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platform: GNOME's light setting reads as light, and Watcher::wait_first for the first frame
platform: GNOME's light setting reads as light, and Watcher::wait_first for the first frame Two fixes in `craft_platform::appearance`. **GNOME light.** On GNOME 42–46, Settings › Appearance › Light writes `org.gnome.desktop.interface color-scheme = 'default'`, and the settings portal reports `org.freedesktop.appearance color-scheme = 0`. Both were read as "no preference", so apps that follow the system fell back to dark on a stock light GNOME. Now: - GNOME's `'default'` is Light. - The standard value 0 is Light when `XDG_CURRENT_DESKTOP` names GNOME, and stays "no preference" elsewhere. 1 and 2 are unchanged. PhotoCraft fixed the same case in its own code (photocraft#4289). **`Wat
- Status
- open
- Score
- 0.00
- Adopters
- 0 other operators
- Author
- aiongg (imported from pull request #403, open)
- Base
b380d16304123f724d8706ce59d24a06999156b8- Size
- +136 −29 in 2 files
- Review
- pending
- Shared
- 2026-10-28
- Id
02afecbff85c33874b5f93fa
How it went
No other operator has reported using it yet.
Diff
raw · crates/platform/README.md crates/platform/src/appearance.rs
@@ -41,7 +41,9 @@ permission to discard work. Run those guards before `craft_quit::on_close_reques `appearance::Watcher` caches the desktop preference and wakes only on changes. Subscription precedes the first read. ReadOne/legacy Read, the standard namespace and GNOME fallback are handled together;-malformed values retain the last valid answer, and explicit no-preference clears it. Disconnection+on GNOME the "default" (Light) setting and portal value 0 read as light; elsewhere 0 is no preference.+Malformed values retain the last valid answer, and explicit no-preference clears it.+`Watcher::wait_first(timeout)` blocks until the first answer, a known absence, or the timeout (about 250 ms in an eframe creator), so the first frame uses the desktop theme. Disconnection retains the last valid value until a fresh answer. A later service owner triggers a reread; session reconnection has bounded backoff. Dropping cancels asynchronous work and waits at most 100 ms for acknowledgement, joining only an already-finished worker. A synchronously blocked OS call or caller wake callback can outlive@@ -3,9 +3,12 @@ //! Derived from PdfCraft's activation-safe subscription and GNOME schema fallback, //! CADCraft's BSD support, and ArtCraft Launcher's ReadOne/Read compatibility. //! Palettes, manual choices and the fallback when no preference exists belong to the host.-use std::sync::{- Arc,- atomic::{AtomicBool, AtomicU8, Ordering},+use std::{+ sync::{+ Arc, Condvar, Mutex, PoisonError,+ atomic::{AtomicBool, AtomicU8, Ordering},+ },+ time::Duration, }; /// Desktop color preference observed independently of the application palette.@@ -20,6 +23,12 @@ pub enum Theme { struct Shared { value: AtomicU8, active: AtomicBool,+ /// True once the source has answered, found no answer, or been cancelled.+ settled: Mutex<bool>,+ settled_changed: Condvar,+ /// `XDG_CURRENT_DESKTOP` names GNOME; read once when the watcher starts.+ #[cfg(all(unix, not(target_os = "macos"), not(target_arch = "wasm32")))]+ gnome: bool, #[cfg(all(unix, not(target_os = "macos"), not(target_arch = "wasm32")))] wake: Box<dyn Fn() + Send + Sync>, }@@ -32,13 +41,20 @@ impl Shared { } } #[cfg(all(unix, not(target_os = "macos"), not(target_arch = "wasm32")))]+ fn settle(&self) {+ *self.settled.lock().unwrap_or_else(PoisonError::into_inner) = true;+ self.settled_changed.notify_all();+ }+ #[cfg(all(unix, not(target_os = "macos"), not(target_arch = "wasm32")))] fn publish(&self, theme: Option<Theme>) { let code = match theme { Some(Theme::Dark) => 1, Some(Theme::Light) => 2, None => 0, };- if self.value.swap(code, Ordering::AcqRel) != code && self.active.load(Ordering::Acquire) {+ let changed = self.value.swap(code, Ordering::AcqRel) != code;+ self.settle();+ if changed && self.active.load(Ordering::Acquire) { (self.wake)(); } }@@ -81,6 +97,20 @@ impl Watcher { pub fn current(&self) -> Option<Theme> { self.shared.get() }+ /// Block until the first answer is known, then return it; at most `timeout`.