Added darkmode detection on Linux

CHANGELOG.md

@@ -18,6 +18,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   underlying window is resized immediately. Notably, this happens on Wayland but
   may happen on some other platforms as well.
 
+### Added
+
+- A new feature `xdg` has been added, enabled by default, that enables detecting
+  dark mode changes on Linux.
+
 ## v0.4.0 (2024-09-14)
 
 ### Breaking Changes

Cargo.lock

@@ -62,6 +62,7 @@ checksum = "fc7eb209b1518d6bb87b283c20095f5228ecda460da70b44f0802523dea6da04"
 name = "appit"
 version = "0.4.0"
 dependencies = [
+ "darkmode",
  "winit",
 ]
 
@@ -260,6 +261,26 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "96a6ac251f4a2aca6b3f91340350eab87ae57c3f127ffeb585e92bd336717991"
 
+[[package]]
+name = "darkmode"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "075a9464059e42ad7f7c487897c1ceb65327daf056c2acf58b27ca62a51db2ab"
+dependencies = [
+ "dbus",
+]
+
+[[package]]
+name = "dbus"
+version = "0.9.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1bb21987b9fb1613058ba3843121dd18b163b254d8a6e797e144cbac14d96d1b"
+dependencies = [
+ "libc",
+ "libdbus-sys",
+ "winapi",
+]
+
 [[package]]
 name = "dispatch"
 version = "0.2.0"
@@ -419,6 +440,15 @@ version = "0.2.158"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d8adc4bb1803a324070e64a98ae98f38934d91957a99cfb3a43dcbc01bc56439"
 
+[[package]]
+name = "libdbus-sys"
+version = "0.2.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06085512b750d640299b79be4bad3d2fa90a9c00b1fd9e1b46364f66f0485c72"
+dependencies = [
+ "pkg-config",
+]
+
 [[package]]
 name = "libloading"
 version = "0.8.5"
@@ -1303,6 +1333,22 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
 [[package]]
 name = "winapi-util"
 version = "0.1.9"
@@ -1312,6 +1358,12 @@ dependencies = [
  "windows-sys 0.59.0",
 ]
 
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
+
 [[package]]
 name = "windows-sys"
 version = "0.45.0"

Cargo.toml

@@ -11,14 +11,18 @@ categories = ["gui"]
 readme = "./README.md"
 
 [features]
-default = ["x11", "wayland", "wayland-dlopen", "wayland-csd-adwaita"]
+default = ["x11", "wayland", "wayland-dlopen", "wayland-csd-adwaita", "xdg"]
 wayland-csd-adwaita = ["winit/wayland-csd-adwaita"]
 x11 = ["winit/x11"]
 wayland = ["winit/wayland"]
 wayland-dlopen = ["winit/wayland-dlopen"]
 rwh_06 = ["winit/rwh_06"]
 rwh_05 = ["winit/rwh_05"]
+xdg = ["dep:darkmode"]
 
 
 [dependencies]
 winit = { version = "0.30.5", default-features = false }
+
+[target.'cfg(target_os = "linux")'.dependencies]
+darkmode = { version = "0.1.0", optional = true }

src/lib.rs

@@ -7,6 +7,9 @@
 mod private;
 mod window;
 
+#[cfg(all(target_os = "linux", feature = "xdg"))]
+mod xdg;
+
 use std::collections::HashMap;
 use std::ops::Deref;
 use std::process::exit;
@@ -253,6 +256,8 @@ where
         let StartCause::Init = cause else {
             return;
         };
+        #[cfg(all(target_os = "linux", feature = "xdg"))]
+        self.observe_darkmode_changes(event_loop.proxy());
         self.running.started.store(true, Ordering::Relaxed);
         for PendingWindow {
             window,
@@ -333,6 +338,10 @@ where
                     exit(0)
                 }
             }
+            #[cfg(all(target_os = "linux", feature = "xdg"))]
+            EventLoopMessage::ThemeChanged(theme) => {
+                self.running.windows.theme_changed(theme);
+            }
         }
     }
 }
@@ -706,6 +715,16 @@ impl<Message> Windows<Message> {
         data.guards -= 1;
         data.should_shutdown()
     }
+
+    #[cfg(all(target_os = "linux", feature = "xdg"))]
+    fn theme_changed(&self, theme: winit::window::Theme) {
+        let data = self.data.lock().unwrap_or_else(PoisonError::into_inner);
+        for window in data.open.values() {
+            let _ = window
+                .sender
+                .send(WindowMessage::Event(WindowEvent::ThemeChanged(theme)));
+        }
+    }
 }
 
 struct OpenWindow<User> {

src/private.rs

@@ -62,6 +62,8 @@ where
     },
     PreventShutdown,
     AllowShutdown,
+    #[cfg(all(target_os = "linux", feature = "xdg"))]
+    ThemeChanged(Theme),
 }
 
 #[derive(Debug)]

src/xdg.rs

@@ -0,0 +1,16 @@
+use winit::{event_loop::EventLoopProxy, window::Theme};
+
+use crate::{private::EventLoopMessage, Message};
+
+fn observe_darkmode_changes<AppMessage>(proxy: EventLoopProxy<EventLoopMessage<AppMessage>>)
+where
+    AppMessage: Message,
+{
+    let _ignored_error = darkmode::subscribe(move |mode| {
+        let _ = proxy.send_event(EventLoopMessage::ThemeChanged(match mode {
+            darkmode::Mode::Dark => Theme::Dark,
+            darkmode::Mode::Light => Theme::Light,
+            darkmode::Mode::Default => return,
+        }));
+    });
+}