Allowing 'none' Values for a Choice

[mcrowson]

In Toga, possible choices are given for display and visibility of 'none'
https://github.com/pybee/toga/blob/master/src/core/toga/style/pack.py#L33

Entering a valid entry of 'none' for these however gets converted to the native Python None
https://github.com/pybee/travertino/blob/master/travertino/declaration.py#L51

Which causes a ValueError to be raised.
ValueError: Invalid value 'none' for property 'visibility'; Valid values are: hidden, none, visible

[stantonxu]

@mcrowson , could you please list out the detailed reproduce steps? I don't have problem to use style=None for my toga GUI.

[mcrowson]

Sure, will do so in a bit. But None (the Python None type) is not an acceptable value for visibility and display, the string ‘none’ is what it wants.

…

On Jul 16, 2018, at 7:51 PM, Stanton ***@***.***> wrote: @mcrowson <https://github.com/mcrowson> , could you please list out the detailed reproduce steps? I don't have problem to use style=None for my toga GUI. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#3 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AGJ2klOG-gEXFY4k_i4Vft7st9uZfjeMks5uHScBgaJpZM4VRY27>.

[mcrowson]

To reproduce:

cookiecutter https://github.com/pybee/briefcase-template
# named the project bug_example
cd bug_example
python3 -m venv env
env/bin/pip install briefcase toga

Then I added a Box named some_content and set its visibility to 'none'. Here is the app.py file with those two lines added.

import toga
from toga.style import Pack
from toga.style.pack import COLUMN, ROW


class BugExample(toga.App):
    def startup(self):
        # Create a main window with a name matching the app
        self.main_window = toga.MainWindow(title=self.name)

        some_content = toga.Box()
        some_content.style.visibility = 'none'

        # Create a main content box
        main_box = toga.Box()

        # Add the content on the main window
        self.main_window.content = main_box

        # Show the main window
        self.main_window.show()


def main():
    return BugExample('Bug Example', 'com.example.bug_example')

Next I ran setup for ios

env/bin/python setup.py ios

I opened the xcode project then in xcode. It builds successfully, The simulator launches and i see the following in the xcode console

2018-07-17 09:27:30.726154-0400 Bug Example[1038:14423]   File "/Users/matthew/Library/Developer/CoreSimulator/Devices/90E3F30B-408D-4D8C-81BE-48E2A139543D/data/Containers/Bundle/Application/5597D9C1-561C-4830-92C8-DAA6C2F3D45F/Bug Example.app/Library/Application Support/com.example.bug_example/app/bug_example/app.py", line 13, in startup
2018-07-17 09:27:30.726382-0400 Bug Example[1038:14423]     some_content.style.visibility = 'none'
2018-07-17 09:27:30.726500-0400 Bug Example[1038:14423]   File "/Users/matthew/Library/Developer/CoreSimulator/Devices/90E3F30B-408D-4D8C-81BE-48E2A139543D/data/Containers/Bundle/Application/5597D9C1-561C-4830-92C8-DAA6C2F3D45F/Bug Example.app/Library/Application Support/com.example.bug_example/app_packages/travertino/declaration.py", line 181, in setter
2018-07-17 09:27:30.726748-0400 Bug Example[1038:14423]     value, name, choices
2018-07-17 09:27:30.726944-0400 Bug Example[1038:14423] ValueError: Invalid value 'none' for property 'visibility'; Valid values are: hidden, none, visible
2018-07-17 09:27:30.731067-0400 Bug Example[1038:14423] App became active.