A PDF fillable textfield which flows with text on a page using Reportlab.

textfield.py

from reportlab.platypus import SimpleDocTemplate, Flowable, Paragraph
from reportlab.lib.styles import getSampleStyleSheet


style = getSampleStyleSheet()['BodyText']


class TextField(Flowable):
    def __init__(self, **options):
        Flowable.__init__(self)
        self.options = options
        # Use Reportlab's default size if not user provided
        self.width = options.get('width', 120)
        self.height = options.get('height', 36)

    def draw(self):
        self.canv.saveState()
        form = self.canv.acroForm
        form.textfieldRelative(**self.options)
        self.canv.restoreState()

        
class ChoiceField(Flowable):
    def __init__(self, **options):
        Flowable.__init__(self)
        options['relative'] = True
        self.options = options
        # Use Reportlab's default size if not user provided
        self.width = options.get('width', 120)
        self.height = options.get('height', 36)

    def draw(self):
        self.canv.saveState()
        form = self.canv.acroForm
        form.choice(**self.options)
        self.canv.restoreState()

        
doc = SimpleDocTemplate('textfield.pdf')
Story = [
    Paragraph('First Name', style=style), 
    TextField(name='first_name', value='John', tooltip='First name', height=18), 
    Paragraph('Last Name', style=style), 
    TextField(name='last_name', value='Doe', tooltip='Last name', height=18),
    Paragraph('Gender', style=style),
    ChoiceField(name='gender', tooltip='Gender', value='male', options=['', 'male', 'female'], height=18)
]
doc.build(Story)

I started by using this and this. This was also helpful in understanding how to use form fields, although it demonstrates absolute positioning them on the page (Reportlab's default behavior).

The resulting document (from the first version of this script) looks like this:

I encountered two bugs when adding the ChoiceField.

1. canvas.acroform.choiceRelative is a textfield, not a choice. Therefore, I had to use choice and manually set options['relative'] = True.

2. A choice always fails if a value it not provided. Passing in an empty value does not fix the issue, even if an empty value is included in options. Therefore, a default (non-empty) value must always be provided. Unfortunately, this is not always desired. Sometimes we want to start out with a blank form field.

   Whenever, value='' is passed in I get the following error:

      File "textfield.py", line 36, in draw
        form.choice(**self.options)
      File "C:\code\md2pdf\venv\lib\site-packages\reportlab\pdfbase\acroform.py", line 1008, in choice
        return self._textfield(
      File "C:\code\md2pdf\venv\lib\site-packages\reportlab\pdfbase\acroform.py", line 844, in _textfield
        **lbextras
    UnboundLocalError: local variable 'lbextras' referenced before assignment
   

Thanks, this has been very helpful!

Did you manage to make the resulting boxes editable? I get such boxes (as a checkbox), but they are not editable (tried Preview.app and Adobe Acrobat Reader DC):

BTW: In the way you are using it self.width and self.height is ignored. I created a text field (screenshot above of the generated PDF) for our purposes like this:

class TextFormField(Flowable):
    def __init__(self, tooltip, name, width=120, height=26):
        Flowable.__init__(self)
        self.tooltip = tooltip
        self.name = name
        self.width = width
        self.height = height

    def draw(self):
        self.canv.saveState()
        form = self.canv.acroForm
        form.textfieldRelative(
            name=self.name,
            tooltip=self.tooltip,
            width=self.width,
            height=self.height,
            borderStyle='inset',
            forceBorder=True
        )
        self.canv.restoreState()

I didn't try checkboxes, so I can't comment on that. I also noticed that width and height are not properly forwarded to textfieldRelative in the original example. My implementation is

class TextField(Flowable):
    def __init__(self, **options):
        Flowable.__init__(self)
        options["width"] = options.get("width", 135)
        options["height"] = options.get("height", 12)
        options["fontSize"] = options.get("fontSize", 10)
        self.options = options

    def draw(self):
        self.canv.saveState()
        form = self.canv.acroForm
        form.textfieldRelative(**self.options)
        self.canv.restoreState()

Okay, I figured out why this didn't work. It was actually a problem with the way we handle the pdf afterwards. We have a background PDF on which we put this form. We merge them with QPDF. QPDF confuses the fonts uses in the two pdf and creates a problem. It's okay, but not helpful that reportlab uses /F1 /F2 and so on for font names and doesn't let us change the prefix. We made a monkey-patch to change the prefix to ATF so fonts are /ATF1 /ATF2 and so on, this merges then correctly

Thank you all for the above! FYI, I found that you can control the x position of the form item in the frame by using an indenter flowable which indents otherflowables after it's used. You add the indenter to the story before your flowables you want to indent, then add a indenter at the end with a negative value to dedent.

from reportlab.platypus import Indenter
indent18 = Indenter(left = 18)
dedent18 = Indenter(left = -18)

self.story = [
            p2,
            indent18,
            p2,
            q1,
            p2,
            dedent18,
            ]