Unable to Change Font Size in Toga Label

Describe the bug I’m building my first proper BeeWare app. My problem is fairly straightforward, but no less infuriating. I can’t seem to increase the font size within any given Label widget. This is what my app.py file looks like:

To Reproduce As per the tutorial, build a basic BeeWare app, and then amend app.py as follows:

import toga
from toga.fonts import Font, SANS_SERIF
from toga.style import Pack
from toga.style.pack import COLUMN, ROW

class Charon(toga.App):
    def startup(self):
        main_box = toga.Box(style=Pack(direction=COLUMN))

        title_label = toga.Label("Hello, world!")
        title_label.font = Font(family=SANS_SERIF, size=50)

        main_box.add(title_label)

        self.main_window = toga.MainWindow(title=self.formal_name)
        self.main_window.content = main_box
        self.main_window.show()

def main():
    result = Charon()
    return result

Then run the app using briefcase dev. (Running the app using briefcase run, or using briefcase run android - the app is intended for Android - seems to reproduce the same error.)

Expected behavior I expected setting title_label.font = Font(family=SANS_SERIF, size=50) would increase the size of the “Hello, world!” label. However, no matter what I do with the snippet size=50 - whether I set the font size to 5 or 500 - the size of the text remains unchanged. If I run the same code within an Android emulator, I run into the same issue: the font size doesn’t change.

Environment:

• Operating System: Linux (Ubuntu 20.04.1 LTS)
• Python version: 3.8.5
• Software versions:
  • Briefcase: 0.3.4
  • Toga: 0.3.0

Additional context I’ve also raised this issue as a StackOverflow question.

[tomhosker]

I’ve also tried this:

title_style = Pack(direction=ROW, font_size=50, padding=50)
title_label = toga.Label("Hello, world!", style=title_style)

The padding=50 works as intended, but font_size=50 still does nothing. No exceptions are raised.

[tomhosker]

@Vipul-Cariappa Okay, I seem to have found a functional stop-gap method for fixing this bug, namely replacing my beeware-env/lib/python3.8/site-packages/toga_gtk/widgets folder with your toga_gtk/widgets folder. It would be awesome if your fix could get incorporated into the master branch. It works!