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      1 <!--
      2   -- Copyright 2013 The Chromium Authors. All rights reserved.
      3   -- Use of this source code is governed by a BSD-style license that can be
      4   -- found in the LICENSE file.
      5   -->
      6 
      7 <polymer-element name="kb-altkey-data" attributes="char list">
      8 <script>
      9   (function() {
     10     var altKeys = {};
     11     var idMap = {};
     12 
     13     function createId(char) {
     14       return 'id' + char.charCodeAt(0);
     15     }
     16 
     17     Polymer('kb-altkey-data', {
     18 
     19       /**
     20        * Retrieves a list of alternative keys to display on a long-press.
     21        * @param {string} char The base character.
     22        * @param {boolean=} opt_force If true, force the creation of a list
     23        *    even if empty. Used when constructing a set of alternates for keys
     24        *    with superscripts.
     25        * @return {?Object.{id: string, list: string}}
     26        */
     27       getAltkeys: function(char, opt_force) {
     28         var id = idMap[char];
     29         if (id) {
     30           return {
     31             'id': id,
     32             'keys': altKeys[id]
     33           };
     34         }
     35         if (opt_force) {
     36           return {
     37             'id': createId(char),
     38             'keys': []
     39           };
     40         }
     41       },
     42 
     43       /**
     44        * Registers lists of alternative keys displayed on a long-press.
     45        * @param {Object.<string, Array.<string>>} data Mapping of characters to
     46        *     lists of alternatives.
     47        */
     48       registerAltkeys: function(data) {
     49         for (var key in data) {
     50           var id = idMap[key];
     51           if (!id)
     52             idMap[key] = id = createId(key);
     53           altKeys[id] = data[key];
     54         }
     55       },
     56 
     57       /**
     58        * Creates a list of alternate candidates to display in a popup on a
     59        * long-press.
     60        * @param {string} char The base character.
     61        * @param {number} maxLeftOffset Limits the number of candidates
     62        *      displayed to the left of the base character to prevent running
     63        *      past the left edge of the keyboard.
     64        * @param {number} maxRightOffset Limits the number of candidates
     65        *     displayed to the right of the base character to prvent running
     66        *     past the right edge of the keyboard.
     67        * @param {string=} opt_additionalKeys Optional list of additional keys
     68        *     to include in the candidates list.
     69        */
     70       createAltkeySet: function(char,
     71                                 maxLeftOffset,
     72                                 maxRightOffset,
     73                                 opt_additionalKeys) {
     74         var altKeys = this.getAltkeys(char, true /* forced */);
     75         if (altKeys) {
     76           var list = altKeys.keys;
     77           if (opt_additionalKeys)
     78             list = opt_additionalKeys.split('').concat(list);
     79           list = [char].concat(list);
     80 
     81           var set = document.createElement('kb-altkey-set');
     82           // Candiates are approximately in decreasing order of usage, and are
     83           // arranged in a single row in the popup display.  To reduce the
     84           // expected length of the drag gesture for selecting a candidate,
     85           // more likely candidates are placed in the center of the popup,
     86           // which is achieved by alternately appending and prepending
     87           // candiates in the alternatives popup.
     88           var prepend = false;
     89           var leftOffset = 0;
     90           var rightOffset = 0;
     91           for (var i = 0; i < list.length; i++) {
     92             var key = document.createElement('kb-altkey');
     93             key.textContent = list[i];
     94             if (prepend) {
     95               set.insertBefore(key, set.firstChild);
     96               leftOffset++;
     97             } else {
     98               set.appendChild(key);
     99               rightOffset++;
    100             }
    101             prepend = !prepend;
    102             // Verify that there is room remaining for an additional character.
    103             if (leftOffset == maxLeftOffset && rightOffset == maxRightOffset)
    104               break;
    105             if (leftOffset == maxLeftOffset)
    106               prepend = false;
    107             else if (rightOffset == maxRightOffset)
    108               prepend = true;
    109           }
    110           set.id = altKeys.id;
    111           set.offset = leftOffset;
    112           return set;
    113         }
    114       },
    115 
    116     });
    117   })();
    118 </script>
    119 </polymer-element>
    120