How would I implement a bare bones function that 're-evaluates' with every key-press? I mean key-press loosely; I'm looking to emulate the behavior of
isearch and friends.
I would be using this to interactively test XPath expressions against an open nxml-mode buffer using something along the lines of buffer narrowing. For the purposes of this question though, just a function that calls
message on whatever is in the minibuffer would be absolutely grand.