Added jQuery.mousewheel support

jQuery.mousewheel will allow us to prevent the dropdown from
automatically closing when the user scrolls to the end of the list.
It is automatically bundled in the full versions of Select2 and
we don't require that it is included in order for Select2 to work.

jQuery.mousewheel was taken directly from the source repository
using the commit at

cc2c5d73ae

Gruntfile.js

@@ -10,6 +10,7 @@ module.exports = function (grunt) {
 
   fullIncludes = [
     'jquery',
+    'jquery.mousewheel',
 
     'select2/compat/matcher',
 
@@ -144,7 +145,8 @@ module.exports = function (grunt) {
           include: amdIncludes.concat(fullIncludes),
           paths: {
             almond: '../../vendor/almond-0.2.9',
-            jquery: '../../vendor/jquery-2.1.0'
+            jquery: '../../vendor/jquery-2.1.0',
+            'jquery.mousewheel': '../../vendor/jquery.mousewheel'
           },
           wrap: grunt.file.readJSON('src/js/banner.json')
         }
@@ -170,7 +172,8 @@ module.exports = function (grunt) {
           out: 'dist/js/select2.amd.full.js',
           include: fullIncludes,
           paths: {
-            jquery: 'empty:'
+            jquery: 'empty:',
+            'jquery.mousewheel': '../../vendor/jquery.mousewheel'
           },
           wrap: grunt.file.readJSON('src/js/banner.json')
         }

dist/js/select2.amd.full.js

@@ -163,8 +163,9 @@ window.$ = window.$ || {};(function() { if ($ && $.fn && $.fn.select2 && $.fn.se
 });
 
 define('select2/results',[
+  'jquery',
   './utils'
-], function (Utils) {
+], function ($, Utils) {
   function Results ($element, options, dataAdapter) {
     this.$element = $element;
     this.data = dataAdapter;
@@ -530,6 +531,33 @@ define('select2/results',[
       self.displayMessage(params);
     });
 
+    if ($.fn.mousewheel) {
+      this.$results.on('mousewheel', function (e) {
+        var top = self.$results.scrollTop();
+
+        var bottom = (
+          self.$results.get(0).scrollHeight -
+          self.$results.scrollTop() +
+          e.deltaY
+        );
+
+        var isAtTop = e.deltaY > 0 && top - e.deltaY <= 0;
+        var isAtBottom = e.deltaY < 0 && bottom <= self.$results.height();
+
+        if (isAtTop) {
+          self.$results.scrollTop(0);
+          e.preventDefault();
+          e.stopPropagation();
+        } else if (isAtBottom) {
+          self.$results.scrollTop(
+            self.$results.get(0).scrollHeight - self.$results.height()
+          );
+          e.preventDefault();
+          e.stopPropagation();
+        }
+      });
+    }
+
     this.$results.on('mouseup', '.select2-results__option[aria-selected]',
       function (evt) {
       var $this = $(this);
@@ -4001,6 +4029,228 @@ define('select2/core',[
   return Select2;
 });
 
