background: transparent doesn't work in fullscreen wayland

[dustdfg]

If I set background: transparent on a tiled window it works good but if I open it in a fullscreen mode, I get black background

OS: Debian testing. Sway (Wayland) 1.9
Lang: Rust

[ogoffart]

I wonder if this is not a sway bug rather than a Slint issue.
My guess is that sway optimizes for fullscreen window and only render then one window. But I might be wrong and the bug may be in winit or in the renderer.
What renderer are you using? Did you try if the problem exist with all the renderer? (skia, femtovg, software).

What is your use case? Maybe you can get the same result with a maximized window?

[dustdfg]

1. I think you are right about sway optimization for rendering only one window but I am not sure about it
2. I've tried to start learning slint several times but something happened each time and I didn't have time for learning so I am able to only to open "basic" window and play with crate features...
3. I've tried all three renderers and it didn't work. I hope that just disabling default features and enabling only one specific was correct way to test all three renderers
4. My use case is custom wlogout which should open on top of all the apps and ideally ignore current open workspace too
5. As I googled I think I need something like wlr-layershell which as I assume isn't implemented in winit

[dustdfg]

It seems that maximized doesn't have any effect...

[dustdfg]

And just in case if you say about popup window for my use case. As I understand popup windows doesn't fit because they are bound to my original window. Thought I don't know slint and can't be sure if it should be bound to a main window or not...

fn main() {
	let app = MainWindow::new().unwrap();
	app.window().set_maximized(true);
	app.run().unwrap();
}

slint::slint! {
	export component MainWindow inherits Window {
		background: transparent;
		no-frame: true;
		popup := PopupWindow {
			Rectangle { height:100%; width: 100%; background: yellow; }
			x: 0px; y: 0px; height: 500px; width: 100px;
		}
		TouchArea {
			height:100%; width: 100%;
			clicked => { popup.show(); }
		}
	}
}

[dustdfg]

And I also found two discussion which are about layer shell:

#3119
#1765

[The-Briel-Deal]

One thing I can confirm is that this isn't specific to just winit or any rust crate.

Kitty does the same thing with transparency enabled.

Guessing this is just how sway works. iirc, I kind of remember this not being an issue in i3? So it might not be by design and it could just be a bug?

Pretty sure this doesn't happen in Hyprland also iirc.

So this might be worth making a bug on sway for.

[tronical]

I think it might be possible to implement the layer shell protocol within the application, outside of winit and Slint.

[ogoffart]

This is intentional in the compositors.
Fullscreen wayland windows can't be transparent.
https://gitlab.gnome.org/GNOME/mutter/-/issues/2520