+ ///+ /// Returns early, with `current()`, when the portal is absent and the `gsettings` fallback+ /// found nothing, or when the desktop reports no preference. Call it once while building the+ /// first frame so a light desktop does not flash dark:+ ///+ /// ```ignore+ /// let theme = watcher.wait_first(std::time::Duration::from_millis(250));+ /// ```+ pub fn wait_first(&self, timeout: Duration) -> Option<Theme> {+ let settled = self.shared.settled.lock().unwrap_or_else(PoisonError::into_inner);+ drop(self.shared.settled_changed.wait_timeout_while(settled, timeout, |settled| !*settled).unwrap_or_else(PoisonError::into_inner));+ self.current()+ } /// Enable or suppress future change notifications without stopping observation. /// Changing this flag does not itself wake the host or clear the cached preference. pub fn set_active(&self, active: bool) {@@ -92,7 +122,15 @@ impl Watcher { wake: impl Fn() + Send + Sync + 'static, source: impl FnOnce(Arc<Shared>) -> F + Send + 'static, ) -> Option<Self> {- let shared = Arc::new(Shared { value: AtomicU8::new(0), active: AtomicBool::new(active), wake: Box::new(wake) });+ let gnome = is_gnome(std::env::var("XDG_CURRENT_DESKTOP").ok().as_deref());+ let shared = Arc::new(Shared {+ value: AtomicU8::new(0),+ active: AtomicBool::new(active),+ settled: Mutex::new(false),+ settled_changed: Condvar::new(),+ gnome,+ wake: Box::new(wake),+ }); let worker_shared = Arc::clone(&shared); let (stop, stopped) = async_channel::bounded::<()>(1); let (done, finished) = std::sync::mpsc::channel();@@ -103,8 +141,9 @@ impl Watcher { async { let _ = stopped.recv().await; },- source(worker_shared),+ source(Arc::clone(&worker_shared)), ));+ worker_shared.settle(); let _ = done.send(()); }) .ok()?;@@ -116,6 +155,7 @@ impl Drop for Watcher { self.set_active(false); #[cfg(all(unix, not(target_os = "macos"), not(target_arch = "wasm32")))] {+ self.shared.settle(); self.stop.close(); if let Some(worker) = self.worker.take() { let _ = self.finished.recv_timeout(std::time::Duration::from_millis(100));@@ -129,6 +169,12 @@ impl Drop for Watcher { } } +/// Whether a colon-separated `XDG_CURRENT_DESKTOP` value names GNOME.+#[cfg(all(unix, not(target_os = "macos"), not(target_arch = "wasm32")))]+fn is_gnome(desktop: Option<&str>) -> bool {+ desktop.is_some_and(|list| list.split(':').any(|name| name.eq_ignore_ascii_case("gnome")))+}+ #[cfg(all(unix, not(target_os = "macos"), not(target_arch = "wasm32")))] mod portal { use super::{Shared, Theme};@@ -144,27 +190,31 @@ mod portal { const TIMEOUT: Duration = Duration::from_secs(2); // Outer None means unknown/malformed; Some(None) is an explicit no-preference answer.- fn decode(namespace: &str, value: &Value<'_>) -> Option<Option<Theme>> {+ // GNOME 42-46 writes 'default' (portal value 0) for Settings > Appearance > Light, so on GNOME+ // both mean light; elsewhere both are no preference.