feat(linux): Add support for system color scheme using xdg-desktop-portal

.changes/linux-system-color-scheme.md

@@ -0,0 +1,5 @@
+---
+tao: minor
+---
+
+Use the Linux XDG Desktop Portal to add support for the system color scheme. Needs `dbus` feature flag.

Cargo.toml

@@ -17,7 +17,7 @@ categories = ["gui"]
 include = ["/README.md", "src/**/*.rs", "examples/**/*.rs", "LICENSE*"]
 
 [package.metadata.docs.rs]
-features = ["rwh_04", "rwh_05", "rwh_06", "serde", "x11"]
+features = ["rwh_04", "rwh_05", "rwh_06", "serde", "x11", "dbus"]
 default-target = "x86_64-unknown-linux-gnu"
 targets = [
   "i686-pc-windows-msvc",
@@ -28,12 +28,13 @@ targets = [
 ]
 
 [features]
-default = ["rwh_06", "x11"]
+default = ["rwh_06", "x11", "dbus"]
 serde = ["dep:serde", "dpi/serde"]
 rwh_04 = ["dep:rwh_04"]
 rwh_05 = ["dep:rwh_05"]
 rwh_06 = ["dep:rwh_06"]
 x11 = ["dep:gdkx11-sys", "dep:x11-dl"]
+dbus = ["dep:dbus"]
 
 [workspace]
 members = ["tao-macros"]
@@ -157,3 +158,4 @@ gdkwayland-sys = "0.18.0"
 x11-dl = { version = "2.21", optional = true }
 parking_lot = "0.12"
 dlopen2 = "0.8.0"
+dbus = { version = "0.9", optional = true }

src/event.rs

@@ -412,7 +412,7 @@ pub enum WindowEvent<'a> {
   ///
   /// ## Platform-specific
   ///
-  /// - **Linux / Android / iOS:** Unsupported
+  /// - **Android / iOS:** Unsupported
   ThemeChanged(Theme),
 
   /// The window decorations has been clicked.

src/platform_impl/linux/event_loop.rs

@@ -284,6 +284,15 @@ impl<T: 'static> EventLoop<T> {
     let mut taskbar = TaskbarIndicator::new();
     let is_wayland = window_target.is_wayland();
 
+    // Receive portal events
+    #[cfg(feature = "dbus")]
+    {
+      let tx_requests_clone = window_target.window_requests_tx.clone();
+      if let Err(e) = super::portal::receive_theme_changed(tx_requests_clone) {
+        log::debug!("Unable to receive theme changed events: {e}");
+      }
+    }
+
     // Window Request
     window_requests_rx.attach(Some(&context), move |(id, request)| {
       if let Some(window) = app_.window_by_id(id.0) {
@@ -947,9 +956,15 @@ impl<T: 'static> EventLoop<T> {
           }
           WindowRequest::SetTheme(theme) => {
             if let Some(settings) = Settings::default() {
-              match theme {
-                Some(Theme::Dark) => settings.set_gtk_application_prefer_dark_theme(true),
-                Some(Theme::Light) | None => settings.set_gtk_application_prefer_dark_theme(false),
+              settings.set_gtk_application_prefer_dark_theme(theme == Some(Theme::Dark));
+              if let Err(e) = event_tx.send(Event::WindowEvent {
+                window_id: RootWindowId(id),
+                event: WindowEvent::ThemeChanged(theme.unwrap_or_default()),
+              }) {
+                log::warn!(
+                  "Failed to send window theme changed event to event channel: {}",
+                  e
+                );
               }
             }
           }

src/platform_impl/linux/mod.rs

@@ -9,6 +9,8 @@ mod icon;
 mod keyboard;
 mod keycode;
 mod monitor;
+#[cfg(feature = "dbus")]
+mod portal;
 mod util;
 mod window;
 

