Changing the language only takes effect after another login

[felix]

When I switch languages in lightdm (GTK greeter), the language settings is stored in ~/.dmrc, but not in the LANG environment variable. Therefore the setting takes effect only after I log out and log in again.

I looked into lightdm's source code, and I noticed a strange asymmetry: in common/user-list.c, common_user_get_language() reads the language from a private variable, while common_user_set_language() writes it to .dmrc but not to the same private variable. There is a similar discrepancy in the common_user_get_session() and common_user_set_session() pair of methods. The getters also call load_dmrc() which loads the contents of .dmrc into the private variables, but the latter function has an if guard that prevent .dmrc from being read twice. Later in src/seat.c, create_user_session() feeds configure_session() with the values read from the getters, and the bug ensues.