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hyperframes/skills/hyperframes-core/references/data-attributes.md
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Miguel Ángel b2fc18b2df fix(skills,lint): correct composition-contract claims the code contradicts (#3468)
The runtime absorbed a series of authoring mistakes over time and `runtime/init.ts`
says so in its own comments, but the skills kept teaching the old rules. Four of
them actively cost an agent a failing run: add `crossorigin` (lint rejects it
unconditionally), never build a timeline inside `async` (lint calls that the
documented contract), never `gsap.set` later-scene clips (two fixHints instruct
exactly that), and 12 copyable media snippets with no `id`, which render silent.

Corrected in every place each claim appeared, including `hyperframes-animation`,
three workflow scripts, the scaffolded project instructions, the CLI `docs`
command, and the public docs site: `data-track-index` is a Studio display lane
the render never reads, `class="clip"` is a layout convention rather than a
visibility requirement, timed elements may nest, the visibility window is
half-open, sub-composition host dimensions are backfilled, and the root-fill rule
applies only to the layered-composite path.

Behaviour changes, each backed by a render rather than by reading code:

- `timeline_registry_missing_init` deleted. The runtime creates the registry
  before any inline script; a composition without the guard line renders and
  animates correctly.
- `video_nested_in_timed_element` kept, message corrected. A rendered repro shows
  the nested-with-local-start case really does break, so the rule guards a real
  defect, but nothing is "FROZEN": the extractor ignores the wrapper's offset
  while visibility uses it, so the clip shows wrong frames and then vanishes.
- `mediaRenderIds` now stamps media whose source is a `<source>` child, closing a
  duplicate-id gap the old `[src]`-only selector left open.
- Stale messages fixed on `subcomposition_root_styled_by_class` and
  `deprecated_data_layer`.

`coreSkillContent.test.ts` pinned the literal sentence that made root
`data-start` look required, so it is narrowed to structure plus the regression it
genuinely catches.

Not covered, and flagged in the PR: the media global-vs-local start heuristic in
`runtime/init.ts` is the root cause behind the nested-video defect. Removing it
changes the meaning of existing compositions and needs its own deprecation.
2026-08-24 18:04:39 -04:00

