Vertically center iOS text if lineHeight is set

[tuckerconnelly]

First PR!!

This fixes #2991 :)

[ghost]

By analyzing the blame information on this pull request, we identified @nicklockwood and @Kudo to be potential reviewers.

[charliesbot]

this is really helpful! please approve this pr

[mkonicek]

@tuckerconnelly Can you provide some screenshots from UIExplorer before and after? This might change how existing apps look so it is likely a breaking change though.

@nicklockwood, @javache What do you think?

[nicklockwood]

Nit: can you replace

[NSNumber numberWithFloat:lineHeight/2 - fontSize/2]

With

@(lineHeight/2 - fontSize/2)

[nicklockwood]

@mkonicek I agree that this should be the default behaviour. Difficult to guess what the impact might be on existing apps though.

[ghost]

@tuckerconnelly updated the pull request.

[ghost]

@tuckerconnelly updated the pull request.

[tuckerconnelly]

Boom, before:

after:

Also added code for adjusting the baseline when fontSize wasn't set.

[nihgwu]

any update? i'm looking forward this pr to be merged

[nicklockwood]

@facebook-github-bot shipit

[ghost]

Thanks for importing. If you are an FB employee go to Phabricator to review.

[bestander]

Shame for shipping this without looking at Travis build status https://travis-ci.org/facebook/react-native/jobs/133786669

This PR broke trunk

[bestander]

After talking to the teams internally, looks like we can't accept this change, have to revert it.
The problem is that it breaks the default behaviour and a lot of apps got broken.

[bestander]

Feel free to do another iteration and submit a new PR

[tuckerconnelly]

That's the nature of a breaking change lol

What would you want in another iteration?