+/*!
+ * jQuery Mousewheel 3.1.12
+ *
+ * Copyright 2014 jQuery Foundation and other contributors
+ * Released under the MIT license.
+ * http://jquery.org/license
+ */
+
+(function (factory) {
+    if ( typeof define === 'function' && define.amd ) {
+        // AMD. Register as an anonymous module.
+        define('jquery.mousewheel',['jquery'], factory);
+    } else if (typeof exports === 'object') {
+        // Node/CommonJS style for Browserify
+        module.exports = factory;
+    } else {
+        // Browser globals
+        factory(jQuery);
+    }
+}(function ($) {
+
+    var toFix  = ['wheel', 'mousewheel', 'DOMMouseScroll', 'MozMousePixelScroll'],
+        toBind = ( 'onwheel' in document || document.documentMode >= 9 ) ?
+                    ['wheel'] : ['mousewheel', 'DomMouseScroll', 'MozMousePixelScroll'],
+        slice  = Array.prototype.slice,
+        nullLowestDeltaTimeout, lowestDelta;
+
+    if ( $.event.fixHooks ) {
+        for ( var i = toFix.length; i; ) {
+            $.event.fixHooks[ toFix[--i] ] = $.event.mouseHooks;
+        }
+    }
+
+    var special = $.event.special.mousewheel = {
+        version: '3.1.12',
+
+        setup: function() {
+            if ( this.addEventListener ) {
+                for ( var i = toBind.length; i; ) {
+                    this.addEventListener( toBind[--i], handler, false );
+                }
+            } else {
+                this.onmousewheel = handler;
+            }
+            // Store the line height and page height for this particular element
+            $.data(this, 'mousewheel-line-height', special.getLineHeight(this));
+            $.data(this, 'mousewheel-page-height', special.getPageHeight(this));
+        },
+
+        teardown: function() {
+            if ( this.removeEventListener ) {
+                for ( var i = toBind.length; i; ) {
+                    this.removeEventListener( toBind[--i], handler, false );
+                }
+            } else {
+                this.onmousewheel = null;
+            }
+            // Clean up the data we added to the element
+            $.removeData(this, 'mousewheel-line-height');
+            $.removeData(this, 'mousewheel-page-height');
+        },
+
+        getLineHeight: function(elem) {
+            var $elem = $(elem),
+                $parent = $elem['offsetParent' in $.fn ? 'offsetParent' : 'parent']();
+            if (!$parent.length) {
+                $parent = $('body');
+            }
+            return parseInt($parent.css('fontSize'), 10) || parseInt($elem.css('fontSize'), 10) || 16;
+        },
+
+        getPageHeight: function(elem) {
+            return $(elem).height();
+        },
+
+        settings: {
+            adjustOldDeltas: true, // see shouldAdjustOldDeltas() below
+            normalizeOffset: true  // calls getBoundingClientRect for each event
+        }
+    };
+
+    $.fn.extend({
+        mousewheel: function(fn) {
+            return fn ? this.bind('mousewheel', fn) : this.trigger('mousewheel');
+        },
+
+        unmousewheel: function(fn) {
+            return this.unbind('mousewheel', fn);
+        }
+    });
+
+
+    function handler(event) {
+        var orgEvent   = event || window.event,
+            args       = slice.call(arguments, 1),
+            delta      = 0,
+            deltaX     = 0,
+            deltaY     = 0,
+            absDelta   = 0,
+            offsetX    = 0,
+            offsetY    = 0;
+        event = $.event.fix(orgEvent);
+        event.type = 'mousewheel';
+
+        // Old school scrollwheel delta
+        if ( 'detail'      in orgEvent ) { deltaY = orgEvent.detail * -1;      }
+        if ( 'wheelDelta'  in orgEvent ) { deltaY = orgEvent.wheelDelta;       }
+        if ( 'wheelDeltaY' in orgEvent ) { deltaY = orgEvent.wheelDeltaY;      }
+        if ( 'wheelDeltaX' in orgEvent ) { deltaX = orgEvent.wheelDeltaX * -1; }
+
+        // Firefox < 17 horizontal scrolling related to DOMMouseScroll event
+        if ( 'axis' in orgEvent && orgEvent.axis === orgEvent.HORIZONTAL_AXIS ) {
+            deltaX = deltaY * -1;
+            deltaY = 0;
+        }
+
+        // Set delta to be deltaY or deltaX if deltaY is 0 for backwards compatabilitiy
+        delta = deltaY === 0 ? deltaX : deltaY;
+
+        // New school wheel delta (wheel event)
+        if ( 'deltaY' in orgEvent ) {
+            deltaY = orgEvent.deltaY * -1;
+            delta  = deltaY;
+        }
+        if ( 'deltaX' in orgEvent ) {
+            deltaX = orgEvent.deltaX;
+            if ( deltaY === 0 ) { delta  = deltaX * -1; }
+        }
+
+        // No change actually happened, no reason to go any further
+        if ( deltaY === 0 && deltaX === 0 ) { return; }
+
+        // Need to convert lines and pages to pixels if we aren't already in pixels
+        // There are three delta modes:
+        //   * deltaMode 0 is by pixels, nothing to do
+        //   * deltaMode 1 is by lines
+        //   * deltaMode 2 is by pages
+        if ( orgEvent.deltaMode === 1 ) {
+            var lineHeight = $.data(this, 'mousewheel-line-height');
+            delta  *= lineHeight;
+            deltaY *= lineHeight;
+            deltaX *= lineHeight;
+        } else if ( orgEvent.deltaMode === 2 ) {
+            var pageHeight = $.data(this, 'mousewheel-page-height');
+            delta  *= pageHeight;
+            deltaY *= pageHeight;
+            deltaX *= pageHeight;
+        }
+
+        // Store lowest absolute delta to normalize the delta values
+        absDelta = Math.max( Math.abs(deltaY), Math.abs(deltaX) );
+
+        if ( !lowestDelta || absDelta < lowestDelta ) {
+            lowestDelta = absDelta;
+
+            // Adjust older deltas if necessary
+            if ( shouldAdjustOldDeltas(orgEvent, absDelta) ) {
+                lowestDelta /= 40;
+            }
+        }
+
+        // Adjust older deltas if necessary
+        if ( shouldAdjustOldDeltas(orgEvent, absDelta) ) {
+            // Divide all the things by 40!
+            delta  /= 40;
+            deltaX /= 40;
+            deltaY /= 40;
+        }
+
+        // Get a whole, normalized value for the deltas
+        delta  = Math[ delta  >= 1 ? 'floor' : 'ceil' ](delta  / lowestDelta);
+        deltaX = Math[ deltaX >= 1 ? 'floor' : 'ceil' ](deltaX / lowestDelta);
+        deltaY = Math[ deltaY >= 1 ? 'floor' : 'ceil' ](deltaY / lowestDelta);
+
+        // Normalise offsetX and offsetY properties
+        if ( special.settings.normalizeOffset && this.getBoundingClientRect ) {
+            var boundingRect = this.getBoundingClientRect();
+            offsetX = event.clientX - boundingRect.left;
+            offsetY = event.clientY - boundingRect.top;
+        }
+
+        // Add information to the event object
+        event.deltaX = deltaX;
+        event.deltaY = deltaY;
+        event.deltaFactor = lowestDelta;
+        event.offsetX = offsetX;
+        event.offsetY = offsetY;
+        // Go ahead and set deltaMode to 0 since we converted to pixels
+        // Although this is a little odd since we overwrite the deltaX/Y
+        // properties with normalized deltas.
+        event.deltaMode = 0;
+
+        // Add event and delta to the front of the arguments
+        args.unshift(event, delta, deltaX, deltaY);
+
+        // Clearout lowestDelta after sometime to better
+        // handle multiple device types that give different
+        // a different lowestDelta
+        // Ex: trackpad = 3 and mouse wheel = 120
+        if (nullLowestDeltaTimeout) { clearTimeout(nullLowestDeltaTimeout); }
+        nullLowestDeltaTimeout = setTimeout(nullLowestDelta, 200);
+
+        return ($.event.dispatch || $.event.handle).apply(this, args);
+    }
+
+    function nullLowestDelta() {
+        lowestDelta = null;
+    }
+
+    function shouldAdjustOldDeltas(orgEvent, absDelta) {
+        // If this is an older event and the delta is divisable by 120,
+        // then we are assuming that the browser is treating this as an
+        // older mouse wheel event and that we should divide the deltas
+        // by 40 to try and get a more usable deltaFactor.
+        // Side note, this actually impacts the reported scroll distance
+        // in older browsers and can cause scrolling to be slower than native.
+        // Turn this off by setting $.event.special.mousewheel.settings.adjustOldDeltas to false.
+        return special.settings.adjustOldDeltas && orgEvent.type === 'mousewheel' && absDelta % 120 === 0;
+    }
+
+}));
+
 define('select2/compat/matcher',[
 
