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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
Timed child elements are clips. class="clip" is required on visible timed elements (<div>, <img>, etc.) — without it the runtime keeps the element visible for the whole composition, ignoring data-start / data-duration. Omit on <video> (framework manages visibility directly) and <audio> (no visual).
Clips must be DIRECT children of the composition root. A clip nested inside a wrapper <div> is not registered — most visibly, a <video> in a wrapper is never seeked/decoded and renders black. To wrap/transform a clip, put the wrapper inside the clip, or animate the clip element itself; do not wrap the clip. (<video>/<audio> additionally must be at the host root, never in a sub-comp <template> — see variables-and-media.md.)
| Attribute | Required | Meaning |
|---|---|---|
id |
Yes | Stable DOM ID for linting, timeline targets, and debugging. |
data-start |
Yes | Start time in seconds, or a supported clip-time reference. |
data-duration |
Required for div, img, and sub-compositions |
Duration in seconds. Video/audio can default to media duration when known. |
data-track-index |
Yes | Timeline track. Clips on the same track must not overlap. |
data-media-start |
No | Offset into the media source, in seconds. |
data-volume |
No | Static audio volume, 0 to 1, default 1. For fades, animate volume on the timeline instead (see variables-and-media.md). |
data-has-audio |
No (<video> only) |
"true" to declare the video carries an audio track when auto-detection would miss it. |
Visibility window is inclusive of both ends. A clip shows while start ≤ t ≤ start + duration — it still renders at exactly t = start + duration, so the final frame holds the animation's resolved end state (the runtime does not hide it one frame early). A reveal/entrance that lands on data-duration is therefore visible on the last frame; you do not need to finish it before data-duration just to guarantee the end state renders. (Climax-dwell guidance in /hyperframes-animation is about pacing, not this boundary.)
Sub-Composition Host Attributes
When a clip is a sub-composition host (loads another composition file):
| Attribute | Required | Meaning |
|---|---|---|
data-composition-id |
Yes | The internal composition ID of the loaded file. |
data-composition-src |
Yes | Path to the sub-composition HTML file. |
data-width / data-height |
Yes | Render dimensions for the sub-composition instance. |
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#rootinstead of[data-composition-id="main"]. Not required by the runtime, but consistent with the rest of the ecosystem.class="clip"— required runtime visibility marker on visible timed elements (<div>,<img>, …). See Clip Attributes above.data-layout-allow-overflow— tellshyperframes checkthat overflow on this element (or its descendants) is intentional. Notes:inspectmeasuresgetBoundingClientRectat sampled timestamps, not rendered pixels —overflow: hiddenclips the visual but does not suppress aninspectoverflow 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 afterinspectflags it. - Blast radius — it silences more than
inspect. The attribute is inherited down the subtree (the perception probe walks ancestors), so it also suppresses the rendered-perception checkstext-clipping,content-cramped-container, andforeground-over-panelfor 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-elementdata-layout-bleed="true"for one intentional primary-text crop. The two canvas/edge checksprimary-offscreenandforeground-over-paneldeliberately 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.
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 |