Clyune Component GalleryScroll Snap · How it works & code
Set scroll-snap-type: y mandatory on the scroll container, and scroll-sn…
Runtime logic
Visiting `/scroll-fx/snap`, DemoHost lazy-loads `demos/kits/kit-scroll.js` (registry `mod: 'kit-scroll'`) and calls `mount(host, { variant: 'snap' })`. mount resolves the variant to family `snap`; `withControls` builds the control panel (6 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; TAU — Constant 2π; fmt — Number formatting (fixed decimals); F — Formula block HTML; S.clear — Clears with the background colour (translucent = trails); S.isAutoDemo — Whether auto demo is on; S.onFrame — Registers a per-frame callback; its return value feeds the info panel; ctx.createLinearGradient() — Creates a linear gradient; ctx.fillRect() — Fills a rectangle; ctx.beginPath() — Starts a new path; ctx.arc() — Adds a circular arc (center, radius, start/end angle); ctx.fill() — Fills the current path; ctx.fillText() — Draws filled text; ctx.moveTo() — Moves the pen without drawing; ctx.arcTo() — Adds an arc using tangent lines; ctx.closePath() — Closes the current sub-path; ctx.stroke() — Strokes the current 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
Source code
frontend/src/demos/kits/kit-scroll.js: FAM.snap (L391-L404)
Code walkthrough
L391-404: Calls the factory `scFam()` to produce the full definition (spec + doc + build) from the options below. L391-391: Title shown in the info and control panels: “Scroll Snap”. L391-391: Range/default of the count slider. L391-391: Extra demo-specific slider/toggle: Snap Strength. L391-391: Range/default of the size slider. L391-391: Default main colour. L392-392: Help text of the count parameter. L392-392: Help text of the extra parameter. L392-392: Help text of the size parameter. L393-393: Preset buttons: name → parameter overrides (5). L394-394: Body of the “Notes” section. L395-395: Main formula of the “Formula” section. L395-395: Second formula line. L396-404: Per-frame draw function: draws with Canvas 2D `createLinearGradient`, `fillRect`, `beginPath`, `arc`, `fill`; math via `Math.floor`, `Math.min`, `Math.round`, `Math.abs`; returns readouts `mode`, `cell`, `pageH`, `sp` to the info panel.
Principles
F = progress · (n − 1)，r = f − ⌊f⌋ Stick to the back = ⌊f⌋ + r + Strength · (Easing³(r) − r) Inertial adsorption (scroll-snap): sets the scroll-snap-type: y paragraph, and each paragraph sets the scroll-snap-align: start, the browser automatically "snap" to the beginning of the most recent paragraph when the user stops rolling. The fraction of the original scroll position is flattened with a number of slows, sorbenting the strength to control the pressure, and the scroll is then moved to the next segment at a standstill. Image simulates a scrollable web page: scrollY 表示页面已经向上滚过了多少像素，这里它自动来回滚动（右侧细条就是滚动条）。元素在屏幕上的位置 = Page Location − scrollY；The degree to which the elements enter the vision is usually used scroll Event or event IntersectionObserver Let's figure this out 0~1 The progress is driven by animations such as transparency, offset, scaling, etc.