my $class = shift;
  my $panel = shift;
  my %args = @_;
  my $stylesheet = $args{-stylesheet};   # optional, for Bio::Das compatibility
  my $map        = $args{-map};          # map type name to glyph name
  my $options    = $args{-options};      # map type name to glyph options
  return bless {
		stylesheet => $stylesheet,
		glyph_map  => $map,
		options    => $options,
		panel      => $panel,
		},$class;

  my $self = shift;
  my %new = %$self;
  my $new = bless\% new,ref($self);
  $new;

 shift->{stylesheet}

 shift->{glyph_map}

 shift->{options}

shift->{global_opts}

 shift->{panel}

 shift->{panel}->scale

  my $self = shift;
  my $glyph = shift;
  $self->option($glyph,'font') || $self->{font};

  my $self = shift;
  my @result = $self->panel->map_pt(@_);
  return wantarray ? @result : $result[0];

  my $self = shift;
  my $color_name = shift;
  $self->panel->translate_color($color_name);

  my $self = shift;
  my @result;
  my $panel = $self->panel;
  my ($leftmost,$rightmost) = ($panel->left,$panel->right);

  for my $f (@_) {

    my $type = $self->feature_to_glyph($f);
    my $glyphclass = 'Bio::Graphics::Glyph';
    $type ||= 'generic';
    $glyphclass .= "\:\:\L$type";

    unless ($LOADED_GLYPHS{$glyphclass}++) {
      carp("the requested glyph class, ``$type'' is not available: $@")
	unless (eval "require $glyphclass");
    }
    my $glyph = $glyphclass->new(-feature  => $f,
				 -factory  => $self);

    # this is removing glyphs that are not onscreen at all.
    # But never remove tracks!
    push @result,$glyph if $type eq 'track'
      || ($glyph->{left} + $glyph->{width} > $leftmost && $glyph->{left} < $rightmost);
  }
  return wantarray ? @result : $result[0];

  my $self    = shift;
  my $feature = shift;

  return scalar $self->{stylesheet}->glyph($feature) if $self->{stylesheet};
  my $map = $self->glyph_map    or return 'generic';
  return $map->($feature)              || 'generic' if ref($map) eq 'CODE';
  return $map->{$feature->primary_tag} || 'generic';

  my $self = shift;
  my ($option_name,$option_value) = @_;
  $self->{overriding_options}{lc $option_name} = $option_value;

  my $self = shift;
  my ($glyph,$option_name,$partno,$total_parts) = @_;
  return unless defined $option_name;
  $option_name = lc $option_name;   # canonicalize

  return $self->{overriding_options}{$option_name} 
    if exists $self->{overriding_options} && exists $self->{overriding_options}{$option_name};

  if (my $map    = $self->option_map) {
    if (defined(my $value  = $map->{$option_name})) {
      my $feature = $glyph->feature;
      return $value unless ref $value eq 'CODE';
      return unless $feature->isa('Bio::SeqFeatureI');
      my $val = $value->($feature,$option_name,$partno,$total_parts);
      return defined $val && $val eq '*default*' ? $GENERIC_OPTIONS{$option_name} : $val;
    }
  }

  if (my $ss = $self->stylesheet) {
    my($glyph,%options) = $ss->glyph($glyph->feature);
    my $value = $options{$option_name};
    return $value if defined $value;
  }

  return $GENERIC_OPTIONS{$option_name};

  my $self = shift;
  my %options;
  if (my $map    = $self->option_map) {
    $options{lc($_)}++ foreach keys %$map;
  }
  $options{lc($_)}++ foreach keys %GENERIC_OPTIONS;
  return keys %options;