Bio::Graphics::Glyph::xyplot - The xyplot glyph

  See L<Bio::Graphics::Panel> and L<Bio::Graphics::Glyph>.

  my $agg = Bio::DB::GFF::Aggregator->new(-method    => 'repeat_density',
                                          -sub_parts => 'density:repeat');
  my $db  = Bio::DB::GFF->new(-dsn=>'my_database',
                              -aggregators => $agg);
  my $segment  = $db->segment('Chr1');
  my @features = $segment->features('repeat_density');

  my $panel = Bio::Graphics::Panel->new(-pad_left=>40,-pad_right=>40);
  $panel->add_track(\@features,
                    -glyph => 'xyplot',
  		    -graph_type=>'points',
		    -point_symbol=>'disc',
		    -point_radius=>4,
		    -scale=>'both',
		    -height=>200,
  );

  aggregators = repeat_density{density:repeat}
                clone alignment etc

  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

  -label        Whether to draw a label	       0 (false)

  -description  Whether to draw a description  0 (false)

  -hilite       Highlight color                undef (no color)

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

  -max_score   Maximum value of the	      Calculated
               feature's "score" attribute

  -min_score   Minimum value of the           Calculated
               feature's "score" attributes

  -graph_type  Type of graph to generate.     Histogram
               Options are: "histogram",
               "boxes", "line", "points",
               or "linepoints".

  -point_symbol Symbol to use. Options are    none
                "triangle", "square", "disc",
                "filled_triangle",
                "filled_square",
                "filled_disc","point",
                and "none".

  -point_radius Radius of the symbol, in      4
                pixels (does not apply
                to "point")

  -scale        Position where the Y axis     none
                scale is drawn if any.
                It should be one of
                "left", "right", "both" or "none"

  -graph_height Specify height of the graph   Same as the
                                              "height" option.

  -part_color  For boxes & points only,       none
               bgcolor of each part (should
               be a callback). Supersedes
               -neg_color.

  -scale_color Color of the scale             Same as fgcolor

  -clip        If min_score and/or max_score  false
               are manually specified, then
               setting this to true will
               cause values outside the
               range to be clipped.

  -bicolor_pivot                              0
               Where to pivot the two colors
               when drawing bicolor plots.
               Scores greater than this value will
               be drawn using -pos_color.
               Scores lower than this value will
               be drawn using -neg_color.

  -pos_color   When drawing bicolor plots,    same as bgcolor
               the fill color to use for
               values that are above 
               the pivot point.

  -neg_color   When drawing bicolor plots,    same as bgcolor
               the fill color to use for values
               that are below the pivot point.

  $panel->add_track->(\@affymetrix_data,
                      -glyph      => 'xyplot',
                      -graph_type => 'boxes',
                      -part_color => sub {
                                   my $score = shift->score;
	                           return 'red' if $score < 0;
	                           return 'lightblue' if $score < 500;
                                   return 'blue'      if $score >= 500;
                                  }
                      );

package Bio::Graphics::Glyph::xyplot;

use strict;
#use GD 'gdTinyFont';

use base qw(Bio::Graphics::Glyph::segments Bio::Graphics::Glyph::minmax);
use constant DEFAULT_POINT_RADIUS=>4;
use Bio::Root::Version;
our $VERSION = ${Bio::Root::Version::VERSION};

use constant DEBUG=>0;
use constant EXTRA_LABEL_PAD=>8;

sub my_description { 
    return <<'END';
This glyph is used for drawing features that have a position on the
genome and a numeric value.  It can be used to represent gene
prediction scores, motif-calling scores, percent similarity,
microarray intensities, or other features that require a line plot.

The plot is designed to work on a single feature group that contains
subfeatures. It is the subfeatures that carry the score
information. For a more efficient implementation that is suitable for
dense genome-wide data, use Bio::Graphics::Wiggle and the
wiggle_xyplot glyph.
END

