I’ve already got a solution to this, I just wanted to post it for anyone else who might be having the same problem.
When using a combo box that autocompletes via an XML request, I was having a problem in Safari where, instead of highlighting just the text from the returned value that I hadn’t typed yet, it highlighted everything, and caused me to erase my value as I was typing.
I started to type “tagged” into the combo box. After typing the “t”, it fetched results from the server and suggested “tagged” as the result. Instead of highlighting “agged”, however, it put a space at the beginning of the value, then highlighted “tagged”, so when I typed the next letter (“a”), it overwrote my “t”, and left me with just the “a”.
This is a whitespace issue in the XML. Essentially, you need to remove any unnecessary whitespace, so the results should look something like this:
rather than the “pretty print” version:
I hope this saves someone else some headaches.