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James RussoandClaude Sonnet 5
24edb15095
* fix(runtime): auto-infer composition duration for CSS/WAAPI/Lottie so data-duration is optional The #2 render failure bucket ("Composition has zero duration") accounts for ~27K errors / ~7K affected users over 30 days (PostHog project 356858). Root cause: only GSAP timelines got their duration auto-detected — CSS, WAAPI, and Lottie compositions had no source of truth for total duration unless the author remembered to set data-duration on the root element, and the render engine hard-failed capture when neither was present. Adds getInferredDurationSeconds() to the CSS, WAAPI, and Lottie runtime adapters (packages/core/src/runtime/adapters/*.ts) — each reports the longest finite end time it can discover from its own animations (CSS: computed timing offset by data-start; WAAPI: effect.getComputedTiming().endTime; Lottie: totalFrames/frameRate or the player's own duration). Infinite/ unbounded animations correctly return null and still require data-duration. Wires this into the runtime's existing duration-floor resolution (resolveAdapterDurationFloorSeconds in runtime/init.ts), alongside the existing media-duration and authored-composition floors, so window.__hf.duration becomes positive without any author action for finite-duration non-GSAP compositions. Three.js is unchanged — no AnimationClip/AnimationMixer inspection exists in that adapter, so data-duration remains required there. Tightens frameCapture.ts's zero-duration fast-fail gate to also check hf.duration directly (not just the two authored signals), so a composition mid-inference isn't fast-failed before its adapter-derived duration lands. Adds a new lint rule (root_composition_missing_duration_source) that errors only on genuinely non-inferable cases: no animation signal at all, Three.js without data-duration, or an infinite/unbounded CSS or WAAPI animation without data-duration. Deliberately silent on finite CSS/WAAPI/Lottie animations, since the runtime now infers those — an autofix that "inserts the inferred value" was considered and rejected: every case the rule flags has no derivable value (an infinite spinner has no finite end time; a duration-less Three.js scene has nothing to measure), so any autofix would have to fabricate a placeholder, trading a loud correct failure for a silent wrong-length render. Updates the CSS/WAAPI/Lottie/Three adapter skill docs and the hyperframes-core determinism-rules/data-attributes references to document the new optionality and the runtime mechanism backing it. Verified end-to-end against the real render pipeline (not just unit tests): a CSS-only composition with a finite 3s animation, no GSAP timeline, and no data-duration now renders a correct 3.000s MP4 via `hyperframes render` (previously: "Composition has zero duration" failure). The infinite-CSS negative control still fails fast with a clear diagnostic, matching the new lint rule. Adds a file-level fallow health exemption for lottie.ts's pre-existing `seek` handler — unrelated to this change, but its line numbers shifted when new functions were added earlier in the file, tripping fallow's inherited-finding fingerprint (documented pattern already used elsewhere in .fallowrc.jsonc for the same reason). Known limitation: the static WAAPI usage detector in the lint rule (/\.animate\(\s*[\[$A-Za-z_]/) can miss unusual call shapes; it only affects whether the "no signal at all" branch fires, and errs toward NOT flagging (reducing false positives) rather than over-flagging. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> * fix(lint): close 3 correctness gaps in root_composition_missing_duration_source - Strip JS/CSS comments before scanning for GSAP/WAAPI/Three/Lottie/CSS animation signals, so a commented-out `.animate()` call or a commented `animation: ... infinite` rule can no longer satisfy the "has a duration source" check and mask a real zero-duration render failure. - Broaden the WAAPI detection regex to also match the object-literal (PropertyIndexedKeyframes) form of `.animate()`, e.g. `el.animate({ opacity: [0,1] }, { duration: 2000 })`, which the previous character class silently missed. Corrected the adjacent comment that incorrectly claimed this shape "can't be a false negative". - Fix hasInfiniteCssAnimation to stop false-positiving on animation NAMEs that merely contain the substring "infinite" (e.g. `infinite-spin`) by anchoring the `infinite` keyword with hyphen-aware boundaries instead of a bare `\b`. Also makes the longhand `animation-name` + separately declared `animation-iteration-count: infinite` pattern detected consistently. Adds targeted unit tests for each fixed false-positive/false-negative. * fix(runtime): keep finite duration signal when an unbounded animation coexists getInferredDurationSeconds in the CSS and WAAPI adapters returned null outright whenever any animation on the composition was unbounded (infinite iteration count), even when other finite animations on the same composition could still supply a valid duration. This disagreed with the new root_composition_missing_duration_source lint rule, which treats any animation-name as sufficient — so a composition mixing a finite fadeIn with a decorative infinite spin passed lint but still failed at render with "zero duration". Unbounded animations are now skipped when computing the max end time