'react to mouse actions:
no mouse: show red mousedrop
LMB: rotate viewport
RMB: move viewport'

def move(self, event):

    if event.Entering():
        self.canvas.SetFocus()
        event.Skip()
        return
    if (event.Dragging() and event.LeftIsDown()):
        self.handle_rotation(event)
    elif (event.Dragging() and event.RightIsDown()):
        self.handle_translation(event)
    elif event.LeftUp():
        self.initpos = None
    elif event.RightUp():
        self.initpos = None
    else:
        event.Skip()
        return
    event.Skip()
    wx.CallAfter(self.Refresh)
