Use case

With the Button.icon() constructor we have the possibility to set the icon at the start or end of the Button with iconAlignment.

It should also be possible to set the iconAlignment inside the ThemeData for the whole app. That way we only have to set the iconAlignment once.

Proposal

Example with TextButton.icon():

ThemeData(
  textButtonTheme: TextButtonThemeData(
    style: ButtonStyle(
      iconAlignment: IconAlignment.end,
//    [...]
    ),
  ),
);

By adding the property to the ButtonStyle class we can use it on all buttons. I think that is a huge benefit for everyone using this Feature!