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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-modifier-key" class="unlocked dark" extends="kb-key"
      8     on-pointerout="{{out}}">
      9   <script>
     10     (function () {
     11 
     12       /**
     13        * The possible states of the key.
     14        * @const
     15        * @type {Enum}
     16        */
     17       var KEY_STATES = {
     18         PRESSED: "pressed", // Key-down.
     19         UNLOCKED: "unlocked", // Default state.
     20         TAPPED: "tapped", // Key-down followed by key-up.
     21         CHORDING: "chording", // Chording mode.
     22       };
     23 
     24       /**
     25        * A map of the state of all modifier keys.
     26        * @type {Object}
     27        */
     28       var states = {};
     29 
     30       Polymer('kb-modifier-key', {
     31         up: function(event) {
     32           if (this.state == KEY_STATES.PRESSED)
     33             this.state = KEY_STATES.TAPPED;
     34           else
     35             this.state = KEY_STATES.UNLOCKED;
     36           this.super([event]);
     37         },
     38 
     39         down: function(event) {
     40           // First transition state so that populateDetails generates
     41           // correct data.
     42           switch (this.state) {
     43             case KEY_STATES.UNLOCKED:
     44               this.state = KEY_STATES.PRESSED;
     45               break;
     46             case KEY_STATES.TAPPED:
     47               this.state = KEY_STATES.UNLOCKED;
     48               break;
     49             case KEY_STATES.PRESSED:
     50             case KEY_STATES.CHORDING:
     51               // We pressed another key at the same time,
     52               // so ignore second press.
     53               return;
     54             default:
     55               console.error("Undefined key state: " + state);
     56               break;
     57           }
     58           this.super([event]);
     59         },
     60 
     61         /**
     62          * Returns whether the modifier for this key is active.
     63          * @return {boolean}
     64          */
     65         isActive: function() {
     66           return this.state != KEY_STATES.UNLOCKED;
     67         },
     68 
     69         /**
     70          * Notifies key that a non-control keyed down.
     71          * A control key is defined as one of shift, control or alt.
     72          */
     73         onNonControlKeyDown: function() {
     74           switch(this.state) {
     75             case (KEY_STATES.PRESSED):
     76               this.state = KEY_STATES.CHORDING;
     77               break;
     78           }
     79         },
     80 
     81         /**
     82          * Notifies key that a non-control keyed was typed.
     83          * A control key is defined as one of shift, control or alt.
     84          */
     85         onNonControlKeyTyped: function() {
     86            switch(this.state) {
     87              case (KEY_STATES.TAPPED):
     88                this.state = KEY_STATES.UNLOCKED;
     89                break;
     90            }
     91         },
     92 
     93         /**
     94          * Called on a pointer-out event. Ends chording.
     95          * @param {event} event The pointer-out event.
     96          */
     97         out: function(event) {
     98           // TODO(rsadam): Add chording event so that we don't reset
     99           // when shift-chording.
    100           if (this.state == KEY_STATES.CHORDING) {
    101             this.state = KEY_STATES.UNLOCKED;
    102           }
    103         },
    104 
    105         /*
    106          * Overrides the autoRelease function to enable chording.
    107          */
    108         autoRelease: function() {
    109         },
    110 
    111         populateDetails: function(caller) {
    112           var detail = this.super([caller]);
    113           if (this.state != KEY_STATES.UNLOCKED)
    114             detail.activeModifier = this.charValue;
    115           return detail;
    116         },
    117 
    118         /**
    119          *  Resets the modifier key state.
    120          */
    121         reset: function() {
    122           this.state = KEY_STATES.UNLOCKED;
    123         },
    124 
    125         get state() {
    126           var key = this.charValue;
    127           if (!key)
    128             console.error("missing key for kb-modifier-key state: " + this);
    129           // All keys default to the unlock state.
    130           if (!(key in states))
    131             states[key] = KEY_STATES.UNLOCKED;
    132           return states[key];
    133         },
    134 
    135         set state(value) {
    136           var key = this.charValue;
    137           states[key] = value;
    138         }
    139       });
    140     })();
    141   </script>
    142 </polymer-element>
    143