title: Qt/QML: how to find TextInput maximum width based on validator
body: <p>Doing my first steps in QML, so this might be obvious...
  When using a TextInput with a simple validator (say an IntValidator), is there a way to know the maximum width that TextInput field will take?
  As an example, if I create a IntValidator for a number from 0 to 999, I would like to find the width required to display that 999 (or whichever will be the widest, based on the font etc...).
  I am trying to wrap that textinput into an item which will have a fixed size, just the right size for the worst case input, nothing less, nothing more?
  Thanks.</p>