instead of short-circuiting the whole calculation. null is only returned when every animation on the composition is unbounded, i.e. there is no finite signal to fall back on at all. Co-Authored-By: Claude <noreply@anthropic.com> * docs(skills): fix table separator width in data-attributes.md oxfmt flagged the merged Composition Root table from the post-rebase merge of the auto-infer-duration docs onto main's reformatted table — the separator row was one dash short of the header width. * fix(lint): keep infinite-CSS duration rule strict but make its message honest Post-review (Vance): after the finite+infinite adapter fix, the runtime infers a length for a mixed finite+infinite CSS composition, but this lint rule still (intentionally) errors on it — an unbounded animation makes the intended total length ambiguous, so we require explicit data-duration. Keep that strictness (lint is advisory by default; it only blocks under --strict, and data-duration is the one duration signal guaranteed correct across every adapter, known and future). But the message wrongly claimed the render "will fail" — false for the mixed case, where the runtime falls back to the finite animation. Rewrite it to describe the ambiguity honestly, correct the rule's block comment, and add a mixed finite+infinite test asserting it still errors with an honest message. --------- Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
69 lines
7.1 KiB
Markdown
69 lines
7.1 KiB
Markdown
# Determinism, Animation Runtime, and Layout
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HyperFrames seeks compositions frame-by-frame. Every frame must be reproducible from its time value alone — same input time → same pixels. Three contracts enforce this: the **animation runtime contract**, the **determinism rules**, and the **layout contract**.
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## Animation Runtime Contract
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GSAP is the primary runtime. The core requirement is generic: animation state must be seekable from HyperFrames time.
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For GSAP:
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- Create the timeline **synchronously** during page initialization.
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- Use `gsap.timeline({ paused: true })`.
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- Register it on `window.__timelines["<composition-id>"]`.
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- The key must match `data-composition-id` on the composition root.
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- **Do not** call `tl.play()` for render-critical motion.
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- **Do not** build timelines inside `async`, `Promise`, `setTimeout`, or event handlers — the renderer can sample before they finish.
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- **Do not** create empty tweens only to set duration; use `data-duration` on the clip instead.
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- **Do not** `gsap.set()` clip elements from later scenes — they are not in the DOM at page load. Use `tl.set(selector, vars, time)` inside the timeline at or after the clip's `data-start`.
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Use the `hyperframes-animation` skill for tween syntax, position parameters, eases, and performance rules.
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### Duration Contract For Non-GSAP Runtimes
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The render engine needs a positive total duration before it will capture a single frame — without one, capture fails outright with "Composition has zero duration." A GSAP timeline supplies this automatically. CSS, WAAPI, and Lottie compositions have no timeline object, so the runtime infers duration itself:
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- **CSS**: longest `animation-delay` + `animation-duration` × finite `animation-iteration-count` across animated elements (offset by each element's `data-start`). `animation-iteration-count: infinite` cannot be inferred.
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- **WAAPI**: longest `element.animate()` effect's `getComputedTiming().endTime`. Infinite `iterations` cannot be inferred.
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- **Lottie**: the registered animation's native length (`totalFrames / frameRate`, or the dotLottie player's own `duration`) — always finite regardless of `loop`.
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- **Three.js**: **not inferable**. The `three` adapter only forwards time via `hf-seek` — it has no `AnimationClip`/`AnimationMixer` inspection.
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`data-duration` on the root `[data-composition-id]` element is therefore optional whenever every non-GSAP animation on the page is finite (CSS/WAAPI with finite iteration counts, or Lottie). It is **required** when: the composition has an infinite/unbounded CSS or WAAPI animation, the composition uses Three.js, or there is no GSAP timeline and no animation signal at all for any adapter to discover. `npx hyperframes lint` enforces exactly this (`root_composition_missing_duration_source`) — see the runtime/adapter-specific docs under `hyperframes-animation/adapters/` for the full contract per runtime.
