Make AngleBox shrink automatically

Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

SS14.Launcher/Views/AngleBox.cs

@@ -16,6 +16,7 @@ public static readonly StyledProperty<AngleBoxSideStyle> SideStyleProperty
 
     static AngleBox()
     {
+        AffectsMeasure<AngleBox>(CornerSizeProperty, SideStyleProperty);
         AffectsGeometry<AngleBox>(BoundsProperty, CornerSizeProperty, SideStyleProperty);
     }
 
@@ -31,6 +32,21 @@ public AngleBoxSideStyle SideStyle
         set => SetValue(SideStyleProperty, value);
     }
 
+    protected override Size MeasureOverride(Size availableSize)
+    {
+        var style = SideStyle;
+        var c = CornerSize;
+
+        var size = new Size();
+        if ((style & AngleBoxSideStyle.OpenRight) == 0)
+            size += new Size(c, c);
+
+        if ((style & AngleBoxSideStyle.OpenLeft) == 0)
+            size += new Size(c, c);
+
+        return size;
+    }
+
     protected override Geometry CreateDefiningGeometry()
     {
         var style = SideStyle;