Fix #2576: poll for fonts font managers activate while the app is in front

Font services (NexusFont, Adobe Fonts) register faces with the OS without
touching font-folder mtimes; only re-asking the platform lister sees them.
Check every two seconds as well as on window focus, and test that path churn
is detected on the system font scan.

Co-authored-by: Cursor <cursoragent@cursor.com>

crates/text/src/fontdb.rs

@@ -1611,6 +1611,12 @@ impl FontDb {
         Self::new(FontPaths::Fixed(font_dirs))
     }
 
+    /// Same scan paths as [`FontDb::global`] (platform lister and font folders), for tests.
+    #[cfg(test)]
+    pub(crate) fn for_system_scan_test() -> Self {
+        Self::new(FontPaths::System)
+    }
+
     fn new(font_paths: FontPaths) -> Self {
         let mut faces = Vec::new();
         // Bundled fonts first, then explicitly supplied craft-fonts faces: Japanese (Mincho

crates/text/src/tests_sysfonts.rs

@@ -331,6 +331,25 @@ fn service_font() -> PathBuf {
     std::env::temp_dir().join(format!("vc-sysfonts-{}-service", std::process::id())).join(".29457")
 }
 
+/// Fonts a font service activates after the first scan are picked up on the next check (#2576).
+#[test]
+fn the_database_tells_when_a_font_service_adds_a_font() {
+    use std::sync::Mutex;
+    static FILES: Mutex<Vec<String>> = Mutex::new(Vec::new());
+    set_platform_font_files(|| FILES.lock().unwrap_or_else(|e| e.into_inner()).clone());
+    let file = service_font();
+    std::fs::create_dir_all(file.parent().unwrap()).unwrap();
+    let db = FontDb::for_system_scan_test();
+    assert!(!db.installed_fonts_changed());
+    db.load_system_fonts();
+    assert!(!db.has_family("Service Sans3"));
+    std::fs::write(&file, renamed_to("SourceSans3-Regular.ttf", "Service Sans3")).unwrap();
+    *FILES.lock().unwrap_or_else(|e| e.into_inner()) = vec![file.to_string_lossy().into_owned()];
+    assert!(db.installed_fonts_changed(), "a font a font service activated since the scan");
+    db.load_system_fonts();
+    assert!(db.has_family("Service Sans3"));
+}
+
 /// The fonts a font service (Adobe Fonts on Windows, through DirectWrite) loads in place are
 /// cataloged: named by the platform's lister, read whatever their file is called (#579).
 #[test]

crates/ui-egui/src/lib.rs

@@ -455,6 +455,8 @@ pub struct VectorcraftApp {
     /// The look for fonts installed or removed while the app was in the background, running
     /// ([`Self::refresh_installed_fonts`]): whether they were.
     font_check: Option<std::sync::mpsc::Receiver<bool>>,
+    /// When installed fonts were last checked in line (app time, s).
+    font_install_check_at: f64,
     /// Keyboard pastes of something other than text (see [`shortcuts::PasteChord`]).
     pub(crate) paste_chord: shortcuts::PasteChord,
     /// Saves and exports running in the background (Preferences → File Handling).
@@ -500,6 +502,8 @@ struct PendingScreenshot {
 
 /// Seconds between two looks at the system clipboard for [`VectorcraftApp::system_paste`].
 const SYSTEM_CLIPBOARD_POLL: f64 = 0.25;
+/// Seconds between looks for fonts a font manager activated while the app stays in front (#2576).
+const FONT_INSTALL_POLL: f64 = 2.0;
 
 impl VectorcraftApp {
     pub fn new(mut session: Session, services: Services) -> Self {
@@ -562,6 +566,7 @@ impl VectorcraftApp {
             picks: picks::Picks::default(),
             screen_sampler: None,
             font_check: None,
+            font_install_check_at: f64::NEG_INFINITY,
             paste_chord: Default::default(),
             background: Default::default(),
             opening: Default::default(),
@@ -1198,6 +1203,11 @@ impl VectorcraftApp {
             self.system_paste_at = now;
             self.system_paste = wanted && self.system_clipboard_pasteable();
         }
+        #[cfg(not(target_arch = "wasm32"))]
+        if !(0.0..FONT_INSTALL_POLL).contains(&(now - self.font_install_check_at)) {
+            self.font_install_check_at = now;
+            self.refresh_installed_fonts();
+        }
         self.poll_font_check(ctx);
         picks::poll(self, ctx);
         self.write_formats_before_text_input(ctx);
@@ -1292,8 +1302,9 @@ impl VectorcraftApp {
         place::drop_files(self, files);
     }
 
-    /// Fonts installed or removed while the app was in the background are listed when it comes
-    /// back (Refresh Font List by itself): a look at the font folders, a scan only when they changed.
+    /// Fonts installed or removed while the app runs are listed without Refresh Font List: a look
+    /// at the font folders and the platform's font list on a timer and when the window comes back,
+    /// a scan only when they changed.
     /// The look runs on another thread (asking DirectWrite for the fonts font services loaded
     /// meanwhile takes tens of milliseconds on Windows, #579), [`Self::poll_font_check`] scans.
     fn refresh_installed_fonts(&mut self) {