}
sub my_options {
    {
	point_radius => [
	      'integer',
	      1,
	      'When drawing data points, this specifies the radius of each point.',
	    ],
	 clip => [
	     'boolean',
	     0,
	     'If min_score and/or max_score are manually specified,',
	     'then setting this to true will cause values outside the',
	     'range to be clipped.'
	    ],
	 graph_type => [
	     ['histogram','boxes','line','points','linepoints'],
	     'histogram',
	     'Type of graph to generate. Options are "histogram", "boxes",',
	     '"line","points", or "linepoints".'
	     ],
	 point_symbol => [
	     'string',
	     'none',
	     'Symbol to use for each data point when drawing line graphs.',
	     'Options are "triangle", "square", "disc", "filled_triangle",',
	     '"filled_square", "filled_disc", "point" and "none"',
	 ],
	 scale => [
	     'string',
	     'three',
	     'Position where the Y axis scale is drawn, if any.',
	     'Options are one of "left", "right", "both", "three" or "none".',
	     '"three" will cause the scale to be drawn in the left, right and center.',
	 ],

	 scale_color => [
	     'color',
	     'fgcolor',
	     'Color of the X and Y scales. Defaults to the same as fgcolor.',
	 ],
    };
}

my %SYMBOLS = (
	       triangle => \&draw_triangle,
	       square   => \&draw_square,
	       disc     => \&draw_disc,
	       point    => \&draw_point,
	      );

sub extra_label_pad {
    return EXTRA_LABEL_PAD;
}

# Default pad_left is recursive through all parts. We certainly
# don't want to do this for all parts in the graph.
sub pad_left {
  my $self = shift;
  return 0 unless $self->level == 0;
  my $left = $self->SUPER::pad_left(@_);
  my $side = $self->_determine_side;
  $left += $self->extra_label_pad if $self->label_position eq 'left' && $side =~ /left|both|three/;
  return $left;
}

# Default pad_left is recursive through all parts. We certainly
# don't want to do this for all parts in the graph.
sub pad_right {
  my $self = shift;
  return 0 unless $self->level == 0;
  return $self->SUPER::pad_right(@_);
}

sub point_radius {
  shift->option('point_radius') || DEFAULT_POINT_RADIUS;
}

sub pad_top {
  my $self = shift;
  my $pad = $self->Bio::Graphics::Glyph::generic::pad_top(@_);
  if ($pad < ($self->font('gdTinyFont')->height+2)) {
    $pad = $self->font('gdTinyFont')->height+2;  # extra room for the scale
  }
  $pad;
}

sub pad_bottom {
  my $self = shift;
  my $pad  = $self->Bio::Graphics::Glyph::generic::pad_bottom(@_);
  if ($pad < ($self->font('gdTinyFont')->height)/4) {
    $pad = ($self->font('gdTinyFont')->height)/4;  # extra room for the scale
  }
  $pad;
}

sub scalecolor {
  my $self = shift;
  my $color = $self->color('scale_color') || $self->fgcolor;
}

sub default_scale
{
  return 'three';
}

sub record_label_positions { 
    my $self = shift;
    my $rlp  = $self->option('record_label_positions');
    return $rlp if defined $rlp;
    return 1;
}

sub graph_type {
    my $self = shift;
	$self->option('graph_type')       || 
	$self->option('graphtype')        ||
	'boxes';
}

sub draw {
  my $self = shift;
  my ($gd,$dx,$dy) = @_;
  my ($left,$top,$right,$bottom) = $self->calculate_boundaries($dx,$dy);
  my @parts = $self->parts;

  return $self->SUPER::draw(@_) unless @parts > 0;

  $self->panel->startGroup($gd);

  my ($min_score,$max_score) = $self->minmax(\@parts);

  my $side = $self->_determine_side();

  # if a scale is called for, then we adjust the max and min to be even
  # multiples of a power of 10.
  if ($side) {
    $max_score = max10($max_score);
    $min_score = min10($min_score);
  }

  my $height = $bottom - $top;
  my $scale  = $max_score > $min_score ? $height/($max_score-$min_score)
                                       : 1;
  my $x = $left;
  my $y = $top + $self->pad_top;

  # position of "0" on the scale
  my $y_origin = $min_score <= 0 ? $bottom - (0 - $min_score) * $scale : $bottom;
  $y_origin    = $top if $max_score < 0;

  my $clip_ok = $self->option('clip');
  $self->{_clip_ok}   = $clip_ok;
  $self->{_scale}     = $scale;
  $self->{_min_score} = $min_score;
  $self->{_max_score} = $max_score;
  $self->{_top}       = $top;
  $self->{_bottom}    = $bottom;

