Track window theme in window::State

core/src/window/event.rs

@@ -1,3 +1,4 @@
+use crate::theme;
 use crate::time::Instant;
 use crate::{Point, Size};
 
@@ -71,4 +72,7 @@ pub enum Event {
     ///
     /// - **Wayland:** Not implemented.
     FilesHoveredLeft,
+
+    /// The theme mode of the window has changed.
+    ThemeModeChanged(theme::Mode),
 }

winit/src/conversion.rs

@@ -5,6 +5,7 @@
 use crate::core::input_method;
 use crate::core::keyboard;
 use crate::core::mouse;
+use crate::core::theme;
 use crate::core::touch;
 use crate::core::window;
 use crate::core::{Event, Point, Size};
@@ -318,6 +319,9 @@ pub fn window_event(
 
             Some(Event::Window(window::Event::Moved(Point::new(x, y))))
         }
+        WindowEvent::ThemeChanged(theme) => Some(Event::Window(
+            window::Event::ThemeModeChanged(theme_mode(theme)),
+        )),
         _ => None,
     }
 }
@@ -440,6 +444,16 @@ pub fn mode(mode: Option<winit::window::Fullscreen>) -> window::Mode {
     }
 }
 
+/// Converts a [`winit`] window theme to a [`theme::Mode`].
+///
+/// [`winit`]: https://github.com/rust-windowing/winit
+pub fn theme_mode(theme: winit::window::Theme) -> theme::Mode {
+    match theme {
+        winit::window::Theme::Light => theme::Mode::Light,
+        winit::window::Theme::Dark => theme::Mode::Dark,
+    }
+}
+
 /// Converts a [`mouse::Interaction`] to a [`winit`] cursor icon.
 ///
 /// [`winit`]: https://github.com/rust-windowing/winit

winit/src/window/state.rs

@@ -20,8 +20,8 @@ where
     viewport_version: u64,
     cursor_position: Option<winit::dpi::PhysicalPosition<f64>>,
     modifiers: winit::keyboard::ModifiersState,
-    theme: P::Theme,
-    theme_mode: theme::Mode,
+    theme: Option<P::Theme>,
+    system_theme: P::Theme,
     style: theme::Style,
 }
 
@@ -30,7 +30,7 @@ where
     P::Theme: theme::Base,
 {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        f.debug_struct("multi_window::State")
+        f.debug_struct("window::State")
             .field("title", &self.title)
             .field("scale_factor", &self.scale_factor)
             .field("viewport", &self.viewport)
@@ -53,15 +53,13 @@ where
     ) -> Self {
         let title = program.title(window_id);
         let scale_factor = program.scale_factor(window_id);
-        let theme_mode = match window.theme() {
-            None => theme::Mode::None,
-            Some(winit::window::Theme::Light) => theme::Mode::Light,
-            Some(winit::window::Theme::Dark) => theme::Mode::Dark,
-        };
-        let theme = program
-            .theme(window_id)
-            .unwrap_or_else(|| <P::Theme as theme::Base>::default(theme_mode));
-        let style = program.style(&theme);
+        let theme_mode = window
+            .theme()
+            .map(conversion::theme_mode)
+            .unwrap_or_default();
+        let theme = program.theme(window_id);
+        let system_theme = <P::Theme as theme::Base>::default(theme_mode);
+        let style = program.style(theme.as_ref().unwrap_or(&system_theme));
 
         let viewport = {
             let physical_size = window.inner_size();
@@ -80,7 +78,7 @@ where
             cursor_position: None,
             modifiers: winit::keyboard::ModifiersState::default(),
             theme,
-            theme_mode,
+            system_theme,
             style,
         }
     }
@@ -132,7 +130,7 @@ where
 
     /// Returns the current theme of the [`State`].
     pub fn theme(&self) -> &P::Theme {
-        &self.theme
+        self.theme.as_ref().unwrap_or(&self.system_theme)
     }
 
     /// Returns the current background [`Color`] of the [`State`].
@@ -183,6 +181,15 @@ where
             WindowEvent::ModifiersChanged(new_modifiers) => {
                 self.modifiers = new_modifiers.state();
             }
+            WindowEvent::ThemeChanged(theme) => {
+                self.system_theme = <P::Theme as theme::Base>::default(
+                    conversion::theme_mode(*theme),
+                );
+
+                if self.theme.is_none() {
+                    window.request_redraw();
+                }
+            }
             _ => {}
         }
     }
@@ -225,9 +232,7 @@ where
         }
 
         // Update theme and appearance
-        self.theme = program.theme(window_id).unwrap_or_else(|| {
-            <P::Theme as theme::Base>::default(self.theme_mode)
-        });
-        self.style = program.style(&self.theme);
+        self.theme = program.theme(window_id);
+        self.style = program.style(self.theme());
     }
 }