I'm a bit torn about this. It is indeed very nice, but at the same time I don't feel like it's the right solution. Ignoring minor complaints I'd have ("it's a very large button!") it doesn't feel right that the user, in order to change login wallpaper, would think that they have to right click on the desktop, click on edit desktop, click on "login and logout settings", and then change it. I think two other solutions that _might_ be better are:

• Decide that login and lockscreen wallpapers are part of the desktop as much as the desktop wallpaper (which doesn't make sense tech-wise, but it might make sense user-wise), rename "Wallpaper" to "Desktop Wallpaper" in the Desktop Settings KCM and embed directly there "Lockscreen Wallpaper" and "Login screen theme". This would mean
  • Splitting the "Appearance" tab from the Screen Locking KCM to a new KCM called "Lockscreen Wallpaper" which would be in the customize desktop window, thus making the content of the Screen Locking KCM just the "activation tab", but adding a button "customize wallpaper..." which would open the "Lockscreen Wallpaper" KCM
  • Doing the same with the "Login Screen" KCM, which would be split in "Login Screen Theme" KCM (shown in customize desktop) and "Login Screen" KCM (shown in SySe) only containing what now is in the "Advanced" tab, but with a "Customize theme..." at the top. OR - probably better - have only one "Login Screen" KCM which only shows the theme selector and is both on the "customize desktop" and current location in system settings, and add "Advanced" as a button that open up a new kirigami page rather than using tabs.
  • All of which kinda feel ugly from a "let's categorize things based on how they work under the hood" point of view, but instead it could make sense from a "let's categorize things based on what the user expects" point of view.
• OR, show the desktop configuration KCM is system settings, and somehow create a category there for wallpapers?
• OR we just go with what you are proposing. I'm not against it, but I feel it's more of a "limiting damage" than a "let's fix the problem at the root"

You're probably right. This was a pretty lazy patch.

The inherent challenge here is that desktop wallpapers are per-containment ("Containment" means a screen or activity), while the lock and login screens are per-session. A further complication is that the login screen is only able to display still images (though maybe that could change?). So there isn't a super clean way to have a single config UI work for everything.

One thing I could imagine would be the following:

We make a new KCM in System Settings called "Wallpaper". This KCM essentially displays the current desktop wallpapers UI with one exception: it has multiple Apply options:

• Apply to desktop (shown when there is only one containment)
• Apply to current desktop (shown when there is more than one containment)
• Choose which desktops to apply it to (shown when there is more than one containment; needs a clever UI)
• Apply to all desktops (shown when there is more than one containment)
• Apply to lock screen (always shown)
• Apply to login screen (always shown, but only enabled when the chosen wallpaper is a still image)

Maybe a sheet with these options could appear when you click on the Apply button. They would each be checkable, so you could apply the wallpapers to everything all at once if you wanted to.

This is similar to how most smartphones handle this (as well as GNOME as of a recent version IIRC) and I think it works pretty well there.

Thoughts?

the length of that button text is quite daunting, i fear imagining how would be in geman :p

In D29798#672886, @mart wrote:

the length of that button text is quite daunting, i fear imagining how would be in geman :p

Indeed, and Brazilian Portuguese, and probably many others too.

What are your thoughts regarding my idea above?

I agree with a single KCM called wallpapers used to set all wallpaper in System Settings. Not a fan of having so many apply buttons, but I'm sure we can come up with something good.

In D29798#672261, @ngraham wrote:

You're probably right. This was a pretty lazy patch.

The inherent challenge here is that desktop wallpapers are per-containment ("Containment" means a screen or activity), while the lock and login screens are per-session. A further complication is that the login screen is only able to display still images (though maybe that could change?). So there isn't a super clean way to have a single config UI work for everything.

One thing I could imagine would be the following:

We make a new KCM in System Settings called "Wallpaper". This KCM essentially displays the current desktop wallpapers UI with one exception: it has multiple Apply options:

• Apply to desktop (shown when there is only one containment)
• Apply to current desktop (shown when there is more than one containment)
• Choose which desktops to apply it to (shown when there is more than one containment; needs a clever UI)
• Apply to all desktops (shown when there is more than one containment)
• Apply to lock screen (always shown)
• Apply to login screen (always shown, but only enabled when the chosen wallpaper is a still image)
  
  Maybe a sheet with these options could appear when you click on the Apply button. They would each be checkable, so you could apply the wallpapers to everything all at once if you wanted to.
  
  This is similar to how most smartphones handle this (as well as GNOME as of a recent version IIRC) and I think it works pretty well there.
  
  Thoughts?

That was basically my suggestion a while back, together with a hovering preview overlay for the grid view in the wallpaper selector. I am totally amped that this is coming to reality!