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README.md

Perfect Arrows

A set of functions for drawing perfect arrows between points and shapes.

Example

👉 Demo

Edit example

  • getArrow - For point-to-point arrows.
  • getBoxToBoxArrow - For rectangle-to-rectangle arrows.

Installation

npm i perfect-arrows

or

yarn add perfect-arrows

Usage

The functions in this library provide only the information needed to draw an arrow. You'll need to draw the arrow yourself using your technology of choice. See below for an example React component with SVG.

getArrow(x0, y0, x1, y1, options)

The getArrow function accepts the position of two points and returns an array containing information for:

  • three points: a start, end, and control point
  • three angles: an end, start, and center

You can use this information to draw an arc and arrow-heads. You can use the options object to tweak the return values.

const arrow = getArrow(0, 0, 100, 200, {
  bow: 0,
  stretch: 0.5,
  stretchMin: 0,
  stretchMax: 420,
  padStart: 0,
  padEnd: 0,
  flip: false,
  straights: true,
})

const [sx, sy, cx, cy, ex, ey, ae, as, sc] = arrow

Arguments

Argument Type Description
x0 number The x position of the starting point.
y0 number The y position of the starting point.
x1 number The x position of the ending point.
y1 number The y position of the ending point.
options object An (optional) object containing one or more of the options described below.

Options

Option Type Default Description
bow number 0 A value representing the natural bow of the arrow. At 0, all lines will be straight.
stretch number .5 The effect that the arrow's length will have, relative to its minStretch and maxStretch, on the bow of the arrow. At 0, the stretch will have no effect.
minStretch number 0 The length of the arrow where the line should be most stretched. Shorter distances than this will have no additional effect on the bow of the arrow.
maxStretch number 420 The length of the arrow at which the stretch should have no effect.
padStart number 0 How far the arrow's starting point should be from the provided start point.
padEnd number 0 How far the arrow's ending point should be from the provided end point.
flip boolean false Whether to reflect the arrow's bow angle.
straights boolean true Whether to use straight lines at 45 degree angles.

Returns

Argument Type Description
x0 number The x position of the (padded) starting point.
y0 number The y position of the (padded) starting point.
x1 number The x position of the (padded) ending point.
y1 number The y position of the (padded) ending point.
ae number The angle (in radians) for an ending arrowhead.
as number The angle (in radians) for a starting arrowhead.
ac number The angle (in radians) for a center arrowhead.

Example: A React Arrow Component

import * as React from "react"
import { getArrow } from "perfect-arrows"

export function PerfectArrow() {
  const p1 = { x: 64, y: 64 }
  const p2 = { x: 128, y: 96 }

  const arrow = getArrow(p1.x, p1.y, p2.x, p2.y, {
    padEnd: 20,
  })

  const [sx, sy, cx, cy, ex, ey, ae, as, ec] = arrow

  const endAngleAsDegrees = ae * (180 / Math.PI)

  return (
    <svg
      viewBox="0 0 720 480"
      style={{ width: 720, height: 480 }}
      stroke="#000"
      fill="#000"
      strokeWidth={3}
    >
      <circle cx={sx} cy={sy} r={4} />
      <path d={`M${sx},${sy} Q${cx},${cy} ${ex},${ey}`} fill="none" />
      <polygon
        points="0,-6 12,0, 0,6"
        transform={`translate(${ex},${ey}) rotate(${endAngleAsDegrees})`}
      />
    </svg>
  )
}

getBoxToBoxArrow(x0, y0, w0, h0, x1, y1, w1, h1, options)

The getBoxToBoxArrow function accepts the position and dimensions of two boxes (or rectangles) and returns an array containing information for:

  • three points: a start, end, and control point
  • three angles: an end, start, and center

You can use this information to draw an arc and arrow-heads. You can use the options object to tweak the return values.

Note: The options and values returned by getBoxToBoxArrow are in the same format as the options and values for getArrow.

const arrow = getBoxToBoxArrow(0, 0, 96, 128, 400, 200, 128, 96, {
  bow: 0,
  stretch: 0.5,
  stretchMin: 0,
  stretchMax: 420,
  padStart: 0,
  padEnd: 0,
  flip: false,
  straights: true,
})

const [sx, sy, cx, cy, ex, ey, ae, as, sc] = arrow

Arguments

Argument Type Description
x0 number The x position of the first rectangle.
y0 number The y position of the first rectangle.
w0 number The width of the first rectangle.
h0 number The height of the first rectangle.
x1 number The x position of the second rectangle.
y1 number The y position of the second rectangle.
w1 number The width of the second rectangle.
h1 number The height of the second rectangle.
options object An (optional) object containing one or more of the options described below.

Options

See options in getArrow above. (Both functions use the same options object.)

Returns

See returns in getArrow above. (Both functions return the same set of values.)

Example: A React Box-to-box Arrow Component

import * as React from "react"
import { getArrow } from "perfect-arrows"

export function PerfectArrow() {
  const p1 = { x: 64, y: 64, w: 64, h: 64 }
  const p2 = { x: 128, y: 96, w: 64, h: 64 }

  const arrow = getBoxToBoxArrow(
    p1.x,
    p1.y,
    p1.w,
    p1.h,
    p2.x,
    p2.y,
    p2.w,
    p2.h,
    {
      bow: 0.2,
      stretch: 0.5,
      stretchMin: 40,
      stretchMax: 420,
      padStart: 0,
      padEnd: 20,
      flip: false,
      straights: true,
    }
  )

  const [sx, sy, cx, cy, ex, ey, ae, as, ec] = arrow

  const endAngleAsDegrees = ae * (180 / Math.PI)

  return (
    <svg
      viewBox="0 0 1280 720"
      style={{ width: 1280, height: 720 }}
      stroke="#000"
      fill="#000"
      strokeWidth={3}
    >
      <circle cx={sx} cy={sy} r={4} />
      <path d={`M${sx},${sy} Q${cx},${cy} ${ex},${ey}`} fill="none" />
      <polygon
        points="0,-6 12,0, 0,6"
        transform={`translate(${ex},${ey}) rotate(${endAngleAsDegrees})`}
      />
    </svg>
  )
}

Author

@steveruizok

About

A minimal tool for drawing perfect arrows between points and shapes.

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