Thanks for the code sample. I'm approaching it slightly different: I'm attempting to EDIT a string and then change the font from a RSC font to a TrueType font. I was (am) "extracting" the string in to a WString and then for my test, using "assign()" to set the character(s) that I wanted. I next used ReplaceText() to update the contents of the TextBlock, followed by ReplaceTextPart to update the ITextEditP.
Maybe I will re-think this approach after I test the sample. The ultimate desire is to "upgrade" our drawing text/textNodes from RSC fonts to TrueType fonts. Unfortunately, back in the day, we created our our RSC fonts, and they are used in our models. Those RSC fonts also had "special characters" defined in them that we need to convert. For the symbols that were put in the "correct" (expected) locations in the font, simply updating the font handled the character mapping. For the others, well, that's what I trying to handle....
Maybe the solution is to just re-build the string from scratch.