import QtQuick

MouseArea {
    id: root

    // signal drag(real dx, real dy)
    signal anchorDrag(real dx, real dy)

    QtObject {
        id: priv
        property bool firstEvent: false
        property real firstx: 0
        property real firsty: 0
    }

    Rectangle {
        anchors.fill: parent
        color: "#20000000"
    }

    function fpos(p) {
        return `${p.x.toFixed(2)},${p.y.toFixed(2)}`
    }

    onPressed: (mouse) => {
                   priv.firstEvent = true
                   console.log(`${fpos(mouse)} press`)
               }
    onReleased: (mouse) => {
                    priv.firstEvent = false
                    console.log(`${fpos(mouse)} release`)
                }

    onPositionChanged: (mouse) => {
                           if (priv.firstEvent) {
                               priv.firstEvent = false
                               priv.firstx = mouse.x
                               priv.firsty = mouse.y
                               let p = root.mapToGlobal(mouse.x, mouse.y)
                               console.log(`${fpos(mouse)} pos change, first event, item ${fpos(mouse)}, global ${fpos(p)}`)
                               return
                           }
                           let dx = mouse.x - priv.firstx
                           let dy = mouse.y - priv.firsty
                           root.anchorDrag(dx, dy)
                           let d = { x: dx, y: dy }

                           let p = root.mapToGlobal(priv.firstx, priv.firsty)
                           mousePos.set(p.x, p.y)
                           console.log(`${fpos(mouse)} pos change, d ${fpos(d)}, set to global ${fpos(p)}`)
                       }
}