Make draggable QWebView inside a transparent QWidget

Ok guys, I got this problem. I've a QWidget window set to transparent as follow:

self.setAttribute(Qt.WA_TranslucentBackground)
self.setWindowFlags(Qt.Tool | Qt.FramelessWindowHint)
self.setWindowFlags(self.windowFlags() | Qt.WindowStaysOnTopHint)

Inside the QWidget there a QWebView. Now I want to make draggable the QWebView, but it don't wanna work. I wrote even these listeners:

def mousePressEvent(self, event):
if event.button() == QtCore.Qt.LeftButton:
self.dragPosition = event.globalPos() - self.frameGeometry().topLeft()
event.accept()

def mouseMoveEvent(self, event):
if event.buttons() == QtCore.Qt.LeftButton:
self.move(event.globalPos() - self.dragPosition)
event.accept()

but nothing.

Any suggestions?