3 files changed, 38 insertions, 25 deletions

diff --git a/widget/src/pane_grid.rs b/widget/src/pane_grid.rs
index 62067e66..ae9cd825 100644
--- a/widget/src/pane_grid.rs
+++ b/widget/src/pane_grid.rs
@@ -112,7 +112,7 @@ pub struct PaneGrid<
     on_click: Option<Box<dyn Fn(Pane) -> Message + 'a>>,
     on_drag: Option<Box<dyn Fn(DragEvent) -> Message + 'a>>,
     on_resize: Option<(f32, Box<dyn Fn(ResizeEvent) -> Message + 'a>)>,
-    style: fn(&Theme) -> Appearance,
+    style: Style<Theme>,
 }
 
 impl<'a, Message, Theme, Renderer> PaneGrid<'a, Message, Theme, Renderer>
@@ -128,7 +128,7 @@ where
         view: impl Fn(Pane, &'a T, bool) -> Content<'a, Message, Theme, Renderer>,
     ) -> Self
     where
-        Theme: Style,
+        Style<Theme>: Default,
     {
         let contents = if let Some((pane, pane_state)) =
             state.maximized.and_then(|pane| {
@@ -160,7 +160,7 @@ where
             on_click: None,
             on_drag: None,
             on_resize: None,
-            style: Theme::style(),
+            style: Style::default(),
         }
     }
 
@@ -221,7 +221,7 @@ where
 
     /// Sets the style of the [`PaneGrid`].
     pub fn style(mut self, style: fn(&Theme) -> Appearance) -> Self {
-        self.style = style;
+        self.style = Style(style);
         self
     }
 
@@ -679,7 +679,7 @@ where
             None
         };
 
-        let appearance = (self.style)(theme);
+        let appearance = (self.style.0)(theme);
 
         for ((id, (content, tree)), pane_layout) in
             contents.zip(layout.children())
@@ -1147,15 +1147,27 @@ pub struct Line {
     pub width: f32,
 }
 
-/// The definiton of the default style of a [`PaneGrid`].
-pub trait Style {
-    /// Returns the default style of a [`PaneGrid`].
-    fn style() -> fn(&Self) -> Appearance;
+/// The style of a [`PaneGrid`].
+#[derive(Debug, PartialEq, Eq)]
+pub struct Style<Theme>(fn(&Theme) -> Appearance);
+
+impl<Theme> Clone for Style<Theme> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<Theme> Copy for Style<Theme> {}
+
+impl Default for Style<Theme> {
+    fn default() -> Self {
+        Style(default)
+    }
 }
 
-impl Style for Theme {
-    fn style() -> fn(&Self) -> Appearance {
-        default
+impl<Theme> From<fn(&Theme) -> Appearance> for Style<Theme> {
+    fn from(f: fn(&Theme) -> Appearance) -> Self {
+        Style(f)
     }
 }
 
diff --git a/widget/src/pane_grid/content.rs b/widget/src/pane_grid/content.rs
index 25b64e17..ce29e8d0 100644
--- a/widget/src/pane_grid/content.rs
+++ b/widget/src/pane_grid/content.rs
@@ -24,7 +24,7 @@ pub struct Content<
 {
     title_bar: Option<TitleBar<'a, Message, Theme, Renderer>>,
     body: Element<'a, Message, Theme, Renderer>,
-    style: fn(&Theme, container::Status) -> container::Appearance,
+    style: container::Style<Theme>,
 }
 
 impl<'a, Message, Theme, Renderer> Content<'a, Message, Theme, Renderer>
@@ -34,12 +34,12 @@ where
     /// Creates a new [`Content`] with the provided body.
     pub fn new(body: impl Into<Element<'a, Message, Theme, Renderer>>) -> Self
     where
-        Theme: container::Style,
+        container::Style<Theme>: Default,
     {
         Self {
             title_bar: None,
             body: body.into(),
-            style: Theme::style(),
+            style: container::Style::default(),
         }
     }
 
@@ -57,7 +57,7 @@ where
         mut self,
         style: fn(&Theme, container::Status) -> container::Appearance,
     ) -> Self {
-        self.style = style;
+        self.style = style.into();
         self
     }
 }
@@ -114,7 +114,7 @@ where
                     container::Status::Idle
                 };
 
-                (self.style)(theme, status)
+                self.style.resolve(theme, status)
             };
 
             container::draw_background(renderer, &style, bounds);
@@ -403,8 +403,8 @@ impl<'a, T, Message, Theme, Renderer> From<T>
     for Content<'a, Message, Theme, Renderer>
 where
     T: Into<Element<'a, Message, Theme, Renderer>>,
-    Theme: container::Style,
     Renderer: crate::core::Renderer,
+    container::Style<Theme>: Default,
 {
     fn from(element: T) -> Self {
         Self::new(element)
diff --git a/widget/src/pane_grid/title_bar.rs b/widget/src/pane_grid/title_bar.rs
index 787510cc..b1cdcde3 100644
--- a/widget/src/pane_grid/title_bar.rs
+++ b/widget/src/pane_grid/title_bar.rs
@@ -25,7 +25,7 @@ pub struct TitleBar<
     controls: Option<Element<'a, Message, Theme, Renderer>>,
     padding: Padding,
     always_show_controls: bool,
-    style: fn(&Theme, container::Status) -> container::Appearance,
+    style: container::Style<Theme>,
 }
 
 impl<'a, Message, Theme, Renderer> TitleBar<'a, Message, Theme, Renderer>
@@ -33,17 +33,18 @@ where
     Renderer: crate::core::Renderer,
 {
     /// Creates a new [`TitleBar`] with the given content.
-    pub fn new<E>(content: E) -> Self
+    pub fn new(
+        content: impl Into<Element<'a, Message, Theme, Renderer>>,
+    ) -> Self
     where
-        Theme: container::Style,
-        E: Into<Element<'a, Message, Theme, Renderer>>,
+        container::Style<Theme>: Default,
     {
         Self {
             content: content.into(),
             controls: None,
             padding: Padding::ZERO,
             always_show_controls: false,
-            style: Theme::style(),
+            style: container::Style::default(),
         }
     }
 
@@ -67,7 +68,7 @@ where
         mut self,
         style: fn(&Theme, container::Status) -> container::Appearance,
     ) -> Self {
-        self.style = style;
+        self.style = style.into();
         self
     }
 
@@ -137,7 +138,7 @@ where
                 container::Status::Idle
             };
 
-            (self.style)(theme, status)
+            self.style.resolve(theme, status)
         };
 
         let inherited_style = renderer::Style {