Ondra-QML

import QtQuick 2.7
//import Qt.WebSockets 1.0

Item {
    id: root

    width: 1200
    height: 816

    Canvas {
        id: canvas

        anchors.fill: parent

        onPaint: {
            console.log(mouseArea.mousePos)
            var ctx = canvas.getContext('2d')
            ctx.clearRect(0, 0, canvas.width, canvas.height)
            ctx.beginPath()
            ctx.strokeStyle = "#FF000"
            ctx.lineWidth = 1
            ctx.moveTo(0, 0)
            ctx.lineTo(mouseArea.mousePos.x, mouseArea.mousePos.y)
            ctx.closePath()
            ctx.stroke()
        }
    }


    MouseArea {
        id: mouseArea

        property var mousePos: Qt.point(0, 0)

        hoverEnabled: true
        anchors.fill: parent

        onMouseXChanged: {
            mousePos.x = mouse.x
            canvas.requestPaint()
        }

        onMouseYChanged: {
            mousePos.y = mouse.y
            canvas.requestPaint()
        }
    }
}