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## Determinism Rules
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Rendered frames must be reproducible from the requested time. Do **not** use any of the following for visual state:
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- `Date.now()`, `performance.now()`, or any render-time clock.
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- Unseeded `Math.random()`. Use a seeded PRNG if random-looking placement is needed.
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- Render-time network fetches for required assets. Inline or pre-bundle them.
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- Hover, scroll, pointer, or focus state. The renderer has no input events.
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- Infinite loops such as `repeat: -1`. Compute a finite count: `repeat: Math.max(0, Math.floor(duration / cycleDuration) - 1)` — **`floor`, not `ceil`** (`ceil` overshoots `data-duration` and trips the `gsap_repeat_ceil_overshoot` lint; `max(0, …)` avoids a negative repeat = infinite).
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Also avoid:
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- Animating anything outside the visual-property allowlist: `opacity`, `x`, `y`, `scale`, `rotation`, `color`, `backgroundColor`, `borderRadius`, transforms. Never animate `display` or `visibility` — use opacity/transforms and timed clip visibility instead.
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- Animating the same property on the same element from multiple timelines at the same time — GSAP's overwrite behavior is order-dependent and can flip between renders.
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## Layout Contract
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Build the visible end-state in static HTML and CSS first, then animate from/to that state.
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- The composition root has fixed pixel frame dimensions.
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- **The root composition's total duration (render length / frame count) is fixed at compile time**, read once from the static root `data-duration` before scripts run, like `data-width` / `data-height`. A script or `--variables` value that rewrites the root `data-duration` afterward is ignored. To vary render length per output, author the root `data-duration` directly. (A _clip's_ own `data-duration` is re-read from the live DOM, so scripts/variables can still drive clip lengths. Only when the root omits `data-duration` does the renderer probe the live DOM / timeline for total length.)
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- Scene containers should fill the scene with `width: 100%; height: 100%; box-sizing: border-box`.
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- Use padding, flex, grid, and `max-width` for layout. Avoid positioning main content with hardcoded `top`/`left` offsets when a layout container can do it.
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- Use `position: absolute` for layers and decorative elements, not as the default content-layout strategy.
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- Prefer transforms and opacity for animation.
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- Keep text inside its intended container. For dynamic text, use `max-width`, wrapping, or `window.__hyperframes.fitTextFontSize(text, { maxWidth, fontFamily, fontWeight })`.
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- For text measurement without DOM reflow, use `window.__hyperframes.pretext`: `pretext.prepare(text, font)` then `pretext.layout(prepared, maxWidth, lineHeight)`. Pure arithmetic, ~0.0002 ms per call — safe for per-frame text reflow, shrinkwrap containers, and computing layout before render. `fitTextFontSize` is built on it.
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- **Do not** use `<br>` in body text. Forced breaks ignore the actual rendered font width and produce an extra break when the line already wraps naturally, causing overlap. Let text wrap via `max-width`. Exception: short display titles where each word is deliberately on its own line.
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- **Transformed elements must be block-level + sized.** `transform`/`scaleX`/`scaleY` is a no-op on an inline `<span>`, and scaling an auto-width (0px) element shows nothing → invisible bars/fills. Give them `display: block`/`inline-block`/flex-item **and** a real `width`/`height` (e.g. `width: 100%` inside a sized parent). _(silent — lint/inspect miss it.)_
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- **Absolutely-positioned decoratives that pulse or overshoot** (`yoyo` scale, `back.out`) need clearance at their **peak** size and must not straddle an `overflow: hidden` edge — else they overlap a neighbor or get clipped. Position for the largest frame, not the resting one. _(silent.)_
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## Why This Matters
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The renderer takes a time value and produces a pixel buffer. There is no notion of "playback" — every frame is a fresh seek. Any state that depends on having reached this frame _through_ a prior frame (timers, accumulated state, event-driven animations) will desync when the renderer samples out of order or in parallel.
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If you find yourself reaching for `setTimeout`, `requestAnimationFrame`, or `addEventListener` to drive a visual, rebuild it as a tween on the timeline instead.
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