pdf.set_display_mode(zoom=...) not working

[macdeport]

I discovered fpdf2 and tried it out. Thanks for this interesting library.

Describe the bug

Error details
I couldn't make

pdf.set_display_mode(zoom=25)

works to produce a PDF that opens at a scale of 25%...

Minimal code
Please include some minimal Python code reproducing your issue:

from fpdf import FPDF
pdf = FPDF()
pdf.add_page()
pdf.set_display_mode(zoom=50)
pdf.output('test_zoom.pdf')

If you don't know how to build a minimal reproducible example, please check this tutorial: https://stackoverflow.com/help/minimal-reproducible-example

Environment
Please provide the following information:

• Operating System: Mac OSX
• Python version: Python 3.9.18
• fpdf2 version used: 2.7.5

Proposed fix
If I'm not mistaken...

In output.py > _finalize_catalog() after :

 # zoom_mode is a number, not one of the allowed strings:
 zoom_config = ["/XYZ", "null", "null", str(fpdf.zoom_mode / 100)]

add :

    zoom_config = [
        pdf_ref(first_page_obj.id),
        *zoom_config]

[andersonhc]

Thank you @macdeport for reporting this bug.

I was able to reproduce it and your proposed fix seems to solve the problem. Do you want to submit a PR fixing the bug?

We have documented our development guidelines if you want to take a look.

[Lucas-C]

Thank you for reporting this @macdeport

We already have some unit tests regarding the zoom:
https://github.com/py-pdf/fpdf2/blob/master/test/metadata/test_display_mode.py
But it seems that we did not test setting a numeric value.

An extra test could be added regarding this case.
If you do not wish to submit a PR, one of the current maintainers can do it,
but we often like to ask fpdf2 users if they want to use this opportunity to contribute to the project 🙂

[macdeport]

@Lucas-C @andersonhc I would have been happy to contribute more, and it could have been instructive for me, but I'm too busy at the moment... thank you for what you do and for your offer.

[andersonhc]

@Lucas-C @andersonhc I would have been happy to contribute more, and it could have been instructive for me, but I'm too busy at the moment... thank you for what you do and for your offer.

No worries. I just opened a PR to fix the bug and added an automated test on this feature to reduce the chances of it breaking again in the future.

Thanks again for taking the time to create the minimal code and investigate the fix.