Draw a line between two mouse clicks.

[Itdoesntwork]

I am trying to make something like a small drawing app and I need to make it draw a line between two mouse clicks. I'm new to qml so I used some code from other websites but my idea was like this:

import QtQuick 2.0

Rectangle {
    width: 720
    height: 720

    property int xpos
    property int ypos
    property int prevxpos
    property int prevypos
    Canvas {
        id: myCanvas
        anchors.rightMargin: 0
        anchors.bottomMargin: 0
        anchors.leftMargin: 0
        anchors.topMargin: 0
        anchors.fill: parent
        renderTarget: Canvas.Image
        renderStrategy: Canvas.Immediate
        onPaint: {
            var ctx = getContext('2d')
            ctx.fillStyle = "blue"
            ctx.fillRect(xpos-3, ypos-1, 5, 5)
            ctx.lineWidth = 7;
                            ctx.strokeStyle = "red"
                            ctx.beginPath()
                            ctx.moveTo(prevxpos, prevypos)
                            ctx.lineTo(xpos, ypos)

                            ctx.stroke()

        }

        MouseArea{
            anchors.fill: parent
            onPressed: {
                prevxpos = ypos
                prevypos = xpos
                xpos = mouseX
                ypos = mouseY
                myCanvas.requestPaint()
            }
            onMouseXChanged: {
                var prevxpos = xpos
                var prevypos = xpos
                xpos = mouseX
                ypos = mouseY
                myCanvas.requestPaint()
            }
            onMouseYChanged: {
                var prevxpos = xpos
                var prevypos = ypos
                xpos = mouseX
                ypos = mouseY
                myCanvas.requestPaint()
            }
}

prevxpos recieves the value of xpos before xpos gets updated and then onPaint darws a line between the two points. However, the line just doesn't appear. What am I doing wrong?