Fix lines with one point

This PR fixes a bug where lines with only one point were causing arrays with NaN values.

https://github.com/steveruizok/perfect-freehand/issues/19

If the library detects a line with only one point, it pushes a second point onto the line with a tiny offset. The bug here was that we were failing to update a variable named len that stores the length of the input points, and which was used to iterate over the points.

  let len = pts.length

  if (len === 1) pts.push(vec.add(pts[0], [1, 0]))

  const strokePoints: StrokePoint[] = [{ ... }]

  for (
    let i = 1, j = 0, curr = pts[i], prev = strokePoints[j];
    i < len; // <---------------------- Would still be 1, but it should be 2!
    i++, curr = pts[i], prev = strokePoints[j]
  ) {
    const point = vec.lrp(prev.point, curr, 1 - streamline)

This is now fixed.

Note

Even though the library won't produce a bad line here, you may want to treat lines with only one point differently. For example, in tldraw.com, I don't render lines with only one point; and if the lines have a length of two, then I render a circle instead of a stroke path. Short lines are this lib's white whale, very hard to get right. 🐋

steveruizok / perfect-freehand

Fix lines with one point #22

Note