Image sequences: a gap in the numbering holds the previous frame, as After Effects

After Effects 2026 shows the last existing file across a gap in a sequence's
numbering (case 860: files 1, 2, 4, 5 show frame 2 at frame 3; VERIFY
read-back). EffectCraft drew colour bars there. The media pool now holds the
previous file (Footage::sequence_file_held); colour bars remain only where no
file precedes the frame. Missing-frame reports on import are unchanged.

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

crates/media/src/pool.rs

@@ -682,9 +682,9 @@ impl Inner {
         match footage.kind {
             FootageKind::Sequence if !footage.sequence.is_empty() => {
                 let i = Self::frame_index(footage.frame_rate, t, footage.sequence_frames(), footage.loop_count);
-                match footage.sequence_file(i) {
+                match footage.sequence_file_held(i) {
                     Some(path) => Loc { key: key(path, 0), media_t: None, float },
-                    // A gap in the numbering: colour bars, as in After Effects.
+                    // No file at or before the frame: colour bars.
                     None => Loc { key: key(PLACEHOLDER, ((footage.width as i64) << 32) | footage.height as i64), media_t: None, float },
                 }
             }

crates/media/tests/footage.rs

@@ -546,10 +546,11 @@ fn png_sequence_import() {
     assert_eq!(*img, load_png(&first.with_file_name("seq_0004.png")));
 }
 
-/// A gap in a sequence's numbering shows colour bars, as in After Effects; in Force
-/// Alphabetical Order the files play back to back (#297).
+/// A gap in a sequence's numbering holds the previous frame, as After Effects 2026 does (files
+/// 1, 2, 4, 5 show frame 2 at frame 3); in Force Alphabetical Order the files play back to back
+/// (#297).
 #[test]
-fn sequence_gaps_show_placeholders() {
+fn sequence_gaps_hold_the_previous_frame() {
     let dir = fixtures().join(format!("gap-seq-{}", std::process::id()));
     std::fs::create_dir_all(&dir).expect("mkdir");
     // Frames 1, 2 and 4: frame 3 is missing. Each frame is a flat grey of its number.
@@ -567,11 +568,8 @@ fn sequence_gaps_show_placeholders() {
     let at = |f: &Footage, n: i64| pool.frame_at(f, t_of(f.frame_rate, n)).expect("frame");
     let level = |img: &Image| (img.get(0, 0)[0] * 255.0).round() as u32;
     assert_eq!(level(&at(&f, 1)), 100);
-    // The placeholder: colour bars across the frame, starting with 75 % white.
-    let bars = at(&f, 2);
-    assert_eq!((bars.width, bars.height), (8, 4));
-    assert_eq!(bars.get(0, 0), [0.75, 0.75, 0.75, 1.0]);
-    assert_eq!(bars.get(7, 3), [0.0, 0.0, 0.75, 1.0], "blue on the right");
+    // The gap holds frame 2.
+    assert_eq!(level(&at(&f, 2)), 100);
     assert_eq!(level(&at(&f, 3)), 200);
     f.alphabetical = true;
     f.sync_sequence_duration();

crates/project/src/sequence.rs

@@ -107,6 +107,18 @@ impl Footage {
         self.sequence.get(k).filter(|p| frame_number(p) == Some(n)).map(String::as_str)
     }
 
+    /// The file an image sequence shows at its frame `i`, holding the last existing file across a
+    /// gap in the numbering (After Effects 2026: files 1, 2, 4, 5 show frame 2 at frame 3).
+    /// `None` only when no file precedes the frame (or there are no files).
+    pub fn sequence_file_held(&self, i: i64) -> Option<&str> {
+        if let Some(p) = self.sequence_file(i) {
+            return Some(p);
+        }
+        let first = self.numbered()?;
+        let k = self.first_file_from(first.saturating_add(i));
+        self.sequence.get(k.checked_sub(1)?).map(String::as_str)
+    }
+
     /// Set an image sequence's duration to its frames at its frame rate (after its files or
     /// frame rate changed).
     pub fn sync_sequence_duration(&mut self) {

docs/agents.md

@@ -275,8 +275,8 @@ build real projects through these interfaces; they are worked examples of everyt
   numbered run as one item (several picked frames: that range; a folder: each run in it;
   `"sequence": false`: one still; dropped files, `"drag": true`, import as stills unless
   `"sequence": true`, as in After Effects; `"alphabetical": true`: Force Alphabetical Order, the files
-  play one after another) at `frameRate` or 30 fps (Settings ▸ Import). Missing frames show
-  colour bars, as in After Effects. `file.interpretFootage {"items":[id], "frameRate":12,
+  play one after another) at `frameRate` or 30 fps (Settings ▸ Import). A gap in the numbering
+  holds the previous frame, as in After Effects. `file.interpretFootage {"items":[id], "frameRate":12,
   "startTimecode":1001}` conforms them and sets Override Start (the item and layers that ran to its end get the new
   length). See [footage.md](footage.md).
 * **Colour of footage**: `file.interpretFootage {"items":[id], "preserveRgb":true}` is Interpret

docs/footage.md

@@ -47,8 +47,8 @@ Stills of any format EffectCraft reads can form a sequence: PNG, JPEG, TIFF, Ope
 WebP. Layered and vector documents (PSD, SVG, PDF) import one by one.
 
 **Missing frames.** Where the numbering skips a number (`shot_0003.png` is missing between
-`0002` and `0004`), the sequence shows a placeholder of colour bars for that frame, as After
-Effects does, so every other frame stays at its number. Render or copy the missing files into the
+`0002` and `0004`), the sequence holds the previous frame (`0002`) there, as After Effects 2026
+does, so every other frame stays at its number. Render or copy the missing files into the
 folder and choose File ▸ Reload Footage to fill the gaps.
 
 Agents: `file.import {"paths": ["/shots/shot_0001.png"], "sequence": true, "frameRate": 24}`.