question/qengine.js

   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')) {
 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 }