SVGGraphAxisDoubleEnded.php

<?php
/**
 * Copyright (C) 2013-2015 Graham Breach
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
/**
 * For more information, please contact <graham@goat1000.com>
 */

require_once 'SVGGraphAxis.php';

/**
 * Class for axis with +ve on both sides of zero
 */
class AxisDoubleEnded extends Axis{

  /**
   * Constructor calls Axis constructor with 1/5 length
   */
  public function __construct($length, $max_val, $min_val, $min_unit, $fit,
    $units_before, $units_after, $decimal_digits, $label_callback)
  {
    if($min_val < 0)
      throw new Exception('Negative value for double-ended axis');
    parent::__construct($length / 2, $max_val, $min_val, $min_unit, $fit,
      $units_before, $units_after, $decimal_digits, $label_callback);
  }

  /**
   * Returns the distance along the axis where 0 should be
   */
  public function Zero()
  {
    return $this->zero = $this->length;
  }

  /**
   * Returns the grid points as an array of GridPoints
   */
  public function GetGridPoints($min_space, $start)
  {
    $points = parent::GetGridPoints($min_space, $start);
    $new_points = array();
    $z = $this->Zero();
    foreach($points as $p) {
      $new_points[] = new GridPoint($p->position + $z, $p->text, $p->value);
      if($p->value != 0)
        $new_points[] = new GridPoint((2 * $start) + $z - $p->position, $p->text, $p->value);
    }

    usort($new_points, ($this->direction < 0 ? 'gridpoint_rsort' : 'gridpoint_sort'));
    return $new_points;
  }

  /**
   * Returns the grid subdivision points as an array
   */
  public function GetGridSubdivisions($min_space, $min_unit, $start, $fixed)
  {
    $divs = parent::GetGridSubdivisions($min_space, $min_unit, $start, $fixed);
    $new_divs = array();
    $z = $this->Zero();
    foreach($divs as $d) {
      $new_divs[] = new GridPoint($d->position + $z, '', 0);
      $new_divs[] = new GridPoint((2 * $start) + $z - $d->position, '', 0);
    }

    return $new_divs;
  }
}