The overprinting @!ab escape sequence cannot handle a font change

[PaulWessel]

We have a mechanism to blend two characters via the @! escape sequence. However, as the example in the forum shows, this does not work if the two characters are from different font sets. This is an unimplemented feature.

[PaulWessel]

I notice that the Symbol character set has lots of openings (34 or more) in the octal table. One option is simply to populate those by reencoding Symbol to Symbol+, adding in a bunch of special symbols from the standard/ISO charset that can be useful in mixing with the other symbols, such as the dotaccent requested by the OP, but also many others, e.g., some fractions, double-dot (2nd time derivative), some of the accent and umlauts for 2nd derivatives as well, and more. It seems tricker to insert a font change in the middle of the overprinting of two characters, but I will look at that as well. So two possible paths for this. BTW, since Symbol+ would just extend Symbol we would do this under the hood and always extend Symbol to include extra glyphs.

[PaulWessel]

Looking at this in the code, it is difficult to do on the fly since we break text strings at @ codes and treat the different pieces separately. This does not work for something like @!\227@~\145@~. I thought it might be easier actually to extend the Symbol font charset, but just now learned the hard way that those characters are not available to be added to the Symbol set. So will look for a solution involving a font switch.