fix(preview): show the modifiers under a trim when the playhead is on it - #553
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A trim is marked by its pill and skipped during playback, but a user can still park the playhead on it. Two things then went wrong at once, and both are about the preview only — the render still cuts. `resolveNativePosition` snapped to the next kept segment's first frame, so the ruler pointed at one moment and the preview showed another. The trim keeps its place on the raw ruler and the decoder holds the whole recording — only the kept window was narrowed — so it now presents the frame that is actually there. `projectRegionsToSource` dropped every region overlapping no kept segment, so an annotation, zoom or Full Camera lying entirely under a cut never reached the compositor. It is now emitted once, marked `underTrim`, borrowing the `clipIndex` of the segment the cut interrupts (`cutAddressingSegmentIndex` — the SAME one the playhead borrows, or `belongs()` would filter it out). The borrowed index is what keeps the old leak dead: the naive fix re-emitted the region with its raw ms and no clipIndex, and native then matched it on any clip whose source window numerically overlapped. A region whose clip has no kept segment left to name it is still dropped. `underTrim` is what keeps the render cutting. Native plays such a region dry: full strength on its own span, nothing outside, no ease-in/out window and no chaining with a neighbouring zoom. An export never composes a frame at those source times, so the entry is inert there — without the gate a zoom's ease-in (1.5 s before its start) would reach the kept frames beside the cut. Speed regions are not emitted at all: a still frame has no rate to show, and those spans drive the export's frame count. `for_clip_window` now reads as its own doc comment always claimed — clipIndex decides when present, window overlap is the fallback for payloads that lack one, not a second condition. Refs #216
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Included review availability: Your plan provides up to 8 included reviews per hour; 6 remain after this review. 📝 WalkthroughWalkthroughThe change preserves regions fully covered by trims with borrowed clip addressing and an ChangesTrimmed region flow
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: ⚪ Minimal · up to This preview-only change makes playheads under trims show the underlying frame and modifiers while preserving export trimming behavior. No actionable merge-blocking risk remains after normal checks and review. Sequence Diagram(s)sequenceDiagram
participant TimelineMap
participant SceneDescription
participant Compositor
participant Playhead
TimelineMap->>TimelineMap: Project trimmed region and assign clipIndex
TimelineMap->>SceneDescription: Pass underTrim region
SceneDescription->>Compositor: Serialize scene region
Playhead->>TimelineMap: Resolve position over trim
TimelineMap-->>Playhead: Return removed source frame
Compositor->>Compositor: Render only within underTrim span
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Full details: Description checkExplanation The description includes all required sections. It explains the behavior change, links issue Full details: Linked Issues checkExplanation The PR satisfies issue Full details: Out of Scope Changes checkExplanation The changes remain within scope. Rust compositor handling, speed-region exclusion, workbench oracle behavior, tests, and documentation support the under-trim preview fix and export parity requirements. Full details: Docstring CoverageExplanation Docstring coverage is 94.74% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 7 files. (1 skipped: 1 unsupported.) ✨ Finishing Touches📝 Generate docstrings
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Inline comments:
In `@src/native/sceneDescription.ts`:
- Line 868: Add serialization tests in the scene description test suite for both
annotation and Full Camera under-trim regions. Assert each emitted payload
includes underTrim set to true and the correct clipIndex, covering the branches
associated with the region serialization logic.
In `@technical-documentation/architecture/timeline-model.md`:
- Around line 74-75: Update the source references for projectRegionsToSource and
resolveNativePosition in the timeline model table to their current starting
lines, 558 and 676 respectively, while preserving the existing descriptions and
mappings.
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crates/compositor/src/regions.rscrates/compositor/src/scene.rssrc/lib/ai-edition/timeline/timelineMap.test.tssrc/lib/ai-edition/timeline/timelineMap.tssrc/native/sceneDescription.test.tssrc/native/sceneDescription.tstechnical-documentation/architecture/timeline-model.mdworkbench/lib/oracles.ts
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The zoom and speed branches were asserted, the other two were not — and the annotation is the case the issue actually opens on. Also asserts the field is OMITTED, not `false`, when nothing is cut under the region. Refreshes the two stale line anchors in the timeline-model table, which the new helpers above them pushed down.
