Hide the old element on attach to grid

src/elements/grid.rs

@@ -375,6 +375,19 @@ impl Grid {
 
         let weak = child_state.downgrade();
 
+        // disable the old element
+        match &grid[pos_x][pos_y] {
+            ChildState::Some { child, .. } => {
+                if self.visible() {
+                    if let Some(child_visibility) = child.visibility() {
+                        child_visibility.set_visibility(false)?;
+                    }
+                }
+            }
+            ChildState::Extend { .. } => todo!(),
+            ChildState::None => (),
+        }
+
         // insert the element
         for x in pos_x..(pos_x + dim_x as usize) {
             for y in pos_y..(pos_y + dim_y as usize) {