text: from .GraphicsObject import GraphicsObject
  from ..Qt import QtGui, QtCore, USE_PYSIDE
  
  if not USE_PYSIDE:
      import sip
  
  __all__ = ['UIGraphicsItem']
  class UIGraphicsItem(GraphicsObject):
      """
      Base class for graphics items with boundaries relative to a GraphicsView or ViewBox.
      The purpose of this class is to allow the creation of GraphicsItems which live inside 
      a scalable view, but whose boundaries will always stay fixed relative to the view's boundaries.
      For example: GridItem, InfiniteLine
      
      The view can be specified on initialization or it can be automatically detected when the item is painted.
      
      NOTE: Only the item's boundingRect is affected; the item is not transformed in any way. Use viewRangeChanged
      to respond to changes in the view.
      """
  
      # sigViewChanged = QtCore.Signal(object)  ## emitted whenever the viewport coords have changed
  
      def __init__(self, bounds=None, parent=None):
          """
          ============== =============================================================================
          **Arguments:**
          bounds         QRectF with coordinates relative to view box. The default is QRectF(0,0,1,1),
                         which means the item will have the same bounds as the view.
          ============== =============================================================================
          """
          GraphicsObject.__init__(self, parent)
          self.setFlag(self.ItemSendsScenePositionChanges)
  
          if bounds is None:
              self._bounds = QtCore.QRectF(0, 0, 1, 1)
          else:
              self._bounds = bounds
  
          self._boundingRect = None
          self._updateView()
  
      def paint(self, *args):
          ## check for a new view object every time we paint.
          #self.updateView()
          pass
  
      def itemChange(self, change, value):
          ret = GraphicsObject.itemChange(self, change, value)
  
          ## workaround for pyqt bug:
          ## http://www.riverbankcomputing.com/pipermail/pyqt/2012-August/031818.html
          if not USE_PYSIDE and change == self.ItemParentChange and isinstance(ret, QtGui.QGraphicsItem):
              ret = sip.cast(ret, QtGui.QGraphicsItem)
  
          if change == self.ItemScenePositionHasChanged:
              self.setNewBounds()
          return ret
  
      # def updateView(self):
      ### called to see whether this item has a new view to connect to
  
      ### check for this item's current viewbox or view widget
      # view = self.getViewBox()
      # if view is None:
      ##print "  no view"
      # return
  
      # if self._connectedView is not None and view is self._connectedView():
      ##print "  already have view", view
      # return
  
      ### disconnect from previous view
      # if self._connectedView is not None:
      # cv = self._connectedView()
      # if cv is not None:
      ##print "disconnect:", self
      # cv.sigRangeChanged.disconnect(self.viewRangeChanged)
  
      ### connect to new view
      ##print "connect:", self
      # view.sigRangeChanged.connect(self.viewRangeChanged)
      # self._connectedView = weakref.ref(view)
      # self.setNewBounds()
  
      def boundingRect(self):
          if self._boundingRect is None:
              br = self.viewRect()
              if br is None:
                  return QtCore.QRectF()
              else:
                  self._boundingRect = br
          return QtCore.QRectF(self._boundingRect)
  
      def dataBounds(self, axis, frac=1.0, orthoRange=None):
          """Called by ViewBox for determining the auto-range bounds.
          By default, UIGraphicsItems are excluded from autoRange."""
          return None
  
      def viewRangeChanged(self):
          """Called when the view widget/viewbox is resized/rescaled"""
          self.setNewBounds()
          self.update()
          
      def setNewBounds(self):
          """Update the item's bounding rect to match the viewport"""
          self._boundingRect = None  ## invalidate bounding rect, regenerate later if needed.
          self.prepareGeometryChange()
  
  
      def setPos(self, *args):
          GraphicsObject.setPos(self, *args)
          self.setNewBounds()
          
      def mouseShape(self):
          """Return the shape of this item after expanding by 2 pixels"""
          shape = self.shape()
          ds = self.mapToDevice(shape)
          stroker = QtGui.QPainterPathStroker()
          stroker.setWidh(2)
          ds2 = stroker.createStroke(ds).united(ds)
          return self.mapFromDevice(ds2)
  