[bug] Additional window rendering

[Burial0268]

Describe the bug

An unexpected window overlay is rendered outside the window border, and the WindowEffect is set as expected

Screenshots:

Reproduction

I have the following code in main.rs:

async fn create_main_window(app_handle: &AppHandle) -> Result<WebviewWindow, tauri::Error> {
    let window = tauri::WebviewWindowBuilder::new(
        app_handle,
        "main",
        tauri::WebviewUrl::App("index.html".into()),
    )
    .title("Tauri Application")
    .inner_size(984.0, 703.0)
    .min_inner_size(700.0, 550.0)
    .decorations(true)
    .resizable(true)
    .maximizable(true)
    .visible(false)
    .additional_browser_args("--enable-features=msWebView2EnableDraggableRegions --disable-features=OverscrollHistoryNavigation,msExperimentalScrolling")
    .transparent(true)
    .effects(WindowEffectsConfig {
        effects: vec![],
        state: None,
        radius: None,
        color: None
    })
    .build()?;

    window.restore_state(StateFlags::all())?;
    setup_window_events(window.clone());

    Ok(window)
}

The function setup_window_events is about listening the window_state and printing them out while debugging, so it would not effect the window's config.

The main.rs has another part below that might effect this, but i'm not sure currently:

pub fn setup_window_decoration(window: &WebviewWindow) -> Result<(), Box<dyn std::error::Error>> {
    window.create_overlay_titlebar()?;

    #[cfg(target_os = "macos")] {
        window.set_traffic_lights_inset(12.0, 16.0)?;
        window.make_transparent()?;
        window.set_window_level(25)?;
    }

    Ok(())
}

Additionally, the window.create_overlay_titlebar()?; is brought by crate tauri-plugin-decorum.

Expected behavior

No extra border

Full tauri info output

> tauri "info"


[✔] Environment
    - OS: Windows 10.0.19045 x86_64 (X64)
    ✔ WebView2: 133.0.3065.82
    ✔ MSVC:
        - Visual Studio Community 2022
        - Visual Studio 生成工具 2019
    ✔ rustc: 1.85.0 (4d91de4e4 2025-02-17)
    ✔ cargo: 1.85.0 (d73d2caf9 2024-12-31)
    ✔ rustup: 1.27.1 (54dd3d00f 2024-04-24)
    ✔ Rust toolchain: stable-x86_64-pc-windows-msvc (default)       
    - node: 20.15.1
    - pnpm: 9.15.0
    - yarn: 1.22.19
    - npm: 9.6.6

[-] Packages
    - tauri 🦀: 2.3.0
    - tauri-build 🦀: 2.0.6
    - wry 🦀: 0.50.1
    - tao 🦀: 0.32.5
    - @tauri-apps/api : 2.1.1 (outdated, latest: 2.3.0)
    - @tauri-apps/cli : 2.1.0 (outdated, latest: 2.3.0)

[-] Plugins
    - tauri-plugin-shell 🦀: 2.2.0
    - @tauri-apps/plugin-shell : 2.0.1 (outdated, latest: 2.2.0)   
    - tauri-plugin-window-state 🦀: 2.2.1
    - @tauri-apps/plugin-window-state : 2.0.0 (outdated, latest: 2.2.1)
    - tauri-plugin-dialog 🦀: 2.2.0
    - @tauri-apps/plugin-dialog : 2.0.1 (outdated, latest: 2.2.0)  
    - tauri-plugin-persisted-scope 🦀: 2.2.0
    - @tauri-apps/plugin-persisted-scope : not installed!
    - tauri-plugin-http 🦀: 2.3.0
    - @tauri-apps/plugin-http : 2.0.1 (outdated, latest: 2.3.0)    
    - tauri-plugin-os 🦀: 2.2.0
    - @tauri-apps/plugin-os : 2.0.0 (outdated, latest: 2.2.0)      
    - tauri-plugin-process 🦀: 2.2.0
    - @tauri-apps/plugin-process : 2.0.0 (outdated, latest: 2.2.0) 
    - tauri-plugin-log 🦀: 2.2.3
    - @tauri-apps/plugin-log : 2.0.0 (outdated, latest: 2.2.3)     
    - tauri-plugin-updater 🦀: 2.5.1
    - @tauri-apps/plugin-updater : 2.0.0 (outdated, latest: 2.5.1) 
    - tauri-plugin-store 🦀: 2.2.0
    - @tauri-apps/plugin-store : 2.1.0 (outdated, latest: 2.2.0)   
    - tauri-plugin-fs 🦀: 2.2.0

[-] App
    - build-type: bundle
    - CSP: unset
    - frontendDist: ../dist
    - devUrl: http://localhost:1420/
    - framework: React
    - bundler: Vite

Stack trace

Additional context

I have try to set the decorations attribute to false but it's useless.
The issue was not found in versions prior to Tauri 2.3.0 using the completely same code.
If additional information is required, I will provide it whenever possible.

[Burial0268]

seems that is about WindowEffect 🤔

When I set the WindowEffect to None, the original WindowEffect will still apply to the outer window, like this:

[Burial0268]

In my operating system it could be reproduction when the WindowEffect has been set.
@amrbashir Would it possible that struct WindowEffect has some bugs?