fix onLayout floating point numbers using roundToNearestPixel

[Freddy03h]

Hi!

I've been using RecyclerListView (and now FlashList) for many years in my project.

I've applied many patches to address different issues, but I’ve noticed that many of them share the same root cause: a probable floating-point precision issue related to React Native's onLayout event.

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Here’s an example of the event.nativeEvent.layout output for seven identical horizontal list components with different data:

Those affected by the floating-point issue experienced problems such as being unable to click on an item or scroll to the last item

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There are many ways to handle this issue, but we don’t want to rely on external dependencies. Instead, we want to track only the changes that produce actual visual differences on screen.

In other words, we don’t want to simply Math.round the values, as that would prevent us from detecting changes smaller than 1 dp. On a device with a pixel ratio of 3, we need to track changes as small as 0.333333 (which corresponds to StyleSheet.hairlineWidth).

That’s why I believe PixelRatio.roundToNearestPixel is a good candidate for this fix: regardless of the reason for the onLayout changes, if a change isn’t significant enough to produce a visible difference on screen, then no action should be taken.