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   1  // This file is part of Moodle - http://moodle.org/
   2  //
   3  // Moodle is free software: you can redistribute it and/or modify
   4  // it under the terms of the GNU General Public License as published by
   5  // the Free Software Foundation, either version 3 of the License, or
   6  // (at your option) any later version.
   7  //
   8  // Moodle is distributed in the hope that it will be useful,
   9  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  // GNU General Public License for more details.
  12  //
  13  // You should have received a copy of the GNU General Public License
  14  // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  15  
  16  /**
  17   * JavaScript required by the question engine.
  18   *
  19   * @package    moodlecore
  20   * @subpackage questionengine
  21   * @copyright  2008 The Open University
  22   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  23   */
  24  
  25  
  26  /**
  27   * Scroll manager is a class that help with saving the scroll positing when you
  28   * click on an action icon, and then when the page is reloaded after processing
  29   * the action, it scrolls you to exactly where you were. This is much nicer for
  30   * the user.
  31   *
  32   * To use this in your code, you need to ensure that:
  33   * 1. The button that triggers the action has to have a click event handler that
  34   *    calls M.core_scroll_manager.save_scroll_pos
  35   * 2. The script that process the action has to grab the scrollpos parameter
  36   *    using $scrollpos = optional_param('scrollpos', 0, PARAM_INT);
  37   * 3. After doing the processing, it must add ->param('scrollpos', $scrollpos)
  38   *    to the URL that it redirects to.
  39   * 4. Finally, on the page that is reloaded (which should be the same as the one
  40   *    the user started on) you need to call M.core_scroll_manager.scroll_to_saved_pos
  41   *    on page load.
  42   */
  43  M.core_scroll_manager = M.core_scroll_manager || {};
  44  
  45  /**
  46   * In the form that contains the element, set the value of the form field with
  47   * name scrollpos to the current scroll position. If there is no element with
  48   * that name, it creates a hidden form field wiht that name within the form.
  49   * @param element the element in the form. Should be something that can be
  50   *      passed to Y.one.
  51   */
  52  M.core_scroll_manager.save_scroll_pos = function(Y, element) {
  53      if (typeof(element) == 'string') {
  54          // Have to use getElementById here because element id can contain :.
  55          element = Y.one(document.getElementById(element));
  56      }
  57      var form = element.ancestor('form');
  58      if (!form) {
  59          return;
  60      }
  61      var scrollpos = form.one('input[name=scrollpos]');
  62      if (!scrollpos) {
  63          scrollpos = form.appendChild(form.create('<input type="hidden" name="scrollpos" />'));
  64      }
  65      scrollpos.set('value', form.get('docScrollY'));
  66  }
  67  
  68  /**
  69   * Event handler that can be used on a link. Assumes that the link already
  70   * contains at least one URL parameter.
  71   */
  72  M.core_scroll_manager.save_scroll_action = function(e) {
  73      var link = e.target.ancestor('a[href]');
  74      if (!link) {
  75          M.core_scroll_manager.save_scroll_pos({}, e.target);
  76          return;
  77      }
  78      link.set('href', link.get('href') + '&scrollpos=' + link.get('docScrollY'));
  79  }
  80  
  81  /**
  82   * If there is a parameter like scrollpos=123 in the URL, scroll to that saved position.
  83   */
  84  M.core_scroll_manager.scroll_to_saved_pos = function(Y) {
  85      var matches = window.location.href.match(/^.*[?&]scrollpos=(\d*)(?:&|$|#).*$/, '$1');
  86      if (matches) {
  87          // onDOMReady is the effective one here. I am leaving the immediate call to
  88          // window.scrollTo in case it reduces flicker.
  89          window.scrollTo(0, matches[1]);
  90          Y.on('domready', function() { window.scrollTo(0, matches[1]); });
  91  
  92          // And the following horror is necessary to make it work in IE 8.
  93          // Note that the class ie8 on body is only there in Moodle 2.0 and OU Moodle.
  94          if (Y.one('body').hasClass('ie')) {
  95              M.core_scroll_manager.force_ie_to_scroll(Y, matches[1])
  96          }
  97      }
  98  }
  99  
 100  /**
 101   * Beat IE into submission.
 102   * @param targetpos the target scroll position.
 103   */
 104  M.core_scroll_manager.force_ie_to_scroll = function(Y, targetpos) {
 105      var hackcount = 25;
 106      function do_scroll() {
 107          window.scrollTo(0, targetpos);
 108          hackcount -= 1;
 109          if (hackcount > 0) {
 110              setTimeout(do_scroll, 10);
 111          }
 112      }
 113      Y.on('load', do_scroll, window);
 114  }
 115  
 116  M.core_question_engine = M.core_question_engine || {};
 117  
 118  /**
 119   * Flag used by M.core_question_engine.prevent_repeat_submission.
 120   */
 121  M.core_question_engine.questionformalreadysubmitted = false;
 122  
 123  /**
 124   * Initialise a question submit button. This saves the scroll position and
 125   * sets the fragment on the form submit URL so the page reloads in the right place.
 126   * @param id the id of the button in the HTML.
 127   * @param slot the number of the question_attempt within the usage.
 128   */
 129  M.core_question_engine.init_submit_button = function(Y, button, slot) {
 130      var buttonel = document.getElementById(button);
 131      Y.on('click', function(e) {
 132          M.core_scroll_manager.save_scroll_pos(Y, button);
 133          buttonel.form.action = buttonel.form.action + '#q' + slot;
 134      }, buttonel);
 135  }
 136  
 137  /**
 138   * Initialise a form that contains questions printed using print_question.
 139   * This has the effect of:
 140   * 1. Turning off browser autocomlete.
 141   * 2. Stopping enter from submitting the form (or toggling the next flag) unless
 142   *    keyboard focus is on the submit button or the flag.
 143   * 3. Removes any '.questionflagsavebutton's, since we have JavaScript to toggle
 144   *    the flags using ajax.
 145   * 4. Scroll to the position indicated by scrollpos= in the URL, if it is there.
 146   * 5. Prevent the user from repeatedly submitting the form.
 147   * @param Y the Yahoo object. Needs to have the DOM and Event modules loaded.
 148   * @param form something that can be passed to Y.one, to find the form element.
 149   */
 150  M.core_question_engine.init_form = function(Y, form) {
 151      Y.one(form).setAttribute('autocomplete', 'off');
 152  
 153      Y.on('submit', M.core_question_engine.prevent_repeat_submission, form, form, Y);
 154  
 155      Y.on('key', function (e) {
 156          if (!e.target.test('a') && !e.target.test('input[type=submit]') &&
 157                  !e.target.test('input[type=img]') && !e.target.test('textarea') && !e.target.test('[contenteditable=true]')) {
 158              e.preventDefault();
 159          }
 160      }, form, 'press:13');
 161  
 162      Y.one(form).all('.questionflagsavebutton').remove();
 163  
 164      M.core_scroll_manager.scroll_to_saved_pos(Y);
 165  }
 166  
 167  /**
 168   * Event handler to stop a question form being submitted more than once.
 169   * @param e the form submit event.
 170   * @param form the form element.
 171   */
 172  M.core_question_engine.prevent_repeat_submission = function(e, Y) {
 173      if (M.core_question_engine.questionformalreadysubmitted) {
 174          e.halt();
 175          return;
 176      }
 177  
 178      setTimeout(function() {
 179          Y.all('input[type=submit]').set('disabled', true);
 180      }, 0);
 181      M.core_question_engine.questionformalreadysubmitted = true;
 182  }