97 lines
3.6 KiB
Markdown
97 lines
3.6 KiB
Markdown
# Timelines and Labels
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HyperFrames is a seek-driven runtime. Build one paused timeline per composition, attach it to `window.__timelines["<composition-id>"]`, and let HyperFrames seek it. Never call `.play()` for render-critical motion.
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## Creating a Timeline
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```javascript
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const tl = gsap.timeline({
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paused: true,
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defaults: { duration: 0.5, ease: "power3.out" },
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});
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tl.to(".a", { x: 100 }).to(".b", { y: 50 }).to(".c", { opacity: 0 });
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```
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Timeline options:
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- **paused: true** — required in HyperFrames. The framework drives the playhead.
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- **repeat**, **yoyo** — apply to the whole timeline. `repeat: -1` is forbidden; use finite counts.
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- **defaults** — vars merged into every child tween. Use this instead of repeating `ease` and `duration` on every line.
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## Position Parameter
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The third argument to `.to()`/`.from()`/`.fromTo()` controls placement on the timeline:
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| Form | Meaning |
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| -------------- | ------------------------------------ |
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| `0`, `1.5` | Absolute time in seconds |
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| `"+=0.5"` | 0.5s after the end of the timeline |
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| `"-=0.2"` | 0.2s before the end of the timeline |
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| `"intro"` | At the `intro` label |
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| `"intro+=0.3"` | 0.3s after the `intro` label |
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| `"<"` | Same start as the previous tween |
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| `">"` | Right after the previous tween ends |
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| `"<0.2"` | 0.2s after the previous tween starts |
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| `">-0.1"` | 0.1s before the previous tween ends |
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```javascript
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tl.to(".a", { x: 100 }, 0);
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tl.to(".b", { y: 50 }, "<"); // same start as .a
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tl.to(".c", { opacity: 0 }, "<0.2"); // 0.2s after .b starts
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```
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Prefer the position parameter over `delay:` — it composes naturally and survives refactors that re-order tweens.
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## Labels
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```javascript
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tl.addLabel("intro", 0);
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tl.to(".a", { x: 100 }, "intro");
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tl.addLabel("outro", "+=0.5");
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tl.to(".a", { opacity: 0 }, "outro");
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```
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Labels make a long timeline readable and let multiple tweens converge on the same beat without re-typing absolute times.
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## Nesting Timelines
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```javascript
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const master = gsap.timeline({ paused: true });
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const child = gsap.timeline();
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child.to(".a", { x: 100 }).to(".b", { y: 50 });
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master.add(child, 0);
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```
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In HyperFrames, **do not** nest sub-composition timelines into the host. Sub-compositions loaded via `data-composition-src` are seeked independently by HyperFrames from their own `data-start`. Nesting is only for grouping pieces of the _same_ composition's timeline.
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## Inside Sub-Compositions: prefer `fromTo` over `from`
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For entrance tweens inside a sub-composition, prefer `gsap.fromTo()` over `gsap.from()`:
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```javascript
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// Sub-composition entrance — survives re-seek cleanly
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tl.fromTo(".title", { y: 60, opacity: 0 }, { y: 0, opacity: 1, duration: 0.6 }, 0.2);
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```
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Why: HyperFrames re-seeks the sub-composition every time its host clip becomes visible. `gsap.from()` snapshots the starting state at **registration time** (page load); when the playhead jumps back past `data-start`, that snapshot can desync from the actual CSS state and the element renders in the wrong position. `gsap.fromTo()` declares both endpoints explicitly, so the seek-back always produces the same start state.
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In top-level (standalone) compositions either form works — there's no re-seek-through-mount cycle.
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## Playback Control (debug / preview only)
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```javascript
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tl.play();
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tl.pause();
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tl.reverse();
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tl.restart();
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tl.time(2);
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tl.progress(0.5);
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tl.kill();
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```
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These are useful when previewing in the browser. In rendered output HyperFrames calls `seek()` internally — your timeline must produce identical state for the same time value every time it is seeked.
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