Draw chart with "tolerance area" and different colored trend-line inside or outside of this area

CompuChino

Hello,

I'm quite new to Qt and QML. I need to draw a chart with a horizontal area drawn in a different color. The trend line I draw should have different colors inside and outside of this "tolerance" area.

Now my questions:

So far I have drawn the horizontal area (tolerance area) with an AreaSeries (look at the source code below). Is there a better way to do this?
I couldn't find a possibility to give my trend line (LineSeries) different colors inside and outside of this horizontal area. How can I do this? It just occured to me, that I could do it with different LineSeries, but this would need a lot of calculating. Is there a better solution?
On the y axis I want to print the value next to the reference line bold or in a bigger font. Can I do this just for one label of the axis?

Here is my actual source code:
import QtQuick 2.3
import QtQuick.Window 2.2
import QtCharts 2.0

Window {
visible: true
width: 720
height: 720

// Pick Count
ChartView {
    backgroundColor: "lightgrey"
    height: parent.height; width: parent.width
    dropShadowEnabled: true
    legend.visible: false
    title: qsTr("Pick count")

    ValueAxis {
        id: axisX
        color: "black"
        min: -100.0
        max: 0.0
        tickCount: 11
        titleText: "m"
    }

    ValueAxis {
        id: axisY
        color: "black"
        min: 14.0
        max: 22.0
        tickCount: 5
        titleText: "F/cm"
    }

    // Trend line
    LineSeries {
        axisX: axisX
        axisY: axisY

        XYPoint { x: 0.0; y: 17.0}
        XYPoint { x: -10.0; y: 17.5}
        XYPoint { x: -20.0; y: 15.9}
        XYPoint { x: -30.0; y: 16.0}
        XYPoint { x: -40.0; y: 16.3}
        XYPoint { x: -50.0; y: 16.4}
        XYPoint { x: -60.0; y: 17.2}
        XYPoint { x: -70.0; y: 17.0}
        XYPoint { x: -80.0; y: 18.3}
        XYPoint { x: -90.0; y: 18.0}
        XYPoint { x: -100.0; y: 19.0}
    }

    // Tolerance area
    AreaSeries {
        axisX: axisX
        axisY: axisY
        borderColor: "transparent"
        borderWidth: 0.0
        opacity: 0.4
        lowerSeries: LineSeries {
            XYPoint { x: 0.0; y: 17.0}
            XYPoint { x: -99.9; y: 17.0}
        }
        upperSeries: LineSeries {
            XYPoint { x: 0.0; y: 19.0}
            XYPoint { x: -99.9; y: 19.0}
        }
    }

    // Reference line
    LineSeries {
        axisX: axisX
        axisY: axisY

        XYPoint { x: 0.0; y: 18.0}
        XYPoint { x: -100.0; y: 18.0}
    }
}

}

Any help is highly appreciated!

Christine