widget.script_calc returns None when JavaScript is evidently present

[poffertje]

Description of the bug

I am using a script to automatically fill in a PDF form with widgets. In the form I am filling out, there are character counters next to each text input widget. The counters get updated automatically when I input the text using Adobe Acrobat, but this does not happen when I update the value of the text widget using PyMuPDF. Upon further inspection, I discovered that widget.script_calc returns None for the fields that clearly have a counter implemented.

How to reproduce the bug

Here is a sample code:

with fitz.open(form_path) as doc:
    for page in doc:
        for widget in page.widgets():
            if widget.field_name == "WbsoProjectomschrijving":
                widget.field_value = "hello world"
                print(f"{widget.field_name=}, {widget.field_value=}, {widget.script_calc=}")

            if widget.field_name == "tellerProjectomschrijving":
                print(f"{widget.field_name=}, {widget.field_value=}, {widget.script_calc=}")

            widget.update()

    doc.save(output_path)

programmatuur.pdf

PyMuPDF version

1.26.4

Operating system

Windows

Python version

3.11

[JorjMcKie]

The widget contains no JavaScript for cross-field calculations! This is how that widget is defined:

print(doc.xref_object(154))
<<
  /AA <<
    /K 138 0 R
  >>
  /AP <<
    /N 41 0 R
  >>
  /DA (/Helv 8 Tf 0 g)
  /F 4
  /FT /Tx
  /Ff 4096
  /MK <<
    /BC [ 0 0 0 ]
    /BG [ 1 1 1 ]
  >>
  /MaxLen 1500
  /P 1 0 R
  /Rect [ 71.2521 505.029 519.39 698.164 ]
  /Subtype /Widget
  /T (WbsoProjectomschrijving)
  /Type /Annot
>>

Cross-calculations are bound to the following prerequisites:

1. Presence of a Javascript stored in key /AA/C of the widget's object definition. Under key /AA, only a /K JavaScript is present.

2. Fields with a /AA/C JavaScript must in addition be defined in the PDF's central /AcroForm/CO dictionary to be eligible for cross-validations.

However, this PDF has no /AcroForm/CO:

So both necessary conditions for cross-field update are not met.

[JorjMcKie]

Actively executing JavaScripts (in your case script_stroke= /AA/K) is currently not supported.

[poffertje]

Thanks for the detailed answer! It is very interesting to learn how PDFs are structured
But since there is no JavaScript in this widget, how does the counter actually get updated?

[poffertje]

Oh, sorry, I now understand what you meant with your last answer, and I see this in the prior issues
Thanks again!