Pushbutton widget appears as check box

[qwkfinger]

Describe the bug (mandatory)

After creating a pushbutton widget, it shows as a checkbox in the final pdf file.

To Reproduce (mandatory)

import fitz

doc = fitz.open()
doc.new_page(0)
page = doc[0]

widget = fitz.Widget()
widget.field_type = fitz.PDF_WIDGET_TYPE_BUTTON
widget.field_flags = fitz.PDF_BTN_FIELD_IS_PUSHBUTTON
widget.rect = fitz.Rect(5, 5, 20, 20)
widget.field_name = "Test"
widget.field_value = "Test button"
widget.fill_color = (0, 0, 1)
annot = page.add_widget(widget)
for w in page.widgets():
    print(w) # prints 'CheckBox' widget on page 0 of <new PDF, doc# 1>
doc.save("button_test.pdf")

Expected behavior (optional)

The widget should show as a button. This worked in older versions (tested with version 1.16.18) and shows the same result in 1.18.4.

Your configuration (mandatory)

• 3.11.0 | packaged by conda-forge | (main, Oct 25 2022, 06:12:32) [MSC v.1929 64 bit (AMD64)]
  win32
• PyMuPDF 1.21.1: Python bindings for the MuPDF 1.21.1 library.
• Version date: 2022-12-13 00:00:01.
• Built for Python 3.11 on win32 (64-bit).
• Windows 10 64bit
• mambaforge
• python 3.7, 3.8, 3.10, 3.11 (all tested, same result)
• pymupdf 1.21.1, installed with wheel and pip

Additional context (optional)

If this is truly a bug, maybe sombeody knows a workaround.

[JorjMcKie]

It is a bug, and it will be fixed in the next version.
Some background:
PDF only knows field type /Btn in the field dictionary object. Differentiation between subtypes like radio button and checkbox only occur via setting different bit positions of the field flags key /Ff. See here:

The bug happens by incorrectly setting the respective bit.
As a workaround try the following:

1. create the button
2. the determine ths xref of the new field
3. "manually" force the field flags to assume the right value:

doc.xref_set_key(field.xref, "Ff", "32768")  # represents value 1 << 15 (radio button)

[qwkfinger]

Thank you,

the workaround changes the widget to a radiobutton, however, the following creates a button:

doc.xref_set_key(annot.xref, "Ff", "65536")

But the button has no caption.

[JorjMcKie]

Thank you,

the workaround changes the widget to a radiobutton, however, the following creates a button:

doc.xref_set_key(annot.xref, "Ff", "65536")

But the button has no caption.

The workaround for a pushbutton would need additional lowlevel code:

caption = fitz.get_pdf_str("push me")
doc.xref_set_key(xref, "MK/CA", caption)