SAT: Tab stacked windows disappear

[mmadia]

hrev44483 gcc2h

Moving a stack of two windows across workspaces can make them invisisble or disappear completely (depending on how the move to another workspace was done).

To reproduce:

• launch Workspaces and resize to a larger size (this makes it easier to visually locate where the invisible windows are.)
• stack two applications together by their tabs
• move the tabbed stacked windows to another workspace.
• poof! the window should now be invisible.

Notes:

1. using SHIFT + CTRL + CMD + <arrow keys> will not trigger this bug.
2. using LeftMouseDown on the tab + CMD + Fn will trigger this bug.
   • The applications will become invisible.
   • Upon switching to another workspace, keep LeftMouseDown and move the invisble application around. Workspaces will show it moving around.
   • Using CMD+CTRL+LeftMouseDown , will allow you to move the application, but not make it visible.
   • If you're able to guess where the focused application tab is, you can make them reappear.
   • To gauge the location of the invisible windows, use LeftMouseDown to select a large area of the Desktop. The hole in the selection will indicate where the invisible applications are.
3. using LeftMouseDown on the Workspaces will completely make the windows disappear.
   • I have not yet be able to figurs out a way to make them reappear. The only solution is to close the app and re-open it.

[humdinger]

(In #8690) Marking this as duplicate of #8855. Though I reported first, Matt's description is more detailed. :)

[czeidler]

Fixed in hrev44782. Thanks!