How to resize automatically the text from a widget(button/label) when i resize the window in kivy with the mouse

Question

I am a beginner to py and kv and i try to figure out how to make the text inside a label or a button to resize automatically when i resize the black kivy window.

import kivy
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.label import Label
from kivy.app import App


class QuizzWindow(BoxLayout):

    def __init__(self, **kwargs):
        super(QuizzWindow, self).__init__(**kwargs)
        self.cols = 1
        self.add_widget(Label(text="quizz"))
        self.add_widget(Button(text="press"))


class MyApp(App):

    def build(self):
        return QuizzWindow()


if __name__ == "__main__":
    MyApp().run()

Thanks for your help !

Answer 1

The simplest way is to use the kv language where you can specify the font size as a function of the window size. Here is a modified version of your code that does it:

from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.app import App

kv = '''
<QuizzWindow>:
    Label:
        text: 'quizz'
        font_size: root.height/15
    Button:
        text: 'press'
        font_size: root.height/15
'''


class QuizzWindow(BoxLayout):
    pass


class MyApp(App):

    def build(self):
        Builder.load_string(kv)
        return QuizzWindow()


if __name__ == "__main__":
    MyApp().run()

Answer 2

To accomplish the same thing in just Python, you can implement what the kv language would do for you. You can implement an on_size() method in the QuizzWindow class that gets called whenever the size of the QuizzWindow changes. Then, in that method you can adjust the font_size of the Label and Button . Of course, to do that, you must have a reference to the Label and Button . Here is a modified version of your code that does it:

from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.app import App


class QuizzWindow(BoxLayout):

    def __init__(self, **kwargs):
        super(QuizzWindow, self).__init__(**kwargs)
        self.label = Label(text="quizz")  # save a reference
        self.button = Button(text="press")  # save a reference
        self.add_widget(self.label)
        self.add_widget(self.button)

    def on_size(self, *args):
        # called when size changes
        self.label.font_size = self.height / 20
        self.button.font_size = self.height / 20


class MyApp(App):

    def build(self):
        return QuizzWindow()


if __name__ == "__main__":
    MyApp().run()