text: # -*- coding: utf-8 -*-
  from OpenGL.GL import *
  from OpenGL import GL
  from ..Qt import QtCore
  from .. import Transform3D
  
  
  GLOptions = {
      'opaque': {
          GL_DEPTH_TEST: True,
          GL_BLEND: False,
          GL_ALPHA_TEST: False,
          GL_CULL_FACE: False,
      },
      'translucent': {
          GL_DEPTH_TEST: True,
          GL_BLEND: True,
          GL_ALPHA_TEST: False,
          GL_CULL_FACE: False,
          'glBlendFunc': (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA),
      },
      'additive': {
          GL_DEPTH_TEST: False,
          GL_BLEND: True,
          GL_ALPHA_TEST: False,
          GL_CULL_FACE: False,
          'glBlendFunc': (GL_SRC_ALPHA, GL_ONE),
      },
  }    
  
  
  class GLGraphicsItem(QtCore.QObject):
      _nextId = 0
      
      def __init__(self, parentItem=None):
          super().__init__()
          self._id = GLGraphicsItem._nextId
          GLGraphicsItem._nextId += 1
          
          self.__parent = None
          self.__view = None
          self.__children = set()
          self.__transform = Transform3D()
          self.__visible = True
          self.__initialized = False
          self.setParentItem(parentItem)
          self.setDepthValue(0)
          self.__glOpts = {}
          
      def setParentItem(self, item):
          """Set this item's parent in the scenegraph hierarchy."""
          if self.__parent is not None:
              self.__parent.__children.remove(self)
          if item is not None:
              item.__children.add(self)
          self.__parent = item
          
          if self.__parent is not None and self.view() is not self.__parent.view():
              if self.view() is not None:
                  self.view().removeItem(self)
              self.__parent.view().addItem(self)
      
      def setGLOptions(self, opts):
          """
          Set the OpenGL state options to use immediately before drawing this item.
          (Note that subclasses must call setupGLState before painting for this to work)
          
          The simplest way to invoke this method is to pass in the name of
          a predefined set of options (see the GLOptions variable):
          
          ============= ======================================================
          opaque        Enables depth testing and disables blending
          translucent   Enables depth testing and blending
                        Elements must be drawn sorted back-to-front for
                        translucency to work correctly.
          additive      Disables depth testing, enables blending.
                        Colors are added together, so sorting is not required.
          ============= ======================================================
          
          It is also possible to specify any arbitrary settings as a dictionary. 
          This may consist of {'functionName': (args...)} pairs where functionName must 
          be a callable attribute of OpenGL.GL, or {GL_STATE_VAR: bool} pairs 
          which will be interpreted as calls to glEnable or glDisable(GL_STATE_VAR).
          
          For example::
              
              {
                  GL_ALPHA_TEST: True,
                  GL_CULL_FACE: False,
                  'glBlendFunc': (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA),
              }
              
          
          """
          if isinstance(opts, str):
              opts = GLOptions[opts]
          self.__glOpts = opts.copy()
          self.update()
          
      def updateGLOptions(self, opts):
          """
          Modify the OpenGL state options to use immediately before drawing this item.
          *opts* must be a dictionary as specified by setGLOptions.
          Values may also be None, in which case the key will be ignored.
          """
          self.__glOpts.update(opts)
          
      
      def parentItem(self):
          """Return a this item's parent in the scenegraph hierarchy."""
          return self.__parent
          
      def childItems(self):
          """Return a list of this item's children in the scenegraph hierarchy."""
          return list(self.__children)
          
      def _setView(self, v):
          self.__view = v
          
      def view(self):
          return self.__view
          
      def setDepthValue(self, value):
          """
          Sets the depth value of this item. Default is 0.
          This controls the order in which items are drawn--those with a greater depth value will be drawn later.
          Items with negative depth values are drawn before their parent.
          (This is analogous to QGraphicsItem.zValue)
          The depthValue does NOT affect the position of the item or the values it imparts to the GL depth buffer.
          """
          self.__depthValue = value
          
      def depthValue(self):
          """Return the depth value of this item. See setDepthValue for more information."""
          return self.__depthValue
          
      def setTransform(self, tr):
          """Set the local transform for this object.
          Must be a :class:`Transform3D <pyqtgraph.Transform3D>` instance. This transform
          determines how the local coordinate system of the item is mapped to the coordinate
          system of its parent."""
          self.__transform = Transform3D(tr)
          self.update()
          