  # now seed all the parts with the information they need to draw their positions
  foreach (@parts) {
    my $s = $_->score;
    $_->{_y_position}   = $self->score2position($s);
    warn "y_position = $_->{_y_position}" if DEBUG;
  }
  my $type           = $self->option('graph_type') || $self->option('graphtype') || 'boxes';
  my (@draw_methods) = $self->lookup_draw_method($type);
  $self->throw("Invalid graph type '$type'") unless @draw_methods;

  $self->panel->startGroup($gd);
  $self->_draw_grid($gd,$scale,$min_score,$max_score,$dx,$dy,$y_origin);
  $self->panel->endGroup($gd);

  for my $draw_method (@draw_methods) {
    $self->$draw_method($gd,$dx,$dy,$y_origin);
  }

  $self->panel->startGroup($gd);
  $self->_draw_scale($gd,$scale,$min_score,$max_score,$dx,$dy,$y_origin);
  $self->panel->endGroup($gd);

  $self->draw_label(@_)       if $self->option('label');
  $self->draw_description(@_) if $self->option('description');

  $self->panel->endGroup($gd);
}

sub lookup_draw_method {
  my $self = shift;
  my $type = shift;

  return '_draw_histogram'            if $type eq 'histogram';
  return '_draw_boxes'                if $type eq 'boxes';
  return qw(_draw_line _draw_points)  if $type eq 'linepoints';
  return '_draw_line'                 if $type eq 'line';
  return '_draw_points'               if $type eq 'points';
  return;
}

sub score {
  my $self    = shift;
  my $s       = $self->option('score');
  return $s   if defined $s;
  return eval { $self->feature->score };
}

sub score2position {
  my $self  = shift;
  my $score = shift;

  return undef unless defined $score;

  if ($self->{_clip_ok} && $score < $self->{_min_score}) {
    return $self->{_bottom};
  }

  elsif ($self->{_clip_ok} && $score > $self->{_max_score}) {
    return $self->{_top};
  }

  else {
    warn "score = $score, _top = $self->{_top}, _bottom = $self->{_bottom}, max = $self->{_max_score}, min=$self->{_min_score}" if DEBUG;
    my $position      = ($score-$self->{_min_score}) * $self->{_scale};
    warn "position =$position" if DEBUG;
    return $self->{_bottom} - $position;
  }
}

sub log10 { log(shift)/log(10) }
sub max10 {
  my $a = shift;
  return 0 if $a==0;
  return -min10(-$a) if $a<0;
  return max10($a*10)/10 if $a < 1;

  my $l=int(log10($a));
  $l = 10**$l; 
  my $r = $a/$l;
  return $r*$l if int($r) == $r;
  return $l*int(($a+$l)/$l);
}
sub min10 {
  my $a = shift;
  return 0 if $a==0;
  return -max10(-$a) if $a<0;
  return min10($a*10)/10 if $a < 1;

  my $l=int(log10($a));
  $l = 10**$l; 
  my $r = $a/$l; 
  return $r*$l if int($r) == $r;
  return $l*int($a/$l);
}

sub _draw_histogram {
  my $self = shift;
  my ($gd,$left,$top,$bottom) = @_;

  my @parts   = $self->parts;
  my $fgcolor = $self->fgcolor;

  # draw each of the component lines of the histogram surface
  for (my $i = 0; $i < @parts; $i++) {
    my $part = $parts[$i];
    my $next = $parts[$i+1];
    my ($x1,$y1,$x2,$y2) = $part->calculate_boundaries($left,$top);
    next unless defined $part->{_y_position};
    $gd->line($x1,$part->{_y_position},$x2,$part->{_y_position},$fgcolor);
    next unless $next;
    my ($x3,$y3,$x4,$y4) = $next->calculate_boundaries($left,$top);
    if ($x2 == $x3) {# connect vertically to next level
      $gd->line($x2,$part->{_y_position},$x2,$next->{_y_position},$fgcolor); 
    } else {
      $gd->line($x2,$part->{_y_position},$x2,$bottom,$fgcolor); # to bottom
      $gd->line($x2,$bottom,$x3,$bottom,$fgcolor);              # to right
      $gd->line($x3,$bottom,$x3,$next->{_y_position},$fgcolor); # up
    }
  }

