Rework theme API

This commit adds support for theming on macOS and
also unifies the system theme handling across platforms.

CHANGELOG.md

@@ -22,6 +22,10 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On Wayland, a new `wayland-csd-adwaita-crossfont` feature was added to use `crossfont` instead of `ab_glyph` for decorations.
 - On Wayland, if not otherwise specified use upstream automatic CSD theme selection.
 - On X11, added `WindowExtX11::with_parent` to create child windows.
+- Added support for `WindowBuilder::with_theme` and `Window::theme` to support per-window dark/light/system theme configuration on macos, windows and wayland.
+- On macOS, added support for `WindowEvent::ThemeChanged`.
+- **Breaking:** Removed `WindowBuilderExtWindows::with_theme` and `WindowBuilderExtWayland::with_wayland_csd_theme` in favour of `WindowBuilder::with_theme`.
+- **Breaking:** Removed `WindowExtWindows::theme` in favour of `Window::theme`.
 
 # 0.27.4
 

FEATURES.md

@@ -130,6 +130,7 @@ If your PR makes notable changes to Winit's features, please update this section
 * Hidden titlebar buttons
 * Full-size content view
 * Accepts first mouse
+* Set a preferred theme and get current theme.
 
 ### Unix
 * Window urgency

examples/theme.rs

@@ -0,0 +1,40 @@
+#![allow(clippy::single_match)]
+
+use simple_logger::SimpleLogger;
+use winit::{
+    event::{Event, WindowEvent},
+    event_loop::{ControlFlow, EventLoop},
+    window::{Theme, WindowBuilder},
+};
+
+fn main() {
+    SimpleLogger::new().init().unwrap();
+    let event_loop = EventLoop::new();
+
+    let window = WindowBuilder::new()
+        .with_title("A fantastic window!")
+        .with_theme(Some(Theme::Dark))
+        .build(&event_loop)
+        .unwrap();
+
+    println!("Initial theme: {:?}", window.theme());
+
+    event_loop.run(move |event, _, control_flow| {
+        *control_flow = ControlFlow::Wait;
+
+        match event {
+            Event::WindowEvent {
+                event: WindowEvent::CloseRequested,
+                ..
+            } => *control_flow = ControlFlow::Exit,
+            Event::WindowEvent {
+                event: WindowEvent::ThemeChanged(theme),
+                window_id,
+                ..
+            } if window_id == window.id() => {
+                println!("Theme is changed: {:?}", theme)
+            }
+            _ => (),
+        }
+    });
+}

src/event.rs

@@ -504,7 +504,7 @@ pub enum WindowEvent<'a> {
     ///
     /// ## Platform-specific
     ///
-    /// At the moment this is only supported on Windows.
+    /// - **iOS / Android / X11 / Wayland:** Unsupported.
     ThemeChanged(Theme),
 
     /// The window has been occluded (completely hidden from view).

src/platform/wayland.rs

@@ -138,14 +138,6 @@ pub trait WindowBuilderExtWayland {
     /// For details about application ID conventions, see the
     /// [Desktop Entry Spec](https://specifications.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html#desktop-file-id)
     fn with_name(self, general: impl Into<String>, instance: impl Into<String>) -> Self;
-
-    /// Build window with certain decoration [`Theme`]
-    ///
-    /// You can also use `WINIT_WAYLAND_CSD_THEME` env variable to set the theme.
-    /// Possible values for env variable are: "dark" and light".
-    ///
-    /// When unspecified a theme is automatically selected.
-    fn with_wayland_csd_theme(self, theme: Theme) -> Self;
 }
 
 impl WindowBuilderExtWayland for WindowBuilder {
@@ -154,12 +146,6 @@ impl WindowBuilderExtWayland for WindowBuilder {
         self.platform_specific.name = Some(ApplicationName::new(general.into(), instance.into()));
         self
     }
-
-    #[inline]
-    fn with_wayland_csd_theme(mut self, theme: Theme) -> Self {
-        self.platform_specific.csd_theme = Some(theme);
-        self
-    }
 }
 
 /// Additional methods on `MonitorHandle` that are specific to Wayland.

src/platform/windows.rs

@@ -6,7 +6,7 @@ use crate::{
     event_loop::EventLoopBuilder,
     monitor::MonitorHandle,
     platform_impl::{Parent, WinIcon},
-    window::{BadIcon, Icon, Theme, Window, WindowBuilder},
+    window::{BadIcon, Icon, Window, WindowBuilder},
 };
 
 /// Window Handle type used by Win32 API
@@ -136,9 +136,6 @@ pub trait WindowExtWindows {
     /// This sets `ICON_BIG`. A good ceiling here is 256x256.
     fn set_taskbar_icon(&self, taskbar_icon: Option<Icon>);
 
-    /// Returns the current window theme.
-    fn theme(&self) -> Theme;
-
     /// Whether to show or hide the window icon in the taskbar.
     fn set_skip_taskbar(&self, skip: bool);
 
