I’ve been having an extremely frustrating experience developing PrayerMate within XCode 7 recently, where the whole editor would just freeze for 30 seconds at a time. It seemed to work fine as long as I stayed within one file, but as soon as I needed to switch to another file, I’d have to wait again. Sometimes I’d see tooltips flash up over various filenames in my project navigator, ones that perhaps the mouse had glanced over half a minute earlier.
Clearly this is a bug in XCode (and an infuriating one at that!) but the workaround was remarkably simple and fixed the problem completely: make the project navigator pane ever so slightly wider, until none of your longer filenames get truncated with “…”.