arrow.py

from PyQt5.QtWidgets import QApplication, QWidget, QMainWindow, QLabel, QAction,\
QStatusBar, QMenuBar, QLineEdit, QPushButton, QSlider, QScrollArea, QVBoxLayout,\
QHBoxLayout, QDockWidget, QToolBar, QMenu, QLayout, QSizePolicy, QListWidget, QListWidgetItem,\
QGraphicsLineItem, QGraphicsWidget
from PyQt5.QtCore import Qt, QSize, QLineF, QPoint, QRectF
from PyQt5.QtGui import QIcon, QFont, QPainter, QPen


class Arrow(QGraphicsLineItem):

    def __init__(self, source, destination, window, parent=None):
        super(Arrow, self).__init__(parent)
        self.source = source
        self.destination = destination
        self._window = window
        self.moveLine()
        self.source.moved.connect(self.moveLine)
        self.destination.moved.connect(self.moveLine)

    def contextMenuEvent(self, event):
        menu = QMenu()
        menu.addAction("Delete", self.remove)
        menu.exec_(self.cursor().pos())

    def remove(self):
        self._window.scene.removeItem(self)
        self._window.signalList.remove(self)

    def moveLine(self):
        self.setPen(QPen(Qt.black, 3))
        self.setLine(QLineF(self.source.operation.x()+self.source.x()+14,\
             self.source.operation.y()+self.source.y()+7.5,\
             self.destination.operation.x()+self.destination.x(),\
             self.destination.operation.y()+self.destination.y()+7.5))