Perfect Arrows

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

👉 Demo

• 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 { getBoxToBoxArrow } 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