new_contents: #------------------------------------------------------------------------------
  #
  #  Copyright (c) 2009, Enthought, Inc.
  #  All rights reserved.
  #  
  #  This software is provided without warranty under the terms of the BSD
  #  license included in enthought/LICENSE.txt and may be redistributed only
  #  under the conditions described in the aforementioned license.  The license
  #  is also available online at http://www.enthought.com/licenses/BSD.txt
  #
  #  Thanks for using Enthought open source!
  #  
  #------------------------------------------------------------------------------
  
  """ Trait definition for an RGB-based color, which is a tuple of the form 
      (*red*, *green*, *blue*), where *red*, *green* and *blue* are floats in the
      range from 0.0 to 1.0.
  """
  
  #-------------------------------------------------------------------------------
  #  Imports:
  #-------------------------------------------------------------------------------
  
  from enthought.traits.api import Trait, TraitError
  from enthought.traits.trait_base import SequenceTypes
  
  from enthought.traits.ui.qt4.color_trait import standard_colors
  
  #-------------------------------------------------------------------------------
  #  Convert a number into an RGB tuple:
  #-------------------------------------------------------------------------------
  
  def range_check(value):
      """ Checks that *value* can be converted to a value in the range 0.0 to 1.0.
      
          If so, it returns the floating point value; otherwise, it raises a
          TraitError.
      """
      value = float(value)
      if 0.0 <= value <= 1.0:
          return value
      raise TraitError
      
  def convert_to_color(object, name, value):
      """ Converts a tuple or an integer to an RGB color value, or raises a 
          TraitError if that is not possible.
      """
      if isinstance(value, SequenceTypes) and len(value) == 3:
          return (range_check(value[0]), 
                  range_check(value[1]), 
                  range_check(value[2]))
      if isinstance(value, int):
          return ((value / 0x10000)        / 255.0,
                  ((value / 0x100) & 0xFF) / 255.0, 
                  (value & 0xFF)           / 255.0)
      raise TraitError
  
  convert_to_color.info = ('a tuple of the form (r,g,b), where r, g, and b '
      'are floats in the range from 0.0 to 1.0, or an integer which in hex is of '
      'the form 0xRRGGBB, where RR is red, GG is green, and BB is blue')
               
  #-------------------------------------------------------------------------------
  #  Standard colors:
  #-------------------------------------------------------------------------------
  
  # RGB versions of standard colors:
  rgb_standard_colors = {}
  for name, color in standard_colors.items():
      rgb_standard_colors[name] = (color.redF(),
                                   color.greenF(),
                                   color.blueF())
  
  #-------------------------------------------------------------------------------
  #  Define wxPython specific color traits:
  #-------------------------------------------------------------------------------
  
  ### Note: Declare the editor to be a function which returns the RGBColorEditor 
  # class from traits ui to avoid circular import issues. For backwards 
  # compatibility with previous Traits versions, the 'editors' folder in Traits 
  # project declares 'from api import *' in its __init__.py. The 'api' in turn 
  # can contain classes that have a RGBColor trait which lead to this file getting 
  # imported. This will lead to a circular import when declaring a RGBColor trait.
  def get_rgb_color_editor(*args, **traits):
      from rgb_color_editor import ToolkitEditorFactory
      return ToolkitEditorFactory(*args, **traits)
  
  # Trait whose value must be an RGB color:
  RGBColor = Trait('white', convert_to_color, rgb_standard_colors, 
                   editor=get_rgb_color_editor)
         
  
  
subject: Implement RGBColor trait for qt4 backend.