QQC2.ScrollBar needs more API for feature-parity with QScrollBar

import QtQuick
import QtQuick.Templates as T
import org.kde.qqc2desktopstyle.private as StylePrivate

T.ScrollBar {
    id: controlRoot

    background: MouseArea {
        anchors.fill: parent
        hoverEnabled: true
        acceptedButtons: Qt.LeftButton | Qt.MiddleButton
        onExited: style.activeControl = "groove";
        onPressed: mouse => {
            const jumpPosition = style.positionFromMouse(mouse);
            if (mouse.buttons & Qt.MiddleButton) {
                style.activeControl = "handle";
                controlRoot.position = jumpPosition;
                mouse.accepted = true;
            } else if (style.activeControl === "down") {
                buttonTimer.increment = 1;
                buttonTimer.running = true;
                mouse.accepted = true;
            } else if (style.activeControl === "up") {
                buttonTimer.increment = -1;
                buttonTimer.running = true;
                mouse.accepted = true;
            } else if (style.activeControl === "downPage") {
                if (style.scrollToClickPosition(mouse)) {
                    controlRoot.position = jumpPosition;
                } else {
                    buttonTimer.increment = controlRoot.size;
                    buttonTimer.running = true;
                }
                mouse.accepted = true;
            } else if (style.activeControl === "upPage") {
                if (style.scrollToClickPosition(mouse)) {
                    controlRoot.position = jumpPosition;
                } else {
                    buttonTimer.increment = -controlRoot.size;
                    buttonTimer.running = true;
                }
                mouse.accepted = true;
            } else {
                mouse.accepted = false;
            }
        }
        onPositionChanged: mouse => {
            style.activeControl = style.hitTest(mouse.x, mouse.y);
            if (mouse.buttons & Qt.MiddleButton) {
                style.activeControl = "handle";
                controlRoot.position = style.positionFromMouse(mouse);
                mouse.accepted = true;
            }
        }
        onReleased: mouse => {
            style.activeControl = style.hitTest(mouse.x, mouse.y);
            buttonTimer.running = false;
            mouse.accepted = false;
        }
        onCanceled: buttonTimer.running = false;

        Timer {
            id: buttonTimer
            property real increment
            repeat: true
            interval: 150
            triggeredOnStart: true
            onTriggered: {
                if (increment === 1) {
                    controlRoot.increase();
                } else if (increment === -1) {
                    controlRoot.decrease();
                } else {
                    controlRoot.position = Math.min(1 - controlRoot.size, Math.max(0, controlRoot.position + increment));
                }
            }
        }

        StylePrivate.StyleItem {
            id: style

            function positionFromMouse(mouse/*: MouseEvent*/): real {
                return Math.min(1 - controlRoot.size, Math.max(0,
                    (controlRoot.horizontal
                        ? mouse.x / width
                        : mouse.y / height
                    ) - controlRoot.size / 2
                ));
            }
        }
    }
}