drawOrderParts

piece, which is in the order it draws, left to right, as the strings a text engine draws in that order (#486). A text engine runs the bidi algorithm, so it would reverse right-to-left letters the layout already reversed. A piece without them stays one part, as it was. Otherwise it is cut where the strong direction changes, and a right-to-left part goes back to logical order inside a right-to-left override, so the engine joins Arabic letters with their logical neighbours and lays them out right to left, which is the order they came in. A left-to-right part beside it takes a left-to-right override, so that its digits and punctuation stay put.