Incorrect Alt-Tab behaviour ordering: not predictable LIFO stack

Binary package hint: unity

With Unity 3.2.0-0ubuntu3 and 1:0.9.2.1+glibmainloop2-0ubuntu3 the behaviour of Alt-Tab is not consistent; the ordering chosen for the list of windows that will be displayed is not predictable ahead of time by the user.

Historically Alt-Tab operates as a pure LIFO stack (Last in, First out). Two alt-tabs takes the user to the window-before-last, three alt-tabs takes the user to window-before-that. In stack terminology, the window N alt-tabs down the stack is removed, placed on the top and everything else moved down one.

The behaviour between the top and next entry is predictable and works. However, when using multiple Alt-Tab presses to descend further through the window stack, the ordering is not consistent and therefore not predictable. The user must wait for the selector box to be faded up, displayed and to parse by sight, then select what ordering has been chosen on this particular occasion and execute further Alt-Tab or Alt-Shift-Tab presses to reach the desired target window.

This is reproducible by opening more than three windows, (eg. 4 Terminal + 3 Firefox). Alt-Tabbing around all of the Terminals in succession should place these in the top four entries of the window stack

  Term, Term, Term, Term, FF4, FF4, FF4 (expected)
  Term, Term, FF4, Term, FF4, Term, FF4 (observed)

Empathy also seems to consistently cause broken stack ordering aswell. It is possible that this is related to applications with multiple windows, but at the same time this does not explain how FF4/Term windows could end up "interlaced" as observed here.