 ], function () {
@@ -4067,6 +4317,11 @@ define('jquery.select2',[
   'jquery',
   'select2/core'
 ], function ($, Select2) {
+  // Force jQuery.mousewheel to be loaded if it hasn't already
+  try {
+    require('jquery.mousewheel');
+  } catch (Exception) { }
+
   if ($.fn.select2 == null) {
     $.fn.select2 = function (options) {
       options = options || {};

dist/js/select2.amd.js

@@ -163,8 +163,9 @@ window.$ = window.$ || {};(function() { if ($ && $.fn && $.fn.select2 && $.fn.se
 });
 
 define('select2/results',[
+  'jquery',
   './utils'
-], function (Utils) {
+], function ($, Utils) {
   function Results ($element, options, dataAdapter) {
     this.$element = $element;
     this.data = dataAdapter;
@@ -530,6 +531,33 @@ define('select2/results',[
       self.displayMessage(params);
     });
 
+    if ($.fn.mousewheel) {
+      this.$results.on('mousewheel', function (e) {
+        var top = self.$results.scrollTop();
+
+        var bottom = (
+          self.$results.get(0).scrollHeight -
+          self.$results.scrollTop() +
+          e.deltaY
+        );
+
+        var isAtTop = e.deltaY > 0 && top - e.deltaY <= 0;
+        var isAtBottom = e.deltaY < 0 && bottom <= self.$results.height();
+
+        if (isAtTop) {
+          self.$results.scrollTop(0);
+          e.preventDefault();
+          e.stopPropagation();
+        } else if (isAtBottom) {
+          self.$results.scrollTop(
+            self.$results.get(0).scrollHeight - self.$results.height()
+          );
+          e.preventDefault();
+          e.stopPropagation();
+        }
+      });
+    }
+
     this.$results.on('mouseup', '.select2-results__option[aria-selected]',
       function (evt) {
       var $this = $(this);
@@ -4005,6 +4033,11 @@ define('jquery.select2',[
   'jquery',
   'select2/core'
 ], function ($, Select2) {
+  // Force jQuery.mousewheel to be loaded if it hasn't already
+  try {
+    require('jquery.mousewheel');
+  } catch (Exception) { }
+
   if ($.fn.select2 == null) {
     $.fn.select2 = function (options) {
       options = options || {};

dist/js/select2.full.js

@@ -9698,8 +9698,9 @@ define('select2/utils',[], function () {
 });
 
 define('select2/results',[
+  'jquery',
   './utils'
-], function (Utils) {
+], function ($, Utils) {
   function Results ($element, options, dataAdapter) {
     this.$element = $element;
     this.data = dataAdapter;
@@ -10065,6 +10066,33 @@ define('select2/results',[
       self.displayMessage(params);
     });
 
