ui/keyboard/resources/elements/kb-key-base.html

<!--
  -- Copyright 2013 The Chromium Authors. All rights reserved.
  -- Use of this source code is governed by a BSD-style license that can be
  -- found in the LICENSE file.
  -->

<polymer-element name="kb-key-base"
    on-pointerdown="down" on-pointerup="up" on-pointerout="out"
    attributes="accents char invert repeat hintText toKeyset toLayout">
  <script>
    /**
     * The long-press delay in milliseconds before long-press handler is
     * invoked.
     * @const
     * @type {number}
     */
    var LONGPRESS_DELAY_MSEC = 500;

    /**
     * The maximum number of elements in one keyset rule.
     * @const
     * @type {number}
     */
    var MAXIMUM_NUM_OF_RULE_ELEMENTS = 3;

    /**
     * The minumum number of elements in one keyset rule.
     * @const
     * @type {number}
     */
    var MINIMUM_NUM_OF_RULE_ELEMENTS = 2;

    /**
     * The index of event type element in the splitted keyset rule.
     * @const
     * @type {number}
     */
    var EVENT_TYPE = 0;

    /**
     * The index of toKeyset element in the splitted keyset rule.
     * @const
     * @type {number}
     */
    var TO_KEYSET = 1;

    /**
     * The index of nextKeyset element in the splitted keyset rule.
     * @const
     * @type {number}
     */
    var NEXT_KEYSET = 2;

    /**
     * The index offset of toKeyset and nextKeyset elements in splitted keyset
     * rule array and the array in keysetRules.
     * @const
     * @type {number}
     */
    var OFFSET = 1;

    /**
     * The minumum number of elements in one keyset rule.
     * @const {number}
     */
    var MINIMUM_NUM_OF_RULE_ELEMENTS = 2;

    Polymer('kb-key-base', {
      repeat: false,
      invert: false,
      longPressTimer: null,
      pointerId: undefined,

      /**
       * The keyset transition rules. It defines which keyset to transit to on
       * which key events. It consists at most four rules (down, up, long, dbl).
       * If no rule is defined for a key event, the event wont trigger a keyset
       * change.
       * @type {Object.<string, Array.<string>}
       */
      keysetRules: null,

      ready: function() {
        if (this.toKeyset) {
          // Parsing keyset rules from toKeyset attribute string.
          // An rule can be defined as: (down|up|long|dbl):keysetid[:keysetid]
          // and each rule are separated by a semicolon. The first element
          // defines the event this rule applies to. The second element defines
          // what keyset to transit to after event received. The third optional
          // element defines what keyset to transit to after a key is pressed in
          // the new keyset. It is useful when you want to transit to a not
          // locked keyset. For example, after transit to a upper case keyset,
          // it may make sense to transit back to lower case after user typed
          // any key at the upper case keyset.
          var rules =
              this.toKeyset.replace(/(\r\n|\n|\r| )/g, '').split(';');
          this.keysetRules = {};
          var self = this;
          rules.forEach(function(element) {
            if (element == '')
              return;
            var keyValues = element.split(':', MAXIMUM_NUM_OF_RULE_ELEMENTS);
            if (keyValues.length < MINIMUM_NUM_OF_RULE_ELEMENTS) {
              console.error('Invalid keyset rules: ' + element);
              return;
            }
            self.keysetRules[keyValues[EVENT_TYPE]] = [keyValues[TO_KEYSET],
                (keyValues[NEXT_KEYSET] ? keyValues[NEXT_KEYSET] : null)];
          });
        }
      },

      down: function(event) {
        this.pointerId = event.pointerId;
        var detail = this.populateDetails('down');
        this.fire('key-down', detail);
        this.longPressTimer = this.generateLongPressTimer();
      },
      out: function(event) {
        this.classList.remove('active');
        clearTimeout(this.longPressTimer);
      },
      up: function(event) {
        this.autoRelease();
      },

      /**
       * Releases the pressed key programmatically and fires key-up event. This
       * should be called if a second key is pressed while the first key is not
       * released yet.
       */
      autoRelease: function() {
        if (this.pointerId === undefined)
          return;

        // Invalidates the pointerId so the subsequent pointerup event is a
        // noop.
        this.pointerId = undefined;
        clearTimeout(this.longPressTimer);
        var detail = this.populateDetails('up');
        this.fire('key-up', detail);
      },

      /**
       * Drops the pressed key.
       */
      dropKey: function() {
        this.classList.remove('active');
        clearTimeout(this.longPressTimer);
        this.pointerId = undefined;
      },

      /**
       * Character value associated with the key. Typically, the value is a
       * single character, but may be multi-character in cases like a ".com"
       * button.
       * @return {string}
       */
      get charValue() {
        return this.invert ? this.hintText : (this.char || this.textContent);
      },

      /* Hint text value associated with the key. Typically, the value is a
       * single character.
       * @return {string}
       */
      get hintTextValue() {
        return this.invert ? (this.char || this.textContent) : this.hintText;
      },

      /**
       * Returns a subset of the key attributes.
       * @param {string} caller The id of the function which called
       *     populateDetails.
       */
      populateDetails: function(caller) {
        var detail = {
          char: this.charValue,
          toLayout: this.toLayout,
          repeat: this.repeat
        };

        switch (caller) {
          case ('up'):
            if (this.keysetRules && this.keysetRules.up != undefined) {
              detail.toKeyset = this.keysetRules.up[TO_KEYSET - OFFSET];
              detail.nextKeyset = this.keysetRules.up[NEXT_KEYSET - OFFSET];
            }
            break;
          case ('down'):
            if (this.keysetRules && this.keysetRules.down != undefined) {
              detail.toKeyset = this.keysetRules.down[TO_KEYSET - OFFSET];
              detail.nextKeyset = this.keysetRules.down[NEXT_KEYSET - OFFSET];
            }
            break;
          default:
            break;
        }
        return detail;
      },

      generateLongPressTimer: function() {
        return this.asyncMethod(function() {
          var detail = {
            char: this.charValue,
            hintText: this.hintTextValue
          };
          if (this.keysetRules && this.keysetRules.long != undefined) {
            detail.toKeyset = this.keysetRules.long[TO_KEYSET - OFFSET];
            detail.nextKeyset = this.keysetRules.long[NEXT_KEYSET - OFFSET];
          }
          this.fire('key-longpress', detail);
        }, null, LONGPRESS_DELAY_MSEC);
      },
    });
  </script>
</polymer-element>