I'm not sure what actually triggers it but when using MacHg 1.0.2 on a MacMini with MacOS X 10.10 Yosemite installed the application becomes unusable at some point: Views don't get refreshed when switching between them. Scroll views don't get updated on scrolling. Preference window does not display toolbar (see screenshot). It reacts to clicks though. The window traffic lights stay grey even if window is active. Resizing the window completely messes up the UI (see screenshot).
Issue #351 new