text: """Represent information for graphical display.
  
  Classes in this module are designed to hold information in a way that
  makes it easy to draw graphical figures.
  """
  # reportlab
  from reportlab.lib import colors
  
  # local stuff
  from Bio.Graphics.BasicChromosome import ChromosomeSegment
  from Bio.Graphics.BasicChromosome import TelomereSegment
  
  # --- constants
  # This is a default color scheme based on the light spectrum.
  # Based on my vague recollections from biology, this is our friend ROY G. BIV
  RAINBOW_COLORS = {(1, 1)  : colors.violet,
                    (2, 2)  : colors.indigo,
                    (3, 3)  : colors.blue,
                    (4, 4)  : colors.green,
                    (5, 5)  : colors.yellow,
                    (6, 6)  : colors.orange,
                    (7, 20) : colors.red}
  
  class ChromosomeCounts:
      """Represent a chromosome with count information.
  
      This is used to display information about counts along a chromosome.
      The segments are expected to have different count information, which
      will be displayed using a color scheme.
  
      I envision using this class when you think that certain regions of
      the chromosome will be especially abundant in the counts, and you
      want to pick those out.
      """
      def __init__(self, segment_names, color_scheme = RAINBOW_COLORS):
          """Initialize a representation of chromosome counts.
  
          Arguments:
  
          o segment_names - An ordered list of all segment names along
          the chromosome. The count and other information will be added to
          these.
  
          o color_scheme - A coloring scheme to use in the counts. This should
          be a dictionary mapping count ranges to colors (specified in
          reportlab.lib.colors).
          """
          self._names = segment_names
          self._count_info = {}
          self._label_info = {}
          self._scale_info = {}
          for name in self._names:
              self._count_info[name] = 0
              self._label_info[name] = None
              self._scale_info[name] = 1
          
          self._color_scheme = color_scheme
  
      def add_count(self, segment_name, count = 1):
          """Add counts to the given segment name.
  
          Arguments:
  
          o segment_name - The name of the segment we should add counts to.
          If the name is not present, a KeyError will be raised.
  
          o count - The counts to add the current segment. This defaults to
          a single count.
          """
          try:
              self._count_info[segment_name] += count
          except KeyError:
              raise KeyError("Segment name %s not found." % segment_name)
  
      def scale_segment_value(self, segment_name, scale_value = None):
          """Divide the counts for a segment by some kind of scale value.
  
          This is useful if segments aren't represented by raw counts, but
          are instead counts divided by some number.
          """
          try:
              self._count_info[segment_name] = \
                float(self._count_info[segment_name]) / float(scale_value)
          except KeyError:
              raise KeyError("Segment name %s not found." % segment_name)
  
      def add_label(self, segment_name, label):
          """Add a label to a specfic segment.
  
          Raises a KeyError is the specified segment name is not found.
          """
          if segment_name in self._label_info:
              self._label_info[segment_name] = label
          else:
              raise KeyError("Segment name %s not found." % segment_name)
  
      def set_scale(self, segment_name, scale):
          """Set the scale for a specific chromosome segment.
  
          By default all segments have the same scale -- this allows scaling
          by the size of the segment.
  
          Raises a KeyError is the specified segment name is not found.
          """
          if segment_name in self._label_info:
              self._scale_info[segment_name] = scale
          else:
              raise KeyError("Segment name %s not found." % segment_name)
  
      def get_segment_info(self):
          """Retrieve the color and label info about the segments.
  
          Returns a list consiting of two tuples specifying the counts and
          label name for each segment. The list is ordered according to the
          original listing of names. Labels are set as None if no label
          was specified.
          """
          order_info = []
  
          for seg_name in self._names:
              order_info.append((self._count_info[seg_name],
                                 self._label_info[seg_name]))
  
          return order_info
  
      def fill_chromosome(self, chromosome):
          """Add the collected segment information to a chromosome for drawing.
  
          Arguments:
  
          o chromosome - A Chromosome graphics object that we can add
          chromosome segments to.
  
          This creates ChromosomeSegment (and TelomereSegment) objects to
          fill in the chromosome. The information is derived from the
          label and count information, with counts transformed to the
          specified color map.
  
          Returns the chromosome with all of the segments added.
          """
          for seg_num in range(len(self._names)):
              is_end_segment = 0
              # make the top and bottom telomeres
              if seg_num == 0:
                  cur_segment = TelomereSegment()
                  is_end_segment = 1
              elif seg_num == len(self._names) - 1:
                  cur_segment = TelomereSegment(1)
                  is_end_segment = 1
              # otherwise, they are just regular segments
              else:
                  cur_segment = ChromosomeSegment()
  
              seg_name = self._names[seg_num]
              if self._count_info[seg_name] > 0:
                  color = self._color_from_count(self._count_info[seg_name])
                  cur_segment.fill_color = color
              
              if self._label_info[seg_name] is not None:
                  cur_segment.label = self._label_info[seg_name]
  
              # give end segments extra size so they look right
              if is_end_segment:
                  cur_segment.scale = 3
              else:
                  cur_segment.scale = self._scale_info[seg_name]
  
              chromosome.add(cur_segment)
  
          return chromosome
  
      def _color_from_count(self, count):
          """Translate the given count into a color using the color scheme.
          """
          for count_start, count_end in self._color_scheme:
              if count >= count_start and count <= count_end:
                  return self._color_scheme[(count_start, count_end)]
  
          # if we got here we didn't find a color for the count
          raise ValueError("Count value %s was not found in the color scheme."
                           % count)
          
          
          
  