fix(ui): Save Arrangement refuses an unknown bin (#3774 follow-up) (#3900)

* fix(ui): Save Arrangement refuses an unknown bin (#3774)

The engine lays out the root bin when it does not find the one asked for, so
a Save Arrangement for a bin that does not exist (a scripted call, or a bin
deleted while the dialog was open) could overwrite a root arrangement of the
same name. The dialog now refuses a bin that does not exist when it opens and
checks it again before saving.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(ui): Save Arrangement refuses a bin that is not a bin id (#3774)

A `bin` such as -1, a string or 1.5 is not an unsigned id, so it was read
as no bin and the dialog opened for the shown view. Any non-null `bin` that
is not a bin id is now refused; an omitted or null one still means the shown
view's. The test checks the arrangements list it meant to (`arrangements`),
and covers these values.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/panels/project.rs

@@ -958,11 +958,24 @@ pub fn route(app: &mut FilmcraftApp, ctx: &egui::Context, op: &str, params: &Val
             Ok(Value::Null)
         }
         "saveArrangement" => {
-            // the canvas the menu was opened on, which may be a floating bin window
-            let bin = params.get("bin").and_then(Value::as_u64).or_else(|| Some(view_of(app, inst).bin.0));
-            let width = params.get("width").and_then(Value::as_f64);
-            app.ui.project_panel.dialog = Some(ProjectDialog::SaveArrangement { name: String::new(), bin, width });
-            Ok(Value::Null)
+            // the canvas the menu was opened on, which may be a floating bin window; a `bin` that is
+            // not a bin id, or names no bin, is refused, as the engine would save to the root bin
+            // instead (an omitted or null `bin` is the shown view's)
+            let given = params.get("bin").filter(|v| !v.is_null());
+            let id = given.map(|v| v.as_u64().ok_or_else(|| format!("`bin` is a bin id, not {v}")));
+            if let Some(Err(e)) = id {
+                Err(e)
+            } else if let Some(Ok(b)) = id
+                && app.session.project.root.find_bin(BinId(b)).is_none()
+            {
+                Err(format!("no bin {b}"))
+            } else {
+                let given = id.and_then(Result::ok);
+                let bin = given.or_else(|| Some(view_of(app, inst).bin.0));
+                let width = params.get("width").and_then(Value::as_f64);
+                app.ui.project_panel.dialog = Some(ProjectDialog::SaveArrangement { name: String::new(), bin, width });
+                Ok(Value::Null)
+            }
         }
         "revealProject" => {
             let Some(p) = app.session.path.clone() else { return Some(Err("the project has not been saved".into())) };

crates/ui-egui/src/panels/project_dialogs.rs

@@ -79,7 +79,14 @@ pub fn show(app: &mut FilmcraftApp, ctx: &egui::Context) {
                     push(app, "projectDialog.name", &r, "Name");
                 });
                 if ok_cancel(app, ui, &mut close) && !name.trim().is_empty() {
-                    run = Some(("project.freeform.saveArrangement".into(), json!({"name": name, "bin": bin, "width": width})));
+                    // the bin may have been deleted while the dialog was open
+                    match bin.filter(|b| app.session.project.root.find_bin(filmcraft_project::BinId(*b)).is_none()) {
+                        Some(b) => {
+                            app.ui.status = format!("no bin {b}");
+                            close = true;
+                        }
+                        None => run = Some(("project.freeform.saveArrangement".into(), json!({"name": name, "bin": bin, "width": width}))),
+                    }
                 }
             }
         }

crates/ui-egui/tests/it/project_panel_ui.rs

@@ -1713,3 +1713,22 @@ fn a_card_menu_stacks_only_the_selected_cards_of_its_bin() {
     assert!(stack(&mut d, items[0]).is_some() && stack(&mut d, items[1]).is_some(), "this bin's cards are stacked");
     assert_eq!(stack(&mut d, other), None, "the other bin's item is left alone");
 }
+
+/// #3774 review: Save Arrangement takes the bin of the canvas it was opened on; an unknown bin
+/// is refused instead of saving to the root bin.
+#[test]
+fn save_arrangement_refuses_an_unknown_bin() {
+    let mut d = project_driver();
+    let (bin, _) = d.footage();
+    for bad in [json!(987_654), json!(-1), json!("footage"), json!(1.5)] {
+        let r = d.call("ui.menu.invoke", json!({"id": "projectPanel.saveArrangement", "params": {"bin": bad, "width": 400.0}}));
+        assert_eq!(r["ok"], json!(false), "bin {bad}: {r}");
+        assert!(d.app().ui.project_panel.dialog.is_none(), "no dialog for bin {bad}");
+    }
+    let root = d.app().session.project.root.id.0;
+    let saved = d.exec("project.freeform.arrangements", json!({"bin": root}));
+    assert_eq!(saved["arrangements"].as_array().map(Vec::len), Some(0), "nothing saved to the root: {saved}");
+    // a bin that exists opens the dialog
+    d.ok("ui.menu.invoke", json!({"id": "projectPanel.saveArrangement", "params": {"bin": bin, "width": 400.0}}));
+    assert!(d.app().ui.project_panel.dialog.is_some());
+}