paper-icon-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-icon/iron-icon.js';
import '@polymer/paper-styles/default-theme.js';

import {PaperInkyFocusBehavior} from '@polymer/paper-behaviors/paper-inky-focus-behavior.js';
import {Polymer} from '@polymer/polymer/lib/legacy/polymer-fn.js';
import {html} from '@polymer/polymer/lib/utils/html-tag.js';

/**
Material design: [Icon
toggles](https://www.google.com/design/spec/components/buttons.html#buttons-toggle-buttons)

`paper-icon-button` is a button with an image placed at the center. When the
user touches the button, a ripple effect emanates from the center of the button.

`paper-icon-button` does not include a default icon set. To use icons from the
default set, include `PolymerElements/iron-icons/iron-icons.html`, and use the
`icon` attribute to specify which icon from the icon set to use.

    <paper-icon-button icon="menu"></paper-icon-button>

See [`iron-iconset`](iron-iconset) for more information about
how to use a custom icon set.

Example:

    <script type="module">
      import '@polymer/iron-icons/iron-icons.js';
    </script>

    <paper-icon-button icon="favorite"></paper-icon-button>
    <paper-icon-button src="star.png"></paper-icon-button>

To use `paper-icon-button` as a link, wrap it in an anchor tag. Since
`paper-icon-button` will already receive focus, you may want to prevent the
anchor tag from receiving focus as well by setting its tabindex to -1.

    <a href="https://www.polymer-project.org" tabindex="-1">
      <paper-icon-button icon="polymer"></paper-icon-button>
    </a>

### Styling

Style the button with CSS as you would a normal DOM element. If you are using
the icons provided by `iron-icons`, they will inherit the foreground color of
the button.

    /* make a red "favorite" button *\/
    <paper-icon-button icon="favorite" style="color: red;"></paper-icon-button>

By default, the ripple is the same color as the foreground at 25% opacity. You
may customize the color using the `--paper-icon-button-ink-color` custom
property.

The following custom properties and mixins are available for styling:

Custom property | Description | Default
----------------|-------------|----------
`--paper-icon-button-disabled-text` | The color of the disabled button | `--disabled-text-color`
`--paper-icon-button-ink-color` | Selected/focus ripple color | `--primary-text-color`
`--paper-icon-button` | Mixin for a button | `{}`
`--paper-icon-button-disabled` | Mixin for a disabled button | `{}`
`--paper-icon-button-hover` | Mixin for button on hover | `{}`

@element paper-icon-button
@demo demo/index.html
*/
Polymer({
  is: 'paper-icon-button',

  /** @override */
  _template: html`
    <style>
      :host {
        display: inline-block;
        position: relative;
        padding: 8px;
        outline: none;
        -webkit-user-select: none;
        -moz-user-select: none;
        -ms-user-select: none;
        user-select: none;
        cursor: pointer;
        z-index: 0;
        line-height: 1;

        width: 40px;
        height: 40px;

        /*
          NOTE: Both values are needed, since some phones require the value to
          be \`transparent\`.
        */
        -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
        -webkit-tap-highlight-color: transparent;

        /* Because of polymer/2558, this style has lower specificity than * */
        box-sizing: border-box !important;

        @apply --paper-icon-button;
      }

      :host #ink {
        color: var(--paper-icon-button-ink-color, var(--primary-text-color));
        opacity: 0.6;
      }

      :host([disabled]) {
        color: var(--paper-icon-button-disabled-text, var(--disabled-text-color));
        pointer-events: none;
        cursor: auto;

        @apply --paper-icon-button-disabled;
      }

      :host([hidden]) {
        display: none !important;
      }

      :host(:hover) {
        @apply --paper-icon-button-hover;
      }

      iron-icon {
        --iron-icon-width: 100%;
        --iron-icon-height: 100%;
      }
    </style>

    <iron-icon id="icon" src="[[src]]" icon="[[icon]]"
               alt$="[[alt]]"></iron-icon>
  `,

  hostAttributes: {role: 'button', tabindex: '0'},

  behaviors: [PaperInkyFocusBehavior],

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

  properties: {
    /**
     * The URL of an image for the icon. If the src property is specified,
     * the icon property should not be.
     */
    src: {type: String},

    /**
     * Specifies the icon name or index in the set of icons available in
     * the icon's icon set. If the icon property is specified,
     * the src property should not be.
     */
    icon: {type: String},

    /**
     * Specifies the alternate text for the button, for accessibility.
     */
    alt: {type: String, observer: '_altChanged'}
  },

  _altChanged: function(newValue, oldValue) {
    var label = this.getAttribute('aria-label');

    // Don't stomp over a user-set aria-label.
    if (!label || oldValue == label) {
      this.setAttribute('aria-label', newValue);
    }
  }
});