If true, allows the drawable's padding to change based on the current state that is selected. If false, the padding will stay the same (based on the maximum padding of all the states). Enabling this feature requires that the owner of the drawable deal with performing layout when the state changes, which is often not supported.

Must be a boolean value, either "true" or "false".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

[Android Documentation]