+ fn decode(namespace: &str, value: &Value<'_>, gnome: bool) -> Option<Option<Theme>> { match (namespace, value) { (STANDARD, Value::U32(n)) => Some(match n { 1 => Some(Theme::Dark), 2 => Some(Theme::Light),+ 0 if gnome => Some(Theme::Light), _ => None, }), (GNOME, Value::Str(s)) => Some(match s.as_str() { "prefer-dark" => Some(Theme::Dark), "prefer-light" => Some(Theme::Light),+ "default" if gnome => Some(Theme::Light), _ => None, }), _ => None, } }- fn reply(namespace: &str, value: &Value<'_>, legacy: bool) -> Option<Option<Theme>> {+ fn reply(namespace: &str, value: &Value<'_>, legacy: bool, gnome: bool) -> Option<Option<Theme>> { if legacy { let Value::Value(inner) = value else { return None };- decode(namespace, inner)+ decode(namespace, inner, gnome) } else {- decode(namespace, value)+ decode(namespace, value, gnome) } } fn combined(standard: Option<Option<Theme>>, gnome: Option<Option<Theme>>) -> Option<Option<Theme>> {@@ -177,11 +227,11 @@ mod portal { }) .await }- async fn read(connection: &zbus::Connection, namespace: &str) -> Option<Option<Theme>> {+ async fn read(connection: &zbus::Connection, namespace: &str, gnome: bool) -> Option<Option<Theme>> { for (method, legacy) in [("ReadOne", false), ("Read", true)] { if let Some(Ok(message)) = bounded(connection.call_method(Some(DEST), PATH, Some(IFACE), method, &(namespace, KEY))).await && let Ok(value) = message.body().deserialize::<OwnedValue>()- && let Some(answer) = reply(namespace, &value, legacy)+ && let Some(answer) = reply(namespace, &value, legacy, gnome) { return Some(answer); }@@ -213,6 +263,8 @@ mod portal { loop { let mut connected = false; let _ = session(&shared, &mut fallback_used, &mut connected).await;+ // No session bus, no portal and an empty fallback all end here without a publish.+ shared.settle(); if connected { retry = Duration::from_secs(5); }@@ -235,7 +287,7 @@ mod portal { && let Some(text) = crate::process::capture(&exe, &["get", GNOME, KEY], TIMEOUT).await { let text = text.trim().trim_matches('\'');- if let Some(answer) = decode(GNOME, &Value::from(text)) {+ if let Some(answer) = decode(GNOME, &Value::from(text), shared.gnome) { shared.publish(answer); } }@@ -255,8 +307,8 @@ mod portal { // MatchRule installs before activation: unlike a proxy subscription it needs no current owner. let mut changes = bounded(zbus::MessageStream::for_match_rule(rule().ok()?, &connection, Some(64))).await?.ok()?; let mut owners = bounded(zbus::MessageStream::for_match_rule(owner_rule().ok()?, &connection, Some(8))).await?.ok()?;- let mut standard = read(&connection, STANDARD).await;- let mut gnome = read(&connection, GNOME).await;+ let mut standard = read(&connection, STANDARD, shared.gnome).await;+ let mut gnome = read(&connection, GNOME, shared.gnome).await; match combined(standard, gnome) { Some(answer) => { *connected = true;@@ -286,7 +338,7 @@ mod portal { if key != KEY { continue; }- let Some(answer) = decode(&namespace, &value) else { continue };+ let Some(answer) = decode(&namespace, &value, shared.gnome) else { continue }; match namespace.as_str() { STANDARD => standard = Some(answer), GNOME => gnome = Some(answer),@@ -323,6 +375,7 @@ mod portal { } use super::{GNOME, STANDARD, combined, decode, reply};+ use crate::appearance::is_gnome; use crate::appearance::{Theme, Watcher}; use std::{ sync::{Arc, atomic::Ordering},@@ -339,18 +392,70 @@ mod portal { } #[test] fn malformed_is_distinct_from_no_preference_and_legacy_is_exact() {- assert_eq!(decode(STANDARD, &Value::U32(0)), Some(None));- assert_eq!(decode(STANDARD, &Value::U32(77)), Some(None));- assert_eq!(decode(STANDARD, &Value::from("dark")), None);- assert_eq!(reply(STANDARD, &Value::Value(Box::new(Value::U32(1))), true), Some(Some(Theme::Dark)));- assert_eq!(reply(STANDARD, &Value::U32(1), true), None);- assert_eq!(reply(STANDARD, &Value::Value(Box::new(Value::Value(Box::new(Value::U32(1))))), true), None);- assert_eq!(decode(STANDARD, &Value::Value(Box::new(Value::U32(1)))), None);- assert_eq!(decode(STANDARD, &Value::I32(1)), None);- assert_eq!