Error in html table rendering when html tags are used inside a cell

[stenci]

The following code should create a table with 3 rows and 3 columns, instead the 2nd row contains 5 columns.

The two font tags are correctly interpreted and they have the expected effect on the font, but they also seem to be interpreted as td.

Example code

from fpdf import FPDF

pdf = FPDF()
pdf.add_page()
pdf.write_html("""
<table border=1>
  <thead>
    <tr>
      <th>Column 1</th>
      <th>Column 2</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td align="center">Cell 1</td>
      <td align="center">Cell 2</td>
    </tr>
    <tr>
      <td align="center">Cell 1</td>
      <td align="center">Some <font size=7>small</font> and some <font size=20>large</font></td>
    </tr>
    <tr>
      <td align="center">Cell 1</td>
      <td align="center">Cell 2</td>
    </tr>
  </tbody>
</table>
""")
pdf.output("html.pdf")

Example output

Environment

• Operating System: Windows
• Python version: 3.7
• fpdf2 version used: 2.7.4

[Lucas-C]

Hi @stenci and thank you for the precise bug report 👍

<font> tags are currently not supported inside <td> elements.

FYI, when using the latest version of fpdf2 from the git master branch (cf. https://pyfpdf.github.io/fpdf2/#installation ),
you would get the following error from the fpdf/table.py module:

fpdf.errors.FPDFException: Inconsistent column count detected on row 3: it has 5 columns, whereas the top row has 2.

We could improve that error message, by generating a more explicit one in the html.py module in that case.

Adding support for <font> tags in <td> elements would be a lot more difficult,
as it would mean supporting table sub-cells.

For reference, this issue is related to issue #640: both reveal fundamental limitations of fpdf2 HTML renderer,
that does not support rendering of nested elements, whereas the HTML spec totally allows them.

We should probably add a mention about this fundamental limitation in our documention
( PRs are welcome to add a mention about this on https://pyfpdf.github.io/fpdf2/HTML.html )

[Lucas-C]

I opened PR #852 in order to improve our documentation and generate a clearer error message

Would you like to review it @stenci? 😊

[stenci]

I opened PR #852 in order to improve our documentation and generate a clearer error message

Would you like to review it @stenci? 😊

I am not familiar with github. I clicked on the PR link on your message, I noticed a "review changes" button, clicked on it and approved.
The changes seem to fully address the problem, and some more.
Thank you for addressing this, and doing it so quickly.

[Lucas-C]

Thank you for your feedback @stenci 🙂

I merged the PR