only consider mouse-move events as "active" (for framerate purposes) if the pointer is in the window area

Program.cs

@@ -425,7 +425,10 @@ public class Game : GameWindow {
     toast.Update(e.Time);
 
     KeyboardState input = KeyboardState;
-    if (input.IsAnyKeyDown || MouseState.IsAnyButtonDown || MouseState.Delta != Vector2i.Zero) {
+    bool mouseInWindow = ClientRectangle.ContainsInclusive((Vector2i) MouseState.Position);
+    if (input.IsAnyKeyDown ||
+        MouseState.IsAnyButtonDown ||
+        (mouseInWindow && MouseState.Delta != Vector2i.Zero)) {
       timeSinceEvent = 0;
     } else {
       timeSinceEvent += e.Time;