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Command Palette · How it works & code

Type keywords character by character, results list filters in real time, highlight items and move up/down, press Enter to execute.

Runtime logic

Visiting `/ui/command`, DemoHost lazy-loads `demos/kits/kit-ui.js` (registry `mod: 'kit-ui'`) and calls `mount(host, { variant: 'command' })`. mount resolves the variant to family `command`; `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); 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.fillRect() — Fills a rectangle; ctx.fill() — Fills the current path; ctx.stroke() — Strokes the current path; ctx.measureText() — Measures text width; 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.lineTo() — Adds a straight line to a point

Source code

frontend/src/demos/kits/kit-ui.js: FAM.command (L537-L551)

Code walkthrough

L537-551: Calls the factory `uiFam()` to produce the full definition (spec + doc + build) from the options below. L537-537: Title shown in the info and control panels: “Command Palette”. L537-537: Range/default of the size slider: Panel width. L537-537: Range/default of the count slider: Results count. L538-538: List of extra controls: Shortcut hints. L538-538: Preset buttons: name → parameter overrides (4). L539-539: Body of the “Notes” section. L539-539: Main formula of the “Formula” section. L539-539: Second formula line. L540-551: Per-frame draw function: draws with Canvas 2D `fillRect`, `fill`, `stroke`, `measureText`; math via `Math.floor`, `Math.min`; returns readouts `mode`, `cell` to the info panel.

Principles

Match = Name contains input Highlight = (t × Speed) mod Results count Command Panel (⌘K): Enter the word word by word, the result list is filtered in real time, the highlight item moves up and down, and back to the car for execution.

Open the interactive demo · GitHub