Every once in a while I manage to activate this feature but then I can't bing it on again
It's about holding the spacebar to use the hand tool, but holding the mouse button and the mouse in one place for a bit. The document would zoom out, with a rectangle showing where I am, then move the mouse to another region and release: it would zoom in to that new location. It's like a hybrid between the navigator window, the zoom tool, the hand tool and the animated hardware accelerated scrubby zoom. It's something like ctrl+spacebar and holding the mouse, but better.
What is this?