Fix two edge cases in multi-select placement

A selection that holds a bin beside items (one id space) made the whole drop
fail with "no such item"; only items are placed now.

Session::edit_group raised the history limit while a group ran and did not
restore it if the group panicked. It now restores it and rolls the group back
before the panic goes on.

crates/engine/src/lib.rs

@@ -840,11 +840,20 @@ impl Session {
             (self.project.clone(), self.state.clone(), self.history.undo.len(), self.history.redo.clone(), self.history.limit);
         // keep every step the group makes, however many, so the first one can be found afterwards
         self.history.limit = usize::MAX;
-        let r = f(self);
+        // a panic inside the group must not leave the history unlimited: restore, then let it go on
+        let r = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| f(self)));
         self.history.limit = limit;
         let first = self.history.undo.get(undo).map(|e| e.1.clone());
+        let rolled_back = |s: &mut Session| {
+            s.history.undo.truncate(undo);
+            s.history.redo = redo.clone();
+            s.history.merge_key = None;
+            s.project = project.clone();
+            s.state = state.clone();
+            s.bump();
+        };
         match (r, first) {
-            (Ok(v), Some(first)) => {
+            (Ok(Ok(v)), Some(first)) => {
                 self.history.undo.truncate(undo);
                 self.history.undo.push((label.to_string(), first));
                 if self.history.undo.len() > limit {
@@ -853,16 +862,15 @@ impl Session {
                 self.history.merge_key = None;
                 Ok(v)
             }
-            (Ok(v), None) => Ok(v),
-            (Err(e), _) => {
-                self.history.undo.truncate(undo);
-                self.history.redo = redo;
-                self.history.merge_key = None;
-                self.project = project;
-                self.state = state;
-                self.bump();
+            (Ok(Ok(v)), None) => Ok(v),
+            (Ok(Err(e)), _) => {
+                rolled_back(self);
                 Err(e)
             }
+            (Err(panic), _) => {
+                rolled_back(self);
+                std::panic::resume_unwind(panic)
+            }
         }
     }
 

crates/engine/src/place_items_tests.rs

@@ -123,3 +123,22 @@ fn items_on_a_new_track_share_that_one_track() {
     s.undo();
     assert_eq!(s.active_sequence().unwrap().video_tracks.len(), tracks, "undo removes the track too");
 }
+
+/// A panic inside a group leaves the project, the history and its limit as they were.
+#[test]
+fn a_panic_in_a_group_rolls_back_and_keeps_the_history_limit() {
+    let (mut s, items) = three();
+    let (steps, limit) = (s.history.undo.len(), s.history.limit);
+    let before = s.project.to_json();
+    let one = items[0];
+    let outcome = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
+        let _ = s.edit_group::<()>("Boom", |s| {
+            s.execute("timeline.place", json!({"item": one.0, "time": 0}))?;
+            panic!("inside the group");
+        });
+    }));
+    assert!(outcome.is_err(), "the panic goes on");
+    assert_eq!(s.history.limit, limit, "the history is not left unlimited");
+    assert_eq!(s.history.undo.len(), steps);
+    assert_eq!(s.project.to_json(), before);
+}

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

@@ -182,7 +182,8 @@ pub fn dragged_project_item(ui: &egui::Ui) -> Option<ItemId> {
 /// one of several selected, otherwise just the dragged item.
 pub fn dragged_selection(app: &FilmcraftApp, item: ItemId) -> Vec<ItemId> {
     let sel = &app.session.state.project_selection;
-    if sel.len() > 1 && sel.contains(&item) { sel.clone() } else { vec![item] }
+    // the selection can hold bins beside items (one id space): only items can be placed
+    if sel.len() > 1 && sel.contains(&item) { sel.iter().copied().filter(|i| app.session.project.item(*i).is_some()).collect() } else { vec![item] }
 }
 pub fn dragged_effect(ui: &egui::Ui) -> Option<String> {
     match payload(ui) {

crates/ui-egui/tests/project_panel_ui.rs

@@ -1039,3 +1039,20 @@ fn marquee_selects_cards_in_freeform_view() {
     assert_eq!(selection(&mut d), sorted(vec![i0, i1]));
     assert!(!d.app().session.project.item(ItemId(i0)).unwrap().metadata.contains_key(FREEFORM_POS), "the marquee moved no card");
 }
+
+/// The Project selection can hold a bin beside items (one id space). Dragging the items still
+/// places them: the bin is left out instead of failing the whole drop.
+#[test]
+fn a_bin_in_the_selection_does_not_stop_the_items_being_placed() {
+    let mut d = Driver::demo();
+    let (bin, items) = d.footage();
+    d.exec("file.newSequence", json!({"name": "Drop", "video": 2, "audio": 2}));
+    d.ok("ui.menu.invoke", json!({"id": "projectPanel.openBin", "params": {"bin": bin, "how": "inPlace"}}));
+    d.wait_for(&format!("project.item.{}", items[0]));
+    d.exec("project.select", json!({"items": [items[0], bin, items[1]]}));
+    d.frames(2);
+    d.ok("ui.drag", json!({"from": {"id": format!("project.item.{}", items[0])}, "to": {"id": "timeline.tracks", "fx": 0.3, "fy": 0.1}, "steps": 16}));
+    d.frames(4);
+    let clips = d.app().session.active_sequence().map(|q| q.video_tracks.iter().map(|t| t.items.len()).sum::<usize>()).unwrap_or(0);
+    assert_eq!(clips, 2, "status: {}", d.app().ui.status);
+}