(decode(GNOME, &Value::from("default")), Some(None));- assert_eq!(decode(GNOME, &Value::U32(1)), None);-- assert_eq!(reply(GNOME, &Value::from("prefer-light"), false), Some(Some(Theme::Light)));+ assert_eq!(decode(STANDARD, &Value::U32(0), false), Some(None));+ assert_eq!(decode(STANDARD, &Value::U32(77), false), Some(None));+ assert_eq!(decode(STANDARD, &Value::from("dark"), false), None);+ assert_eq!(reply(STANDARD, &Value::Value(Box::new(Value::U32(1))), true, false), Some(Some(Theme::Dark)));+ assert_eq!(reply(STANDARD, &Value::U32(1), true, false), None);+ assert_eq!(reply(STANDARD, &Value::Value(Box::new(Value::Value(Box::new(Value::U32(1))))), true, false), None);+ assert_eq!(decode(STANDARD, &Value::Value(Box::new(Value::U32(1))), false), None);+ assert_eq!(decode(STANDARD, &Value::I32(1), false), None);+ assert_eq!(decode(GNOME, &Value::U32(1), false), None);+ assert_eq!(reply(GNOME, &Value::from("prefer-light"), false, false), Some(Some(Theme::Light)));+ }+ #[test]+ fn gnome_light_setting_reads_as_light_and_zero_is_no_preference_elsewhere() {+ assert_eq!(decode(GNOME, &Value::from("default"), true), Some(Some(Theme::Light)));+ // A GNOME schema installed on another desktop doesn't make that desktop light.+ assert_eq!(decode(GNOME, &Value::from("default"), false), Some(None));+ assert_eq!(decode(GNOME, &Value::from("prefer-dark"), false), Some(Some(Theme::Dark)));+ assert_eq!(decode(GNOME, &Value::from("prefer-light"), false), Some(Some(Theme::Light)));+ assert_eq!(decode(STANDARD, &Value::U32(0), true), Some(Some(Theme::Light)));+ assert_eq!(decode(STANDARD, &Value::U32(0), false), Some(None));+ for gnome in [true, false] {+ assert_eq!(decode(STANDARD, &Value::U32(1), gnome), Some(Some(Theme::Dark)));+ assert_eq!(decode(STANDARD, &Value::U32(2), gnome), Some(Some(Theme::Light)));+ }+ assert!(is_gnome(Some("GNOME")));+ assert!(is_gnome(Some("ubuntu:GNOME")));+ assert!(is_gnome(Some("gnome-classic:gnome")));+ assert!(!is_gnome(Some("KDE")));+ assert!(!is_gnome(Some("X-Cinnamon")));+ assert!(!is_gnome(None));+ }+ fn spawn_idle(source: impl FnOnce(Arc<crate::appearance::Shared>) + Send + 'static) -> Result<Watcher, &'static str> {+ Watcher::spawn(false, || {}, move |shared| async move { source(shared) }).ok_or("worker creation failed")+ }+ #[test]+ fn wait_first_returns_at_once_after_a_publish() -> Result<(), Box<dyn std::error::Error>> {+ let watcher = spawn_idle(|shared| {+ shared.publish(Some(Theme::Light));+ std::thread::sleep(Duration::from_millis(500));+ })?;+ let started = std::time::Instant::now();+ assert_eq!(watcher.wait_first(Duration::from_secs(2)), Some(Theme::Light));+ assert!(started.elapsed() < Duration::from_secs(1));+ Ok(())+ }+ #[test]+ fn wait_first_times_out_without_an_answer_and_drop_stays_bounded() -> Result<(), Box<dyn std::error::Error>> {+ let watcher = Watcher::spawn(false, || {}, |_| futures_lite::future::pending::<()>()).ok_or("worker creation failed")?;+ let started = std::time::Instant::now();+ assert_eq!(watcher.wait_first(Duration::from_millis(50)), None);+ assert!(started.elapsed() >= Duration::from_millis(50));+ drop(watcher);+ Ok(())+ }+ #[test]+ fn wait_first_returns_early_for_no_preference_and_for_a_source_that_ends_empty() -> Result<(), Box<dyn std::error::Error>> {+ let none = spawn_idle(|shared| shared.publish(None))?;+ let ended = spawn_idle(|_| {})?;+ for watcher in [none, ended] {+ let started = std::time::Instant::now();+ assert_eq!(watcher.wait_first(Duration::from_secs(2)), None);+ assert!(started.elapsed() < Duration::from_secs(1));+ }+ Ok(()) } #[test] fn manual_cache_changes_do_not_wake_and_drop_cancels_pending_source() -> Result<(), Box<dyn std::error::Error>> {