Bug#855022: [gnome-shell] regularly SEGFAULTs while switching between windows with Alt-Tab

[Thibaut Paumard]

Dear Maintainers,

I am now able to reproduce this 100% of the time with a narrowed-down
context:

- external monitor attached;
- icedove running;
- hit Alt-Tab in such a way that the icedove drawer opens;
- use the keyboard arrow keys until the SEGFAULT happens.

By opening the "drawer", I mean the sub-window that shows the various
icedove windows. I can open it by hitting "down" arrow even when there
is only the main window open, or it will open automatically it there are
several icedove windows.

It is not always necessary to use the arrow keys to trigger the bug.
When icedove really has two windows so that the drawer opens
automatically after some timeout, the bug can trigger on its own.
Difficult to say  whether that's 100% of the times, but very often.

I have not witnessed the bug on other windows than icedove, and I was
not able to reproduce it without my external monitor being connected.

Regards, Thibaut.