+    if ($.fn.mousewheel) {
+      this.$results.on('mousewheel', function (e) {
+        var top = self.$results.scrollTop();
+
+        var bottom = (
+          self.$results.get(0).scrollHeight -
+          self.$results.scrollTop() +
+          e.deltaY
+        );
+
+        var isAtTop = e.deltaY > 0 && top - e.deltaY <= 0;
+        var isAtBottom = e.deltaY < 0 && bottom <= self.$results.height();
+
+        if (isAtTop) {
+          self.$results.scrollTop(0);
+          e.preventDefault();
+          e.stopPropagation();
+        } else if (isAtBottom) {
+          self.$results.scrollTop(
+            self.$results.get(0).scrollHeight - self.$results.height()
+          );
+          e.preventDefault();
+          e.stopPropagation();
+        }
+      });
+    }
+
     this.$results.on('mouseup', '.select2-results__option[aria-selected]',
       function (evt) {
       var $this = $(this);
@@ -13536,6 +13564,228 @@ define('select2/core',[
   return Select2;
 });
 
+/*!
+ * jQuery Mousewheel 3.1.12
+ *
+ * Copyright 2014 jQuery Foundation and other contributors
+ * Released under the MIT license.
+ * http://jquery.org/license
+ */
+
+(function (factory) {
+    if ( typeof define === 'function' && define.amd ) {
+        // AMD. Register as an anonymous module.
+        define('jquery.mousewheel',['jquery'], factory);
+    } else if (typeof exports === 'object') {
+        // Node/CommonJS style for Browserify
+        module.exports = factory;
+    } else {
+        // Browser globals
+        factory(jQuery);
+    }
+}(function ($) {
+
+    var toFix  = ['wheel', 'mousewheel', 'DOMMouseScroll', 'MozMousePixelScroll'],
+        toBind = ( 'onwheel' in document || document.documentMode >= 9 ) ?
+                    ['wheel'] : ['mousewheel', 'DomMouseScroll', 'MozMousePixelScroll'],
+        slice  = Array.prototype.slice,
+        nullLowestDeltaTimeout, lowestDelta;
+
+    if ( $.event.fixHooks ) {
+        for ( var i = toFix.length; i; ) {
+            $.event.fixHooks[ toFix[--i] ] = $.event.mouseHooks;
+        }
+    }
+
+    var special = $.event.special.mousewheel = {
+        version: '3.1.12',
+
+        setup: function() {
+            if ( this.addEventListener ) {
+                for ( var i = toBind.length; i; ) {
+                    this.addEventListener( toBind[--i], handler, false );
+                }
+            } else {
+                this.onmousewheel = handler;
+            }
+            // Store the line height and page height for this particular element
+            $.data(this, 'mousewheel-line-height', special.getLineHeight(this));
+            $.data(this, 'mousewheel-page-height', special.getPageHeight(this));
+        },
+
+        teardown: function() {
+            if ( this.removeEventListener ) {
+                for ( var i = toBind.length; i; ) {
+                    this.removeEventListener( toBind[--i], handler, false );
+                }
+            } else {
+                this.onmousewheel = null;
+            }
+            // Clean up the data we added to the element
+            $.removeData(this, 'mousewheel-line-height');
+            $.removeData(this, 'mousewheel-page-height');
+        },
+
+        getLineHeight: function(elem) {
+            var $elem = $(elem),
+                $parent = $elem['offsetParent' in $.fn ? 'offsetParent' : 'parent']();
+            if (!$parent.length) {
+                $parent = $('body');
+            }
+            return parseInt($parent.css('fontSize'), 10) || parseInt($elem.css('fontSize'), 10) || 16;
+        },
+
+        getPageHeight: function(elem) {
+            return $(elem).height();
+        },
+
+        settings: {
+            adjustOldDeltas: true, // see shouldAdjustOldDeltas() below
+            normalizeOffset: true  // calls getBoundingClientRect for each event
+        }
+    };
+
+    $.fn.extend({
+        mousewheel: function(fn) {
+            return fn ? this.bind('mousewheel', fn) : this.trigger('mousewheel');
+        },
+
+        unmousewheel: function(fn) {
+            return this.unbind('mousewheel', fn);
+        }
+    });
+
+
+    function handler(event) {
+        var orgEvent   = event || window.event,
+            args       = slice.call(arguments, 1),
+            delta      = 0,
+            deltaX     = 0,
+            deltaY     = 0,
+            absDelta   = 0,
+            offsetX    = 0,
+            offsetY    = 0;
+        event = $.event.fix(orgEvent);
+        event.type = 'mousewheel';
+
+        // Old school scrollwheel delta
+        if ( 'detail'      in orgEvent ) { deltaY = orgEvent.detail * -1;      }
+        if ( 'wheelDelta'  in orgEvent ) { deltaY = orgEvent.wheelDelta;       }
+        if ( 'wheelDeltaY' in orgEvent ) { deltaY = orgEvent.wheelDeltaY;      }
