Delay in loop mode and Arial trouble

• android
• react-native-swiper v1.5.12
• react-native v0.47.0
• expo v20.0.0

1. First thing I encountered was lack of Arial in my stock based rom. I attempted to download font file but found that it is commercial and price is incredible. Anyway I don't need this functionality, so I just deleted style rule. It will be much better if you change Arial to something free/open-source so this font could be added to app package for better rom support.

2. Second thing was delay while loop. I use loop and dynamic content change to create infinity scroll effect. My app is a kind of calendar and its draft looks so:

//functions to screen weekends 
function getDays(c){
  let center = findNext(c,1);
  let arr = [center];
  for(let i=0;i<3;i++){
    arr.push(findNext(arr[i * 2] + 1000 * 60 * 60 * 24,1));
    arr.unshift(findNext(arr[0] - 1000 * 60 * 60 * 24,-1));
  }
  return arr;
}
function findNext(candidate,direction){
  if(new Date(candidate).getDay() != 0 && new Date(candidate).getDay() !=6){
    return candidate;
  }
  else {
    if(new Date(candidate + 1000 * 60 * 60 * 24 * direction).getDay() == new Date(candidate).getDay()){
      return findNext(candidate + 1000 * 60 * 60 * 24 * direction + 1000*60*60* direction,direction);
    }
    return findNext(candidate + 1000 * 60 * 60 * 24 * direction,direction);
  }
}



export default class App extends React.Component {
  constructor(props) {
    super(props);
    let days = getDays(Date.now());

    this.state = {
      dates:days,
      current: 3,
    };
  }

//dynamic content changing
  onScrollEnd (e,state) {
    let newDates = getDays(this.state.dates[state.index]);

//shifting array to match old locations
    for(let i=0; newDates[state.index] != this.state.dates[state.index] ;i++){
        newDates.push(newDates.shift());
    }
    
    this.setState({
      dates: newDates,
      current: state.index,
    });
  }
  render() {
    return (
      <View style={styles.container}>
        <Swiper style={styles.wrapper} loop={true} index={3} showsPagination={false} onMomentumScrollEnd ={this.onScrollEnd.bind(this)}>
          <View style={styles.slide1}>
            <Card date={this.state.dates[0]}/>
          </View>
          <View style={styles.slide2}>
            <Card date={this.state.dates[1]}/>
          </View>
          <View style={styles.slide3}>
            <Card date={this.state.dates[2]}/>
          </View>
          <View style={styles.slide4}>
            <Card date={this.state.dates[3]}/>
          </View>
          <View style={styles.slide5}>
            <Card date={this.state.dates[4]}/>
          </View>
          <View style={styles.slide6}>
            <Card date={this.state.dates[5]}/>
          </View>
          <View style={styles.slide7}>
            <Card date={this.state.dates[6]}/>
          </View>
        </Swiper>
      </View>
    );
  }
}

In first draft I used only 3 exemplars of <Card/> and loop worked perfect but contemplation of content rendering was disgusting. To hide it I added 4 extra cards. I achieved my goal, but then I spotted delay while loop. It wasn't graphic freeze or lag: android showed end of list ripple. Delay was from 0.5 to 2-3 seconds and only on 6>5 and 0>1 transitions. It was shot in the dark, but I overcame this trouble with changing timeout delay to 0 in loopJump method:

//react-native-swiper/src/index.js
loopJump = () => {
    if (!this.state.loopJump) return
    const i = this.state.index + (this.props.loop ? 1 : 0)
    const scrollView = this.scrollView
    this.loopJumpTimer = setTimeout(() => scrollView.setPageWithoutAnimation &&
      scrollView.setPageWithoutAnimation(i), 0)
  }

Obviously there was a reason to set initially this timeout different from 0, can you clarify that?

Anyway thanks for great work!

Start with src/index.js and the loopJump method; reproduce the reported 6→5 and 0→1 transitions on the listed React Native and Android versions, then compare the behavior with the timeout set to 0. Also locate the style rule using Arial. Done means the affected loop transitions no longer show the reported delay and the font choice does not require a commercial font.