Clyune Component GalleryTop Banner · How it works & code
Top-page notification bar that slides down from the top; long text can scroll horizontally with a close button on the right.
Runtime logic
Visiting `/ui/banner`, DemoHost lazy-loads `demos/kits/kit-ui.js` (registry `mod: 'kit-ui'`) and calls `mount(host, { variant: 'banner' })`. mount resolves the variant to family `banner`; `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; F — Formula block HTML; getLang — Current UI language (zh/en); tx — Runtime zh→en translation; 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.fill() — Fills the current path; ctx.save() — Saves the drawing state (transform, styles, clip); ctx.clip() — Turns the current path into the clipping region; ctx.measureText() — Measures text width; ctx.restore() — Restores the saved drawing state; ctx.fillText() — Draws filled text; ctx.beginPath() — Starts a new path; 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.fillRect() — Fills a rectangle
Source code
frontend/src/demos/kits/kit-ui.js: FAM.banner (L613-L628)
Code walkthrough
L613-628: Calls the factory `uiFam()` to produce the full definition (spec + doc + build) from the options below. L613-613: Title shown in the info and control panels: “Banner”. L613-613: Range/default of the size slider: Banner Height. L613-613: Range/default of the count slider: Banner Count. L614-614: List of extra controls: Scrolling Text. L614-614: Preset buttons: name → parameter overrides (4). L615-615: Body of the “Notes” section. L615-615: Main formula of the “Formula” section. L615-615: Second formula line. L616-628: Per-frame draw function: draws with Canvas 2D `fill`, `save`, `clip`, `measureText`, `restore`; math via `Math.min`; returns readouts `mode`, `cell` to the info panel.
Principles
Scroll x = −fract(t×Speed)×Text width Enter the venue translateY(−100%→0) Announced banners: hints at the top of the page slide from above; long text can scroll horizontally, with a closed button on the right.