lightning documentation.

This glyph draws a lightning bolt of specified height with relative
width, with the point of the lightning bolt centered on the
feature. The height of the bolt is specified by the "height"
option. Due to the complexity of this glyph, it doesn't resolve well
with heights less than 11 pixels.
This glyph was designed to indicate point mutations on a nucleotide or
protein backbone. The following options are standard among all Glyphs. See
Bio::Graphics::Glyph for a full explanation.

  Option      Description                      Default
  ------      -----------                      -------

  -fgcolor      Foreground color	       black

  -outlinecolor	Synonym for -fgcolor

  -bgcolor      Background color               turquoise

  -fillcolor    Synonym for -bgcolor

  -linewidth    Line width                     1

  -height       Height of glyph		       10

  -font         Glyph font		       gdSmallFont

  -connector    Connector type                 0 (false)

  -connector_color
                Connector color                black

  -label        Whether to draw a label	       0 (false)

  -description  Whether to draw a description  0 (false)

  -hilite       Highlight color                undef (no color)

The following options are specific to this Glyph.

  Option      Description                      Default
  ------      -----------                      -------  
  -orient     direction of lightning bolt      N

sub draw_component {

  my $self = shift;
  my $gd   = shift;
  my $fg   = $self->fgcolor;

  # find the center and vertices
  my ($x1,$y1,$x2,$y2) = $self->calculate_boundaries(@_);

  my $h = $self->option('height');
  my $w = $h*0.6;

  my $poly_pkg = $self->polygon_package;
  my $polygon   = $poly_pkg->new();

  # lightning bolt points up or down
  if ($self->option('orient') eq 'N') {
    $y1 = $y1 + $h/4;
    $polygon->addPt($x2,$y1+($h/2));
    $polygon->addPt($x2-($w*0.7),$y1+($h/2));
    $polygon->addPt($x2-($w*0.2),$y1+($h*0.15));
    $polygon->addPt($x2-($w*0.6),$y1+($h*0.15));
    $polygon->addPt($x2,$y1-$h/2);
    $polygon->addPt($x2-($w*0.1),$y1-($h*0.05));
    $polygon->addPt($x2+($w*0.5),$y1-($h*0.05));
    $polygon->addPt($x2,$y1+($h/2));
  }
  else {
    $y1 = $y1 + $h/2;
    $polygon->addPt($x1,$y1-($h/2));
    $polygon->addPt($x1+($w*0.7),$y1-($h/2));
    $polygon->addPt($x1+($w*0.2),$y1-($h*0.15));
    $polygon->addPt($x1+($w*0.6),$y1-($h*0.15));
    $polygon->addPt($x1,$y1+$h/2);
    $polygon->addPt($x1+($w*0.1),$y1+($h*0.05));
    $polygon->addPt($x1-($w*0.5),$y1+($h*0.05));
    $polygon->addPt($x1,$y1-($h/2));
}

  # Have to draw TWO polygons for fills in order to get an outline
  # because filledPolygon in GD croaks with extra parameters (and
  # doesn't support drawing of stroke anyways).
  if (my $c = $self->bgcolor) {
      $gd->filledPolygon($polygon,$c);
      $gd->polygon($polygon,$fg);
  } else {
    $gd->polygon($polygon,$fg);
  }

}