client/core,app: Fix rate/volume decimal precision

[martonp]

Closes #2174

[buck54321]

I think the point is to lop off extra zeros in the decimals. In many cases, this new scheme will force the showing of decimal places we don't care about. For example, if the current rate is 1,284.0, and the rate step is 1e4, this will show 1,284.0000, which is clearly not what we want. Sig figs is the way to go. Nobody should care about seeing more than 3 or 4. We just need to clean up the max number of decimals too.

Edit: Actually, with the integer handling, a better example would be a price of 98.0 and a rate step of 1e2, resulting in 98.000000 displayed. The point is that we don't need or want exact values to the decimal place in these displays. Sig figs is better.

[martonp]

You're right, no need for exact values.

[chappjc]

Isn't the intent then to be using maximumFractionDigits, not maximumSignificantDigits (for the big numbers)?

Also, regardless of value, I feel like we'd want at least one decimal e.g. 1,284.0 is Buck's example.

[chappjc]

For instance:

const FourSigFigsSmall = new Intl.NumberFormat('en-US', {
  minimumFractionDigits: 1,
  maximumSignificantDigits: 5
})

const FourSigFigsBig = new Intl.NumberFormat('en-US', {
  minimumFractionDigits: 1,
  maximumFractionDigits: 1
})

function fourSigFigs (v) {
  if (v<1000) return FourSigFigsSmall.format(v)
  return FourSigFigsBig.format(v)
}

console.log(fourSigFigs(123456.789))
console.log(fourSigFigs(123456))
console.log(fourSigFigs(1234.789))
console.log(fourSigFigs(123.789))
console.log(fourSigFigs(0.01357))
console.log(fourSigFigs(0.0121357))
console.log(fourSigFigs(0.0001357))

Output:

> "123,456.8"
> "123,456.0"
> "1,234.8"
> "123.79"
> "0.01357"
> "0.012136"
> "0.0001357"

(excuse the use of 5 there however)

[martonp]

The minimumFractionDigit is ignored in FourSigFigsSmall because it is overridden by the default minimumSignificantDigits of 1. You can't really mix those.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat#roundingpriority

I've changed it so that it always adds a decimal though.