feat: lock screen screenshot background and transitions

[RainAfterDark]

Pull Request

Motivation

This adds a setting to use a screenshot of the desktop as a background of the lock screen, with just ScreencopyView. I've also added a fade in/out transition for the lock screen, enabled with the lock screen animations setting.

Only tested in Niri so far. There is a bug, where the very first time the lock screen is invoked, ScreencopyView.hasContent is false, because the WlSessionLockSurface.screen seems to be null just before the lock. I've tried not using loaders in LockScreen.qml but the issue persists. I'm not sure if this is just an issue with Niri or with quickshell. Other than the first lock, it works as expected.

EDIT: Improved implementation on SCVs using grabToImage should resolve this particular bug.

Type of Change

• Bug fix
• New feature
• Breaking change
• Refactoring

Related Issue

• Implements [Feature] Blurred screenshot as lockscreen background #1696

Testing

Describe how you tested your changes and mark the relevant items.

• Tested on niri
• Tested on Hyprland
• Tested on sway
• Tested with different bar positions and density settings
• Tested at different interface scaling values
• Tested with multiple monitors (if applicable)

Screenshots / Videos

2026.03.29.16.12.10_00m01s133ms-00m06s883ms.mp4

Checklist

• Code follows project style guidelines
• Self-reviewed my code
• No new warnings or errors
• Documentation or comments updated (if relevant)

Additional Notes

• Some changes to shell.nix to add python3 as a package for the lefthook script, and a shellHook to install the hooks when entering the dev shell.

[andresparrab]

Hi @RainAfterDark iwas wondering something about the lock screen
how did you get that when typing the password you get different kind of inputs forms? like in the screenshot..some round some star some square and so on? it look very nice but i dont know how i can change things in my lockscreen.
or add javascript or css to make it look better.

[RainAfterDark]

how did you get that when typing the password you get different kind of inputs forms?

It's in the settings Lock Screen > Appearance > Random passsword icons