Floating point precision runs into weird behavior in looping mode

[TheHacky]

286 # Is this a bug report, a feature request, or a question?

bug report

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• [x] I have read the guidelines regarding bug report.
• [x] I have reviewed the documentation in its entirety, including the dedicated documentations :books:.
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Have you made sure that it wasn't a React Native bug?

I can't find anything about this issue.

Is the bug specific to iOS or Android? Or can it be reproduced on both platforms?

iOS 12.2 Android Simulator on Snack

Is the bug reproductible in a production environment (not a debug one)?

Yes.

Environment

Environment: React: 16.5.0 React native: 0.57 (Expo SDK 32.0.0) react-native-snap-carousel: 3.8.0

Target Platform: Android (5.0) iOS (9.2)

Expected Behavior

The slides looping on both sides endlessly.

Actual Behavior

The slides loop only once (regarding loopClonesPerSide) on the right side (swiping to left). On the other side, everything works as intended.

Reproducible Demo

https://snack.expo.io/@thehacky/floating-point-error-in-carousel

Steps to Reproduce

1. Swipe to left until no item will be rendered

[ghost]

+1

[ghost]

@TheHacky Have you found a solution?

[TheHacky]

@TheHacky Have you found a solution?

I used integers for all my values. Because I want to use a percentage for my size, I use Math.floor to break it down to integer pixel.

[ghost]

@TheHacky Sorry, I don't understand you very much. Is there any code for me to see?

[TheHacky]

@TheHacky Sorry, I don't understand you very much. Is there any code for me to see?

If you calculate your sizes with a percentage, e.g.

width: '50%'

or with a package like react-native-responsive-dimensions:

width: responsiveWidth(50)

then you got floating numbers. Instead, I use Math.floor to round up the value

width: Math.floor(responsiveWidth(50))

[ghost]

@TheHacky Sorry, I don't understand you very much. Is there any code for me to see?

If you calculate your sizes with a percentage, e.g.

width: '50%'

or with a package like react-native-responsive-dimensions:

width: responsiveWidth(50)

then you got floating numbers. Instead, I use Math.floor to round up the value

width: Math.floor(responsiveWidth(50))

This does not seem to solve the problem of sliding to the right when the loop slides, it will not loop.

[TheHacky]

This does not seem to solve the problem of sliding to the right when the loop slides, it will not loop.

I think you are right. It works than for iOS, but not for Android. Maybe, it refers to #529.

[Foskas]

Same here! Any updates on this issue ?

[junhoyeo]

@TheHacky Sorry, I don't understand you very much. Is there any code for me to see?

If you calculate your sizes with a percentage, e.g.

width: '50%'

or with a package like react-native-responsive-dimensions:

width: responsiveWidth(50)

then you got floating numbers. Instead, I use Math.floor to round up the value

width: Math.floor(responsiveWidth(50))

I solved this issue using this comment's solution - by providing integer values in sliderWidth and itemWidth properties in Carousel component. So my code is like this:

const carouselItemWidth = Math.floor(screenWidth * 0.68);

<Carousel
  sliderWidth={carouselItemWidth}
  itemWidth={carouselItemWidth}
  {...otherProps}
/>

[dohooo]

Sorry, please allow me to advertise for my open source library! ~ I think this library react-native-reanimated-carousel will solve your problem. It is a high performance and very simple component, complete with React-Native reanimated 2