Merge pull request #623 from ahmedhosnypro/fix/system-theme-linux

Fix the system theme mode always drawing light on Linux and the BSDs

Cargo.lock

@@ -1527,6 +1527,7 @@ dependencies = [
  "windows",
  "winit",
  "winresource",
+ "zbus",
 ]
 
 [[package]]

apps/figcraft/Cargo.toml

@@ -36,6 +36,12 @@ env_logger = { version = "0.11", default-features = false, features = ["auto-col
 craft-update = { workspace = true }
 windows = { version = "0.62", default-features = false, features = ["UI_ViewManagement", "System_UserProfile", "Foundation_Collections", "Gaming_Input"] }
 
+# The system colour scheme (org.freedesktop.portal.Settings): winit reports no theme on Linux and
+# the BSDs, so the interface's "system" mode follows the portal's instead. zbus comes in through
+# accesskit already; this only makes it direct.
+[target.'cfg(all(unix, not(target_os = "macos")))'.dependencies]
+zbus = { version = "5", default-features = false, features = ["async-io", "blocking-api"] }
+
 # Finder double-clicks, Open With, Dock drops and `open -a FigCraft file.figcraft` arrive as a
 # kAEOpenDocuments Apple event, which winit 0.30 doesn't handle. This crate (also used by GridCraft,
 # EffectCraft and PhotoCraft) registers the handler behind a safe API (Objective-C interop needs

apps/figcraft/src/main.rs

@@ -170,21 +170,23 @@ fn main() -> eframe::Result {
     // System fonts: index them in the background, then wake the UI (an idle window draws no frames)
     // to lay text out again with them.
     let ctx_slot: Arc<Mutex<Option<egui::Context>>> = Arc::new(Mutex::new(None));
-    let fonts_slot = ctx_slot.clone();
+    // Wakes the window (once it is there) from another thread.
+    let wake = |slot: &Arc<Mutex<Option<egui::Context>>>| {
+        let slot = slot.clone();
+        move || {
+            if let Some(c) = slot.lock().unwrap_or_else(std::sync::PoisonError::into_inner).as_ref() {
+                c.request_repaint();
+            }
+        }
+    };
+    let fonts_wake = wake(&ctx_slot);
     std::thread::spawn(move || {
         figcraft_text::scan_system_fonts();
-        if let Some(c) = fonts_slot.lock().unwrap_or_else(std::sync::PoisonError::into_inner).as_ref() {
-            c.request_repaint();
-        }
+        fonts_wake();
     });
     let mut session = Session::empty();
     // Live sessions: the network threads wake the window when something arrives.
-    let wake_slot = ctx_slot.clone();
-    session.live.install(Box::new(figcraft_collab_net::NetLink::new(Arc::new(move || {
-        if let Some(c) = wake_slot.lock().unwrap_or_else(std::sync::PoisonError::into_inner).as_ref() {
-            c.request_repaint();
-        }
-    }))));
+    session.live.install(Box::new(figcraft_collab_net::NetLink::new(Arc::new(wake(&ctx_slot)))));
     for f in &args.files {
         if let Err(e) = session.execute("file.open", &json!({"path": f})) {
             log::error!("{f}: {e}");
@@ -196,6 +198,7 @@ fn main() -> eframe::Result {
     // The preferences first: they hold the online files a recovered document may be one of.
     let recovery = recovery::Shared::default();
     let svc = services::Desktop::load(recovery.clone());
+    svc.follow_system_dark(wake(&ctx_slot));
     if let Some(prefs) = svc.prefs.clone() {
         session.prefs = prefs;
     }

apps/figcraft/src/services.rs

@@ -2,7 +2,7 @@
 
 use std::cell::RefCell;
 use std::path::{Path, PathBuf};
-use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicU8, Ordering};
 use std::sync::{Arc, Mutex};
 
