'react to mouse actions:
no mouse: show red mousedrop
LMB: move active object,
with shift rotate viewport
RMB: nothing
with shift move viewport'

def move(self, event):

    self.mousepos = event.GetPositionTuple()
    if (event.Dragging() and event.LeftIsDown()):
        self.handle_rotation(event)
    elif (event.Dragging() and event.RightIsDown()):
        self.handle_translation(event)
    elif event.ButtonUp(wx.MOUSE_BTN_LEFT):
        if (self.initpos is not None):
            self.initpos = None
    elif event.ButtonUp(wx.MOUSE_BTN_RIGHT):
        if (self.initpos is not None):
            self.initpos = None
    else:
        event.Skip()
        return
    event.Skip()
    wx.CallAfter(self.Refresh)
