Clyune Component GalleryKaraoke Subtitles · How it works & code
Current line highlights like a progress bar moving from left to right, glowing and shining as it passes; once a line is finished, it moves to the next line, up and down...
Runtime logic
Visiting `/text-fx/karaoke`, DemoHost lazy-loads `demos/kits/kit-text.js` (registry `mod: 'kit-text'`) and calls `mount(host, { variant: 'karaoke' })`. mount resolves the variant to family `karaoke`; `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°); TAU — Constant 2π; fmt — Number formatting (fixed decimals); F — Formula block HTML; getLang — Current UI language (zh/en); S.clear — Clears with the background colour (translucent = trails); S.onFrame — Registers a per-frame callback; its return value feeds the info panel; ctx.measureText() — Measures text width; ctx.fillText() — Draws filled text; ctx.save() — Saves the drawing state (transform, styles, clip); ctx.beginPath() — Starts a new path; ctx.rect() — Adds a rectangle to the path; ctx.clip() — Turns the current path into the clipping region; ctx.restore() — Restores the saved drawing state; ctx.arc() — Adds a circular arc (center, radius, start/end angle); ctx.fill() — Fills the current 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-text.js: FAM.karaoke (L327-L337)
Code walkthrough
L327-337: Calls the factory `tFam()` to produce the full definition (spec + doc + build) from the options below. L327-327: Title shown in the info and control panels: “Karaoke Subtitles”. L327-327: Range/default of the count slider. L327-327: Extra demo-specific slider/toggle: Glow Halo. L327-327: Range/default of the size slider: FontSize. L327-327: Default main colour. L327-327: Help text of the count parameter. L327-327: Preset buttons: name → parameter overrides (5). L328-328: Body of the “Notes” section. L328-328: Main formula of the “Formula” section. L328-328: Second formula line. L329-337: Per-frame draw function: draws with Canvas 2D `measureText`, `fillText`, `save`, `beginPath`, `rect`, `clip` …; math via `Math.floor`, `Math.abs`, `Math.round`; returns readouts `mode`, `cell` to the info panel.
Principles
Conductivity = line width · fract(t / 3) Current Line = ⌊t / 3-mod lines Cara OK Subtitles: The line that you're singing, the color goes from "brush" to "brush" from the left to the right, and the brushes turn to bright and light; the line is replaced by the next line, and the top and bottom lines become smaller. 文字被拆成一个个字（字形），每个字的位置、颜色、透明度都由「字的序号 i + Time t」Count it out so you can make animated verbatim.