suspected bug with removing text input text color

[areslagae]

Hi all,

I was looking for a way to indicate validation status on a text input. In the end I came up with the idea to temporarily change the text color to red for input that does not validate. See example below.

It generally works but not completely. The red text style works, but after the del I get white, black and white and black combinations of text in the input. However, I am not sure if this is the way I am supposed to restore the original text color. I cannot simply set it to white or black since I do not know the theme (dark/light). So I am posting this here instead of filing a bug report.

def _toga_parameter_text_input_set_valid(self, valid):
        if valid:
            try:
                del self._toga_parameter_text_input.style.color
            except AttributeError:
                pass
        else:
            self._toga_parameter_text_input.style.update(color='red')

[freakboy3742]

You can determine if the app is in dark mode with App.dark_mode.

Regarding the specific use case - setting the text color red for validation - I wanted to confirm that you're aware that Toga has validation as a built-in feature.

As for the specific approach you're taking - clearing the color attribute should restore to "default" colors. I think I'm seeing the same behavior as you, though. If I clear the text color attribute, the text color is set to None. In dark mode, that should set the color of the text to white - but in my testing, it's using black. I can't explain why that would be, but it definitely seems like a bug. The initial text color value is set to None, and it's white text then... but resetting to None later seems to forget that setting. More investigation is clearly needed; if you want to turn this into a full bug report, that would be very helpful.

[areslagae]

Bug report submitted.

Thanks for the suggestion. Snippet at bottom seems to be a good workaround (at least on macOS, no extensive testing).

I was aware of the validators but I initially ignored them because I did not want to port the validation logic which was already in the domain layer to the ui layer. However, I now realize that I can just do as below.

    def _toga_parameter_text_input_set_valid(self, valid):
        self._toga_parameter_text_input.validators = [lambda _: None if valid else "invalid parameter"]

        if valid:
            try:
                # del self._toga_parameter_text_input.style.color
                # workaround for Toga issue #3919
                if self._toga_parameter_text_input.app.dark_mode:
                    self._toga_parameter_text_input.style.update(color='white')
                else:
                    self._toga_parameter_text_input.style.update(color='black')
            except AttributeError:
                pass
        else:
            self._toga_parameter_text_input.style.update(color='red')

lambda text: None if valid else "invalid"