Tldraw/utils/dashes.ts

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1.1 KiB
TypeScript

/**
* Get balanced dash-strokearray and dash-strokeoffset properties for a path of a given length.
* @param length The length of the path.
* @param strokeWidth The shape's stroke-width property.
* @param style The stroke's style: "dashed" or "dotted" (default "dashed").
* @param snap An interval for dashes (e.g. 4 will produce arrays with 4, 8, 16, etc dashes).
*/
export function getPerfectDashProps(
length: number,
strokeWidth: number,
style: 'dashed' | 'dotted' = 'dashed',
snap = 1
): {
strokeDasharray: string
strokeDashoffset: string
} {
let dashLength: number
let strokeDashoffset: string
let ratio: number
if (style === 'dashed') {
dashLength = strokeWidth * 2
ratio = 1
strokeDashoffset = (dashLength / 2).toString()
} else {
dashLength = strokeWidth / 100
ratio = 100
strokeDashoffset = '0'
}
let dashes = Math.floor(length / dashLength / (2 * ratio))
dashes -= dashes % snap
if (dashes === 0) dashes = 1
const gapLength = (length - dashes * dashLength) / dashes
return {
strokeDasharray: [dashLength, gapLength].join(' '),
strokeDashoffset,
}
}