[XeTeX] Overriding directionality and mirrored shapes

[Jonathan Kew]

On 17/09/2017 20:26, David J. Perry wrote:
> The OpenType spec says that when a layout engine encounters a situation 
> where mirrored glyphs are required, it should automatically apply the 
> <rtla> or <rtlm> features (assuming they exist in the font). LibreOffice 
> and TextEdit / Nisus Writer (latter Mac only) do this. See the "Simple 
> RLO Test" screen shot.  (BTW: I attached the screen shots.  Does this 
> list allow images in the body of a message?)
> 
> XeLaTeX does not. It correctly places the characters RTL after inserting 
> a right to left override (RLO, U+202E), but the shapes are not mirrored. 
> See the minimal example below and the screen shot taken from the output 
> PDF. The same font was used to generate both of the screen shots. (If 
> you wish to try this for yourself, you will need a font that includes 
> both the Old Italic block of Unicode and the appropriate OT features. I 
> will share the one I’m making if anybody is really interested.)

Does it work if you explicitly apply the rtla and/or rtlm features (e.g. 
using fontspec's RawFeature option)?

JK