jsPDF context2d closePath() method adds extra segment

The current implementation of closePath in context2d.js very deliberately adds not just the beginning of the path but the next point as well, causing one path segment to be drawn twice:

    if (
      typeof this.path[i + 2] === "object" &&
      typeof this.path[i + 2].x === "number"
    ) {
      this.path.push(JSON.parse(JSON.stringify(this.path[i + 2])));
    }

This is quite noticeably wrong if one turns on line dashing, since the segment drawn twice is not aligned the same way with respect to dashes. I'm sure these lines of code were added for a reason, but it seems to work more correctly without them. So whatever problem was being addressed by this code probably should have been fixed some other way...

Apr 19 '21 16:04 andrewcmyers

You are right, this looks very fishy. I can't explain why it's there, but I agree with you that these lines are probably there for a reason. Unfortunately the lines are quite hard to track in the git history because of prettier commits and bad "merge" commits. Maybe we can find the respective commit in the commits before the merge of yWorks/jsPDF. Could you maybe dig into that? Although I'm quite sure we can remove these lines, I would be better to know for sure.

Apr 22 '21 08:04 HackbrettXXX

I'm probably not the right person to do that detective work. My random guess is that it has to do with drawing corners with appropriate mitering, though I would not expect the extra line segment to be necessary for that.

Apr 22 '21 14:04 andrewcmyers

The line seems to originate from this commit with the very expressive commit message "modify context2d" :D https://github.com/MrRio/jsPDF/commit/7d2695c75405e62a80bf63a1a933e1286d637b16

I would suggest, let's remove these lines and wait until someone complains ;)

Jul 16 '21 13:07 HackbrettXXX

I remember. That was pain to implement context2d better. Invested multiple hours to get it run as compliant to the html5 interface. Just be careful.