Arch Linux

Description:

My user passwords often have letters with diacritics (e.g.: á, õ, î) or just the diacritics (e.g. ~, `, ¨). I also use a Portuguese layout for most of my input necessities in no small part because of these characters and I use ibus as the input method. This has allowed me to write these characters by chain pressing the accent followed by the letter (e.g. ` + a = à), or confirming the diacritic by pressing it twice (e.g. ~ + ~ = ~). Specifically _without_ using the compose key.

I used to be able to login with these passwords, but not any longer. ` + a now yields a instead of à and ` + ` yields nothing, as if I never pressed the diacritic keys.

I also tried enabling the compose key, but that doesn't seem to work either, though I've never tried that before in GDM, so I have no point of comparison.

I also verified that the Portuguese layout is still in effect by checking plenty of other special characters in the same password field, matching the expected positions in this layout. Only characters that would trigger a 'compose' style input stopped working, which in my layout are all the diacritics.

```
$localectl status
System Locale: LANG=en_GB.UTF-8
VC Keymap: pt-latin1
X11 Layout: pt
```

After login (with a different password), just about everything else works fine input wise.

Additional info:
* Happened after a system wide update which included a GNOME 41->42 update, specifically including GDM 41.3-2 -> 42.0-1.
* Using reasonably standard GNOME system with ibus with the main input source being Portuguese.

Steps to reproduce:
* Bulk update GNOME packages from 41.* to 42.*.
* Try to input letters with diacritics or just diacritics in the manner described in the login password box with a suitable keyboard layout. Compare with any non-GDM input field.