PySimpleGUI/Demo_Font_Sizer.py

# Testing async form, see if can have a slider
# that adjusts the size of text displayed
import sys
if sys.version_info[0] >= 3:
    import PySimpleGUI as sg
else:
    import PySimpleGUI27 as sg

fontSize = 12
layout = [[sg.Spin([sz for sz in range(6, 172)], font=('Helvetica 20'), initial_value=fontSize, change_submits=True, key='spin'),
           sg.Slider(range=(6,172), orientation='h', size=(10,20), change_submits=True, key='slider', font=('Helvetica 20')),  sg.Text("Aa", size=(2, 1), font="Helvetica " + str(fontSize), key='text')]]
sz = fontSize
window = sg.Window("Font size selector", grab_anywhere=False)
window.Layout(layout)
while True:
    event, values= window.Read()
    if event is None or event == 'Quit':
        break
    sz_spin = int(values['spin'])
    sz_slider = int(values['slider'])
    sz = sz_spin if sz_spin != fontSize else sz_slider
    if sz != fontSize:
        fontSize = sz
        font = "Helvetica " + str(fontSize)
        window.FindElement('text').Update(font=font)
        window.FindElement('slider').Update(sz)
        window.FindElement('spin').Update(sz)

print("Done.")