UI: Cancel in Preferences restores the interface language

crates/ui-egui/src/control.rs

@@ -302,8 +302,7 @@ pub fn handle(app: &mut DesignApp, ctx: &egui::Context, req: &ControlRequest) ->
         }
         "ui.dialog.confirm" => wrap(crate::dialogs::confirm(app)),
         "ui.dialog.cancel" => {
-            app.cancel_pdf_import();
-            app.ui.dialog = None;
+            crate::dialogs::cancel(app);
             ok(Value::Null)
         }
         "ui.resize" => {

crates/ui-egui/src/dialogs.rs

@@ -1754,14 +1754,25 @@ pub fn show(app: &mut DesignApp, ctx: &egui::Context) {
         Some(true) => {
             let _ = confirm(app);
         }
-        Some(false) => {
-            app.ui.dialog = None;
-            app.cancel_pdf_import();
-        }
+        Some(false) => cancel(app),
         None => {}
     }
 }
 
+/// Close the open dialog without applying it. Preferences also puts back the interface language
+/// it opened with, since choosing one previews it at once.
+pub fn cancel(app: &mut DesignApp) {
+    let d = app.ui.dialog.take();
+    app.cancel_pdf_import();
+    if let Some(d) = d
+        && d.id == "preferences"
+        && let Some(lang) = d.fields.get("openedLanguage").and_then(Value::as_str)
+        && lang != app.ui.language
+    {
+        let _ = app.run("app.language", json!({"lang": lang}));
+    }
+}
+
 /// Apply the open dialog.
 pub fn confirm(app: &mut DesignApp) -> Result<Value, String> {
     let Some(d) = app.ui.dialog.take() else { return Err("no dialog open".into()) };
@@ -3899,6 +3910,20 @@ mod tests {
         let labels = dialog_frame(&mut app, &ctx, screen, vec![]);
         assert!(labels.iter().any(|(text, _, _)| text == "日本語"));
         assert!(labels.iter().any(|(text, _, _)| text == crate::i18n::tr("ja", "Interface Language")));
+
+        // Cancel puts back the language the dialog opened with; OK keeps the choice.
+        let cancel_button = visible_label(&labels, screen, crate::i18n::tr("ja", "Cancel")).center();
+        click_dialog(&mut app, &ctx, screen, cancel_button);
+        assert!(app.ui.dialog.is_none());
+        assert_eq!(app.ui.language, "");
+        app.run("app.preferences", json!({})).unwrap();
+        app.run("app.language", json!({"lang": "it"})).unwrap();
+        confirm(&mut app).unwrap();
+        assert_eq!(app.ui.language, "it");
+        app.run("app.preferences", json!({})).unwrap();
+        app.run("app.language", json!({"lang": "uk"})).unwrap();
+        cancel(&mut app);
+        assert_eq!(app.ui.language, "it");
     }
 
     #[test]

crates/ui-egui/src/menus.rs

@@ -1044,6 +1044,8 @@ pub fn run_ui(app: &mut DesignApp, id: &str, p: &Value) -> Option<Result<Value,
             let list = app.session.prefs.autocorrect_list.iter().map(|(a, b)| format!("{a} → {b}")).collect::<Vec<_>>().join("\n");
             f["autocorrectText"] = json!(list);
             f["section"] = json!("general");
+            // The language previews as it changes; Cancel goes back to this one.
+            f["openedLanguage"] = json!(app.ui.language);
             app.ui.dialog = Some(crate::dialogs::Dialog::new("preferences", f));
             Ok(Value::Null)
         }