      def resetTransform(self):
          """Reset this item's transform to an identity transformation."""
          self.__transform.setToIdentity()
          self.update()
          
      def applyTransform(self, tr, local):
          """
          Multiply this object's transform by *tr*. 
          If local is True, then *tr* is multiplied on the right of the current transform::
          
              newTransform = transform * tr
              
          If local is False, then *tr* is instead multiplied on the left::
          
              newTransform = tr * transform
          """
          if local:
              self.setTransform(self.transform() * tr)
          else:
              self.setTransform(tr * self.transform())
          
      def transform(self):
          """Return this item's transform object."""
          return self.__transform
          
      def viewTransform(self):
          """Return the transform mapping this item's local coordinate system to the 
          view coordinate system."""
          tr = self.__transform
          p = self
          while True:
              p = p.parentItem()
              if p is None:
                  break
              tr = p.transform() * tr
          return Transform3D(tr)
          
      def translate(self, dx, dy, dz, local=False):
          """
          Translate the object by (*dx*, *dy*, *dz*) in its parent's coordinate system.
          If *local* is True, then translation takes place in local coordinates.
          """
          tr = Transform3D()
          tr.translate(dx, dy, dz)
          self.applyTransform(tr, local=local)
          
      def rotate(self, angle, x, y, z, local=False):
          """
          Rotate the object around the axis specified by (x,y,z).
          *angle* is in degrees.
          
          """
          tr = Transform3D()
          tr.rotate(angle, x, y, z)
          self.applyTransform(tr, local=local)
      
      def scale(self, x, y, z, local=True):
          """
          Scale the object by (*dx*, *dy*, *dz*) in its local coordinate system.
          If *local* is False, then scale takes place in the parent's coordinates.
          """
          tr = Transform3D()
          tr.scale(x, y, z)
          self.applyTransform(tr, local=local)
      
      
      def hide(self):
          """Hide this item. 
          This is equivalent to setVisible(False)."""
          self.setVisible(False)
          
      def show(self):
          """Make this item visible if it was previously hidden.
          This is equivalent to setVisible(True)."""
          self.setVisible(True)
      
      def setVisible(self, vis):
          """Set the visibility of this item."""
          self.__visible = vis
          self.update()
          
      def visible(self):
          """Return True if the item is currently set to be visible.
          Note that this does not guarantee that the item actually appears in the
          view, as it may be obscured or outside of the current view area."""
          return self.__visible
      
      def initialize(self):
          self.initializeGL()
          self.__initialized = True
  
      def isInitialized(self):
          return self.__initialized
      
      def initializeGL(self):
          """
          Called after an item is added to a GLViewWidget. 
          The widget's GL context is made current before this method is called.
          (So this would be an appropriate time to generate lists, upload textures, etc.)
          """
          pass
      
      def setupGLState(self):
          """
          This method is responsible for preparing the GL state options needed to render 
          this item (blending, depth testing, etc). The method is called immediately before painting the item.
          """
          for k,v in self.__glOpts.items():
              if v is None:
                  continue
              if isinstance(k, str):
                  func = getattr(GL, k)
                  func(*v)
              else:
                  if v is True:
                      glEnable(k)
                  else:
                      glDisable(k)
      
      def paint(self):
          """
          Called by the GLViewWidget to draw this item.
          It is the responsibility of the item to set up its own modelview matrix,
          but the caller will take care of pushing/popping.
          """
          self.setupGLState()
          
      def update(self):
          """
          Indicates that this item needs to be redrawn, and schedules an update 
          with the view it is displayed in.
          """
          v = self.view()
          if v is None:
              return
          v.update()
          
      def mapToParent(self, point):
          tr = self.transform()
          if tr is None:
              return point
          return tr.map(point)
          
      def mapFromParent(self, point):
          tr = self.transform()
          if tr is None:
              return point
          return tr.inverted()[0].map(point)
          
      def mapToView(self, point):
          tr = self.viewTransform()
          if tr is None:
              return point
          return tr.map(point)
          
      def mapFromView(self, point):
          tr = self.viewTransform()
          if tr is None:
              return point
          return tr.inverted()[0].map(point)
          
          
          
  