tldraw/components/canvas/hovered-shape.tsx

import { memo } from 'react'
import tld from 'utils/tld'
import { getShapeUtils } from 'state/shape-utils'
import vec from 'utils/vec'
import styled from 'styles'
import { useSelector } from 'state'
import { getShapeStyle } from 'state/shape-styles'

function HoveredShape({ id }: { id: string }) {
  const transform = useSelector((s) => {
    const shape = tld.getShape(s.data, id)
    const center = getShapeUtils(shape).getCenter(shape)
    const rotation = shape.rotation * (180 / Math.PI)
    const parentPoint = tld.getShape(s.data, shape.parentId)?.point || [0, 0]

    return `
      translate(${vec.neg(parentPoint)})
      rotate(${rotation}, ${center})
      translate(${shape.point})
  `
  })

  const strokeWidth = useSelector((s) => {
    const shape = tld.getShape(s.data, id)
    const style = getShapeStyle(shape.style, s.data.settings.isDarkMode)
    return +style.strokeWidth
  })

  return (
    <StyledHoverShape
      href={'#' + id}
      transform={transform}
      strokeWidth={strokeWidth + 8}
    />
  )
}

const StyledHoverShape = styled('use', {
  stroke: '$selected',
  opacity: 0.1,
})

export default memo(HoveredShape)