QML ScrollBar.AsNeeded background track always visible on empty ListView when using Basic style

Gary90

Hi everyone,

I am working with Qt 6.9.3 and customizing a ScrollBar using the QtQuick.Controls.Basic style. I have encountered an issue where the ScrollBar.AsNeeded policy does not work as expected when attached to a ListView.When the ListView is completely empty (or content fits within bounds), the scroll handle/thumb correctly hides, but the custom background track remains permanently visible on the screen. If I switch back to the default QtQuick.Controls style without customization, the AsNeeded policy works perfectly.

Here is the custom ScrollBar implementation I am using in a standalone file:

// CustomScrollBar.qml
import QtQuick
import QtQuick.Controls.Basic

ScrollBar {
    id: control
    policy: ScrollBar.AsNeeded
    minimumSize: 0.1
    hoverEnabled: false

    contentItem: Rectangle {
        implicitWidth: 10
        implicitHeight: 10
        color: control.pressed ? "#444" : "#888"
        // Handle correctly tracks active/size states
        visible: control.policy === ScrollBar.AlwaysOn || (control.active && control.size < 1.0)
    }

    background: Rectangle {
        implicitWidth: control.implicitWidth
        color: "#E0E0E0"
        // This background remains visible even when ListView is empty (control.size == 1.0)
    }
}

And how it is attached:

ListView {
    id: listView
    Layout.fillHeight: true
    Layout.fillWidth: true
    clip: true
    model: 0 // Empty for testing

    ScrollBar.vertical: CustomScrollBar {
        anchors.right: listView.right
    }
}

Is there a specific internal property or visibility binding for the background item in the Basic style template that I need to manually handle to make it respect the AsNeeded policy when the view has no overflow?

Thanks for your help!

Nils Sjoberg

Add a similar visible property to the background element inside your CustomScrollBar.qml.

Gary90

Thanks for the answer, @Nils-Sjoberg , but unfortunately, that solution didn't work.

When I add the visibility logic directly to the background property in

CustomScrollBar.qml (visible: control.policy === ScrollBar.AlwaysOn || (control.active && control.size < 1.0)),

the scrollbar appearing only when scrolling overflowing items. But the scrollbar is not visible when items are overflowing the list without scrolling.

However, according to QML specifications, we shouldn't need to manually override the background's visible property to get standard policy behavior.

Nils Sjoberg

@Gary90 said in QML ScrollBar.AsNeeded background track always visible on empty ListView when using Basic style:

Thanks for the answer, @Nils-Sjoberg , but unfortunately, that solution didn't work.

When I add the visibility logic directly to the background property in

CustomScrollBar.qml (visible: control.policy === ScrollBar.AlwaysOn || (control.active && control.size < 1.0)),

the scrollbar appearing only when scrolling overflowing items. But the scrollbar is not visible when items are overflowing the list without scrolling.

However, according to QML specifications, we shouldn't need to manually override the background's visible property to get standard policy behavior.

background: Rectangle {
    implicitWidth: control.implicitWidth
    color: "#E0E0E0"
    visible: control.policy === ScrollBar.AlwaysOn || control.size < 1.0
}

Nils Sjoberg

Remove control.active && from the condition.