+        if ( 'wheelDeltaX' in orgEvent ) { deltaX = orgEvent.wheelDeltaX * -1; }
+
+        // Firefox < 17 horizontal scrolling related to DOMMouseScroll event
+        if ( 'axis' in orgEvent && orgEvent.axis === orgEvent.HORIZONTAL_AXIS ) {
+            deltaX = deltaY * -1;
+            deltaY = 0;
+        }
+
+        // Set delta to be deltaY or deltaX if deltaY is 0 for backwards compatabilitiy
+        delta = deltaY === 0 ? deltaX : deltaY;
+
+        // New school wheel delta (wheel event)
+        if ( 'deltaY' in orgEvent ) {
+            deltaY = orgEvent.deltaY * -1;
+            delta  = deltaY;
+        }
+        if ( 'deltaX' in orgEvent ) {
+            deltaX = orgEvent.deltaX;
+            if ( deltaY === 0 ) { delta  = deltaX * -1; }
+        }
+
+        // No change actually happened, no reason to go any further
+        if ( deltaY === 0 && deltaX === 0 ) { return; }
+
+        // Need to convert lines and pages to pixels if we aren't already in pixels
+        // There are three delta modes:
+        //   * deltaMode 0 is by pixels, nothing to do
+        //   * deltaMode 1 is by lines
+        //   * deltaMode 2 is by pages
+        if ( orgEvent.deltaMode === 1 ) {
+            var lineHeight = $.data(this, 'mousewheel-line-height');
+            delta  *= lineHeight;
+            deltaY *= lineHeight;
+            deltaX *= lineHeight;
+        } else if ( orgEvent.deltaMode === 2 ) {
+            var pageHeight = $.data(this, 'mousewheel-page-height');
+            delta  *= pageHeight;
+            deltaY *= pageHeight;
+            deltaX *= pageHeight;
+        }
+
+        // Store lowest absolute delta to normalize the delta values
+        absDelta = Math.max( Math.abs(deltaY), Math.abs(deltaX) );
+
+        if ( !lowestDelta || absDelta < lowestDelta ) {
+            lowestDelta = absDelta;
+
+            // Adjust older deltas if necessary
+            if ( shouldAdjustOldDeltas(orgEvent, absDelta) ) {
+                lowestDelta /= 40;
+            }
+        }
+
+        // Adjust older deltas if necessary
+        if ( shouldAdjustOldDeltas(orgEvent, absDelta) ) {
+            // Divide all the things by 40!
+            delta  /= 40;
+            deltaX /= 40;
+            deltaY /= 40;
+        }
+
+        // Get a whole, normalized value for the deltas
+        delta  = Math[ delta  >= 1 ? 'floor' : 'ceil' ](delta  / lowestDelta);
+        deltaX = Math[ deltaX >= 1 ? 'floor' : 'ceil' ](deltaX / lowestDelta);
+        deltaY = Math[ deltaY >= 1 ? 'floor' : 'ceil' ](deltaY / lowestDelta);
+
+        // Normalise offsetX and offsetY properties
+        if ( special.settings.normalizeOffset && this.getBoundingClientRect ) {
+            var boundingRect = this.getBoundingClientRect();
+            offsetX = event.clientX - boundingRect.left;
+            offsetY = event.clientY - boundingRect.top;
+        }
+
+        // Add information to the event object
+        event.deltaX = deltaX;
+        event.deltaY = deltaY;
+        event.deltaFactor = lowestDelta;
+        event.offsetX = offsetX;
+        event.offsetY = offsetY;
+        // Go ahead and set deltaMode to 0 since we converted to pixels
+        // Although this is a little odd since we overwrite the deltaX/Y
+        // properties with normalized deltas.
+        event.deltaMode = 0;
+
+        // Add event and delta to the front of the arguments
+        args.unshift(event, delta, deltaX, deltaY);
+
+        // Clearout lowestDelta after sometime to better
+        // handle multiple device types that give different
+        // a different lowestDelta
+        // Ex: trackpad = 3 and mouse wheel = 120
+        if (nullLowestDeltaTimeout) { clearTimeout(nullLowestDeltaTimeout); }
+        nullLowestDeltaTimeout = setTimeout(nullLowestDelta, 200);
+
+        return ($.event.dispatch || $.event.handle).apply(this, args);
+    }
+
+    function nullLowestDelta() {
+        lowestDelta = null;
+    }
+
+    function shouldAdjustOldDeltas(orgEvent, absDelta) {
+        // If this is an older event and the delta is divisable by 120,
+        // then we are assuming that the browser is treating this as an
+        // older mouse wheel event and that we should divide the deltas
+        // by 40 to try and get a more usable deltaFactor.
+        // Side note, this actually impacts the reported scroll distance
+        // in older browsers and can cause scrolling to be slower than native.
+        // Turn this off by setting $.event.special.mousewheel.settings.adjustOldDeltas to false.
+        return special.settings.adjustOldDeltas && orgEvent.type === 'mousewheel' && absDelta % 120 === 0;
+    }
+
+}));
+
 define('select2/compat/matcher',[
 
