Default colors should adapt to macOS Mojave dark mode

[sbenitezb]

What did you do?

Rendered a chart under dark mode in Mojave.

What did you expect to happen?

Labels, grids, etc, to show in white color.

What happened instead?

Labels, grids, etc, show in black.

Charts Environment

Charts version/Branch/Commit Number:master
Xcode version:10.1
Swift version:4.2
Platform(s) running Charts:macOS
macOS version running Xcode:10.14.1 Mojave

[liuxuan30]

welcome a PR. We don't have the man power for the fancy features.

[sbenitezb]

welcome a PR. We don't have the man power for the fancy features.

Fancy? A chart library has to look good and legible. Black text over a dark background makes it useless for presenting information. You can’t read numbers or labels. I agree that you don’t have the man power, but this is no fancy feature, it’s just how things are now that we have a dark mode, like it or not. Mojave brought semantic colors. Charts should use that.

Anyway, I’ll see what I can do.

[liuxuan30]

OK. Maybe not the right word.. cause this is for iOS mainly, not sure how often it's used in macOS.

[Jean-Daniel]

Replacing NSUIColor.black by NSUIColor.labelColor for default text color should solve most of the color issues.

The grid color is less an issue. Gray still looks good on a dark background.

And please, don't use white color or any non semantic value. Label color automatically switch to the right value depending the display mode, so it does not require any extra work.

If you need to use specific colors for light and dark modes, you really should define them in a Asset catalog and reference them by name in the code, so they also will benefit from automatic adjustment as the display mode change.