Test Mix in a separate window: the toggle and closing it

window.mix_separate toggles (and takes a value), Toggle Mix/Edit keeps Edit
in the main window while Mix is separate, a few frames draw both, and
closing the Mix window brings Mix back into the main one. The close handling
moves into mix_window::separate_closed so the test can reach it.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/ui-egui/src/mix_window.rs

@@ -32,12 +32,17 @@ pub fn show_separate(app: &mut SoundApp, ctx: &egui::Context) {
         }
         show(app, ui);
         if ui.ctx().input(|i| i.viewport().close_requested()) {
-            app.ui.mix_separate = false;
-            app.ui.window = crate::MainWindow::Mix;
+            separate_closed(app);
         }
     });
 }
 
+/// The separate Mix window was closed: Mix goes back into the main window.
+pub fn separate_closed(app: &mut SoundApp) {
+    app.ui.mix_separate = false;
+    app.ui.window = crate::MainWindow::Mix;
+}
+
 pub(crate) fn content(app: &mut SoundApp, ui: &mut Ui) {
     let ids: Vec<TrackId> = app.engine.session().tracks.iter().filter(|x| !x.hidden && x.kind != TrackKind::Video).map(|x| x.id).collect();
     // Per-channel peaks for multichannel meters (read once per frame).

crates/ui-egui/tests/mix_separate.rs

@@ -0,0 +1,37 @@
+//! Window › Mix in Separate Window: Edit stays in the main window, and closing the Mix window
+//! brings Mix back into it.
+use egui::vec2;
+use egui_kittest::Harness;
+use serde_json::json;
+use soundcraft_ui_egui::{MainWindow, Services, SoundApp, mix_window};
+
+#[test]
+fn mix_in_a_separate_window_toggles_and_closing_it_returns_to_the_main_window() {
+    let mut app = SoundApp::new(soundcraft_engine::demo::demo_engine(), None, Services::default());
+    assert!(!app.ui.mix_separate);
+    app.run("window.mix_separate", json!({})).unwrap();
+    assert!(app.ui.mix_separate);
+    app.run("window.toggle_mix_edit", json!({})).unwrap();
+    assert_eq!(app.ui.window, MainWindow::Edit, "Mix is already on screen: the main window keeps Edit");
+
+    let mut h = Harness::builder().with_size(vec2(1600.0, 1000.0)).build_ui_state(
+        |ui, app: &mut SoundApp| {
+            app.logic(&ui.ctx().clone());
+            app.ui(ui);
+        },
+        app,
+    );
+    h.run_steps(3);
+    let app = h.state_mut();
+    assert!(app.ui.mix_separate, "drawing both windows keeps them both");
+
+    mix_window::separate_closed(app);
+    assert!(!app.ui.mix_separate);
+    assert_eq!(app.ui.window, MainWindow::Mix, "closing the Mix window shows Mix in the main one");
+    h.run_steps(3);
+
+    let app = h.state_mut();
+    app.run("window.mix_separate", json!({"value": true})).unwrap();
+    app.run("window.mix_separate", json!({"value": false})).unwrap();
+    assert!(!app.ui.mix_separate);
+}