GroupedBarGraph::Draw PHP Method

    protected function Draw()
    {
        $body = $this->Grid() . $this->Guidelines(SVGG_GUIDELINE_BELOW);
        $chunk_count = count($this->values);
        $gap_count = $chunk_count - 1;
        $bar_width = $this->bar_space >= $this->bar_unit_width ? '1' : $this->bar_unit_width - $this->bar_space;
        $chunk_gap = $gap_count > 0 ? $this->group_space : 0;
        if ($gap_count > 0 && $chunk_gap * $gap_count > $bar_width - $chunk_count) {
            $chunk_gap = ($bar_width - $chunk_count) / $gap_count;
        }
        $chunk_width = ($bar_width - $chunk_gap * ($chunk_count - 1)) / $chunk_count;
        $chunk_unit_width = $chunk_width + $chunk_gap;
        $bar_style = array();
        $this->SetStroke($bar_style);
        $bar = array('width' => $chunk_width);
        $b_start = $this->pad_left + $this->bar_space / 2;
        $bspace = $this->bar_space / 2;
        $bnum = 0;
        $ccount = count($this->colours);
        $groups = array_fill(0, $chunk_count, '');
        foreach ($this->multi_graph->all_keys as $k) {
            $bar_pos = $this->GridPosition($k, $bnum);
            if (!is_null($bar_pos)) {
                for ($j = 0; $j < $chunk_count; ++$j) {
                    $bar['x'] = $bspace + $bar_pos + $j * $chunk_unit_width;
                    $value = $this->multi_graph->GetValue($k, $j);
                    $this->Bar($value, $bar);
                    if ($bar['height'] > 0) {
                        $bar_style['fill'] = $this->GetColour($j % $ccount);
                        if ($this->show_tooltips) {
                            $this->SetTooltip($bar, $value, null, !$this->compat_events && $this->show_bar_labels);
                        }
                        if ($this->show_bar_labels) {
                            $rect = $this->Element('rect', $bar, $bar_style);
                            $rect .= $this->BarLabel($value, $bar);
                            $body .= $this->GetLink($k, $rect);
                        } else {
                            $rect = $this->Element('rect', $bar);
                            $groups[$j] .= $this->GetLink($k, $rect);
                        }
                        unset($bar['id']);
                        // clear for next generated value
                        if (!array_key_exists($j, $this->bar_styles)) {
                            $this->bar_styles[$j] = $bar_style;
                        }
                    }
                }
            }
            ++$bnum;
        }
        if (!$this->show_bar_labels) {
            foreach ($groups as $j => $g) {
                if (array_key_exists($j, $this->bar_styles)) {
                    $body .= $this->Element('g', NULL, $this->bar_styles[$j], $g);
                }
            }
        }
        $body .= $this->Guidelines(SVGG_GUIDELINE_ABOVE) . $this->Axes();
        return $body;
    }