paper-toggle-button.js

/**
@license
Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
*/
import '@polymer/polymer/polymer-legacy.js';
import '@polymer/iron-flex-layout/iron-flex-layout.js';
import '@polymer/paper-styles/color.js';
import '@polymer/paper-styles/default-theme.js';

import {PaperCheckedElementBehavior} from '@polymer/paper-behaviors/paper-checked-element-behavior.js';
import {PaperRippleBehavior} from '@polymer/paper-behaviors/paper-ripple-behavior.js';
import {Polymer} from '@polymer/polymer/lib/legacy/polymer-fn.js';
import {setTouchAction} from '@polymer/polymer/lib/utils/gestures.js';
import {html} from '@polymer/polymer/lib/utils/html-tag.js';
import {afterNextRender} from '@polymer/polymer/lib/utils/render-status.js';

/**
Material design: [Switch](https://www.google.com/design/spec/components/selection-controls.html#selection-controls-switch)

`paper-toggle-button` provides a ON/OFF switch that user can toggle the state
by tapping or by dragging the switch.

Example:

    <paper-toggle-button></paper-toggle-button>

### Styling

The following custom properties and mixins are available for styling:

Custom property | Description | Default
----------------|-------------|----------
`--paper-toggle-button-unchecked-bar-color` | Slider color when the input is not checked | `#000000`
`--paper-toggle-button-unchecked-button-color` | Button color when the input is not checked | `--paper-grey-50`
`--paper-toggle-button-unchecked-ink-color` | Selected/focus ripple color when the input is not checked | `--dark-primary-color`
`--paper-toggle-button-checked-bar-color` | Slider button color when the input is checked | `--primary-color`
`--paper-toggle-button-checked-button-color` | Button color when the input is checked | `--primary-color`
`--paper-toggle-button-checked-ink-color` | Selected/focus ripple color when the input is checked | `--primary-color`
`--paper-toggle-button-invalid-bar-color` | Slider button color when the input is invalid | `--error-color`
`--paper-toggle-button-invalid-button-color` | Button color when the input is invalid | `--error-color`
`--paper-toggle-button-invalid-ink-color` | Selected/focus ripple color when the input is invalid | `--error-color`
`--paper-toggle-button-unchecked-bar` | Mixin applied to the slider when the input is not checked | `{}`
`--paper-toggle-button-unchecked-button` | Mixin applied to the slider button when the input is not checked | `{}`
`--paper-toggle-button-unchecked-ink` | Mixin applied to the ripple when the input is not checked | `{}`
`--paper-toggle-button-checked-bar` | Mixin applied to the slider when the input is checked | `{}`
`--paper-toggle-button-checked-button` | Mixin applied to the slider button when the input is checked | `{}`
`--paper-toggle-button-checked-ink` | Mixin applied to the ripple when the input is checked | `{}`
`--paper-toggle-button-label-color` | Label color | `--primary-text-color`
`--paper-toggle-button-label-spacing` | Spacing between the label and the button | `8px`

This element applies the mixin `--paper-font-common-base` but does not import `paper-styles/typography.html`.
In order to apply the `Roboto` font to this element, make sure you've imported `paper-styles/typography.html`.

@element paper-toggle-button
@demo demo/index.html
*/
Polymer({
  is: 'paper-toggle-button',
  /** @override */
  _template: html`
    <style>
      :host {
        display: inline-block;
        @apply --layout-horizontal;
        @apply --layout-center;
        @apply --paper-font-common-base;
      }

      :host([disabled]) {
        pointer-events: none;
      }

      :host(:focus) {
        outline:none;
      }

      .toggle-bar {
        position: absolute;
        height: 100%;
        width: 100%;
        border-radius: 8px;
        pointer-events: none;
        opacity: 0.4;
        transition: background-color linear .08s;
        background-color: var(--paper-toggle-button-unchecked-bar-color, #000000);

        @apply --paper-toggle-button-unchecked-bar;
      }

      .toggle-button {
        position: absolute;
        top: -3px;
        left: 0;
        right: auto;
        height: 20px;
        width: 20px;
        border-radius: 50%;
        box-shadow: 0 1px 5px 0 rgba(0, 0, 0, 0.6);
        transition: -webkit-transform linear .08s, background-color linear .08s;
        transition: transform linear .08s, background-color linear .08s;
        will-change: transform;
        background-color: var(--paper-toggle-button-unchecked-button-color, var(--paper-grey-50));

        @apply --paper-toggle-button-unchecked-button;
      }

      :host(:dir(rtl)) .toggle-button,
      /* Shady DOM workaround */
      :host([dir="rtl"]) .toggle-button {
        right: 0;
        left: auto;
      }

      .toggle-button.dragging {
        -webkit-transition: none;
        transition: none;
      }

      :host([checked]:not([disabled])) .toggle-bar {
        opacity: 0.5;
        background-color: var(--paper-toggle-button-checked-bar-color, var(--primary-color));

        @apply --paper-toggle-button-checked-bar;
      }

      :host([disabled]) .toggle-bar {
        background-color: #000;
        opacity: 0.12;
      }