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15 KiB
Markdown

# Data Attributes Reference
Every HyperFrames composition uses `data-*` attributes to declare timing and structure to the framework. This is the full attribute table — pair with `tracks-and-clips.md` for the rules behind `data-track-index`.
## Composition Root
Every renderable composition needs one root element:
| Attribute | Required | Meaning |
| ---------------------------- | ------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `data-composition-id` | Yes | Unique ID. Must match the animation registry key on `window.__timelines`. |
| `data-width` / `data-height` | Yes | Pixel frame size. Common values: `1920x1080`, `1080x1920`, `1080x1080`. |
| `data-duration` | Conditional\* | Render duration in seconds (total length / frame count), not the GSAP timeline length. **Read once at compile time, like `data-width` / `data-height`**: a static root `data-duration` is locked before scripts run, so a script (`root.setAttribute("data-duration", ...)`) or a `--variables`-driven value cannot change the render length. To vary length per render, author the root `data-duration` directly. (A clip's `data-duration` is different: re-read from the live DOM, so scripts/variables can drive it.) Only when the root omits `data-duration` does the renderer derive total length from the live DOM / timeline after scripts run. |
| `data-fps` | No | Optional frame rate hint. CLI render flags can override output fps. |
| `data-composition-variables` | No | JSON array of variable declarations (on `<html>`). See `variables-and-media.md`. |
\*`data-duration` is optional whenever the runtime can auto-infer duration: a registered GSAP timeline, a finite CSS animation, a finite WAAPI `element.animate()`, or a registered Lottie animation. It is **required** for Three.js (no auto-inference), for infinite/unbounded CSS or WAAPI animations, and for any composition with no GSAP timeline and no animation signal at all. `npx hyperframes lint` enforces this (`root_composition_missing_duration_source`). See `determinism-rules.md` → "Duration Contract For Non-GSAP Runtimes" for the per-runtime breakdown.
The root should be `position: relative`, have explicit pixel dimensions, and hide overflow unless intentionally composing outside the frame.
## Clip Attributes
**`data-start` is what makes an element a clip.** The runtime collects `[data-start]` and drives visibility off that attribute, so any element carrying it is timed.
`class="clip"` is a **convention, not a requirement**: the runtime never reads it. Keep writing it, because the scaffold's shared `.clip { position: absolute; inset: 0 }` rule is what gives a scene its full-frame box, Studio uses it as an edit hint, and `lint` warns (`timed_element_missing_clip_class`) when a timed element lacks it. If you drop the class you must supply that layout yourself. Omit it on `<video>` and `<audio>`.
**Nesting is allowed.** A timed element inside a wrapper is still timed, and a timed ancestor clamps its descendants: a child cannot be visible while its timed ancestor is hidden. Direct children of the root get automatic layout (see "Root-level clips get automatic layout" below); nested ones do not, so give them their own positioning.
| Attribute | Required | Meaning |
| ------------------ | ----------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `id` | Yes on `<video>`/`<audio>`, else recommended | `lint` errors with `media_missing_id` on media without one, and an id-less `<audio>` is never mixed, so the render is **silent**. Elsewhere it is a warning (`studio_missing_editable_id`): Studio needs a stable edit target, and timeline targets reference it. |
| `data-start` | Yes | Start time in seconds, or a supported clip-time reference. This attribute is what marks the element as timed. |
| `data-duration` | Required for `div`, `img`, and sub-compositions | Duration in seconds. Video/audio can default to media duration when known. Without any resolvable duration the element has no end and stays visible for the rest of the composition. |
| `data-track-index` | No | Studio timeline lane, display only. The render never reads it, and clips on one track may overlap in time. Absent, the parser defaults it and Studio lays out one lane per clip. Two `<audio>` elements on the same index that overlap in time raise a `lint` warning. |
| `data-media-start` | No | Offset into the media source, in seconds. |
| `data-volume` | No | Static audio gain, default `1` (0 dB). `0` is silence and values above `1` boost, up to `3.98` (+12 dB) — Studio's fader writes this. For fades, animate `volume` on the timeline instead (see `variables-and-media.md`); a tween's own values replace this baseline entirely. |
| `data-has-audio` | No (`<video>` only) | `"true"` to declare the video carries an audio track when auto-detection would miss it. |
**The visibility window is half-open: `[start, start + duration)`.** A clip shows while `start ≤ t < start + duration` and is hidden at exactly `t = start + duration`. Land an animation's resolved end state slightly **before** `data-duration`, not on it, or its last frame is never rendered. Two clips can therefore be authored back to back (`b.start === a.start + a.duration`) with no overlapping frame.
**Root-level clips get automatic layout.** For direct children of the composition root that carry `data-start`, the runtime forces `position: absolute` and anchors them at `top: 0; left: 0`, sizing them to 100% when they have no computed size, so scenes stack in the same viewport layer. Elements **without** `data-start` are skipped entirely: an untimed full-bleed background needs its own `position: absolute; inset: 0`, or it collapses to zero height.
## Sub-Composition Host Attributes
When a clip is a sub-composition host (loads another composition file):
| Attribute | Required | Meaning |
| ---------------------------- | ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `data-composition-id` | Recommended | The composition ID of the loaded file. Matching it is the convention; a host that names a different id, or none at all, is supported but resolves silently. |
| `data-composition-src` | Yes | Path to the sub-composition HTML file. |
| `data-width` / `data-height` | No | Render dimensions for the instance. The compiler backfills them from the loaded file's root when absent. |
| `data-variable-values` | No | Per-instance variable overrides as JSON. See `variables-and-media.md`. |
| `data-var-src` | No | Binds the element's `src` to a declared variable id (media/image substitution, authored src = fallback). |
| `data-var-text` | No | Binds the element's own text to a scalar variable id; children are preserved. |
See `sub-compositions.md` for the full wiring pattern.
## Authoring Hints
- `id="root"` — template convention used by scaffolds and the transition catalog so CSS can target the composition root with `#root` instead of `[data-composition-id="main"]`. Not required by the runtime, but consistent with the rest of the ecosystem.
- `class="clip"`: layout and tooling convention on visible timed elements (`<div>`, `<img>`, …), not a runtime requirement. See Clip Attributes above.
- `data-root="true"`: names the composition root explicitly. Without it the runtime picks the outermost `[data-composition-id]` element, which is right for almost every file; set it when compositions nest and you need to be unambiguous.
- `data-layout-allow-overflow` — tells `hyperframes check` that overflow on this element (or its descendants) is intentional. Notes:
- The `check` layout audit measures `getBoundingClientRect` at sampled timestamps, not rendered pixels. `overflow: hidden` clips the visual but does **not** suppress a layout finding. This attribute is the escape hatch; CSS overflow is not.
- Can be set on the composition **root** as well as on any child. When the cited offender is `div.<comp>-root inside div.<comp>-root` (the root reports its own children's union as overflowing), the fix goes on the root, not on individual text descendants — shrinking font sizes will not converge.
- In a multi-scene `group_wN.html` (continue runs), every scene-local element stays in the DOM during the other scenes' time windows; the layout-box union almost always overflows the canvas during morph seams. Mark the root and every scene-local primary/supporting element with this attribute **at construction**, not after `check` flags it.
- **Blast radius — it silences more than the overflow audit.** The attribute is inherited down the subtree (the perception probe walks ancestors), so it also suppresses the rendered-perception checks `text-clipping`, `content-cramped-container`, and `foreground-over-panel` for every descendant. Putting it on a persistent panel that also hosts real foreground content disables collision checks on that content for the panel's whole lifetime. Prefer the narrowest opt-out: scope it to the smallest decorative wrapper, or use per-element `data-layout-bleed="true"` for one intentional primary-text crop. The two canvas/edge checks `primary-offscreen` and `foreground-over-panel` deliberately run **even under** allow-overflow, so it cannot hide a wordmark sliced by the frame or text bleeding onto a panel edge.
- `data-layout-ignore` — exclude this element from layout audits entirely.
- `data-layout-allow-caption-zone` — opt out of `--caption-zone` / `caption_zone_collision` for intentional lower-third copy (applies to the element and every descendant via `closest`; does **not** suppress overflow, overlap, occlusion, or other layout audits — pair those attrs if needed).
## Legacy / Removed Attributes
These names appear in older projects and examples. Use the current names when authoring or editing:
| Legacy name | Use instead |
| ------------ | ------------------ |
| `data-layer` | `data-track-index` |
| `data-end` | `data-duration` |