Hello,

Im fairly new to the GraphicsScene and GraphicsView in PyQt5, im trying to wrap my head around how to use it efficiently, and i have just bumped into an issue.

I am looking for a way to change the default mousebutton that moves the items in the GraphicsView.

This is the way i would like the graphicsScene UI to work :

LeftMouse button click on Item = ItemClick signal (like a regular button widget would do)
RightMouse button click on Item = ItemLeftClick signal (open a context menu with a few options specific to the item)

RightMouse button click on Empty space = Open's context menu for GraphicsView (so far so good).

#here
LeftMouse button click on Empty space and drag select rubberband = This Can stay as currently is, clears selection on click then it selects any of the items inside the rubberband rectangle on mouse click release.

MiddleMouse button drag = If items selected, i want this button to be moving my items position.
so far im kinda unable to do this..

this is a snippet of my current mouse logic inside the QtWidgets.QGraphicsView class , im not sure what i would need to do to replace the default leftMouse drag behaviour.

Qt Code: 
  1. def mousePressEvent(self, event):
  2.         if event.button() == QtCore.Qt.MiddleButton and event.modifiers() == QtCore.Qt.AltModifier:
  3.             self.setDragMode(QtWidgets.QGraphicsView.NoDrag)
  4.             self.drag = True
  5.             self.prev_pos = event.pos()
  6.             self.setCursor(QtCore.Qt.SizeAllCursor)
  7.         elif event.button() == QtCore.Qt.LeftButton:
  8.             self.setDragMode(QtWidgets.QGraphicsView.RubberBandDrag)
  9.  
  10.         # This does not work as i wanted, it is only changing the mouse icon
  11.         elif event.button() == QtCore.Qt.MiddleButton:
  12.             # set hand icon..
  13.             self.setDragMode(QtWidgets.QGraphicsView.DragMode.ScrollHandDrag)
  14.             # print selected item position in scene.
  15.             for x in self.scene().selectedItems() :
  16.                 print( x.scenePos() )
  17.  
  18.         super(View, self).mousePressEvent(event)
  19.  
  20.     def mouseMoveEvent(self, event):
  21.         if self.drag:
  22.             new_scale = self.matrix().m11()
  23.             delta = (self.mapToScene(event.pos()) - self.mapToScene(self.prev_pos)) * -1.0 * new_scale
  24.             center = QtCore.QPoint(self.viewport().width() / 2 + delta.x(), self.viewport().height() / 2 + delta.y())
  25.             new_center = self.mapToScene(center)
  26.             self.centerOn(new_center)
  27.             self.prev_pos = event.pos()
  28.             return
  29.         super(View, self).mouseMoveEvent(event)
  30.  
  31.     def mouseReleaseEvent(self, event):
  32.         if self.drag:
  33.             self.drag = False
  34.             self.setCursor(QtCore.Qt.ArrowCursor)
  35.         super(View, self).mouseReleaseEvent(event)
  36.  
  37.         if event.button() == QtCore.Qt.RightButton:
  38.             # Context Menu
  39.             menu = QtWidgets.QMenu()
  40.             save = menu.addAction('save')
  41.             load = menu.addAction('load')
  42.             selectedAction = menu.exec_(event.globalPos())
  43.  
  44.             if selectedAction == save:
  45.                 common.scene_save(self)
  46.             if selectedAction == load:
  47.                 common.scene_load(self)
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