When you click the close button on a window, the window can have a hint on it which tells the window manager not to close it immediately. Instead, it should ask the window to close itself, and if the window doesn’t respond within a certain amount of time, it should put up a dialogue box which asks whether to kill the process which owns the window.
At present, this amount of time is fixed in Metacity to 2.25 seconds.
GNOME bug 121934 suggests that this timeout could be different in some cases:
- If the window usually takes “a long time to exit”. This would require window matching.
- Generally, because 2.25 seconds is too short a time to wait. On the other hand, if it was much longer, the user might have forgotten closing the window and would be surprised by the “force quit” dialogue.
- When the system is under heavy load, so the program is less likely to be able to respond.
Photo © rwangsa, cc-by-nc-nd.