\DeclareTextCompositeCommand

Synopsis:

\DeclareTextCompositeCommand{cmd}{encoding}{arg}{code}

A more general version of \DeclareTextComposite that runs arbitrary code with cmd.

This allows accents on ‘i’ to act like accents on dotless i, \i.

\DeclareTextCompositeCommand{\'}{OT1}{i}{\'\i}

See fontenc package, for a list of common encodings. Normally cmd will have already been declared with \DeclareTextAccent or as a one argument \DeclareTextCommand.