title: PyQt5: Check if mouse is held down in enter-event
body: <p>My actual application is much more complicated than this, but the example below sums up the majority of my problem.  I have multiple QLabels that I've subclassed to make them clickable.  The labels display 16x16 images which requires a process of loading the images via Pillow, converting them to ImageQt objects, and then setting the pixmap of the label.  In the example, I have 3 clickable QLabels that run the print_something function each time I click on them.  My goal is to be able to hold the mouse down, and for each label I hover over, the function gets called. Any pointers would be great.</p>
  
  <pre><code>from PyQt5 import QtCore, QtWidgets, QtGui
  from PIL import Image
  from PIL.ImageQt import ImageQt
  import sys
  
  
  class ClickableLabel(QtWidgets.QLabel):
  
      def __init__(self):
          super().__init__()
  
      clicked = QtCore.pyqtSignal()
  
      def mousePressEvent(self, ev):
          if app.mouseButtons() &amp; QtCore.Qt.LeftButton:
              self.clicked.emit()
  
  
  class MainWindow(QtWidgets.QMainWindow):
  
      def __init__(self):
          super().__init__()
          central_widget = QtWidgets.QWidget()
  
          self.setFixedSize(300, 300)
          image = Image.open("16x16image.png")
          image_imageqt = ImageQt(image)
  
          hbox = QtWidgets.QHBoxLayout()
          hbox.setSpacing(0)
          hbox.addStretch()
  
          label01 = ClickableLabel()
          label01.setPixmap(QtGui.QPixmap.fromImage(image_imageqt))
          label01.clicked.connect(self.print_something)
          hbox.addWidget(label01)
  
          label02 = ClickableLabel()
          label02.setPixmap(QtGui.QPixmap.fromImage(image_imageqt))
          label02.clicked.connect(self.print_something)
          hbox.addWidget(label02)
  
          label03 = ClickableLabel()
          label03.setPixmap(QtGui.QPixmap.fromImage(image_imageqt))
          label03.clicked.connect(self.print_something)
          hbox.addWidget(label03)
  
          hbox.addStretch()
  
          central_widget.setLayout(hbox)
  
          self.setCentralWidget(central_widget)
  
      def print_something(self):
          print("Printing something..")
  
  
  if __name__ == "__main__":
      app = QtWidgets.QApplication(sys.argv)
      main_window = MainWindow()
      main_window.show()
      sys.exit(app.exec_())
  </code></pre>