PyQt5 program demonstrating a bug with tablet events

import sys

from PyQt5 import QtCore
from PyQt5 import QtGui
from PyQt5 import QtWidgets


class TouchWidget(QtWidgets.QWidget):

  escPressed = QtCore.pyqtSignal()

  def __init__(self, parent=None):
    super(TouchWidget, self).__init__(parent)
    self.setAttribute(QtCore.Qt.WA_AcceptTouchEvents)

  def keyPressEvent(self, event):
    if event.key() == QtCore.Qt.Key_Escape:
      self.escPressed.emit()
    return super(TouchWidget, self).keyPressEvent(event)

  def event(self, event):
    if event.type() == QtCore.QEvent.TouchUpdate:
      self.onTouchUpdate(event)
    return super(TouchWidget, self).event(event)

  def onTouchUpdate(self, event: QtGui.QTouchEvent):
    tps = event.touchPoints()
    released = False
    for i, tp in enumerate(tps):
      if i:
        print("  ", end="")
      print("p%d: %.2f/%.2f" % (i, tp.pos().x(), tp.pos().y()), end="")
      if tp.state() == QtCore.Qt.TouchPointPressed:
        print("    (PRESSED)", end="")
      elif tp.state() == QtCore.Qt.TouchPointMoved:
        print("      (MOVED)", end="")
      elif tp.state() == QtCore.Qt.TouchPointStationary:
        print(" (STATIONARY)", end="")
      elif tp.state() == QtCore.Qt.TouchPointReleased:
        print("   (RELEASED)", end="")
        released = True
    print()
    if released:
      print()
      print()
      print()


if __name__ == "__main__":
  print("""
  This program demonstrates a bug in Qt5's handling of touch gestures.

  A touch gesture event is made of touchpoints. Every time that event fires,
  the touchpoints that it carries can have one of four states: PRESSED,
  RELEASED, STATIONARY, or MOVED. Those touchpoints also contain the
  coordinates at which the touch occurred.

  In order to use this program, run it, move the mouse pointer to the new
  window, and perform a two-finder pinch/rotate gesture.

  The output of this program shows that touchpoints report spurious coordinates
  while in state PRESSED, and tend to keep doing so until the touchpoint gets
  to state MOVED for the first time. A TouchPoint in state RELEASED also tends
  to "jump" some distance from its last known position.

  This is with the TouchPoint.pos() method. When using
  TouchPoint.normalizedPos() instead, the coordinates are correct, expect when
  the TouchPoint is in state RELEASED, where the same "jump" as above can be
  observed.

  Quit this program by pressing Escape.

  """)
  app = QtWidgets.QApplication(sys.argv)
  w = TouchWidget()
  w.show()
  w.escPressed.connect(app.quit)
  app.exec_()