Allow parent opacity without propagating to child subtree (for glassy UI effects)

[mitsubishirgb]

I'm building a glassy (frosted glass) UI effect and need to apply semi-transparency to a parent container without affecting its children (e.g., text labels becoming too faint or invisible). From the docs, I understand Slint composites the entire subtree into an intermediate layer and applies opacity to that layer for performance, which causes this propagation. Is there a built-in way to isolate the parent's opacity (e.g., a "local-only" mode, or using layers/clipping)? If not, could we add support for it?

[bowenxuuu]

export component Glassy inherits Window {
    title: "Glassy Window";
    preferred-width: 600px;
    preferred-height: 400px;
    Image {
        source: @image-url("../images/bg.jpg");
    }

    // glassy widget
    Rectangle {
        width: 300px;
        height: 200px;

        // glassy effect
        Rectangle {
            background: white;
            opacity: 0.3;
            drop-shadow-color: black;
            drop-shadow-blur: 20px;
        }

        // content inside the glassy rectangle
        Text {
            color: red;
            font-size: 28px;
            text: "Hello World!\nThis is a glassy effect.";
        }
    }
}