 use figcraft_engine::{Prefs, Session};
@@ -16,6 +16,8 @@ pub struct Desktop {
     pub prefs: Option<Prefs>,
     /// The system's reduce-motion setting (read in the background at startup).
     reduce_motion: Arc<AtomicBool>,
+    /// The system's colour scheme ([`watch_system_dark`]): 0 unknown, 1 dark, 2 light.
+    dark: Arc<AtomicU8>,
     /// The system's interface language (read at startup).
     language: Option<String>,
     /// Recovery copies of unsaved files (written at once after a panic).
@@ -56,16 +58,33 @@ impl Desktop {
         let reduce_motion = Arc::new(AtomicBool::new(false));
         let flag = reduce_motion.clone();
         std::thread::spawn(move || flag.store(system_reduce_motion(), Ordering::Relaxed));
+        let dark = Arc::new(AtomicU8::new(DARK_UNKNOWN));
         Self {
             clipboard: arboard::Clipboard::new().ok(),
             dir,
             prefs,
             reduce_motion,
+            dark,
             language: system_language(),
             recovery,
             last_folder: Arc::default(),
         }
     }
+
+    /// winit reports no system theme on Linux and the BSDs: there the freedesktop colour scheme
+    /// answers instead, read once and then watched in the background, calling `wake` when it
+    /// changes (an idle window draws no frames). Elsewhere this does nothing.
+    pub fn follow_system_dark(&self, wake: impl Fn() + Send + 'static) {
+        #[cfg(all(unix, not(target_os = "macos")))]
+        if let Err(e) = std::thread::Builder::new().name("figcraft-theme".into()).spawn({
+            let dark = self.dark.clone();
+            move || watch_system_dark(&dark, &wake)
+        }) {
+            log::info!("colour scheme: can't start the watcher: {e}");
+        }
+        #[cfg(not(all(unix, not(target_os = "macos"))))]
+        let _ = wake;
+    }
 }
 
 /// The system's preferred interface languages, most preferred first, comma-separated
@@ -146,6 +165,71 @@ fn command_says(program: &str, args: &[&str], want: &str) -> bool {
         .is_some_and(|o| String::from_utf8_lossy(&o.stdout).trim() == want)
 }
 
+/// [`Desktop::dark`]: the colour scheme is unknown, dark, or light.
+const DARK_UNKNOWN: u8 = 0;
+const DARK_DARK: u8 = 1;
+const DARK_LIGHT: u8 = 2;
+
+/// The desktop's colour scheme through the freedesktop settings portal
+/// (`org.freedesktop.appearance` / `color-scheme`: 1 dark, 2 light, 0 no preference, which is
+/// light), read once and then watched for changes, each one calling `wake`. Without a session bus
+/// or a portal the scheme stays unknown and the UI keeps its light fallback.
+#[cfg(all(unix, not(target_os = "macos")))]
+fn watch_system_dark(dark: &AtomicU8, wake: &dyn Fn()) {
+    use zbus::zvariant::Value;
+    const PORTAL: &str = "org.freedesktop.portal.Desktop";
+    const SETTINGS: &str = "org.freedesktop.portal.Settings";
+    const APPEARANCE: &str = "org.freedesktop.appearance";
+    // `Read` (portals before 1.17, which lack `ReadOne`) wraps the value in one more variant.
+    let scheme = |v: &Value| match v {
+        Value::U32(x) => *x,
+        Value::Value(inner) => match **inner {
+            Value::U32(x) => x,
+            _ => 0,
+        },
+        _ => 0,
+    };
+    let store = |v: u32| {
+        let new = match v {
+            1 => DARK_DARK,
+            2 => DARK_LIGHT,
+            _ => DARK_UNKNOWN,
+        };
+        if dark.swap(new, Ordering::Relaxed) != new {
+            wake();
+        }
+    };
+    let Ok(conn) = zbus::blocking::connection::Builder::session().and_then(|b| b.build()) else {
+        log::info!("colour scheme: no session bus: the system theme isn't followed");
+        return;
+    };
+    let read = |method: &str| -> zbus::Result<u32> {
+        let reply = conn.call_method(Some(PORTAL), "/org/freedesktop/portal/desktop", Some(SETTINGS), method, &(APPEARANCE, "color-scheme"))?;
+        let body = reply.body();
+        Ok(scheme(&body.deserialize::<Value>()?))
+    };
+    match read("ReadOne").or_else(|_| read("Read")) {
+        Ok(v) => store(v),
+        Err(e) => log::info!("colour scheme: can't read the system setting: {e}"),
+    }
+    let watch = || -> zbus::Result<()> {
+        let rule =
+            zbus::MatchRule::builder().msg_type(zbus::message::Type::Signal).sender(PORTAL)?.interface(SETTINGS)?.member("SettingChanged")?.build();
+        for msg in zbus::blocking::MessageIterator::for_match_rule(rule, &conn, Some(8))? {
+            let msg = msg?;
+            let body = msg.body();
+            let Ok((namespace, key, value)) = body.deserialize::<(String, String, Value<'_>)>() else { continue };
+            if namespace == APPEARANCE && key == "color-scheme" {
+                store(scheme(&value));
+            }
+        }
+        Ok(())
+    };
+    if let Err(e) = watch() {
+        log::info!("colour scheme: can't watch the system setting: {e}");
+    }
+}
+
 /// Show `path` in the file manager: selected in Finder and Explorer, its folder elsewhere.
 fn reveal(path: &Path) -> std::io::Result<()> {
     #[cfg(target_os = "macos")]
@@ -372,6 +456,13 @@ impl Services for Desktop {
     fn reduce_motion(&self) -> bool {
         self.reduce_motion.load(Ordering::Relaxed)
     }
+    fn system_dark(&self) -> Option<bool> {
+        match self.dark.load(Ordering::Relaxed) {
+            DARK_DARK => Some(true),
+            DARK_LIGHT => Some(false),
+            _ => None,
+        }
+    }
     fn gamepad_held(&mut self) -> u32 {
         crate::gamepad::held()
     }

