import sys
from PyQt5 import QtWidgets, uic
Ui_MainWindow, QtBaseClass = uic.loadUiType("Op4.ui")


class CPoint:
    def __init__(self, x ,y):
        self._x = x
        self._y = y

class CLine:
    def __init__(self, P1, P2):
        self._P1 = P1
        self._P2 = P2

class MyApp(QtWidgets.QMainWindow):
    def __init__(self):
        self._CurP1 = CPoint(0,0)
        self._CurP2 = CPoint(0,0)
        self._allPoints = []
        super(MyApp, self).__init__()

        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
        self._scene = QtWidgets.QGraphicsScene()
        self._scene.setSceneRect(0,0,100,100)
        self.ui.graphicsView.setScene(self._scene)
        self.ui.graphicsView.mousePressEvent = self.mouseDown
        self.ui.graphicsView.mouseReleaseEvent = self.mouseUp
        self.ui.graphicsView.mouseMoveEvent = self.mouseMove


        self._allPoints.append(CLine(CPoint(10,10), CPoint(30,50)))
        self._allPoints.append(CLine(CPoint(30,50), CPoint(40,20)))
        self._allPoints.append(CLine(CPoint(40,20), CPoint(100,35)))
        self._allPoints.append(CLine(CPoint(100,35), CPoint(105,60)))
        self.drawAllLines()

    def mouseDown(self, event):
        point = self.ui.graphicsView.mapToScene(event.pos())
        MX = point.x()
        MY = point.y()
        self._CurP1 = CPoint(MX,MY)


    def mouseUp(self, event):
        point = self.ui.graphicsView.mapToScene(event.pos())
        MX = point.x()
        MY = point.y()
        self._CurP2 = CPoint(MX,MY)
        self._allPoints.append(CLine(self._CurP1, self._CurP2))
        self.drawAllLines()

    def mouseMove(self, event):
        point = self.ui.graphicsView.mapToScene(event.pos())
        MX = point.x()
        MY = point.y()
        self.drawAllLines()
        item = QtWidgets.QGraphicsLineItem(self._CurP1._x, self._CurP1._y, MX,MY)
        self._scene.addItem(item)



    def drawAllLines(self):
        self._scene.clear()
        for a in self._allPoints:
            item = QtWidgets.QGraphicsLineItem(a._P1._x, a._P1._y, a._P2._x, a._P2._y)
            self._scene.addItem(item)



if __name__ == "__main__":
     app = 0 # lost Kernal died probeem op bij herhaald opstarten
     app = QtWidgets.QApplication(sys.argv)
     window = MyApp()
     window.show()
     sys.exit(app.exec_())