Clear: lift clips removed by id in Shuffle so crossfade partners don't overlap

crates/engine/src/edit.rs

@@ -177,28 +177,21 @@ pub fn clear_range(s: &mut Session, track: TrackId, range: Range, shuffle: bool)
     removed
 }
 
-/// Remove the clips `ids` from every track. In Shuffle the later clips on each track close the gaps they leave,
-/// the latest gap first so the earlier ones stay where they were. Returns how many clips went.
+/// Remove the clips `ids` from every track. In Shuffle the later clips on each track close the holes the movable
+/// ones leave, as a Shuffle move lifts them (see [`lift_plan`]), so a crossfade partner keeps its material. Returns
+/// how many clips went.
 pub fn remove_clips(s: &mut Session, ids: &[ClipId], shuffle: bool) -> usize {
-    let mut gaps: Vec<(TrackId, Range)> = Vec::new();
-    for t in &mut s.tracks {
-        let track = t.id;
-        if let Some(pl) = t.playlist_mut() {
-            pl.clips.retain(|c| {
-                let gone = ids.contains(&c.id);
-                if gone {
-                    gaps.push((track, c.range()));
-                }
-                !gone
-            });
+    let ids: HashSet<ClipId> = ids.iter().copied().collect();
+    let mut n = 0;
+    for track in s.tracks.iter().map(|t| t.id).collect::<Vec<_>>() {
+        if shuffle {
+            n += lift_all(s, track, &ids).len();
         }
-    }
-    let n = gaps.len();
-    if shuffle {
-        gaps.sort_by_key(|(t, r)| (t.0, std::cmp::Reverse(r.start)));
-        for (track, r) in gaps {
-            let moved = ripple(s, track, r.end, -r.len());
-            follow_automation(s, track, r.end, moved);
+        // Locked clips don't lift; they go without closing up, as everything does outside Shuffle.
+        if let Some(pl) = s.track_mut(track).and_then(|t| t.playlist_mut()) {
+            let before = pl.clips.len();
+            pl.clips.retain(|c| !ids.contains(&c.id));
+            n += before - pl.clips.len();
         }
     }
     n

crates/engine/src/edit/tests.rs

@@ -175,6 +175,24 @@ fn remove_clips_closes_each_gap_in_shuffle_only() {
     assert_eq!(split(true), vec![(1000, 1000, 2000), (2000, 1000, 4000)]);
 }
 
+#[test]
+fn remove_clips_in_shuffle_keeps_crossfade_partners_apart() {
+    // `(start, end)` of each clip; the second one goes.
+    let remove_second = |spans: &[(Samples, Samples)]| {
+        let (mut s, t) = session_with_clip();
+        let ids: Vec<ClipId> = spans.iter().map(|_| s.new_clip_id()).collect();
+        if let Some(pl) = s.track_mut(t).and_then(|t| t.playlist_mut()) {
+            pl.clips = ids.iter().zip(spans).map(|(id, (a, b))| Clip::audio(*id, "c", SourceId(500), *a, *a, b - a)).collect();
+        }
+        assert_eq!(remove_clips(&mut s, &[ids[1]], true), 1);
+        clips(&s, t).into_iter().map(|(start, len, _)| (start, start + len)).collect::<Vec<_>>()
+    };
+    // Crossfaded with the clip before: the hole starts where that one ends.
+    assert_eq!(remove_second(&[(0, 1050), (950, 2000), (2000, 3000)]), vec![(0, 1050), (1050, 2050)]);
+    // Crossfaded with the clip after: the hole ends where that one starts.
+    assert_eq!(remove_second(&[(0, 1000), (1000, 2050), (1950, 3000), (4000, 5000)]), vec![(0, 1000), (1000, 2050), (3050, 4050)]);
+}
+
 #[test]
 fn copy_paste_overwrites() {
     let (mut s, t) = session_with_clip();