 ], function () {
@@ -13602,6 +13852,11 @@ define('jquery.select2',[
   'jquery',
   'select2/core'
 ], function ($, Select2) {
+  // Force jQuery.mousewheel to be loaded if it hasn't already
+  try {
+    require('jquery.mousewheel');
+  } catch (Exception) { }
+
   if ($.fn.select2 == null) {
     $.fn.select2 = function (options) {
       options = options || {};

dist/js/select2.js

@@ -591,8 +591,9 @@ define('select2/utils',[], function () {
 });
 
 define('select2/results',[
+  'jquery',
   './utils'
-], function (Utils) {
+], function ($, Utils) {
   function Results ($element, options, dataAdapter) {
     this.$element = $element;
     this.data = dataAdapter;
@@ -958,6 +959,33 @@ define('select2/results',[
       self.displayMessage(params);
     });
 
+    if ($.fn.mousewheel) {
+      this.$results.on('mousewheel', function (e) {
+        var top = self.$results.scrollTop();
+
+        var bottom = (
+          self.$results.get(0).scrollHeight -
+          self.$results.scrollTop() +
+          e.deltaY
+        );
+
+        var isAtTop = e.deltaY > 0 && top - e.deltaY <= 0;
+        var isAtBottom = e.deltaY < 0 && bottom <= self.$results.height();
+
+        if (isAtTop) {
+          self.$results.scrollTop(0);
+          e.preventDefault();
+          e.stopPropagation();
+        } else if (isAtBottom) {
+          self.$results.scrollTop(
+            self.$results.get(0).scrollHeight - self.$results.height()
+          );
+          e.preventDefault();
+          e.stopPropagation();
+        }
+      });
+    }
+
     this.$results.on('mouseup', '.select2-results__option[aria-selected]',
       function (evt) {
       var $this = $(this);
@@ -4433,6 +4461,11 @@ define('jquery.select2',[
   'jquery',
   'select2/core'
 ], function ($, Select2) {
+  // Force jQuery.mousewheel to be loaded if it hasn't already
+  try {
+    require('jquery.mousewheel');
+  } catch (Exception) { }
+
   if ($.fn.select2 == null) {
     $.fn.select2 = function (options) {
       options = options || {};

src/js/jquery.select2.js

@@ -2,6 +2,11 @@ define([
   'jquery',
   'select2/core'
 ], function ($, Select2) {
+  // Force jQuery.mousewheel to be loaded if it hasn't already
+  try {
+    require('jquery.mousewheel');
+  } catch (Exception) { }
+
   if ($.fn.select2 == null) {
     $.fn.select2 = function (options) {
       options = options || {};

src/js/select2/results.js

@@ -1,6 +1,7 @@
 define([
+  'jquery',
   './utils'
-], function (Utils) {
+], function ($, Utils) {
   function Results ($element, options, dataAdapter) {
     this.$element = $element;
     this.data = dataAdapter;
@@ -366,6 +367,35 @@ define([
       self.displayMessage(params);
     });
 
