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   1  YUI.add('moodle-core-lockscroll', function (Y, NAME) {
   2  
   3  /**
   4   * Provides the ability to lock the scroll for a page, allowing nested
   5   * locking.
   6   *
   7   * @module moodle-core-lockscroll
   8   */
   9  
  10  /**
  11   * Provides the ability to lock the scroll for a page.
  12   *
  13   * This is achieved by applying the class 'lockscroll' to the body Node.
  14   *
  15   * Nested widgets are also supported and the scroll lock is only removed
  16   * when the final plugin instance is disabled.
  17   *
  18   * @class M.core.LockScroll
  19   * @extends Plugin.Base
  20   */
  21  Y.namespace('M.core').LockScroll = Y.Base.create('lockScroll', Y.Plugin.Base, [], {
  22  
  23      /**
  24       * Whether the LockScroll has been activated.
  25       *
  26       * @property _enabled
  27       * @type Boolean
  28       * @protected
  29       */
  30      _enabled: false,
  31  
  32      /**
  33       * Handle destruction of the lockScroll instance, including disabling
  34       * of the current instance.
  35       *
  36       * @method destructor
  37       */
  38      destructor: function() {
  39          this.disableScrollLock();
  40      },
  41  
  42      /**
  43       * Start locking the page scroll.
  44       *
  45       * This is achieved by applying the lockscroll class to the body Node.
  46       *
  47       * A count of the total number of active, and enabled, lockscroll instances is also kept on
  48       * the body to ensure that premature disabling does not occur.
  49       *
  50       * @method enableScrollLock
  51       * @param {Boolean} forceOnSmallWindow Whether to enable the scroll lock, even for small window sizes.
  52       * @chainable
  53       */
  54      enableScrollLock: function(forceOnSmallWindow) {
  55          if (this.isActive()) {
  56              Y.log('LockScroll already active. Ignoring enable request', 'warn', 'moodle-core-lockscroll');
  57              return;
  58          }
  59  
  60          var dialogueHeight = this.get('host').get('boundingBox').get('region').height,
  61              // Most modern browsers use win.innerHeight, but some older versions of IE use documentElement.clientHeight.
  62              // We fall back to 0 if neither can be found which has the effect of disabling scroll locking.
  63              windowHeight = Y.config.win.innerHeight || Y.config.doc.documentElement.clientHeight || 0;
  64  
  65          if (!forceOnSmallWindow && dialogueHeight > (windowHeight - 10)) {
  66              Y.log('Dialogue height greater than window height. Ignoring enable request.', 'warn', 'moodle-core-lockscroll');
  67              return;
  68          }
  69  
  70          Y.log('Enabling LockScroll.', 'debug', 'moodle-core-lockscroll');
  71          this._enabled = true;
  72          var body = Y.one(Y.config.doc.body);
  73  
  74          // We use a CSS class on the body to handle the actual locking.
  75          body.addClass('lockscroll');
  76  
  77          // Increase the count of active instances - this is used to ensure that we do not
  78          // remove the locking when parent windows are still open.
  79          // Note: We cannot use getData here because data attributes are sandboxed to the instance that created them.
  80          var currentCount = parseInt(body.getAttribute('data-activeScrollLocks'), 10) || 0,
  81              newCount = currentCount + 1;
  82          body.setAttribute('data-activeScrollLocks', newCount);
  83          Y.log("Setting the activeScrollLocks count from " + currentCount + " to " + newCount,
  84                  'debug', 'moodle-core-lockscroll');
  85  
  86          return this;
  87      },
  88  
  89      /**
  90       * Stop locking the page scroll.
  91       *
  92       * The instance may be disabled but the scroll lock not removed if other instances of the
  93       * plugin are also active.
  94       *
  95       * @method disableScrollLock
  96       * @chainable
  97       */
  98      disableScrollLock: function() {
  99          if (this.isActive()) {
 100              Y.log('Disabling LockScroll.', 'debug', 'moodle-core-lockscroll');
 101              this._enabled = false;
 102  
 103              var body = Y.one(Y.config.doc.body);
 104  
 105              // Decrease the count of active instances.
 106              // Note: We cannot use getData here because data attributes are sandboxed to the instance that created them.
 107              var currentCount = parseInt(body.getAttribute('data-activeScrollLocks'), 10) || 1,
 108                  newCount = currentCount - 1;
 109  
 110              if (currentCount === 1) {
 111                  body.removeClass('lockscroll');
 112              }
 113  
 114              body.setAttribute('data-activeScrollLocks', currentCount - 1);
 115              Y.log("Setting the activeScrollLocks count from " + currentCount + " to " + newCount,
 116                      'debug', 'moodle-core-lockscroll');
 117          }
 118  
 119          return this;
 120      },
 121  
 122      /**
 123       * Return whether scroll locking is active.
 124       *
 125       * @method isActive
 126       * @return Boolean
 127       */
 128      isActive: function() {
 129          return this._enabled;
 130      }
 131  
 132  }, {
 133      NS: 'lockScroll',
 134      ATTRS: {
 135      }
 136  });
 137  
 138  
 139  }, '@VERSION@', {"requires": ["plugin", "base-build"]});