Clyune Component GalleryStreamgraph · How it works & code
Stacked area chart with time scrolling, comparing three baseline modes.
Runtime logic
Visiting `/dataviz/stream`, DemoHost lazy-loads `demos/kits/kit-dataviz.js` (registry `mod: 'kit-dataviz'`) and calls `mount(host, { variant: 'stream' })`. mount resolves the variant to family `stream`; `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; rng — Seeded deterministic PRNG (same seed, same result); 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.get — Reads current control values; S.onFrame — Registers a per-frame callback; its return value feeds the info panel; ctx.beginPath() — Starts a new path; ctx.lineTo() — Adds a straight line to a point; ctx.moveTo() — Moves the pen without drawing; ctx.closePath() — Closes the current sub-path; ctx.fill() — Fills the current path; ctx.stroke() — Strokes the current path; ctx.arcTo() — Adds an arc using tangent lines; ctx.fillText() — Draws filled text; ctx.measureText() — Measures text width
Source code
frontend/src/demos/kits/kit-dataviz.js: FAM.stream (L467-L506)
Code walkthrough
L468-468: Control definitions (colour/speed/size/count/extras): Starting hue, Volatility magnitude, Number of layers, Baseline mode, Time window (number of points), Monochrome. L469-469: Preset buttons: name → parameter overrides (6). L470-478: Info-panel content: live rows(v), formula, notes, params, steps. L479-505: Init function: sets up state and returns the per-frame callback: draws with Canvas 2D `beginPath`, `lineTo`, `moveTo`, `closePath`, `fill`, `stroke`; math via `Math.round`, `Math.sin`, `Math.max`, `Math.min`, `Math.ceil`, `Math.floor`; returns readouts `n`, `win`, `bm`, `tx`, `layer`, `lv`, `tot` … to the info panel.
Principles
Stack: No i Lower Layer yᵢ = g₀ + Σ_{j Symmetric baseline g₀ = −½ Σ fⱼ Weighted center g₀ = −Σ (n − i + ½)·fᵢ / n Streamgraph （Streamgraph）是堆叠面积图的变体：每一层是一个类别（比如音乐流派的播放量），横轴是时间，每层的 Thickness That's what it was at the time, and the total thickness of all layers combined to be total. Different Baseline Decision as a whole"River"摆在哪里：零基线从底部往上堆（最容易读总量）；对称基线让河流沿中线左右对称；加权居中让每一层的上下摆动尽量小，看起来最平滑。 Time is scrolling constantly to the left; the pointer is placed at a time, on a layer, showing its value and proportion on the right.