tldraw/components/canvas/brush.tsx

import { useSelector } from "state"
import styled from "styles"

export default function Brush() {
  const brush = useSelector(({ data }) => data.brush)

  if (!brush) return null

  return (
    <BrushRect
      x={brush.minX}
      y={brush.minY}
      width={brush.width}
      height={brush.height}
    />
  )
}

const BrushRect = styled("rect", {
  fill: "$brushFill",
  stroke: "$brushStroke",
  zStrokeWidth: 1,
})