I just had an idea: Is it possible to put DRC violation markers into a magic file?

DRC violation markers are part of the magic file. Unfortunately there's only three types representing all DRC errors, so no meaningful information about the error. So "drc why" forces magic to recompute the DRC. Working out a method by which each DRC error has a type corresponding to the error message is on my list of things to do. I have an implementation in mind, just no time at present to work on it.