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)

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,
            ]