I find myself talking about these pretty frequently, and it seems many people have never actually heard about them, so a blog post seems appropriate.
Window managers traditionally present (for “advanced” users) “virtual” desktops and/or “multiple” desktops. Different window managers will have slightly different implementations and terminology, but typically I think of virtual desktops as being an MxN matrix of screen-sized desktops, and multiple desktops as being some number of disjoint MxN matrices. (In some cases there are only multiple 1×1 desktops) If you’re a MacOS user, I believe you’re limited to a linear array (say, 5 desktops), but even tvtwm back in the early 90s did matrices. In the late 90s Enlightenment offered a cool way of combining virtual and multiple desktops: As usual, you could go left/right/up/down to switch between virtual desktops, but in addition you had a bar across one edge of the screen which you could use to drag the current desktop so as to reveal the underlying desktop. Then you could do it again to see the next underlying one, etc. So you could peek and move windows between the multiple desktops.
Now, if you are using a tiling window manager like dwm, wmii, or awesome, you may think you have the same kinds of virtual desktops. But in fact what you have is a clever ‘tagged view’ implementation. This lets you pretend that you have virtual desktops, but tagged views are far more powerful.
In a tagged view, you define ‘tags’ (like desktop names), and assign one or more tags to each window. Your current screen is a view of one or more tags. In this way you can dynamically switch the set of windows displayed.
For instance, you could assign tag ‘1’ or ‘mail’ to your mail window; ‘2’ or ‘web’ to your browser; ‘3’ or ‘work’ as well as ‘1’ to one terminal, and ‘4’ or ‘notes’ to another terminal. Now if you view tag ‘1’, you will see the mail and first terminal; if you view 1+2, you will see those plus your browser. If you view 2+3, you will see the browser and first terminal but not the mail window.
As you can see, if you don’t know about this, you can continue to use tagged views as though they were simply multiple desktops. But you can’t get this flexibility with regular multiple or virtual desktops.
(This may be a case where a video would be worth more than a bunch of text.)
So in conclusion – when I complain about the primitive window manager on MacOS, I’m not just name-calling. A four-finger gesture to expose the 1xN virtual desktops just isn’t nearly as useful as being able to precisely control which windows I see together on the desktop.