Code review comment for lp://qastaging/~attente/unity-gtk-module/gtk-enable-mnemonics

trying to dynamically handle the settings changing at runtime is maybe a bit insane.... but assuming that indeed you do want to do this:

unity_gtk_menu_shell_handle_item_notify() only uses the pspec to get the name -- why not just modify this function to take the name directly, removing the need to lookup the pspec...

keeping a gtksettings per menuitem is definitely overkill -- it's exceptionally unlikely that we will ever see more than one gtksettings per program. just use the global one. cache it in a static if you really don't trust that it will never change...

since you will just use the global gtksettings, no need to remove/readd the signal handler every time. also: don't bother with handler ids: they don't really make much of an improvement in performance. just disconnect by funcs/data.

finally: you shouldn't try to do this for every single menu item: only for toplevel ones in menubars.

one unrelated note: your underscore removal algorithm's attempt to be correct on non-ascii utf8 strings is not really necessary. all non-ascii utf8 sequences are composed entirely of non-ascii characters (ie: every byte is > 0x80). it is therefore impossible for '_' to appear in the middle of the sequence. just do the naive thing here and it will be correct.