app/resources/qml/components/FancyBusyIndicator.qml

import QtQuick 2.3
import QtQuick.Controls 2.4

BusyIndicator {
    id: control

    property double animationSpeed: 1000
    property double formFactor: 4.5

    property color lineColor: "#21be2b"

    contentItem: Item {
        implicitWidth: 64
        implicitHeight: 64

        Item {
            id: item

            anchors.fill: parent

            property int currentHeight: 0

            SequentialAnimation {
                running: control.running
                loops: Animation.Infinite

                NumberAnimation {
                    target: item
                    property: "currentHeight"
                    from: 0
                    to: 800
                    duration: control.animationSpeed
                }
            }

            Row {

                anchors.fill: parent

                spacing: item.width / 9

                Repeater {
                    id: repeater
                    model: 5

                    Rectangle {

                        property double heightMultiplier: Math.abs( Math.sin( ( ((item.currentHeight/100) + (index*(control.formFactor/repeater.model)))) * (Math.PI/8) ) )

                        anchors.verticalCenter: parent.verticalCenter

                        width: item.width / 9
                        height: ( heightMultiplier ) * ( item.height - 1 ) + 1

                        radius: width * 0.5

                        color: control.lineColor

                    }
                }
            }
        }
    }
}