mistakes were fixed and sins were committed

src/core/mask.rs

@@ -9,4 +9,12 @@ impl Widget for Masked {
         painter.set_mask(painter.region());
         painter.widget(&self.inner);
     }
+
+    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
+        ctx.width(&self.inner)
+    }
+
+    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
+        ctx.height(&self.inner)
+    }
 }