paper-item.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 './paper-item-shared-styles.js';

import {Polymer} from '@polymer/polymer/lib/legacy/polymer-fn.js';
import {html} from '@polymer/polymer/lib/utils/html-tag.js';

import {PaperItemBehavior} from './paper-item-behavior.js';

/**
Material design:
[Lists](https://www.google.com/design/spec/components/lists.html)

`<paper-item>` is an interactive list item. By default, it is a horizontal
flexbox.

    <paper-item>Item</paper-item>

Use this element with `<paper-item-body>` to make Material Design styled
two-line and three-line items.

    <paper-item>
      <paper-item-body two-line>
        <div>Show your status</div>
        <div secondary>Your status is visible to everyone</div>
      </paper-item-body>
      <iron-icon icon="warning"></iron-icon>
    </paper-item>

To use `paper-item` as a link, wrap it in an anchor tag. Since `paper-item` 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-item raised>Polymer Project</paper-item>
    </a>

If you are concerned about performance and want to use `paper-item` in a
`paper-listbox` with many items, you can just use a native `button` with the
`paper-item` class applied (provided you have correctly included the shared
styles):

    <style is="custom-style" include="paper-item-shared-styles"></style>

    <paper-listbox>
      <button class="paper-item" role="option">Inbox</button>
      <button class="paper-item" role="option">Starred</button>
      <button class="paper-item" role="option">Sent mail</button>
    </paper-listbox>

### Styling

The following custom properties and mixins are available for styling:

Custom property | Description | Default
----------------|-------------|----------
`--paper-item-min-height` | Minimum height of the item | `48px`
`--paper-item` | Mixin applied to the item | `{}`
`--paper-item-selected-weight` | The font weight of a selected item | `bold`
`--paper-item-selected` | Mixin applied to selected paper-items | `{}`
`--paper-item-disabled-color` | The color for disabled paper-items | `--disabled-text-color`
`--paper-item-disabled` | Mixin applied to disabled paper-items | `{}`
`--paper-item-focused` | Mixin applied to focused paper-items | `{}`
`--paper-item-focused-before` | Mixin applied to :before focused paper-items | `{}`

### Accessibility

This element has `role="listitem"` by default. Depending on usage, it may be
more appropriate to set `role="menuitem"`, `role="menuitemcheckbox"` or
`role="menuitemradio"`.

    <paper-item role="menuitemcheckbox">
      <paper-item-body>
        Show your status
      </paper-item-body>
      <paper-checkbox></paper-checkbox>
    </paper-item>

@element paper-item
@demo demo/index.html
*/
Polymer({
  /** @override */
  _template: html`
    <style include="paper-item-shared-styles">
      :host {
        @apply --layout-horizontal;
        @apply --layout-center;
        @apply --paper-font-subhead;

        @apply --paper-item;
      }
    </style>
    <slot></slot>
`,

  is: 'paper-item',
  behaviors: [PaperItemBehavior]
});