CB-11836 Allow setting of 'ForegroundText' property via config.xml

[tsschaffert]

We had a problem when trying to release an app in the Windows Store with BackgroundColor set to white because of the contrast between background and foreground color. With this PR, you can set the foreground color to 'dark' in these cases to pass store certification.

[codecov-io]

Current coverage is 74.34% (diff: 100%)

Merging #195 into master will increase coverage by 0.09%

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[daserge]

LGTM, thanks for your contribution!
I've documented this in apache/cordova-docs#638

[daserge]

OK, actually there are some points which need to be updated:

1. Windows 10 does not support ForegroundText (so we'll get a build failure if manifest contains ForegroundText),
2. It is better to avoid color argument reassignment,
3. It would be nice to cover the feature with some tests.

[daserge]

@tsschaffert, please let me know if you plan to address the comments.

[tsschaffert]

@daserge I will look into it

[tsschaffert]

1. The issue with Windows 10 should be fixed now, I handled it similarly to the 'ToastCapable' property.
2. The color argument is now passed to the manifest file unchecked, so invalid values return an error like 'App manifest validation failed.' when building the project. Alternatively, we could throw a TypeError for invalid values?
3. I added only a very basic test, as there were no comparable tests for the visualElement methods and I don't know enough about the internals to write really meaningful tests

[daserge]

Thanks for the update!
I've left some comments.

[daserge]

Instead of if (color) { visualElements.attrib.ForegroundText = color; } would it be better to use visualElements.attrib.ForegroundText = color || 'light' so that ForegroundText would be reset as default light if we set dark via preference for example and then remove the preference from config.xml entirely?

[daserge]

It also would be good to add a case for missing preference:

            // Simulate the absence of preference, should default to 'light'
            visualElementsWindows.setForegroundText(undefined);
            expect(visualElementsWindows.getForegroundText()).toEqual(foregroundTextLight);

[tsschaffert]

Good points, I updated the changes accordingly.

[daserge]

Looks good to me, thanks @tsschaffert!
I'm going to test and merge this.