Flickable (Scrollview) does not update viewport when content changes

[jmEvoqua]

Bug Description

If there is dynamically visible content inside a flickable, the viewport does not respond to content changes. It will only update on scrolling.

For example:
When scrolling down and hide some content the viewport stays at that position and the screen could get potentially empty, which is confusing to the user.

Flickable.webm

Reproducible Code (if applicable)

import { AboutSlint, Button, VerticalBox, ScrollView } from "std-widgets.slint";

export component Demo {
    property <bool> hidden;
    ScrollView {
        VerticalBox {
            alignment: start;
            Text {
                text: "Hello World!";
                font-size: 24px;
                horizontal-alignment: center;
            }

            if !root.hidden: AboutSlint {
                preferred-height: 150px;
            }

            HorizontalLayout {
                alignment: center;
                Button {
                    text: "Toggle";
                    clicked => {
                        root.hidden = !root.hidden;
                    }
                }
            }
        }
    }
}

Environment Details

• Slint Version: 1.9.2

Product Impact

No response