See HandyOrg#818

In default, set Window.SizeToContent to Width or Height or WidthAndHeight, when the content size changed, the window will not re-center to screen or owner. After add this attached property, it will auto re-center.

src/Shared/HandyControl_Shared/Controls/Attach/WindowAttach.cs

@@ -145,5 +145,39 @@ public static void SetHideWhenClosing(DependencyObject element, bool value)
 
  public static bool GetHideWhenClosing(DependencyObject element)
  => (bool) element.GetValue(HideWhenClosingProperty);
+
+ public static readonly DependencyProperty KeepCenterOnSizeChangedProperty =
+ DependencyProperty.RegisterAttached("KeepCenterOnSizeChanged", typeof(bool), typeof(WindowAttach),
+ new PropertyMetadata(ValueBoxes.FalseBox, KeepCenterOnSizeChangedPropertyChanged));
+
+ [AttachedPropertyBrowsableForType(typeof(System.Windows.Window))]
+ [AttachedPropertyBrowsableForType(typeof(Window))]
+ public static bool GetKeepCenterOnSizeChanged(DependencyObject obj) => (bool) obj.GetValue(KeepCenterOnSizeChangedProperty);
+
+ public static void SetKeepCenterOnSizeChanged(DependencyObject obj, bool value) => obj.SetValue(KeepCenterOnSizeChangedProperty, value);
+
+ private static void KeepCenterOnSizeChangedPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+ {
+ if (d is Window window)
+ {
+ if ((bool) e.NewValue)
+ window.SizeChanged += Window_SizeChanged;
+ else
+ window.SizeChanged -= Window_SizeChanged;
+ }
+
+ static void Window_SizeChanged(object sender, SizeChangedEventArgs e)
+ {
+ var window = (Window) sender;
+ if (window.WindowStartupLocation == WindowStartupLocation.CenterOwner ||
+ window.WindowStartupLocation == WindowStartupLocation.CenterScreen)
+ {
+ if (e.WidthChanged)
+ window.Left += (e.PreviousSize.Width - e.NewSize.Width) / 2;
+ if (e.HeightChanged)
+ window.Top += (e.PreviousSize.Height - e.NewSize.Height) / 2;
+ }
+ }
+ }
  }
 }