close emacs with mouse

[ramestica]

C-x C-c is bound to save-buffers-kill-emacs which is nice because it
warns about unsaved buffers and closes all subrrogate minibuffer
frames. On the other hand, when I close emacs using the mouse on the
button at the title window (xwindows) it will still warn about unsaved
buffers but it will not get rid automatically of subrrogate minibuffer
frames. I'm not sure which exact function is bound to the title
button, and I could not find information about how to default it to
something else, like save-buffers-kill-emacs.

Any hint?

many thanks,