Clyune Component GalleryDouble-tap Zoom · How it works & code
Quickly tap twice on an image to smoothly zoom in centered at the tap location (like a phone photo viewer), then tap again to zoom back out.
Runtime logic
Visiting `/micro/dblzoom`, DemoHost lazy-loads `demos/kits/kit-micro.js` (registry `mod: 'kit-micro'`) and calls `mount(host, { variant: 'dblzoom' })`. mount resolves the variant to family `dblzoom`; `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. Pointer down/drag/move updates the interaction (drag handles, hover readouts); when untouched and auto-demo is on, the pointer follows a Lissajous path. 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; TAU — Constant 2π; fmt — Number formatting (fixed decimals); F — Formula block HTML; S.onDown — Pointer down; S.onUp — Pointer up; 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.save() — Saves the drawing state (transform, styles, clip); ctx.clip() — Turns the current path into the clipping region; ctx.translate() — Translates the coordinate system; ctx.scale() — Scales the coordinate system; ctx.createLinearGradient() — Creates a linear gradient; ctx.fillRect() — Fills a rectangle; ctx.beginPath() — Starts a new path; 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.lineTo() — Adds a straight line to a point
Source code
frontend/src/demos/kits/kit-micro.js: FAM.dblzoom (L460-L479)
Code walkthrough
L460-479: Calls the factory `mFam()` to produce the full definition (spec + doc + build) from the options below. L460-460: Title shown in the info and control panels: “Double-tap Zoom”. L460-460: Range/default of the count slider. L460-460: Extra demo-specific slider/toggle: Zoom Factor. L460-460: Range/default of the size slider. L460-460: Default main colour. L460-460: Animation period (s). L461-461: Help text of the count parameter. L461-461: Help text of the extra parameter. L461-461: Help text of the size parameter. L462-462: Preset buttons: name → parameter overrides (5). L463-463: Body of the “Notes” section. L464-464: Main formula of the “Formula” section. L464-464: Second formula line. L465-479: Per-frame draw function: draws with Canvas 2D `save`, `clip`, `translate`, `scale`, `createLinearGradient`, `fillRect` …; returns readouts `mode`, `cell` to the info panel.
Principles
Scale = 1 + (multiple - 1) · Spring (e) Translate (point) · scale · Translate (-point) Double-click magnify: Two quick clicks on the picture, and the picture is smoother and amplified (like a mobile phone album) with two clicks at its centre. The key is to scale the centre: move the point of origin of the coordinates to the double-click point and then move back, so that the double-click point remains the same before and after the zoom. There's no real use here DOM 控件：每个微交互都在画布上逐帧画出来。动画按固定周期自动循环播放，并用一个「演示指针」模拟用户的点击、按住或拖动；你在画布上点一下，动画就会从头重新播放一遍。右侧滑条改动后立刻生效，下方信息面板实时显示当前状态。