In unity, if I click an icon in the launcher with multiple windows open it doesn't show me all open windows for that application. However, this works in unity2d.

I known there have a same question asked before: here! But I think my condition is not as same as the previous question.

ubuntu 12.04 64-bit
unity 5.16.0
kernel linux 3.2.0-33-generic
gnome 3.4.2

Edit I just find a interest thing: There are four workspace, label it as A, B, C, D. If I firstly open two windows of firefox in A, as I mentioned above, second click on the firefox icon does nothing. But after I open a window of firefox in B, the second click on the firefox icon in workspace A magically works!!

And then, I open two terminal in workspace C, second click doesnot work until I open another terminal window in D.

So, it seems that the second click only work if the application be opened more than one workspace.