gistfile1.txt

import QtQuick 2.0

SequentialAnimation {
    id: root
    property QtObject target
    property string fadeProperty: "opacity"
    property int fadeDuration: 150
    property alias outValue: outAnimation.to
    property alias inValue: inAnimation.to
    property alias outEasingType: outAnimation.easing.type
    property alias inEasingType: inAnimation.easing.type
    property string easingType: "Quad"

    NumberAnimation {
        id: outAnimation
        target: root.target
        property: root.fadeProperty
        duration: root.target.visible ? root.fadeDuration : 0
        to: 0
        easing.type: Easing["In"+root.easingType]
    }
    PropertyAction { } // actually change the property between the 2 other animations
    NumberAnimation {
        id: inAnimation
        target: root.target
        property: root.fadeProperty
        duration: root.target.visible ? 0 : root.fadeDuration // the duration seems to be read at the start of the SequentialAnimation or Behavior
        to: 1
        easing.type: Easing["Out"+root.easingType]
    }
}