1 participant
Summary
A trim is marked by its pill and skipped during playback — but a user can still move the playhead onto it, and there is no reason to hide what sits underneath. Today two things go wrong at once, both preview-only. The render still cuts, unchanged.
The image was the wrong one.
resolveNativePositionsnapped a playhead over a cut to the next kept segment's first frame, so the ruler pointed at one moment and the preview showed another. The trim keeps its place on the raw ruler and the decoder holds the whole recording — only the kept window was narrowed — so it now presents the frame that is actually there.The modifiers were dropped.
projectRegionsToSourcediscarded every region overlapping no kept segment, so an annotation, zoom or Full Camera lying entirely under a cut never reached the compositor (the reported symptom, and not only for annotations). It is now emitted once, markedunderTrim, borrowing theclipIndexof the segment the cut interrupts — the same one the playhead borrows, orbelongs()would filter it out.That borrowed index is what keeps the old leak dead. The naive fix, documented in the issue, re-emitted the region with its RAW-virtual ms and no
clipIndex; native'sbelongs()then accepted it on any clip whose source window numerically overlapped those numbers, and the effect fired later on an unrelated clip. An index pins it to one clip. A region whose clip has no kept segment left to name it is still dropped.How the render stays cut
underTrimtells native to play the region dry: full strength on its own span, nothing outside, no ease-in/ease-out window (zoom_region_strength) and no chaining with a neighbouring zoom (connected_pairs). An export never composes a frame at those source times, so the entry is inert there. Without the gate a zoom's ease-in — 1.5 s before its start — would reach the kept frames beside the cut, and the preview would show what the export does not.Speed regions are deliberately not emitted under a trim: a still frame has no rate to show, and those spans drive the export's frame count. Nothing to gain, an arithmetic to put at risk.
for_clip_windownow reads as its own doc comment always claimed:clipIndexdecides when present, window overlap is the fallback for payloads that lack one — not a second condition. That is the only behavioural change on the Rust filter, and it can only differ for an out-of-window region, which only anunderTrimone is.Related issue
The issue laid out three options and preferred (c). The maintainer's call was different: a trim is marked by its pill, playback skips it, and a playhead placed on it deliberately should show what is underneath — effects included. This implements that.
Fixes #216
Type of change
Release impact
Desktop impact
The Rust change is in
scene.rs/regions.rs, shared by all three back-ends. Only the Windows back-end was exercised at runtime (see below); macOS and Linux rest on CI'scargo test.Screenshots / video
Not attachable from the CLI — reproduced below as measurements. Rendered through the freshly built
compositor_view.nodeon a real recording, driven exactly as the preview drives it (setScene→setActiveClip→presentTime→readFrame). Fixture: clip source[0, 4.774]identity on the ruler, trim removing source[2.046, 4.400], a text annotation at source[2.213, 4.213]and a zoom at[3.5, 4.2], both entirely under the cut.The two "identical" rows are the preview/export-parity check; the two middle rows are the fix.
Testing
npx vitest --run— 2222 passed / 5 skipped, 186 files. New cases intimelineMap.test.ts(under-trim emission, head-trim addressing, the drop when no segment can name the clip, and the playhead/region agree on the same index property) andsceneDescription.test.ts(underTrimon the wire, speed regions excluded).cargo test -p openscreen-compositor --lib— 160 passed. New cases inregions.rs(no transition window, no chaining) andscene.rs(for_clip_windowkeeps an under-trim region of the composed clip; still falls back to window overlap without aclipIndex).npx tsc --noEmit,npx tsc -p tsconfig.test.json --noEmit,npm run wb:typecheck,npm run lint,npm run docs:check,cargo check -p openscreen-compositor -p compositor-view-napi --all-targets— all clean.wb:l0has 44 pre-existing failures in this environment, all from the missingworkbench/fixtures/real-screencastfixture;oracles.wb.ts(the file this PR touches) passes.🤖 Generated with Claude Code
Summary by CodeRabbit
New Features
Bug Fixes