Comment 6 for bug 91784

About the alternative "Show Desktop" plugin that can be activated by CompizConfig Settings Manager, I think this is badly designed from a usability point of view also. It has the same problem that the current default behaviour has, that sometimes the Show Desktop button will show the desktop, and other times it will cause hidden windows to unhide. In other words the button is modal, which is a bad thing. The Show Desktop plugin is slightly better because when there are hidden windows you can see still see them in the corners, so at least you have an indication of what mode you are in, but this is still modal.

In metacity Show Desktop simply shows the desktop whenever you click it. It's not modal. This is the right way.

Modal interfaces are bad because human users cannot pay attention to both system state (mode) and the task they are performing at the same time. So they end up performing actions for one mode while the system is in another mode, producing the wrong results. For example with Ubuntu/Compiz right now users frequently forget the mode of the Show Desktop button and click, expecting to see the desktop, only to be baffled when instead a new window pops up, and they have to click the button again. Accidentally typing a password with your keyboard in caps-lock mode is another example of a mistake caused by a modal interface.

But all this is just details ... it is simply baffling right now when you click the "Show Desktop" button and a bunch of minimised windows pop up instead. New users will not understand what is going on at all.