Window.hide() on a sub-window closes the live preview

[LeonMatthes]

Bug Description

Clicking the button in the below example closes the live preview, even if it should just hide the sub window.

Reproducible Code (if applicable)

import { Button } from "std-widgets.slint";

export component App inherits Window {
    background: red;
    sub := Window {
        background: green;
        width: 100px;
        height: 100px;
        visible: true;
    }

    Button {
        clicked => {
            sub.hide();
        }
    }
}

Environment Details

• Slint Version: master
• Platform/OS: Linux
• Programming Language: Slint
• Backend/Renderer: Qt

Product Impact

No response

[ogoffart]

Note that it doesn't need to be in a sub-window:

Same problem with

import { Button } from "std-widgets.slint";
export component Demo inherits Window {
    preferred-height: 200px;
    preferred-width: 200px;
    Button {
        text: "Hide!";
        clicked => {
            root.hide();
        }
    }
}

On slintpad, this "crashes" the preview.

That's because the previewed component is a sub-element of the live preview window.

The issue here is that hide() should only hide the Window corresponding to the element it points to.

[ogoffart]

Window.hide is being makred as experimental in #10505 partially for this reason.