crates/ui-egui/src/lib.rs

@@ -307,6 +307,11 @@ pub trait Services {
     fn reduce_motion(&self) -> bool {
         false
     }
+    /// The system asks for the dark interface (the freedesktop colour scheme): for platforms whose
+    /// windowing stack doesn't report a theme (winit gives none on Linux and the BSDs).
+    fn system_dark(&self) -> Option<bool> {
+        None
+    }
     /// After a panic in a frame: keep recovery copies of unsaved files.
     fn emergency_save(&mut self, _session: &Session) {}
     /// Keep the preferences now (the installed plugins or their settings changed), as the app
@@ -1719,9 +1724,10 @@ impl FigApp {
         }
         let dark = match self.session.prefs.theme.as_str() {
             "dark" => true,
-            // The active visuals were set by us last frame (possibly for a manual theme).
-            // Read the integration's OS theme instead; without one, keep the light fallback.
-            "system" => ctx.system_theme() == Some(egui::Theme::Dark),
+            // The active visuals were set by us last frame (possibly for a manual theme). Read the
+            // integration's OS theme; winit reports none on Linux and the BSDs, where the platform
+            // services' colour scheme answers instead. Without either, keep the light fallback.
+            "system" => ctx.system_theme().map(|t| t == egui::Theme::Dark).or_else(|| self.services.system_dark()).unwrap_or(false),
             _ => false,
         };
         self.ui.dark = dark;

crates/ui-egui/src/theme_startup_tests.rs

@@ -4,7 +4,7 @@ use egui::{Context, RawInput, Theme};
 use figcraft_engine::{Prefs, Session};
 use serde_json::json;
 
-use crate::{FigApp, NoServices, theme::Tokens};
+use crate::{FigApp, NoServices, Services, theme::Tokens};
 
 fn frame(ctx: &Context, app: &mut FigApp, system: Option<Theme>) {
     let mut output = ctx.run_ui(RawInput { system_theme: system, ..Default::default() }, |ui| app.ui(ui));
@@ -84,6 +84,47 @@ fn unavailable_system_theme_uses_the_existing_light_fallback() {
     assert_eq!(Tokens::get(&ctx), Tokens::light());
 }
 
+/// Services whose colour scheme answer stands in for the platform's (winit gives no theme on Linux
+/// and the BSDs, where the freedesktop colour scheme takes over).
+struct Scheme(Option<bool>);
+impl Services for Scheme {
+    fn system_dark(&self) -> Option<bool> {
+        self.0
+    }
+}
+
+#[test]
+fn without_a_system_theme_the_colour_scheme_services_decide() {
+    for (dark, expected) in [(Some(true), Tokens::dark()), (Some(false), Tokens::light())] {
+        let ctx = Context::default();
+        let mut app = FigApp::new(Session::empty(), Box::new(Scheme(dark)));
+        app.session.execute("view.themeSystem", &json!({})).unwrap();
+        frame(&ctx, &mut app, None);
+        assert_eq!(Tokens::get(&ctx), expected);
+        assert_eq!(app.ui.dark, expected.dark);
+    }
+}
+
+#[test]
+fn the_os_theme_wins_over_the_colour_scheme_services() {
+    for (os, scheme) in [(Theme::Light, Some(true)), (Theme::Dark, Some(false))] {
+        let ctx = Context::default();
+        let mut app = FigApp::new(Session::empty(), Box::new(Scheme(scheme)));
+        app.session.execute("view.themeSystem", &json!({})).unwrap();
+        frame(&ctx, &mut app, Some(os));
+        assert_eq!(Tokens::get(&ctx).dark, os == Theme::Dark);
+    }
+}
+
+#[test]
+fn manual_themes_ignore_the_colour_scheme_services() {
+    let ctx = Context::default();
+    let mut app = FigApp::new(Session::empty(), Box::new(Scheme(Some(false))));
+    app.session.execute("view.themeDark", &json!({})).unwrap();
+    frame(&ctx, &mut app, None);
+    assert_eq!(Tokens::get(&ctx), Tokens::dark());
+}
+
 /// Checks that the test graph enables egui's `default_fonts` and `monochrome_emoji_fonts`
 /// features by asserting both a Latin and an emoji glyph are available.
 #[test]