Avalonia/src/Avalonia.Controls/WindowTransparencyLevel.cs

namespace Avalonia.Controls
{
    public enum WindowTransparencyLevel
    {
        /// <summary>
        /// The window background is Black where nothing is drawn in the window.
        /// </summary>
        None,

        /// <summary>
        /// The window background is Transparent where nothing is drawn in the window.
        /// </summary>
        Transparent,

        /// <summary>
        /// The window background is a blur-behind where nothing is drawn in the window.
        /// </summary>
        Blur,

        /// <summary>
        /// The window background is a blur-behind with a high blur radius. This level may fallback to Blur.
        /// </summary>
        AcrylicBlur,
        
        /// <summary>
        /// The window background is based on desktop wallpaper tint with a blur. This will only work on Windows 11 
        /// </summary>
        Mica
    }
}