Clyune Component GalleryDrop-shadow Glow · How it works & code
Unlike box-shadow, drop-shadow generates shadows along the actual outline of the graphic, including transparent areas, so stars...
Runtime logic
Visiting `/filters/drop-shadow`, DemoHost lazy-loads `demos/kits/kit-filters.js` (registry `mod: 'kit-filters'`) and calls `mount(host, { variant: 'drop-shadow' })`. mount resolves the variant to family `drop-shadow`; `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; TAU — Constant 2π; 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.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.save() — Saves the drawing state (transform, styles, clip); ctx.restore() — Restores the saved drawing state; 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.rect() — Adds a rectangle to the path; ctx.clip() — Turns the current path into the clipping region; ctx.translate() — Translates the coordinate system; ctx.lineTo() — Adds a straight line to a point
Source code
frontend/src/demos/kits/kit-filters.js: FAM.drop-shadow (L259-L272)
Code walkthrough
L259-272: Calls the factory `fFam()` to produce the full definition (spec + doc + build) from the options below. L259-259: Title shown in the info and control panels: “Drop-shadow Glow”. L259-259: Range/default of the count slider. L259-259: Extra demo-specific slider/toggle: Shadow blur. L259-259: Range/default of the size slider. L259-259: Default main colour. L259-259: Hide sample photo. L260-260: Help text of the count parameter. L260-260: Help text of the extra parameter. L260-260: Help text of the size parameter. L261-261: Preset buttons: name → parameter overrides (5). L262-262: Body of the “Notes” section. L263-263: Main formula of the “Formula” section. L263-263: Second formula line. L264-272: Per-frame draw function: draws with Canvas 2D `fillRect`, `beginPath`, `arc`, `fill`, `save`, `restore`; math via `Math.sin`, `Math.hypot`, `Math.round`; returns readouts `mode`, `cell` to the info panel.
Principles
Shadow Offset = (chart center - light source) · 0.12 (maximum 40px) Filter: drop-shadow (dx dy blur colour) Projection drop- 44, Love also has the shadow of a shape. The direction of the shadow is determined by the light source: the light source here is your pointer, and the shadow always falls on the side of the graphic back to pointer, and the longer the shadow is.