mistakes were fixed and sins were committed

src/core/position/stack.rs

@@ -24,10 +24,17 @@ impl Widget for Stack {
         }
     }
 
-    fn desired_size(&mut self, ctx: &mut SizeCtx) -> Size {
+    fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len {
         match self.size {
-            StackSize::Default => Size::default(),
-            StackSize::Child(i) => ctx.size(&self.children[i]),
+            StackSize::Default => Len::default(),
+            StackSize::Child(i) => ctx.width(&self.children[i]),
+        }
+    }
+
+    fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len {
+        match self.size {
+            StackSize::Default => Len::default(),
+            StackSize::Child(i) => ctx.height(&self.children[i]),
         }
     }
 }