dynamic - Rounding problems inside InputField

The community needs to determine if this is behavior is a bug or not. – Mr.Wizard

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Consider the following InputField

InputField[Dynamic[h2,
  If[# === Null, h2 = h2, h2 = Round[#, 0.001]] &], Number]

The purpose of the second argument of Dynamic is to avoid someone entering a value with more than 3 decimal places (or emptying the field after some value has been assigned).

For example, entering 0.4691 immediately reassigns the InputField to 0.469.

The problem is that entering the number 0.468 renders 0.4680000000000001. I imagine it’s something to do with the representation of 0.468 in binary, etc.

How can I avoid this after rounding action?

EDIT:

After some more testings, I see that it is the Number part that is causing the problem.

This works "badly":

InputField[Dynamic[h2], Number]

This works OK:

InputField[Dynamic[h2]]

If you do Do[h2 = i; Pause[0.1], {i, 0.04, 0.08, 0.001}], you can get a good picture of the problem:

How can I avoid this Number side effect?

Answer

This seems to work for me, is it what you need?

InputField[Dynamic[h2, If[NumericQ[#], h2 = Round[#, 0.001], h2 = h2] &]]