src/platform_impl/linux/portal.rs

@@ -0,0 +1,78 @@
+#[cfg(feature = "dbus")]
+use dbus::{
+  arg::Variant,
+  blocking::{Connection, SyncConnection},
+  message::MatchRule,
+  Error,
+};
+use gtk::glib::{ControlFlow, MainContext, Priority, Sender};
+use log::warn;
+use std::{thread, time::Duration};
+
+use crate::{
+  platform_impl::{platform::window::WindowRequest, WindowId},
+  window::Theme,
+};
+
+pub fn theme() -> Result<Theme, Error> {
+  let conn = Connection::new_session()?;
+  let proxy = conn.with_proxy(
+    "org.freedesktop.portal.Desktop",
+    "/org/freedesktop/portal/desktop",
+    Duration::from_secs(5),
+  );
+
+  let result: (Variant<Variant<u32>>,) = proxy.method_call(
+    "org.freedesktop.portal.Settings",
+    "Read",
+    ("org.freedesktop.appearance", "color-scheme"),
+  )?;
+
+  Ok(color_scheme_to_theme(result.0 .0 .0))
+}
+
+pub fn receive_theme_changed(window_tx: Sender<(WindowId, WindowRequest)>) -> Result<(), Error> {
+  let conn = SyncConnection::new_session()?;
+  let match_rule = MatchRule::new_signal("org.freedesktop.portal.Settings", "SettingChanged");
+  let (tx, rx) = MainContext::channel(Priority::DEFAULT);
+
+  conn.add_match(match_rule, move |_: (), _, msg| {
+    let mut iter = msg.iter_init();
+    if let (Ok("org.freedesktop.appearance"), Ok("color-scheme"), Ok(value)) = (
+      iter.read::<&str>(),         // Namespace
+      iter.read::<&str>(),         // Key
+      iter.read::<Variant<u32>>(), // Value
+    ) {
+      if let Err(e) = tx.send(color_scheme_to_theme(value.0)) {
+        warn!("Failed to send theme change via channel: {}", e);
+      }
+    }
+    true
+  })?;
+
+  rx.attach(None, move |theme| {
+    if let Err(e) = window_tx.send((WindowId::dummy(), WindowRequest::SetTheme(Some(theme)))) {
+      warn!("Failed to send theme change request: {}", e);
+      ControlFlow::Break
+    } else {
+      ControlFlow::Continue
+    }
+  });
+
+  thread::spawn(move || loop {
+    if let Err(e) = conn.process(Duration::from_secs(5)) {
+      warn!("D-Bus message processing error: {}", e);
+      break;
+    }
+  });
+
+  Ok(())
+}
+
+fn color_scheme_to_theme(color_scheme: u32) -> Theme {
+  match color_scheme {
+    1 => Theme::Dark,  // Prefer Dark
+    2 => Theme::Light, // Prefer Light
+    _ => Theme::Light, // No Preference, default to Light
+  }
+}

src/platform_impl/linux/window.rs

@@ -43,10 +43,6 @@ impl WindowId {
   }
 }
 
-// Currently GTK doesn't provide feature for detect theme, so we need to check theme manually.
-// ref: https://github.com/WebKit/WebKit/blob/e44ffaa0d999a9807f76f1805943eea204cfdfbc/Source/WebKit/UIProcess/API/gtk/PageClientImpl.cpp#L587
-const GTK_THEME_SUFFIX_LIST: [&str; 3] = ["-dark", "-Dark", "-Darker"];
-
 pub struct Window {
   /// Window id.
   pub(crate) window_id: WindowId,
@@ -197,29 +193,17 @@ impl Window {
       window.stick();
     }
 
-    let preferred_theme = if let Some(settings) = Settings::default() {
-      if let Some(preferred_theme) = attributes.preferred_theme {
-        match preferred_theme {
-          Theme::Dark => settings.set_gtk_application_prefer_dark_theme(true),
-          Theme::Light => {
-            if let Some(theme) = settings.gtk_theme_name() {
-              let theme = theme.as_str();
-              // Remove dark variant.
-              if let Some(theme) = GTK_THEME_SUFFIX_LIST
-                .iter()
-                .find(|t| theme.ends_with(*t))
-                .map(|v| theme.strip_suffix(v))
-              {
-                settings.set_gtk_theme_name(theme);
-              }
-            }
-          }
-        }
+    // Set initial `preferred_theme` value to current portal color-scheme
+    #[cfg(feature = "dbus")]
+    let preferred_theme = super::portal::theme().ok();
+    #[cfg(not(feature = "dbus"))]
+    let preferred_theme = None;
+
+    if let Some(theme) = preferred_theme {
+      if let Some(settings) = Settings::default() {
+        settings.set_gtk_application_prefer_dark_theme(theme == Theme::Dark);
       }
-      attributes.preferred_theme
-    } else {
-      None
-    };
+    }
 
     if attributes.visible {
       window.show_all();
@@ -1029,11 +1013,9 @@ impl Window {
       return theme;
     }
 
-    if let Some(theme) = Settings::default().and_then(|s| s.gtk_theme_name()) {
-      let theme = theme.as_str();
-      if GTK_THEME_SUFFIX_LIST.iter().any(|t| theme.ends_with(t)) {
-        return Theme::Dark;
-      }
+    #[cfg(feature = "dbus")]
+    if let Ok(portal_theme) = super::portal::theme() {
+      return portal_theme;
     }
 
     Theme::Light