Implement `Widget::overlay` for `PaneGrid`

native/src/widget/pane_grid.rs

@@ -29,8 +29,8 @@ pub use state::{Focus, State};
 pub use title_bar::TitleBar;
 
 use crate::{
-    container, keyboard, layout, mouse, row, text, Clipboard, Element, Event,
+    container, keyboard, layout, mouse, overlay, row, text, Clipboard, Element,
-    Hasher, Layout, Length, Point, Rectangle, Size, Vector, Widget,
+    Event, Hasher, Layout, Length, Point, Rectangle, Size, Vector, Widget,
 };
 
 /// A collection of panes distributed using either vertical or horizontal splits
@@ -636,6 +636,17 @@ where
             element.hash_layout(state);
         }
     }
+
+    fn overlay(
+        &mut self,
+        layout: Layout<'_>,
+    ) -> Option<overlay::Element<'_, Message, Renderer>> {
+        self.elements
+            .iter_mut()
+            .zip(layout.children())
+            .filter_map(|((_, pane), layout)| pane.overlay(layout))
+            .next()
+    }
 }
 
 /// The renderer of a [`PaneGrid`].

native/src/widget/pane_grid/content.rs

@@ -1,5 +1,6 @@
 use crate::container;
 use crate::layout;
+use crate::overlay;
 use crate::pane_grid::{self, TitleBar};
 use crate::{Clipboard, Element, Event, Hasher, Layout, Point, Size};
 
@@ -184,6 +185,24 @@ where
     pub(crate) fn hash_layout(&self, state: &mut Hasher) {
         self.body.hash_layout(state);
     }
+
+    pub(crate) fn overlay(
+        &mut self,
+        layout: Layout<'_>,
+    ) -> Option<overlay::Element<'_, Message, Renderer>> {
+        let body_layout = if self.title_bar.is_some() {
+            let mut children = layout.children();
+
+            // Overlays only allowed in the pane body, for now at least.
+            let _title_bar_layout = children.next();
+
+            children.next()?
+        } else {
+            layout
+        };
+
+        self.body.overlay(body_layout)
+    }
 }
 
 impl<'a, T, Message, Renderer> From<T> for Content<'a, Message, Renderer>