
     AddTextBlockHeader("Some settings").TopLeftInPanel();
     _cbExampleToggle = AddCheckBox("Something to toggle").Below();
     InsertLabelAbove("A label above, to show it off");
-    _tbExampleString = AddTextBox().Below(_cbExampleToggle);
+    _tbExampleString = AddTextBox().Below(_cbExampleToggle).WithInitialFocus();
     InsertLabelLeftOf("Checkbox:", _cbExampleToggle, LABEL_WIDTH);
     InsertLabelLeftOf("Text:", _tbExampleString, LABEL_WIDTH);
 
     AddButton("Reset defaults", OnResetSettingsClick).BottomLeftInPanel();
     AddButton("Cancel", OnCancelClick).BottomRightInPanel();
     AddButton("Ok", OnSaveClick).LeftOf();
-
-    InitialControlToFocus = _tbExampleString;
   }
 
   protected override void OnInitialized() {