Clyune Component GalleryScrollTrigger · How it works & code
When a section passes the trigger line, the card slides in and fades in with scroll progress.
Runtime logic
Visiting `/gsap/scroll`, DemoHost lazy-loads `demos/kits/kit-gsap.js` (registry `mod: 'kit-gsap'`) and calls `mount(host, { variant: 'scroll' })`. mount resolves the variant to family `scroll`; `withControls` builds the control panel (several presets + sliders). `createCanvasStage` creates the `<canvas>` (HiDPI ≤ 2×, ResizeObserver) and the info panel. The family’s `build(S)` initialises state and returns the per-frame callback. Every `requestAnimationFrame`: read controls, advance a speed-scaled clock (dt ≤ 50 ms), run the frame callback; returned readouts go to the info panel. Changing parameters: colour/speed/size apply live; structural ones remount; leaving the page cancels rAF, removes listeners and frees resources.
Environment
Canvas 2D: 2D canvas drawing; requestAnimationFrame: Display-synced animation loop; ResizeObserver: Canvas follows container size; Pointer Events: Unified mouse/touch/pen events; devicePixelRatio: Crisp HiDPI rendering (capped at 2×) · react 18.3.1, react-router-dom 6.30.6, vite 5.4.21
Dependencies
react 18.3.1
Imported APIs
withControls — Wraps the demo in the shared control panel (presets, sliders, reset); hot-updates or remounts on change; paramsFromSpec — Turns the spec (colour/speed/size/count/extras) into control-panel parameter definitions; createCanvasStage — Shared Canvas 2D stage: canvas + info panel, HiDPI, one rAF loop, pointer state, idle auto-pointer; hueOf — Hue of a colour (0–360°); clamp — Clamps a value to a range; F — Formula block HTML; S.clear — Clears with the background colour (translucent = trails); S.onFrame — Registers a per-frame callback; its return value feeds the info panel; ctx.fillRect() — Fills a rectangle; ctx.fill() — Fills the current path; ctx.setLineDash() — Sets the dash pattern for strokes; ctx.beginPath() — Starts a new path; ctx.moveTo() — Moves the pen without drawing; ctx.lineTo() — Adds a straight line to a point; ctx.stroke() — Strokes the current path; ctx.fillText() — Draws filled text; ctx.arcTo() — Adds an arc using tangent lines; ctx.closePath() — Closes the current sub-path; ctx.save() — Saves the drawing state (transform, styles, clip); ctx.rect() — Adds a rectangle to the path; ctx.clip() — Turns the current path into the clipping region; ctx.translate() — Translates the coordinate system; ctx.restore() — Restores the saved drawing state
Source code
frontend/src/demos/kits/kit-gsap.js: FAM.scroll (L213-L233)
Code walkthrough
L213-233: Calls the factory `gFam()` to produce the full definition (spec + doc + build) from the options below. L213-213: Title shown in the info and control panels: “ScrollTrigger”. L213-213: Range/default of the count slider. L213-213: Extra demo-specific slider/toggle: Trigger position. L213-213: Range/default of the size slider. L213-213: Default main colour. L214-214: Help text of the count parameter. L214-214: Help text of the extra parameter. L214-214: Help text of the size parameter. L215-215: Preset buttons: name → parameter overrides (5). L216-216: Body of the “Notes” section. L217-217: Main formula of the “Formula” section. L217-217: Second formula line. L218-233: Per-frame draw function: draws with Canvas 2D `fillRect`, `fill`, `setLineDash`, `beginPath`, `moveTo`, `lineTo` …; math via `Math.cos`, `Math.min`, `Math.max`, `Math.round`; returns readouts `mode`, `cell` to the info panel.
Principles
Progress = clap (trigger line - top of block) / (High blocks) · 0.6), 0, 1) gsap.from(card, { x: 120, opacity: 0, scrollTrigger: { trigger: section, start: "top 80%", scrub: true } }) ScrollTrigger scroll triggers: let animation follow the page scroll. When the top of each block touches the trigger line (fiction line), the card starts to slide and fade from the right, the more progress rolls (scrub mode), and the more it rolls back, the more it moves backwards. The page will automatically roll up and down, and when you put the pointer in the picture, the top and bottom position of the pointer is the rolling position. The right side is the scroll bar, the top line is the scroll progress of the entire page. There's no load here GSAP 库，而是用几十行代码复刻了它最核心的几个概念：补间（tween，从 A Smooth transition of value B Value, slow motion ease，Control the slow pace of transition, the time axis timeline，Sort multi-part patches in order) and staggered ( stagger，让一组元素依次出发）。每一帧都直接根据「当前时间」算出画面，所以拖动右侧滑条会立即看到变化。公式区给出了对应的 GSAP In writing, you can move directly to the real project.