@@ -169,11 +166,6 @@ impl WindowExtWindows for Window {
         self.window.set_taskbar_icon(taskbar_icon)
     }
 
-    #[inline]
-    fn theme(&self) -> Theme {
-        self.window.theme()
-    }
-
     #[inline]
     fn set_skip_taskbar(&self, skip: bool) {
         self.window.set_skip_taskbar(skip)
@@ -232,9 +224,6 @@ pub trait WindowBuilderExtWindows {
     /// See <https://docs.microsoft.com/en-us/windows/win32/api/objbase/nf-objbase-coinitialize#remarks> for more information.
     fn with_drag_and_drop(self, flag: bool) -> WindowBuilder;
 
-    /// Forces a theme or uses the system settings if `None` was provided.
-    fn with_theme(self, theme: Option<Theme>) -> WindowBuilder;
-
     /// Whether show or hide the window icon in the taskbar.
     fn with_skip_taskbar(self, skip: bool) -> WindowBuilder;
 
@@ -282,12 +271,6 @@ impl WindowBuilderExtWindows for WindowBuilder {
         self
     }
 
-    #[inline]
-    fn with_theme(mut self, theme: Option<Theme>) -> WindowBuilder {
-        self.platform_specific.preferred_theme = theme;
-        self
-    }
-
     #[inline]
     fn with_skip_taskbar(mut self, skip: bool) -> WindowBuilder {
         self.platform_specific.skip_taskbar = skip;

src/platform_impl/android/mod.rs

@@ -24,7 +24,7 @@ use crate::{
     error,
     event::{self, VirtualKeyCode},
     event_loop::{self, ControlFlow},
-    window::{self, CursorGrabMode},
+    window::{self, CursorGrabMode, Theme},
 };
 
 static CONFIG: Lazy<RwLock<Configuration>> = Lazy::new(|| {
@@ -852,6 +852,10 @@ impl Window {
     pub fn content_rect(&self) -> Rect {
         ndk_glue::content_rect()
     }
+
+    pub fn theme(&self) -> Option<Theme> {
+        None
+    }
 }
 
 #[derive(Default, Clone, Debug)]

src/platform_impl/ios/window.rs

@@ -23,7 +23,8 @@ use crate::{
         monitor, view, EventLoopWindowTarget, Fullscreen, MonitorHandle,
     },
     window::{
-        CursorGrabMode, CursorIcon, UserAttentionType, WindowAttributes, WindowId as RootWindowId,
+        CursorGrabMode, CursorIcon, Theme, UserAttentionType, WindowAttributes,
+        WindowId as RootWindowId,
     },
 };
 
@@ -341,6 +342,11 @@ impl Inner {
     pub fn raw_display_handle(&self) -> RawDisplayHandle {
         RawDisplayHandle::UiKit(UiKitDisplayHandle::empty())
     }
+
+    pub fn theme(&self) -> Option<Theme> {
+        warn!("`Window::theme` is ignored on iOS");
+        None
+    }
 }
 
 pub struct Window {

src/platform_impl/linux/mod.rs

@@ -31,8 +31,6 @@ pub use self::x11::XNotSupported;
 use self::x11::{ffi::XVisualInfo, util::WindowType as XWindowType, XConnection, XError};
 #[cfg(feature = "x11")]
 use crate::platform::x11::XlibErrorHook;
-#[cfg(feature = "wayland")]
-use crate::window::Theme;
 use crate::{
     dpi::{PhysicalPosition, PhysicalSize, Position, Size},
     error::{ExternalError, NotSupportedError, OsError as RootOsError},
@@ -41,7 +39,7 @@ use crate::{
         ControlFlow, DeviceEventFilter, EventLoopClosed, EventLoopWindowTarget as RootELW,
     },
     icon::Icon,
-    window::{CursorGrabMode, CursorIcon, UserAttentionType, WindowAttributes},
+    window::{CursorGrabMode, CursorIcon, Theme, UserAttentionType, WindowAttributes},
 };
 
 pub(crate) use crate::icon::RgbaIcon as PlatformIcon;
@@ -104,8 +102,6 @@ pub struct PlatformSpecificWindowBuilderAttributes {
     pub x11_window_types: Vec<XWindowType>,
     #[cfg(feature = "x11")]
     pub gtk_theme_variant: Option<String>,
-    #[cfg(feature = "wayland")]
-    pub csd_theme: Option<Theme>,
 }
 
 impl Default for PlatformSpecificWindowBuilderAttributes {
@@ -126,8 +122,6 @@ impl Default for PlatformSpecificWindowBuilderAttributes {
             x11_window_types: vec![XWindowType::Normal],
             #[cfg(feature = "x11")]
             gtk_theme_variant: None,
-            #[cfg(feature = "wayland")]
-            csd_theme: None,
         }
     }
 }
@@ -590,6 +584,11 @@ impl Window {
     pub fn raw_display_handle(&self) -> RawDisplayHandle {
         x11_or_wayland!(match self; Window(window) => window.raw_display_handle())
     }
+
+    #[inline]
+    pub fn theme(&self) -> Option<Theme> {
+        x11_or_wayland!(match self; Window(window) => window.theme())
+    }
 }
 