  # end points: from bottom to first
  my ($x1,$y1,$x2,$y2) = $parts[0]->calculate_boundaries($left,$top);
  $gd->line($x1,$bottom,$x1,$parts[0]->{_y_position},$fgcolor);
  # from last to bottom
  my ($x3,$y3,$x4,$y4) = $parts[-1]->calculate_boundaries($left,$top);
  $gd->line($x4,$parts[-1]->{_y_position},$x4,$bottom,$fgcolor);

  # That's it.  Not too hard.
}

sub _draw_boxes {
  my $self = shift;
  my ($gd,$left,$top,$y_origin) = @_;

  my @parts    = $self->parts;
  my $lw       = $self->linewidth;
  my $positive = $self->pos_color;
  my $negative = $self->neg_color;
  my $height   = $self->height;

  my $midpoint = $self->midpoint ? $self->score2position($self->midpoint) 
                                 : $y_origin;

  my $partcolor = $self->code_option('part_color');
  my $factory  = $self->factory;

  # draw each of the boxes as a rectangle
  for (my $i = 0; $i < @parts; $i++) {

    my $part = $parts[$i];
    my $next = $parts[$i+1];

    my ($color,$negcolor);

    # special check here for the part_color being defined so as not to introduce lots of
    # checking overhead when it isn't
    if ($partcolor) {
	$color    = $factory->translate_color($factory->option($part,'part_color',0,0));
	$negcolor = $color;
    } else {
	$color    = $positive;
	$negcolor = $negative;
    }

    my ($x1,$y1,$x2,$y2) = $part->calculate_boundaries($left,$top);
    next unless defined $part->{_y_position};
    # prevent boxes from being less than 1 pixel
    $x2 = $x1+1 if $x2-$x1 < 1;
    if ($part->{_y_position} < $midpoint) {
	$gd->filledRectangle($x1,$part->{_y_position},$x2,$y_origin,$color);
    } else {
	$gd->filledRectangle($x1,$y_origin,$x2,$part->{_y_position},$negcolor);
    }
  }

  # That's it.
}

sub _draw_line {
  my $self = shift;
  my ($gd,$left,$top) = @_;

  my @parts  = $self->parts;
  my $fgcolor = $self->fgcolor;
  my $bgcolor = $self->bgcolor;

  # connect to center positions of each interval
  my $first_part = shift @parts;
  my ($x1,$y1,$x2,$y2) = $first_part->calculate_boundaries($left,$top);
  my $current_x = ($x1+$x2)/2;
  my $current_y = $first_part->{_y_position};

  for my $part (@parts) {
    ($x1,$y1,$x2,$y2) = $part->calculate_boundaries($left,$top);
    my $next_x = ($x1+$x2)/2;
    my $next_y = $part->{_y_position};
    $gd->line($current_x,$current_y,$next_x,$next_y,$fgcolor)
	if defined $current_y and defined $next_y;
    ($current_x,$current_y) = ($next_x,$next_y);
  }

}

sub _draw_points {
  my $self = shift;
  my ($gd,$left,$top) = @_;
  my $symbol_name = $self->option('point_symbol') || 'point';
  my $filled      = $symbol_name =~ s/^filled_//;
  my $symbol_ref  = $SYMBOLS{$symbol_name};

  my @parts   = $self->parts;
  my $fgcolor = $self->fgcolor;
  my $bgcolor = $self->bgcolor;
  my $pr      = $self->point_radius;

  my $partcolor = $self->code_option('part_color');
  my $factory  = $self->factory;

  for my $part (@parts) {
    my ($x1,$y1,$x2,$y2) = $part->calculate_boundaries($left,$top);
    my $x = ($x1+$x2)/2;
    my $y = $part->{_y_position};
    next unless defined $y;

    my $color;
    if ($partcolor) {
      $color    = $factory->translate_color($factory->option($part,'part_color',0,0));
    } else {
      $color    = $fgcolor;
    }

