Here's a patch for something that's been bugging me. This makes Cmd-` cycle
through only the current space's windows, which is consistent with other
programs on OS X. It also matches the behavior of other-frame on X11 for
window managers that implement virtual desktops by mapping and unmapping
windows. The patch is attached.

It's not perfect; if you go into Mission Control or so and move a window
onto another space without switching spaces, it won't notice until you
switch spaces again. I wasn't able to find a notification to listen to;
it'd be nice to replace the visible field in a frame with some virtual call
that, in Cocoa, would just call out to [win isVisible] and [win
isOnActiveSpace], but that'd be a more invasive change. It also doesn't fix
the behavior where closing the last window on a space warps you to a window
on another space. I'm not sure yet what's causing that.

As far as copyright goes, if this is a large enough change to matter (a
decent chunk of the diff is just moving some code around), I'm a Google
employee. I'm told we already have an agreement on file with the FSF.

David Benjamin