+    if ($.fn.mousewheel) {
+      this.$results.on('mousewheel', function (e) {
+        var top = self.$results.scrollTop();
+
+        var bottom = (
+          self.$results.get(0).scrollHeight -
+          self.$results.scrollTop() +
+          e.deltaY
+        );
+
+        var isAtTop = e.deltaY > 0 && top - e.deltaY <= 0;
+        var isAtBottom = e.deltaY < 0 && bottom <= self.$results.height();
+
+        if (isAtTop) {
+          self.$results.scrollTop(0);
+
+          e.preventDefault();
+          e.stopPropagation();
+        } else if (isAtBottom) {
+          self.$results.scrollTop(
+            self.$results.get(0).scrollHeight - self.$results.height()
+          );
+
+          e.preventDefault();
+          e.stopPropagation();
+        }
+      });
+    }
+
     this.$results.on('mouseup', '.select2-results__option[aria-selected]',
       function (evt) {
       var $this = $(this);

vendor/jquery.mousewheel.js

@@ -0,0 +1,221 @@
+/*!
+ * jQuery Mousewheel 3.1.12
+ *
+ * Copyright 2014 jQuery Foundation and other contributors
+ * Released under the MIT license.
+ * http://jquery.org/license
+ */
+
+(function (factory) {
+    if ( typeof define === 'function' && define.amd ) {
+        // AMD. Register as an anonymous module.
+        define(['jquery'], factory);
+    } else if (typeof exports === 'object') {
+        // Node/CommonJS style for Browserify
+        module.exports = factory;
+    } else {
+        // Browser globals
+        factory(jQuery);
+    }
+}(function ($) {
+
+    var toFix  = ['wheel', 'mousewheel', 'DOMMouseScroll', 'MozMousePixelScroll'],
+        toBind = ( 'onwheel' in document || document.documentMode >= 9 ) ?
+                    ['wheel'] : ['mousewheel', 'DomMouseScroll', 'MozMousePixelScroll'],
+        slice  = Array.prototype.slice,
+        nullLowestDeltaTimeout, lowestDelta;
+
+    if ( $.event.fixHooks ) {
+        for ( var i = toFix.length; i; ) {
+            $.event.fixHooks[ toFix[--i] ] = $.event.mouseHooks;
+        }
+    }
+
+    var special = $.event.special.mousewheel = {
+        version: '3.1.12',
+
+        setup: function() {
+            if ( this.addEventListener ) {
+                for ( var i = toBind.length; i; ) {
+                    this.addEventListener( toBind[--i], handler, false );
+                }
+            } else {
+                this.onmousewheel = handler;
+            }
+            // Store the line height and page height for this particular element
+            $.data(this, 'mousewheel-line-height', special.getLineHeight(this));
+            $.data(this, 'mousewheel-page-height', special.getPageHeight(this));
+        },
+
+        teardown: function() {
+            if ( this.removeEventListener ) {
+                for ( var i = toBind.length; i; ) {
+                    this.removeEventListener( toBind[--i], handler, false );
+                }
+            } else {
+                this.onmousewheel = null;
+            }
+            // Clean up the data we added to the element
+            $.removeData(this, 'mousewheel-line-height');
+            $.removeData(this, 'mousewheel-page-height');
+        },
+
+        getLineHeight: function(elem) {
+            var $elem = $(elem),
+                $parent = $elem['offsetParent' in $.fn ? 'offsetParent' : 'parent']();
+            if (!$parent.length) {
+                $parent = $('body');
+            }
+            return parseInt($parent.css('fontSize'), 10) || parseInt($elem.css('fontSize'), 10) || 16;
+        },
+
+        getPageHeight: function(elem) {
+            return $(elem).height();
+        },
+
+        settings: {
+            adjustOldDeltas: true, // see shouldAdjustOldDeltas() below
+            normalizeOffset: true  // calls getBoundingClientRect for each event
+        }
+    };
+
+    $.fn.extend({
+        mousewheel: function(fn) {
+            return fn ? this.bind('mousewheel', fn) : this.trigger('mousewheel');
+        },
+
+        unmousewheel: function(fn) {
+            return this.unbind('mousewheel', fn);
+        }
+    });
+
+
+    function handler(event) {
+        var orgEvent   = event || window.event,
+            args       = slice.call(arguments, 1),
+            delta      = 0,
+            deltaX     = 0,
+            deltaY     = 0,
+            absDelta   = 0,
+            offsetX    = 0,
+            offsetY    = 0;
+        event = $.event.fix(orgEvent);
+        event.type = 'mousewheel';
+
+        // Old school scrollwheel delta
+        if ( 'detail'      in orgEvent ) { deltaY = orgEvent.detail * -1;      }
+        if ( 'wheelDelta'  in orgEvent ) { deltaY = orgEvent.wheelDelta;       }
+        if ( 'wheelDeltaY' in orgEvent ) { deltaY = orgEvent.wheelDeltaY;      }
