ImplicitWidth of ScrollView handle doesn't work

[Kamichanw]

In following code, I want width of ScrollView handle can be changed when SplitHandle.hovered or SplitHandle.pressed is true.

import QtQuick
import QtQuick.Controls

SplitView {
    id: control

    handle: Rectangle {
        id: splitViewHandle
        implicitWidth: SplitHandle.hovered || SplitHandle.pressed ? 4 : 1
        implicitHeight: implicitWidth
        color: SplitHandle.hovered || SplitHandle.pressed ? "#0078D4" : "#313131"
        Behavior on color {
            ColorAnimation {
                duration: 130
            }
        }
        containmentMask: Item {
            height: splitViewHandle.height
            width: 10
            x: (splitViewHandle.width - width) / 2
        }
    }
}

However, it seems that my binding for implitWidth has no effect. The width of handle is constantly 1.

[Kamichanw]

I found that the reason why implicitWidth doesn't change is that attched properties don't affect binding, that is, when SplitHandle.hovered, SplitHandle.pressed etc are changed, implicitWidth won't change just like there is no xxxChanged signal emiited. However, SplitHandle.onHoveredChanged still makes sense. Is this qt bug?