app.md

app running on iOS screenshot

app running on OS-X screenshot

app layout

main.py

from __future__ import print_function, unicode_literals, absolute_import

import toga


def build(app):
    container = toga.Container()

    c_label = toga.Label('Celcius', alignment=toga.LEFT_ALIGNED)
    c_input = toga.TextInput(readonly=True)

    f_label = toga.Label('Fahrenheit', alignment=toga.LEFT_ALIGNED)
    f_input = toga.TextInput()

    join_label = toga.Label('is equivalent to', alignment=toga.LEFT_ALIGNED)

    def calculate(widget):
        try:
            c_input.value = (float(f_input.value)- 32.0) * 5.0 / 9.0
        except:
            c_input.value = '???'

    button = toga.Button('Calculate', on_press=calculate)

    container.add(c_label)
    container.add(c_input)

    container.add(f_label)
    container.add(f_input)

    container.add(join_label)

    container.add(button)

    container.constrain(f_label.TOP == container.TOP + 20)
    container.constrain(f_label.LEADING == container.LEADING + 20)
    container.constrain(f_label.WIDTH == container.WIDTH - 40)

    container.constrain(f_input.TOP == f_label.TOP + 30)
    container.constrain(f_input.LEADING == container.LEADING + 20)
    container.constrain(f_input.WIDTH == container.WIDTH - 40)

    container.constrain(join_label.TOP == f_input.TOP + 50)
    container.constrain(join_label.LEADING == container.LEADING + 20)
    container.constrain(join_label.WIDTH == container.WIDTH - 40)

    container.constrain(c_label.TOP == join_label.TOP + 50)
    container.constrain(c_label.LEADING == container.LEADING + 20)
    container.constrain(c_label.WIDTH == container.WIDTH - 40)

    container.constrain(c_input.TOP == c_label.TOP + 20)
    container.constrain(c_input.LEADING == container.LEADING + 20)
    container.constrain(c_input.WIDTH == container.WIDTH - 40)

    container.constrain(button.TOP == c_input.TOP + 50)
    container.constrain(button.LEADING == container.LEADING + 20)
    container.constrain(button.WIDTH == container.WIDTH - 40)

    return container


if __name__ == '__main__':
    app = toga.App('Temperature Converter', 'org.pybee.f_to_c', startup=build)
    app.main_loop()