    $symbol_ref->($gd,$x,$y,$pr,$color,$filled);
  }
}

sub _determine_side
{
  my $self = shift;
  my $side = $self->option('scale');
  return if $side eq 'none';
  $side   ||= $self->default_scale();
  return $side;
}

sub _draw_scale {
  my $self = shift;
  my ($gd,$scale,$min,$max,$dx,$dy,$y_origin) = @_;
  my ($x1,$y1,$x2,$y2) = $self->calculate_boundaries($dx,$dy);

  my $crosses_origin = $min < 0 && $max > 0;

  my $side = $self->_determine_side();

  my $fg    = $self->scalecolor;
  my $font  = $self->font('gdTinyFont');

  my $middle = ($x1+$x2)/2;

  # minor ticks - multiples of 10
  my $y_scale = $self->minor_ticks($min,$max,$y1,$y2);

  my $p  = $self->panel;
  my $gc = $p->translate_color($p->gridcolor);
  my $mgc= $p->translate_color($p->gridmajorcolor);

  # if ($side ne 'none') {
  #     for (my $y = $y2-$y_scale; $y > $y1; $y -= $y_scale) {
  # 	  my $yr = int($y+0.5);
  # 	  $gd->line($x1-1,$yr,$x2,$yr,$gc);
  #     }
  #     $gd->line($x1,$y1,$x2,$y1,$gc);
  #     $gd->line($x1,$y2,$x2,$y2,$gc);
  # }
  
  $gd->line($x1,$y1,$x1,$y2,$fg) if $side eq 'left'  || $side eq 'both' || $side eq 'three';
  $gd->line($x2,$y1,$x2,$y2,$fg) if $side eq 'right' || $side eq 'both' || $side eq 'three';
  $gd->line($middle,$y1,$middle,$y2,$fg) if $side eq 'three';

  $gd->line($x1,$y_origin,$x2,$y_origin,$mgc);

  my @points = ([$y1,$max],[$y2,$min]);
  push @points,$crosses_origin ? [$y_origin,0] : [($y1+$y2)/2,($min+$max)/2];

  my $last_font_pos = -99999999999;

  for (sort {$a->[0]<=>$b->[0]} @points) {
    $gd->line($x1-3,$_->[0],$x1,$_->[0],$fg) if $side eq 'left'  || $side eq 'both' || $side eq 'three';
    $gd->line($x2,$_->[0],$x2+3,$_->[0],$fg) if $side eq 'right' || $side eq 'both' || $side eq 'three';
    $gd->line($middle,$_->[0],$middle+3,$_->[0],$fg) if $side eq 'three';

    my $font_pos = $_->[0]-($font->height/2);
    $font_pos-=2 if $_->[1] < 0;  # jog a little bit for neg sign

    next unless $font_pos > $last_font_pos + $font->height/2; # prevent labels from clashing
    if ($side eq 'left' or $side eq 'both' or $side eq 'three') {
      $gd->string($font,
		  $x1 - $font->width * length($_->[1]) - 3,$font_pos,
		  $_->[1],
		  $fg);
    }
    if ($side eq 'right' or $side eq 'both' or $side eq 'three') {
      $gd->string($font,
		  $x2 + 5,$font_pos,
		  $_->[1],
		  $fg);
    }
#    if ($side eq 'three' && $_->[1] != 0) {
    if ($side eq 'three') {
      $gd->string($font,
		  $middle + 5,$font_pos,
		  $_->[1],
		  $fg);
    }
    $last_font_pos = $font_pos;
  }

  for (my $y = $y2-$y_scale; $y > $y1; $y -= $y_scale) {
      my $yr = int($y+0.5);
      $gd->line($x1-3,$yr,$x1,$yr,$fg) if $side eq 'left' or $side eq 'both' or $side eq 'three';
      $gd->line($x2,$yr,$x2+3,$yr,$fg) if $side eq 'right' or $side eq 'both' or $side eq 'three';
      $gd->line($middle-1,$yr,$middle+2,$yr,$fg) if $side eq 'three';
  }


}

sub _draw_grid {
    my $self = shift;
    my ($gd,$scale,$min,$max,$dx,$dy,$y_origin) = @_;
    my $side = $self->_determine_side();
    return if $side eq 'none';

    my ($x1,$y1,$x2,$y2) = $self->calculate_boundaries($dx,$dy);
    my $p  = $self->panel;
    my $gc = $p->translate_color($p->gridcolor);
    my $y_scale = $self->minor_ticks($min,$max,$y1,$y2);

    for (my $y = $y2-$y_scale; $y > $y1; $y -= $y_scale) {
	my $yr = int($y+0.5);
	$gd->line($x1-1,$yr,$x2,$yr,$gc);
    }
    $gd->line($x1,$y1,$x2,$y1,$gc);
    $gd->line($x1,$y2,$x2,$y2,$gc);
}

sub minor_ticks {
    my $self = shift;
    my ($min,$max,$top,$bottom) = @_;

    my $interval = 1;
    my $height   = $bottom-$top;
    my $y_scale  = 1;
    if ($max > $min) {
	while ($height/(($max-$min)/$interval) < 2) { $interval *= 10 }
	$y_scale = $height/(($max-$min)/$interval);
    }

