How do I revert the alt-tab behavior so that switching to an app brings to the front all the windows of that app?

In 11.10, the Unity alt-tab switcher brought all the windows belonging to an application to the front when switching to the application like on Mac (unless you waited for long enough that the app's switcher entry expanded to a window selection in which case you got to select which window to switch to).

In 12.04, switching to an app with multiple window open (in the same workspace) brings to the from one of the windows. (I see no logic in which one is brought to the front.)

How do I, under 12.04, revert to the alt-tab behavior of 11.10 so that switching to an app brings to the front all the windows of that app?

Unfortunately this is not configurable, but you can easily get this back manually compiling the unity source (please, file a bug to ask to add an option, btw).

As I was saying, you can get this back editing the file BamfLauncherIcon.cpp changing the line: bool only_top_win = !any_urgent; to bool only_top_win = true;

I know this is not the best solution, but since this has been a late change we had not the time to introduce a new ccsm option.

I don't know if this configurable, but it is by design: https://bugs.launchpad.net/unity/+bug/959339. The window that is brought to the front is the most recently focused one.

As Yann indicated, this was changed by design. I HIGHLY recommend that you voice your support for making the behavior configurable here:

https://bugs.launchpad.net/unity/+bug/1055478