Clyune Component GalleryFlowing Dashes · How it works & code
stroke-dashoffset cycling
Runtime logic
Visiting `/svg/dash`, DemoHost lazy-loads `demos/kits/kit-svg.js` (registry `mod: 'kit-svg'`) and calls `mount(host, { variant: 'dash' })`. mount resolves the variant to family `dash`; `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; 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.stroke() — Strokes 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.arcTo() — Adds an arc using tangent lines; ctx.closePath() — Closes the current sub-path; ctx.fill() — Fills the current path; ctx.fillRect() — Fills a rectangle; 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-svg.js: FAM.dash (L322-L337)
Code walkthrough
L322-337: Calls the factory `sFam()` to produce the full definition (spec + doc + build) from the options below. L322-322: Title shown in the info and control panels: “Flowing Dashes”. L322-322: Range/default of the count slider. L322-322: Extra demo-specific slider/toggle: Gap ratio. L322-322: Range/default of the size slider. L322-322: Default main colour. L323-323: Help text of the count parameter. L323-323: Help text of the extra parameter. L323-323: Help text of the size parameter. L324-324: Preset buttons: name → parameter overrides (5). L325-325: Body of the “Notes” section. L326-326: Main formula of the “Formula” section. L326-326: Second formula line. L327-337: Per-frame draw function: draws with Canvas 2D `stroke`, `setLineDash`; math via `Math.round`; returns readouts `mode`, `cell` to the info panel.
Principles
a = (L / n) · (1 - gap), b = (L Reduction) / n) · Gap dashoffset = ±1.2 · t · L/n Fault-line flow: troke-dasharay= "a b" and press a long line, b Long blanks' repeat. As long as the stoke-dashoffset increases over time, the dotted pattern flows along the path and is often used to indicate data Stream, Loading and selecting boxes (antline 35. The middle path moves backwards. SVG It's "The Vector Chart in Text":<path d="M… L… C… A…"> 里 M Means moving to a point, L Draw straight lines, C Draw three Bézier curves, A Draw round a Elimination Translate. Here Canvas 的 Path2D Parsing the same path, then pressing time t 改变描边、形状、颜色等属性，效果与网页里的 SVG Animated same.