+        if ( 'wheelDeltaX' in orgEvent ) { deltaX = orgEvent.wheelDeltaX * -1; }
+
+        // Firefox < 17 horizontal scrolling related to DOMMouseScroll event
+        if ( 'axis' in orgEvent && orgEvent.axis === orgEvent.HORIZONTAL_AXIS ) {
+            deltaX = deltaY * -1;
+            deltaY = 0;
+        }
+
+        // Set delta to be deltaY or deltaX if deltaY is 0 for backwards compatabilitiy
+        delta = deltaY === 0 ? deltaX : deltaY;
+
+        // New school wheel delta (wheel event)
+        if ( 'deltaY' in orgEvent ) {
+            deltaY = orgEvent.deltaY * -1;
+            delta  = deltaY;
+        }
+        if ( 'deltaX' in orgEvent ) {
+            deltaX = orgEvent.deltaX;
+            if ( deltaY === 0 ) { delta  = deltaX * -1; }
+        }
+
+        // No change actually happened, no reason to go any further
+        if ( deltaY === 0 && deltaX === 0 ) { return; }
+
+        // Need to convert lines and pages to pixels if we aren't already in pixels
+        // There are three delta modes:
+        //   * deltaMode 0 is by pixels, nothing to do
+        //   * deltaMode 1 is by lines
+        //   * deltaMode 2 is by pages
+        if ( orgEvent.deltaMode === 1 ) {
+            var lineHeight = $.data(this, 'mousewheel-line-height');
+            delta  *= lineHeight;
+            deltaY *= lineHeight;
+            deltaX *= lineHeight;
+        } else if ( orgEvent.deltaMode === 2 ) {
+            var pageHeight = $.data(this, 'mousewheel-page-height');
+            delta  *= pageHeight;
+            deltaY *= pageHeight;
+            deltaX *= pageHeight;
+        }
+
+        // Store lowest absolute delta to normalize the delta values
+        absDelta = Math.max( Math.abs(deltaY), Math.abs(deltaX) );
+
+        if ( !lowestDelta || absDelta < lowestDelta ) {
+            lowestDelta = absDelta;
+
+            // Adjust older deltas if necessary
+            if ( shouldAdjustOldDeltas(orgEvent, absDelta) ) {
+                lowestDelta /= 40;
+            }
+        }
+
+        // Adjust older deltas if necessary
+        if ( shouldAdjustOldDeltas(orgEvent, absDelta) ) {
+            // Divide all the things by 40!
+            delta  /= 40;
+            deltaX /= 40;
+            deltaY /= 40;
+        }
+
+        // Get a whole, normalized value for the deltas
+        delta  = Math[ delta  >= 1 ? 'floor' : 'ceil' ](delta  / lowestDelta);
+        deltaX = Math[ deltaX >= 1 ? 'floor' : 'ceil' ](deltaX / lowestDelta);
+        deltaY = Math[ deltaY >= 1 ? 'floor' : 'ceil' ](deltaY / lowestDelta);
+
+        // Normalise offsetX and offsetY properties
+        if ( special.settings.normalizeOffset && this.getBoundingClientRect ) {
+            var boundingRect = this.getBoundingClientRect();
+            offsetX = event.clientX - boundingRect.left;
+            offsetY = event.clientY - boundingRect.top;
+        }
+
+        // Add information to the event object
+        event.deltaX = deltaX;
+        event.deltaY = deltaY;
+        event.deltaFactor = lowestDelta;
+        event.offsetX = offsetX;
+        event.offsetY = offsetY;
+        // Go ahead and set deltaMode to 0 since we converted to pixels
+        // Although this is a little odd since we overwrite the deltaX/Y
+        // properties with normalized deltas.
+        event.deltaMode = 0;
+
+        // Add event and delta to the front of the arguments
+        args.unshift(event, delta, deltaX, deltaY);
+
+        // Clearout lowestDelta after sometime to better
+        // handle multiple device types that give different
+        // a different lowestDelta
+        // Ex: trackpad = 3 and mouse wheel = 120
+        if (nullLowestDeltaTimeout) { clearTimeout(nullLowestDeltaTimeout); }
+        nullLowestDeltaTimeout = setTimeout(nullLowestDelta, 200);
+
+        return ($.event.dispatch || $.event.handle).apply(this, args);
+    }
+
+    function nullLowestDelta() {
+        lowestDelta = null;
+    }
+
+    function shouldAdjustOldDeltas(orgEvent, absDelta) {
+        // If this is an older event and the delta is divisable by 120,
+        // then we are assuming that the browser is treating this as an
+        // older mouse wheel event and that we should divide the deltas
+        // by 40 to try and get a more usable deltaFactor.
+        // Side note, this actually impacts the reported scroll distance
+        // in older browsers and can cause scrolling to be slower than native.
+        // Turn this off by setting $.event.special.mousewheel.settings.adjustOldDeltas to false.
+        return special.settings.adjustOldDeltas && orgEvent.type === 'mousewheel' && absDelta % 120 === 0;
+    }
+
+}));