Add support for gnome 42 dark mode

[wmcmillian-coalmarch]

This adds support for gnome 42's new dark mode. So that the wall paper changes even if it is in dark mode.

[gw8ndal]

Looks good, I would love to see it merged

[DonFruendo]

+1 for this. With more people using dark mode and Gnome dedicating a setting to it, this is a really good addition!

[HaydenS3]

Works but creates a file with $1 as name on Ubuntu 22.04. Removing the 2>$1 from scripts fixed the issue.

[vintagefuture]

I'd suggest to replace 2>$1 with 2>/dev/null
Otherwise an empty file called -c might be generated.

[adi1090x]

Sorry for being way too late.

Nice PR, can you resolve conflicts and reproduce it?

[vintagefuture]

@wmcmillian-coalmarch Are you able to resolve the conflict?
@adi1090x I'm happy to submit a new PR with these same changes if it helps

[dukercs]

I had the same issue on GNOME 42 (X11) running on Ubuntu 22.04.
When the script /usr/share/dynamic-wallpaper/dwall.sh it's trying to set a wallpaper using this command:

gsettings set org.gnome.desktop.background picture-uri 'file:///usr/share/dynamic-wallpaper/images/room/9.jpg'

…it did not work and gave no error.

🕵️ Root cause:

GNOME uses the key picture-uri-dark instead of picture-uri when dark mode is enabled.

We can check the current color scheme with:

gsettings get org.gnome.desktop.interface color-scheme

If it returns 'prefer-dark', then we need to use:

gsettings set org.gnome.desktop.background picture-uri-dark 'file:///usr/share/dynamic-wallpaper/images/room/9.jpg'

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✅ Suggestion: Handle both themes in set_gnome() function, something like

set_gnome() {
    THEME_MODE=$(gsettings get org.gnome.desktop.interface color-scheme)

    if [[ "$THEME_MODE" == "'prefer-dark'" ]]; then
        gsettings set org.gnome.desktop.background picture-uri-dark "file:///$1"
    else
        gsettings set org.gnome.desktop.background picture-uri "file:///$1"
    fi
	gsettings set org.gnome.desktop.screensaver picture-uri "file:///$1"
}

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Hope this helps others who run into the same issue.  
Great project, by the way! 👏  
Cheers from Brazil 🇧🇷!