percentage support for transform translate

Description

3f49e74 added support for percentages in some style properties, and its awesome. we should also have support for transform translates.

Reproduction

I want to absolutely position a view and center it vertically. I can now do top: '50%', but thats not centered. To make it centered I would also need transform: [{translateY: '50%'}].

Solution

Add support for percentages for translates

Additional Information

• React Native version: 0.42.3
• Platform: iOS
• Development Operating System: MacOS
• Dev tools: Xcode

[pvinis]

i think it is important, since we have percentages for the top-level styles, to also have it for transforms.

[leggomuhgreggo]

Example Workaround with RN onLayout event:

class Foo extends Component {
  ...
  onLayout = event => {
    const { width } = event.nativeEvent.layout;
    this.setState({ myWidth: width });
  };
  ...
  render() {
    const { myWidth } = this.state;

    return(
      <View
        onLayout={this.onLayout}
        style={{transform: [{translateY: myWidth / 2 }]}}>
          ...
      <View/>
    )
  }
}