Web: the page title names the open photo and unsaved changes (#2397)

eframe's web runner doesn't handle ViewportCommand::Title, so the web
build never named what was open, and a host embedding the page could
only guess whether a dropped file had opened. The page title is now
"<file name> — LightCraft" for the active photo, with " •" after the
name while changes are not yet written to browser storage, and the
window title when no photo is active. It is set only when it changes.

apps/lightcraft-web/src/web.rs

@@ -383,6 +383,8 @@ struct WebApp {
     lib_dir: String,
     bench: Option<Bench>,
     first_frame_logged: bool,
+    /// The page title last set (`document.title`), so it is written only when it changes.
+    title: String,
     last_save: f64,
     ui_written: Vec<u8>,
 }
@@ -475,6 +477,7 @@ impl WebApp {
             lib_dir,
             bench: opts.bench.then(|| Bench::new(origin)),
             first_frame_logged: false,
+            title: String::new(),
             last_save: 0.0,
             ui_written,
         }
@@ -660,6 +663,14 @@ impl eframe::App for WebApp {
 
     fn ui(&mut self, ui: &mut egui::Ui, _frame: &mut eframe::Frame) {
         self.app.ui(ui);
+        // eframe's web runner ignores `ViewportCommand::Title`: name the open photo in the page title
+        let title = self.app.page_title(self.files.is_dirty() || self.flushing.get());
+        if title != self.title
+            && let Some(doc) = window().and_then(|w| w.document())
+        {
+            doc.set_title(&title);
+            self.title = title;
+        }
         if !self.first_frame_logged && !self.app.widgets.is_empty() {
             self.first_frame_logged = true;
             log::info!("lightcraft first UI frame at {:.0} ms after navigation start", perf_now());

crates/ui-egui/src/lib.rs

@@ -1418,6 +1418,18 @@ impl LightcraftApp {
         }
     }
 
+    /// The browser page's title: "<file name>[ •] — LightCraft" for the active photo (• while
+    /// `unsaved`: changes not yet written to storage), else the window title. The web build has no
+    /// window for `ViewportCommand::Title`; a host embedding it reads this title to tell which
+    /// document a drop opened and whether it is saved (issue #2397).
+    pub fn page_title(&self, unsaved: bool) -> String {
+        let dot = if unsaved { " •" } else { "" };
+        match self.session.active().and_then(|id| self.session.catalog.photo(id)) {
+            Some(p) => format!("{}{dot} — LightCraft", p.file_name),
+            None => format!("{}{dot}", self.window_title()),
+        }
+    }
+
     /// Lay out the whole window.
     pub fn ui(&mut self, ui: &mut egui::Ui) {
         i18n::set_language(self.ui.language);

crates/ui-egui/src/tests_switch_library.rs

@@ -220,3 +220,22 @@ fn library_names_must_work_as_folder_names_on_every_system() {
     assert_eq!(app.session.library.as_ref().unwrap().dir, dir.join("Trip 2026"));
     let _ = std::fs::remove_dir_all(&dir);
 }
+
+/// The web build's page title names the active photo (a host embedding the page reads it to know
+/// which document a drop opened), with • while changes are not yet in storage (issue #2397).
+#[test]
+fn page_title_names_the_active_photo_and_unsaved_changes() {
+    let mut app = LightcraftApp::new(lightcraft_engine::Session::with_demo(), Services::default());
+    let ids = app.session.visible_cloned();
+    let name = |app: &LightcraftApp, id: lightcraft_catalog::PhotoId| app.session.catalog.photo(id).unwrap().file_name.clone();
+    app.run("library.select", json!({"ids": [ids[0].0]})).unwrap();
+    assert_eq!(app.page_title(false), format!("{} — LightCraft", name(&app, ids[0])));
+    assert_eq!(app.page_title(true), format!("{} • — LightCraft", name(&app, ids[0])));
+    app.run("library.select", json!({"ids": [ids[1].0]})).unwrap();
+    assert_eq!(app.page_title(false), format!("{} — LightCraft", name(&app, ids[1])));
+    // no photo: the window title
+    let empty = LightcraftApp::new(lightcraft_engine::Session::new(), Services::default());
+    assert!(empty.session.active().is_none());
+    assert_eq!(empty.page_title(false), "LightCraft");
+    assert_eq!(empty.page_title(true), "LightCraft •");
+}

docs/web.md

@@ -152,6 +152,10 @@ are the same in every version, so serve them with `Cache-Control: no-cache` (not
 - **Automation.** `await lightcraft.command("library.info", "{}")` runs any engine or UI command
   by id on the next frame and resolves to the JSON result (`web.stats` reports storage, workers
   and the render queue). This is how the headless-Chrome checks drive the page.
+- **The page title names the open photo**: `<file name> — LightCraft`, with ` •` after the name while
+  changes are not yet written to browser storage (`LightcraftApp::page_title`). eframe's web runner
+  ignores the window title the desktop app sets, and a host that embeds the page reads this title to
+  tell which photo a drop opened and whether it is saved (issue #2397).
 
 ## Not yet