Replace stateful widgets with new iced_pure API

native/src/widget/pane_grid/content.rs

@@ -5,6 +5,7 @@ use crate::overlay;
 use crate::renderer;
 use crate::widget::container;
 use crate::widget::pane_grid::{Draggable, TitleBar};
+use crate::widget::Tree;
 use crate::{Clipboard, Element, Layout, Point, Rectangle, Shell, Size};
 
 /// The content of a [`Pane`].
@@ -59,11 +60,37 @@ where
     Renderer: crate::Renderer,
     Renderer::Theme: container::StyleSheet,
 {
+    pub(super) fn state(&self) -> Tree {
+        let children = if let Some(title_bar) = self.title_bar.as_ref() {
+            vec![Tree::new(&self.body), title_bar.state()]
+        } else {
+            vec![Tree::new(&self.body), Tree::empty()]
+        };
+
+        Tree {
+            children,
+            ..Tree::empty()
+        }
+    }
+
+    pub(super) fn diff(&self, tree: &mut Tree) {
+        if tree.children.len() == 2 {
+            if let Some(title_bar) = self.title_bar.as_ref() {
+                title_bar.diff(&mut tree.children[1]);
+            }
+
+            tree.children[0].diff(&self.body);
+        } else {
+            *tree = self.state();
+        }
+    }
+
     /// Draws the [`Content`] with the provided [`Renderer`] and [`Layout`].
     ///
-    /// [`Renderer`]: crate::Renderer
+    /// [`Renderer`]: iced_native::Renderer
     pub fn draw(
         &self,
+        tree: &Tree,
         renderer: &mut Renderer,
         theme: &Renderer::Theme,
         style: &renderer::Style,
@@ -89,6 +116,7 @@ where
             let show_controls = bounds.contains(cursor_position);
 
             title_bar.draw(
+                &tree.children[1],
                 renderer,
                 theme,
                 style,
@@ -98,7 +126,8 @@ where
                 show_controls,
             );
 
-            self.body.draw(
+            self.body.as_widget().draw(
+                &tree.children[0],
                 renderer,
                 theme,
                 style,
@@ -107,7 +136,8 @@ where
                 viewport,
             );
         } else {
-            self.body.draw(
+            self.body.as_widget().draw(
+                &tree.children[0],
                 renderer,
                 theme,
                 style,
@@ -131,7 +161,7 @@ where
 
             let title_bar_size = title_bar_layout.size();
 
-            let mut body_layout = self.body.layout(
+            let mut body_layout = self.body.as_widget().layout(
                 renderer,
                 &layout::Limits::new(
                     Size::ZERO,
@@ -149,12 +179,13 @@ where
                 vec![title_bar_layout, body_layout],
             )
         } else {
-            self.body.layout(renderer, limits)
+            self.body.as_widget().layout(renderer, limits)
         }
     }
 
     pub(crate) fn on_event(
         &mut self,
+        tree: &mut Tree,
         event: Event,
         layout: Layout<'_>,
         cursor_position: Point,
@@ -169,6 +200,7 @@ where
             let mut children = layout.children();
 
             event_status = title_bar.on_event(
+                &mut tree.children[1],
                 event.clone(),
                 children.next().unwrap(),
                 cursor_position,
@@ -185,7 +217,8 @@ where
         let body_status = if is_picked {
             event::Status::Ignored
         } else {
-            self.body.on_event(
+            self.body.as_widget_mut().on_event(
+                &mut tree.children[0],
                 event,
                 body_layout,
                 cursor_position,
@@ -200,6 +233,7 @@ where
 
     pub(crate) fn mouse_interaction(
         &self,
+        tree: &Tree,
         layout: Layout<'_>,
         cursor_position: Point,
         viewport: &Rectangle,
@@ -218,6 +252,7 @@ where
                 }
 
                 let mouse_interaction = title_bar.mouse_interaction(
+                    &tree.children[1],
                     title_bar_layout,
                     cursor_position,
                     viewport,
@@ -230,25 +265,46 @@ where
             };
 
         self.body
-            .mouse_interaction(body_layout, cursor_position, viewport, renderer)
+            .as_widget()
+            .mouse_interaction(
+                &tree.children[0],
+                body_layout,
+                cursor_position,
+                viewport,
+                renderer,
+            )
             .max(title_bar_interaction)
     }
 
-    pub(crate) fn overlay(
-        &mut self,
+    pub(crate) fn overlay<'b>(
+        &'b self,
+        tree: &'b mut Tree,
         layout: Layout<'_>,
         renderer: &Renderer,
-    ) -> Option<overlay::Element<'_, Message, Renderer>> {
-        if let Some(title_bar) = self.title_bar.as_mut() {
+    ) -> Option<overlay::Element<'b, Message, Renderer>> {
+        if let Some(title_bar) = self.title_bar.as_ref() {
             let mut children = layout.children();
             let title_bar_layout = children.next()?;
 
-            match title_bar.overlay(title_bar_layout, renderer) {
+            let mut states = tree.children.iter_mut();
+            let body_state = states.next().unwrap();
+            let title_bar_state = states.next().unwrap();
+
+            match title_bar.overlay(title_bar_state, title_bar_layout, renderer)
+            {
                 Some(overlay) => Some(overlay),
-                None => self.body.overlay(children.next()?, renderer),
+                None => self.body.as_widget().overlay(
+                    body_state,
+                    children.next()?,
+                    renderer,
+                ),
             }
         } else {
-            self.body.overlay(layout, renderer)
+            self.body.as_widget().overlay(
+                &mut tree.children[0],
+                layout,
+                renderer,
+            )
         }
     }
 }