Comment 17 for bug 883189

In addition to everything else said here, the relationship between /etc/lightdm.conf and the lightdm-set-defaults program needs clarifying.

https://wiki.ubuntu.com/LightDM#Configuration_and_Tweaks suggests that "[lightdm.conf is not] suppose to be directly edited, instead use: lightdm-set-defaults".

Is that actually true? On Precise at least, the program is not mentioned in lightdm(1) (where lightdm.conf is mentioned), nor in /etc/lightdm.conf, nor in /usr/share/doc/lightdm/lightdm.conf.gz. Also, the program doesn't have its own man page, and lives in /usr/lib/lightdm/lightdm-set-defaults where it's not obvious to find. And according to its --help it only allow changing a small subset of the options mentioned in the example lightdm.conf.

That suggests to me that it's intended to be a helper progam for use by packages or GUI configuration tools. If so, and as a system administrator I'm expected to edit lightdm.conf directly, what rules do I have to follow to not clash with automatically made changes from lightdm-set-defaults?