\DeclareTextAccent ¶Synopsis:
\DeclareTextAccent{cmd}{encoding}{slot}
Define an accent, to be put on top of other glyphs, in the encoding encoding at the location slot.
A slot is the number identifying a glyph within a font.
This line from t1enc.def declares that to make a circumflex
accent as in \^A, the system will put the accent in slot 2
over the ‘A’ character, which is represented in ASCII as 65.
(This holds unless there is a relevant DeclareTextComposite or
\DeclareTextCompositeCommand declaration;
see \DeclareTextComposite.)
\DeclareTextAccent{\^}{T1}{2}
If cmd has already been defined then \DeclareTextAccent
does not give an error but it does log the redefinition in the
transcript file.