Description:

I just now opened the following upstream bug (against version 1:1.10.0-1):

https://bugs.launchpad.net/lightdm-gtk-greeter/+bug/1307764

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With at least the lightdm-gtk2-greeter; even though it visually has focus upon startup, the password entry box eats the first key GAINING focus when the mouse pointer was on it (or on the user-select box).

Both the login window and the mouse pointer are centered on startup, and for me and with at least the gtk2 greeter, this means that the mouse pointer is actually on the password entry box -- and therefore that lightdm seems to malfunction. It's only until I figured out that I first needed to kick my mouse out of the way upon startup that I understood that lightdm wasn't in fact more seriously broken...

I've "fixed" this manually by specifying a position= statement in the config file that avoid the centered mouse being on the password entry box after which things work fine, but this is of course not a nice thing to have to do.

Although I don't suppose it's THAT specific: I'm on a 1280x1024 screen...
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Given that the MATE desktop environment, which recommends LightDM as its diplay manager and is itself fully and explicitly GTK2, has been only recently officially adopted by Arch, I suppose a relatively large number of Arch users will run into this the same as I did. Since the decribed cause moreover isn't in fact readily apparent, lightdm might then appear to be more seriously broken than it is. I also commented on the Wiki:

https://wiki.archlinux.org/index.php/LightDM#Login_window_eats_first_character_of_password

but I thought we might want to track this on bugs.archlinux.org as well due to this recent adoption...