Zero-division error

[Andlet95]

There is a chance for a zero-division error in weasyprint/layout/table.py this line

A few lines prior, it checks for equality between the lists, but it doesn't account for upper_guess - lower_guess becoming a list that sums to zero

e.g.:

upper_guess: [126.9765625, 492.49902874615935, 330.0644425076814, 492.49902874615935]
lower_guess: [126.9765625, 507.35531887654616, 300.3518622469078, 507.35531887654616]
added_widths: [0.0, -14.85629013038681, 29.71258026077362, -14.85629013038681]

This is my printout, which In this instance, sum(added_widths becomes zero, and we have a zero-division.

I did some testing, and changed this line from if assignable_width <= sum(max_content_guess): to if assignable_width < sum(max_content_guess): which helped in my case. I have a feeling that's not safeguarding the zero-division though, but only sidestepping the issue for my use-case.

I tested this both with python-weasyprint-62.3-2 using the installation on my laptop and weasyprint-63 using a virtual env

I can't share the html file I'm trying to convert, but if there's a way I can figure out what lines is causing this, I can see if there's sensitive information and possibly share that part.

[liZe]

Thanks for the report. We already discussed about it in #2276 and got a document to reproduce, but we didn’t take the time yet to fix it and add a non-regression test.

[liZe]

Here’s a sample to reproduce:

<table style="font-family: DejaVu Serif">
  <thead>
    <tr>
      <th colspan="2">aaaaaaaaaaaaaaaaaa</th>
    </tr>
    <tr>
      <th style="width:80px"></th>
      <th style="width:80px">rrrrr</th>
    </tr>
  </thead>
</table>

[liZe]

I did some testing, and changed this line from if assignable_width <= sum(max_content_guess): to if assignable_width < sum(max_content_guess): which helped in my case.

I think that this change makes sense: if the assignable width equals to the max-content guess, and the added widths can be 0. In this case, we can use the max-content guess values, as done in the else part.