Error when trying to create a dotted line

[florian-escola]

Bug Report

Description of the problem

I get an Error: dash([0,2], {}) invalid, lengths must be numeric and greater than zero Error when tying to create a dotted line unsing .lineCap('round').dash(0, { space: 2 }).

From some research I found this was introduced because of #949 in #969. This bit of the PDF spec was mentioned there:

The dash array’s elements are numbers that specify the lengths of alternating dashes and gaps; the numbers must be nonnegative and not all zero.

The way I interpret that is that the length and the space can't both be zero.

So [0 2] 0 d would be valid whereas [0] 0 d or [0 0] 0 d would be invalid.

As far as I understand it, this is the only way to create a dotted line.

Workaround

Do it manually:

doc
    .moveTo(0, 10)
    .lineTo(100, 10)
    .lineCap('round')
    .addContent('[0 2] 0 d')
    .stroke();

Code sample

const PDFDocument = require('pdfkit');
const fs = require('fs');

const doc = new PDFDocument;

doc.pipe(fs.createWriteStream('output.pdf'));

doc
    .moveTo(0, 10)
    .lineTo(100, 10)
    .lineCap('round')
    .dash(0, { space: 2 })
    .stroke();

doc.end();

Your environment

• pdfkit version: 0.10.0
• Node version: 12.13.1
• Browser version (if applicable):
• Operating System: Ubuntu

[blikblum]

@floyd-may , can you take a look at it?

[PascalPixel]

Downgrading to 0.9.1 will fix this, which is before they added this error.
The error notes it was added because some viewers can't view dash with values of 0, so I guess I'm exposing to risk, but I truly need a 0 in there. 🤷🏻‍♂️

[blikblum]

@PascalPixel do mind creating a PR with an unit test (basically the code from OP)?

[floyd-may]

@blikblum sorry I didn't see this earlier! I switched jobs and my subscription to this repo was pointed at my work email address =(

I agree that this appears to be over-zealous validation. I was able to use this code to produce a dotted line that renders correctly in MS Edge:

doc
    .moveTo(0, 10)
    .lineTo(100, 10)
    .lineCap('round')
    .addContent('[0 2] 0 d')
    .stroke();

I don't know that I have the bandwidth to make a PR for at least a week, but if this is still unaddressed by that time, please ping me here and I'll try to carve out a couple hours.

[PascalPixel]

Google Chrome renders without issues as well 🎉

Referring to your PR @floyd-may #969, do you remember which renderers specifically had an issue?

[floyd-may]

@PascalPixel it was MS Edge and Adobe Reader that had issues.

[PascalPixel]

Ok Adobe Reader is pretty important 😅