Scroll captures

Long-form scrolling captures (one tall PNG that stitches the whole scrollable region) and animated GIFs of the scroll itself, driven through the renderer extension pipeline.

At a glance


Kinds	`render/scroll/long`, `render/scroll/gif`
Schema version	n/a (image-only)
Modules	`:data-scroll-core`
Render mode	default
Cost	medium (extra renders per scroll step)
Token usage	Image-only — ~1.5 k tok per `render/scroll/*` PNG read; payload itself is a `path`. See token usage.
Transport	path (PNG / GIF)
Platforms	Android · Desktop · shared

What it answers

What does the entire scrollable region look like, end to end, not just the viewport at rest?
What does the scroll motion look like over time (entry animations, sticky headers settling, LazyColumn item placement)?
Does a nestedScroll collapse / expand land in the right state at the end of a fling?

data/scroll/core ships scroll-scenario drivers (ScrollDriver, ScrollGifEncoder, ScrollPreviewExtension) that the renderer composes through the regular extension pipeline.

What it does NOT answer

Scroll is renderer-side only — it produces image artifacts, not a JSON payload, so it has no kind on the daemon’s initialize.capabilities.dataProducts list. There is no data-scroll-connector. It never round-trips through data/fetch or data/subscribe; instead the renderer drives it directly via PreviewPipelineStep / scenario-driver hooks.
It does not measure scroll performance — for that, instrument compose/recomposition over the same scrolled frames.

Use cases

Render a tall settings screen as one PNG for design review.
GIF a LazyColumn to verify item-key stability across data changes.
Capture the full scroll of a Wear ScalingLazyColumn to confirm the curvature target.

Payload shape

Image-only artifacts. Produced via :data-scroll-core extensions. Output paths under build/compose-previews/renders/<id>-long.png and build/compose-previews/renders/<id>.gif.

Enabling

Annotate the preview with the matching multi-preview annotation (e.g. @ScrollingPreview) — see skills/compose-preview/design/CAPTURE_MODES.md for the multi-preview / scenario annotations the scroll extension recognises.

Companion products

Recomposition — compose/recomposition to attribute scroll cost to specific composables.
History diff — history/diff/regions against a long-PNG baseline to catch list-item layout regressions.