This page from Wikipedia says:
A positive rolling motion lifts the left wing and lowers the right wing.
Which means that if an aircraft has a roll of +20 degrees, it would bank towards the right. And for a roll of -20 degrees, it would roll to the left.
But when I used this flight indicators library, for a roll of +20 degrees the attitude indicator showed that the aircraft was banking left and vice versa.
Are there any conventions for the roll angle/attitude indicator?