 /// Hooks for X11 errors.

src/platform_impl/linux/wayland/window/mod.rs

@@ -170,7 +170,7 @@ impl Window {
         // Set CSD frame config from theme if specified,
         // otherwise use upstream automatic selection.
         #[cfg(feature = "sctk-adwaita")]
-        if let Some(theme) = platform_attributes.csd_theme.or_else(|| {
+        if let Some(theme) = attributes.preferred_theme.or_else(|| {
             std::env::var(WAYLAND_CSD_THEME_ENV_VAR)
                 .ok()
                 .and_then(|s| s.as_str().try_into().ok())
@@ -619,6 +619,11 @@ impl Window {
         self.window_requests.lock().unwrap().push(request);
         self.event_loop_awakener.ping();
     }
+
+    #[inline]
+    pub fn theme(&self) -> Option<Theme> {
+        None
+    }
 }
 
 impl Drop for Window {

src/platform_impl/linux/x11/window.rs

@@ -20,7 +20,7 @@ use crate::{
         Fullscreen, MonitorHandle as PlatformMonitorHandle, OsError,
         PlatformSpecificWindowBuilderAttributes, VideoMode as PlatformVideoMode,
     },
-    window::{CursorGrabMode, CursorIcon, Icon, UserAttentionType, WindowAttributes},
+    window::{CursorGrabMode, CursorIcon, Icon, Theme, UserAttentionType, WindowAttributes},
 };
 
 use super::{
@@ -1546,4 +1546,9 @@ impl UnownedWindow {
         display_handle.screen = self.screen_id;
         RawDisplayHandle::Xlib(display_handle)
     }
+
+    #[inline]
+    pub fn theme(&self) -> Option<Theme> {
+        None
+    }
 }

src/platform_impl/macos/appkit/appearance.rs

@@ -0,0 +1,29 @@
+use objc2::foundation::{NSArray, NSObject, NSString};
+use objc2::rc::{Id, Shared};
+use objc2::{extern_class, extern_methods, msg_send_id, ClassType};
+
+extern_class!(
+    #[derive(Debug, PartialEq, Eq, Hash)]
+    pub(crate) struct NSAppearance;
+
+    unsafe impl ClassType for NSAppearance {
+        type Super = NSObject;
+    }
+);
+
+type NSAppearanceName = NSString;
+
+extern_methods!(
+    unsafe impl NSAppearance {
+        pub fn appearanceNamed(name: &NSAppearanceName) -> Id<Self, Shared> {
+            unsafe { msg_send_id![Self::class(), appearanceNamed: name] }
+        }
+
+        pub fn bestMatchFromAppearancesWithNames(
+            &self,
+            appearances: &NSArray<NSAppearanceName>,
+        ) -> Id<NSAppearanceName, Shared> {
+            unsafe { msg_send_id![self, bestMatchFromAppearancesWithNames: appearances,] }
+        }
+    }
+);

src/platform_impl/macos/appkit/application.rs

@@ -4,7 +4,7 @@ use objc2::runtime::Object;
 use objc2::{extern_class, extern_methods, msg_send_id, ClassType};
 use objc2::{Encode, Encoding};
 
-use super::{NSEvent, NSMenu, NSResponder, NSWindow};
+use super::{NSAppearance, NSEvent, NSMenu, NSResponder, NSWindow};
 
 extern_class!(
     #[derive(Debug, PartialEq, Eq, Hash)]
@@ -82,6 +82,13 @@ extern_methods!(
         #[sel(setMainMenu:)]
         pub fn setMainMenu(&self, menu: &NSMenu);
 
+        pub fn effectiveAppearance(&self) -> Id<NSAppearance, Shared> {
+            unsafe { msg_send_id![self, effectiveAppearance] }
+        }
+
+        #[sel(setAppearance:)]
+        pub fn setAppearance(&self, appearance: &NSAppearance);
+
         #[sel(run)]
         pub unsafe fn run(&self);
     }

src/platform_impl/macos/appkit/mod.rs

@@ -11,6 +11,7 @@
 #![allow(clippy::enum_variant_names)]
 #![allow(non_upper_case_globals)]
 
+mod appearance;
 mod application;
 mod button;
 mod color;
@@ -28,6 +29,7 @@ mod version;
 mod view;
 mod window;
 
+pub(crate) use self::appearance::NSAppearance;
 pub(crate) use self::application::{
     NSApp, NSApplication, NSApplicationActivationPolicy, NSApplicationPresentationOptions,
     NSRequestUserAttentionType,