`wf-locker`: invalid GTK CSS color `#0000` causes background configuration to be ignored

Description

wf-locker in wf-shell 0.11 appears to generate invalid GTK CSS for its fade-in animation:

@keyframes slowfade {
    from { opacity: 0; background: #0000; }
    to   { opacity: 1; }
}

GTK rejects #0000 with:

Gtk-WARNING **: Theme parser error: <data>:1:30-31: Expected a valid color.

As a result, the locker background configured with background_color does not appear to be applied. The lock screen remains transparent/whitish regardless of the configured value.

Reproduction

With wf-locker running in debug mode:

WF_LOCKER_DEBUG=1 wf-locker --now

Configure:

[locker]
background_image = false
background_color = #ff0000

The result is still a white/whitish or transparent background rather than red.

The locker emits:

Gtk-WARNING **: Theme parser error: <data>:1:30-31: Expected a valid color.

and the generated CSS contains:

.fade-in {animation-name: slowfade;animation-duration: 3.000000s; animation-timing-function: linear; animation-iteration-count: 1; animation-fill-mode: forwards;}
@keyframes slowfade {
    from {opacity:0; background: #0000;}
    to {opacity:1;}
}

Additional observation

The configuration option in the implementation/metadata is named:

locker/background_color

and the source uses:

new CssFromConfigString(
    "locker/background_color",
    ".wf-locker {background-color:",
    ";}"
);

However, the shipped wf-shell.ini.example documents the option as:

background-color = #0000

rather than:

background_color = ...

So there also appears to be a typo in the example configuration.

Expected behavior

A valid background_color should be applied to the locker, e.g.:

background_color = #ff0000

should produce an opaque red background.

The fade-in animation should also use a GTK-compatible representation of transparent black, such as:

background: rgba(0, 0, 0, 0);

or another color syntax accepted by GTK CSS.

Environment

• Fedora 44
• Wayfire 0.11
• wf-shell 0.11
• GTK4
• Reproduced with WF_LOCKER_DEBUG=1

Start by reproducing the warning with WF_LOCKER_DEBUG=1 wf-locker --now, then locate wf-locker’s CSS generation around CssFromConfigString and the slowfade animation. Check wf-shell.ini.example alongside the locker/background_color configuration metadata. Done means GTK accepts the generated transparent color, the configured color appears, and the example uses the actual option name.