The OT spec
When an OpenType text layout engine applies the Unicode bidi algorithm
and gets to the point where mirroring needs to be performed . . . The engine applies the ‘rtla’ feature to the entire RTL run.
I'm working on a font that supports the Old Italic range of Unicode. These characters are strongly LTR, but are sometimes used for RTL text. The usual recommendation is to insert a right to left override, terminated by a pop directional format. Assuming that the application respects these bidi controls (not all do, but that's another discussion), is the presence of the RLO enough to get the layout engine to apply the rtla feature? One would hope so, but . . . . If adding a RLO doesn't work, is there any way to get this feature applied without users doing it manually? Thanks!