test of https://stackoverflow.com/questions/54907311

main.py

from PySide2 import QtCore, QtGui, QtWidgets

class InfoBox(QtWidgets.QGraphicsItem):
	Type = QtWidgets.QGraphicsItem.UserType + 1

	def __init__(self, parent=None):
		super(InfoBox, self).__init__(parent)
		self.setZValue(4)
		proxy = QtWidgets.QGraphicsProxyWidget(self)
		widget = QtWidgets.QLabel("TEST!")
		widget.setAttribute(QtCore.Qt.WA_TransparentForMouseEvents)
		widget.setWindowModality(QtCore.Qt.NonModal)
		proxy.setWidget(widget)

	def boundingRect(self):
		return QtCore.QRectF(0, 0, 100, 100)

	def paint(self, *args):
		pass

class GraphicsView(QtWidgets.QGraphicsView):
	def __init__(self, parent=None):
		super(GraphicsView, self).__init__(parent)
		self.setScene(QtWidgets.QGraphicsScene(QtCore.QRectF(-400, -400, 800, 800)))
		self.setDragMode(QtWidgets.QGraphicsView.ScrollHandDrag)
		self.viewport().setCursor(QtCore.Qt.ArrowCursor)
		self.create_items()

		self.info_box = None

	def create_items(self):
		rect_item = QtWidgets.QGraphicsRectItem(QtCore.QRect(0, 0, 100, 100))
		rect_item.setBrush(QtGui.QColor("#00ff54"))
		self.scene().addItem(rect_item)

		circle_item = QtWidgets.QGraphicsEllipseItem(QtCore.QRect(-100, -100, 100, 100))
		circle_item.setBrush(QtGui.QColor("salmon"))
		self.scene().addItem(circle_item)

		
	def mousePressEvent(self, event):
		super(GraphicsView, self).mousePressEvent(event)
		if self.info_box is None:
			self.info_box = InfoBox()
			self.scene().addItem(self.info_box)
			self.info_box.setPos(self.mapToScene(event.pos()))

	def mouseReleaseEvent(self, event):
		super(GraphicsView, self).mouseReleaseEvent(event)
		self.viewport().setCursor(QtCore.Qt.ArrowCursor)

class MainWindow(QtWidgets.QMainWindow):
	def __init__(self, parent=None):
		super(MainWindow, self).__init__(parent)
		self.setCentralWidget(GraphicsView())
		self.resize(640, 480)

if __name__ == '__main__':
	import sys
	app = QtWidgets.QApplication.instance()
	if app is None:
		app = QtWidgets.QApplication(sys.argv)
	w = MainWindow()
	w.show()
	sys.exit(app.exec_())