      :host([checked]) .toggle-button {
        -webkit-transform: translate(16px, 0);
        transform: translate(16px, 0);
      }

      :host(:dir(rtl)):host([checked]) .toggle-button,
      /* Shady DOM workaround */
      :host([dir="rtl"][checked]) .toggle-button {
        -webkit-transform: translate(-16px, 0);
        transform: translate(-16px, 0);
      }

      :host([checked]:not([disabled])) .toggle-button {
        background-color: var(--paper-toggle-button-checked-button-color, var(--primary-color));

        @apply --paper-toggle-button-checked-button;
      }

      :host([disabled]) .toggle-button {
        background-color: #bdbdbd;
        opacity: 1;
      }

      .toggle-ink {
        position: absolute;
        top: -14px;
        left: -14px;
        right: auto;
        bottom: auto;
        width: 48px;
        height: 48px;
        opacity: 0.5;
        pointer-events: none;
        color: var(--paper-toggle-button-unchecked-ink-color, var(--primary-text-color));

        @apply --paper-toggle-button-unchecked-ink;
      }

      :host([checked]) .toggle-ink {
        color: var(--paper-toggle-button-checked-ink-color, var(--primary-color));

        @apply --paper-toggle-button-checked-ink;
      }

      .toggle-container {
        display: inline-block;
        position: relative;
        width: 36px;
        height: 14px;
        /* The toggle button has an absolute position of -3px; The extra 1px
        /* accounts for the toggle button shadow box. */
        margin: 4px 1px;
      }

      .toggle-label {
        position: relative;
        display: inline-block;
        vertical-align: middle;
        padding-left: var(--paper-toggle-button-label-spacing, 8px);
        pointer-events: none;
        color: var(--paper-toggle-button-label-color, var(--primary-text-color));
      }

      /* invalid state */
      :host([invalid]) .toggle-bar {
        background-color: var(--paper-toggle-button-invalid-bar-color, var(--error-color));
      }

      :host([invalid]) .toggle-button {
        background-color: var(--paper-toggle-button-invalid-button-color, var(--error-color));
      }

      :host([invalid]) .toggle-ink {
        color: var(--paper-toggle-button-invalid-ink-color, var(--error-color));
      }
    </style>

    <div class="toggle-container">
      <div id="toggleBar" class="toggle-bar"></div>
      <div id="toggleButton" class="toggle-button"></div>
    </div>

    <div class="toggle-label"><slot></slot></div>
  `,


  behaviors: [PaperCheckedElementBehavior],

  /** @private */
  hostAttributes: {role: 'button', 'aria-pressed': 'false', tabindex: 0},

  properties: {
      /**
       * Fired when the checked state changes due to user interaction.
       *
       * @event change
       */
      /**
       * Fired when the checked state changes.
       *
       * @event iron-change
       */
  },

  listeners: {track: '_ontrack'},

  __calculateIsRtl: function() {
    const compStyle = window.getComputedStyle(this);
    const dir = compStyle.direction;
    return dir === 'rtl';
  },

  /** @override */
  attached: function() {
    var isRtl = this.__calculateIsRtl();
    if (isRtl) {
      this.setAttribute('dir', 'rtl');
    }

    afterNextRender(this, function() {
      setTouchAction(this, 'pan-y');
    });
  },

  _ontrack: function(event) {
    var track = event.detail;
    if (track.state === 'start') {
      this._trackStart(track);
    } else if (track.state === 'track') {
      this._trackMove(track);
    } else if (track.state === 'end') {
      this._trackEnd(track);
    }
  },

  _trackStart: function(track) {
    this._isRtl = this.__calculateIsRtl()
    this._width = this.$.toggleBar.offsetWidth / 2;
    /*
     * keep an track-only check state to keep the dragging behavior smooth
     * while toggling activations
     */
    this._trackChecked = this.checked;
    this.$.toggleButton.classList.add('dragging');
  },

  _trackMove: function(track) {
    var dx = track.dx;

    if (this._isRtl) {
      this._x = Math.max(
        -this._width, Math.min(0, this._trackChecked ? -this._width + dx : dx));
    } else {
      this._x = Math.min(
          this._width, Math.max(0, this._trackChecked ? this._width + dx : dx));
    }

    this.translate3d(this._x + 'px', 0, 0, this.$.toggleButton);

    if (this._isRtl) {
      this._userActivate(this._x < (-this._width / 2));
    } else {
      this._userActivate(this._x > (this._width / 2));
    }
  },

  _trackEnd: function(track) {
    this.$.toggleButton.classList.remove('dragging');
    this.transform('', this.$.toggleButton);
  },

  // customize the element's ripple
  _createRipple: function() {
    this._rippleContainer = this.$.toggleButton;
    var ripple = PaperRippleBehavior._createRipple();
    ripple.id = 'ink';
    ripple.setAttribute('recenters', '');
    ripple.classList.add('circle', 'toggle-ink');
    return ripple;
  },

  /** @override */
  registered() {
    this._template.setAttribute('strip-whitespace', '');
  }

});