Clyune Component GalleryKen Burns · How it works & code
Image smooth zoom and pan.
Runtime logic
Visiting `/css-fx/kenburns`, DemoHost lazy-loads `demos/kits/kit-css.js` (registry `mod: 'kit-css'`) and calls `mount(host, { variant: 'kenburns' })`. mount resolves the variant to family `kenburns`; `withControls` builds the control panel (4 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.onFrame — Registers a per-frame callback; its return value feeds the info panel; ctx.save() — Saves the drawing state (transform, styles, clip); ctx.translate() — Translates the coordinate system; ctx.scale() — Scales the coordinate system; 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.restore() — Restores the saved drawing state; 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
Source code
frontend/src/demos/kits/kit-css.js: FAM.kenburns (L927-L954)
Code walkthrough
L928-931: Control definitions (colour/speed/size/count/extras): Primary Color, Zoom Level, Path. L932-932: Preset buttons: name → parameter overrides (4). L933-933: Info-panel content: live rows(v), formula, notes, params, steps. L934-953: Init function: sets up state and returns the per-frame callback: draws with Canvas 2D `save`, `translate`, `scale`, `createLinearGradient`, `fillRect`, `beginPath` …; math via `Math.round`, `Math.sin`, `Math.cos`; returns readouts `mode`, `ph`, `cell`, `colorHex` to the info panel.
Principles
progress = fract(t × speed) Ken Burns: Slow scaling+Flattening, often for slide documentaries.