}

# Let the feature attributes override the labelcolor
sub labelcolor {
  my $self = shift;
  my ($labelcolor) = eval {$self->feature->get_tag_values('labelcolor')};
  return $labelcolor ? $self->translate_color($labelcolor)
                     : $self->SUPER::labelcolor;
}

# we are unbumpable!
sub bump {
  return 0;
}

sub connector {
  my $self = shift;
  my $type = $self->option('graph_type');
  return 1 if $type eq 'line' or $type eq 'linepoints';
}

sub height {
  my $self = shift;
  return $self->option('graph_height') || $self->SUPER::height;
}

sub draw_triangle {
  my ($gd,$x,$y,$pr,$color,$filled) = @_;
  $pr /= 2;
  my ($vx1,$vy1) = ($x-$pr,$y+$pr);
  my ($vx2,$vy2) = ($x,  $y-$pr);
  my ($vx3,$vy3) = ($x+$pr,$y+$pr);
  my $poly = GD::Polygon->new;
  $poly->addPt($vx1,$vy1,$vx2,$vy2);
  $poly->addPt($vx2,$vy2,$vx3,$vy3);
  $poly->addPt($vx3,$vy3,$vx1,$vy1);
  if ($filled) {
    $gd->filledPolygon($poly,$color);
  } else {
    $gd->polygon($poly,$color);
  }
}

sub draw_square {
  my ($gd,$x,$y,$pr,$color,$filled) = @_;
  $pr /= 2;
  my $poly = GD::Polygon->new;
  $poly->addPt($x-$pr,$y-$pr);
  $poly->addPt($x+$pr,$y-$pr);
  $poly->addPt($x+$pr,$y+$pr);
  $poly->addPt($x-$pr,$y+$pr);
  if ($filled) {
    $gd->filledPolygon($poly,$color);
  } else {
    $gd->polygon($poly,$color);
  }
}
sub draw_disc {
  my ($gd,$x,$y,$pr,$color,$filled) = @_;
  if ($filled) {
    $gd->filledArc($x,$y,$pr,$pr,0,360,$color);
  } else {
    $gd->arc($x,$y,$pr,$pr,0,360,$color);
  }
}
sub draw_point {
  my ($gd,$x,$y,$pr,$color) = @_;
  $gd->setPixel($x,$y,$color);
}

sub keyglyph {
  my $self = shift;

  my $scale = 1/$self->scale;  # base pairs/pixel

  my $feature =
    Bio::Graphics::Feature->new(
				-segments=>[ [ 0*$scale,9*$scale],
					     [ 10*$scale,19*$scale],
					     [ 20*$scale, 29*$scale]
					   ],
				-name => 'foo bar',
				-strand => '+1');
  ($feature->segments)[0]->score(10);
  ($feature->segments)[1]->score(50);
  ($feature->segments)[2]->score(25);
  my $factory = $self->factory->clone;
  $factory->set_option(label => 1);
  $factory->set_option(bump  => 0);
  $factory->set_option(connector  => 'solid');
  my $glyph = $factory->make_glyph(0,$feature);
  return $glyph;
}

sub symbols {
    my $self = shift;
    return \%SYMBOLS;
}

sub draw_label {
  my $self = shift;
  my ($gd,$left,$top,$partno,$total_parts) = @_;

  my $label = $self->label or return;
  return $self->SUPER::draw_label(@_) unless $self->label_position eq 'left';

  my $font = $self->labelfont;
  my $x = $self->left + $left - $font->width*length($label) - $self->extra_label_pad;
  my $y = $self->{top} + $top;

  $self->render_label($gd,
		      $font,
		      $x,
		      $y,
		      $label);
}


1;

__END__