New dirty flag system. Avoid calling updates in rendering (yuck!)

TestGame/TestGame.cs

@@ -20,7 +20,7 @@ public class TestGame : Game
         InitializeSystemsDefault();
 
         _uiSystem = new UISystem(Input);
-        _uiSystem.RenderDebugRects = true;
+        _uiSystem.RenderDebugRects = false;
 
         ResourceManager.EnableFileWatching();
 
@@ -73,7 +73,7 @@ public class TestGame : Game
 
         _uiSystem.SetStyleSheet(_styleSheet);
 
-        var addButton = new Button("", _defaultFontSet);
+        var addButton = new Button("Default button", _defaultFontSet);
 
         var removeButton = new Button("Danger button", _defaultFontSet);
 
@@ -90,7 +90,7 @@ public class TestGame : Game
         {
             StyleVariant = "Layer01",
             ConfineToContents = true,
-            Anchor = Anchor.TopCenter
+            Anchor = Anchor.TopCenter,
         };
 
         var inputField = new InputField(string.Empty, _defaultFontSet)
@@ -124,6 +124,8 @@ public class TestGame : Game
             // ResourceManager.Reload();
             // _particleSystem!.RestartEmitter(_emitterId);
         }
+
+        _uiSystem.SetWindowSize(Renderer.WindowSize);
     }
 
     protected override void Render(double deltaTime)