Translucent window outline (window shadow) appears when moving windows with a transparent background with a transparent window

[P-Asta]

Bevy version 0.13

The release number or commit hash of the version you're using.

[Optional] Relevant system information

cargo version: cargo 1.78.0-nightly (a4c63fe53 2024-03-06)

`SystemInfo { os: "MacOS 14.2.1 ", kernel: "23.2.0", cpu: "Apple M1", core_count: "8", memory: "16.0 GiB" }`

What you did

I made the background transparent in the desk_toy example and moved the sprite around, and it ended up like this.

What went wrong

Ghostly semi-translucent outline appeared.

[P-Asta]

What OS are you on? This is likely OS-specific, so this is vital information :)

i use macos m1

[alice-i-cecile]

Looks like this should just be able to be toggled, but I can't figure out how to control this via winit. I'll open an issue upstream.

[xav-ie]

This seems to fix it! I am happy I found this issue and was able to diagnose!

    App::new()
        .insert_resource(ClearColor(Color::NONE))
        .add_plugins(DefaultPlugins.set(WindowPlugin {
            primary_window: Some(Window {
                // fixes window border appearing on macos
                has_shadow: false,
                // you probably also want all this below vvv
                transparent: true,
                decorations: false,
                window_level: WindowLevel::AlwaysOnTop,
                #[cfg(target_os = "macos")]
                composite_alpha_mode: CompositeAlphaMode::PostMultiplied,
                position: WindowPosition::At(IVec2::new(0, 0)),
                cursor_options: CursorOptions {
                    // TODO There is a bug on windows. https://github.com/bevyengine/bevy/issues/7975
                    // If we set hit_test false, we can't get cursor position.
                    #[cfg(target_os = "windows")]
                    hit_test: true,
                    #[cfg(not(target_os = "windows"))]
                    hit_test: false,
                    ..default()
                },
                ..default()
            }),
            ..default()
        }))
        .add_plugin(...)