I tried to find out how PowerPoint shows birectional text from the "Office Open XML File Format Implementation" forum. Unfortunately, because Office Open XML File Format does not specify how text stored in DrawingML format should exactly be shown, that forum could not provide the answer. The specific discussion thread resides in:
http://social.msdn.microsoft.com/Forums/en-US/os_openXML-ecma/thread/2d24887e-37aa-4a32-8422-8ebd18ac01c4
The text run properties within DrawingML may contain a "lang" attribute. PowerPoint uses the "lang" attribute somehow for the classification of characters. Because the effect of the "lang" attribute into the classification of characters is not specified in the DrawingML format, the interoperability of different products using Office Open XML File Format can not be achieved. Files created with PowerPoint can not be read correctly by other programs and files created with other programs can not be read correctly by PowerPoint.
Could someone explain to me how PowerPoint uses the "lang" attribute when it performs the classification of characters?
Tero