paper-card.html

<!--
@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
-->

<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../iron-flex-layout/iron-flex-layout.html">
<link rel="import" href="../iron-image/iron-image.html">
<link rel="import" href="../paper-material/paper-material.html">
<link rel="import" href="../paper-styles/default-theme.html">

<!--
Material design: [Cards](https://www.google.com/design/spec/components/cards.html)

`paper-card` is a container with a drop shadow.

Example:

    <paper-card heading="Card Title">
      <div class="card-content">Some content</div>
      <div class="card-actions">
        <paper-button>Some action</paper-button>
      </div>
    </paper-card>

Example - top card image:

    <paper-card heading="Card Title" image="/path/to/image.png" alt="image">
      ...
    </paper-card>

### Accessibility

By default, the `aria-label` will be set to the value of the `heading` attribute.

### Styling

The following custom properties and mixins are available for styling:

Custom property | Description | Default
----------------|-------------|----------
`--paper-card-background-color` | The background color of the card | `--primary-background-color`
`--paper-card-header-color` | The color of the header text | `#000`
`--paper-card-header` | Mixin applied to the card header section | `{}`
`--paper-card-header-text` | Mixin applied to the title in the card header section | `{}`
`--paper-card-header-image` | Mixin applied to the image in the card header section | `{}`
`--paper-card-header-image-text` | Mixin applied to the text overlapping the image in the card header section | `{}`
`--paper-card-content` | Mixin applied to the card content section| `{}`
`--paper-card-actions` | Mixin applied to the card action section | `{}`
`--paper-card` | Mixin applied to the card | `{}`

@group Paper Elements
@element paper-card
@demo demo/index.html
-->

<dom-module id="paper-card">
  <template>
    <style include="paper-material">
      :host {
        display: inline-block;
        position: relative;
        box-sizing: border-box;
        background-color: var(--paper-card-background-color, --primary-background-color);
        border-radius: 2px;

        @apply(--paper-font-common-base);
        @apply(--paper-card);
      }

      /* IE 10 support for HTML5 hidden attr */
      [hidden] {
        display: none !important;
      }

      .header {
        position: relative;
        border-top-left-radius: inherit;
        border-top-right-radius: inherit;
        overflow: hidden;

        @apply(--paper-card-header);
      }

      .header iron-image {
        display: block;
        width: 100%;
        --iron-image-width: 100%;
        pointer-events: none;

        @apply(--paper-card-header-image);
      }

      .header .title-text {
        padding: 16px;
        font-size: 24px;
        font-weight: 400;
        color: var(--paper-card-header-color, #000);

        @apply(--paper-card-header-text);
      }

      .header .title-text.over-image {
        position: absolute;
        bottom: 0px;

        @apply(--paper-card-header-image-text);
      }

      :host ::content .card-content {
        padding: 16px;
        position:relative;

        @apply(--paper-card-content);
      }

      :host ::content .card-actions {
        border-top: 1px solid #e8e8e8;
        padding: 5px 16px;
        position:relative;

        @apply(--paper-card-actions);
      }
    </style>

    <div class="header">
      <iron-image
          hidden$="[[!image]]"
          aria-hidden$="[[_isHidden(image)]]"
          src="[[image]]"
          alt="[[alt]]"
          placeholder="[[placeholderImage]]"
          preload="[[preloadImage]]"
          fade="[[fadeImage]]"></iron-image>
      <div hidden$="[[!heading]]" class$="title-text [[_computeHeadingClass(image)]]">[[heading]]</div>
    </div>

    <content></content>
  </template>

  <script>
    Polymer({
      is: 'paper-card',

      properties: {
        /**
         * The title of the card.
         */
        heading: {
          type: String,
          value: '',
          observer: '_headingChanged'
        },

        /**
         * The url of the title image of the card.
         */
        image: {
          type: String,
          value: ''
        },

        /**
         * The text alternative of the card's title image.
         */
        alt: {
          type: String
        },

        /**
         * When `true`, any change to the image url property will cause the
         * `placeholder` image to be shown until the image is fully rendered.
         */
        preloadImage: {
          type: Boolean,
          value: false
        },

        /**
         * When `preloadImage` is true, setting `fadeImage` to true will cause the
         * image to fade into place.
         */
        fadeImage: {
          type: Boolean,
          value: false
        },

        /**
         * This image will be used as a background/placeholder until the src image has
         * loaded. Use of a data-URI for placeholder is encouraged for instant rendering.
         */
        placeholderImage: {
          type: String,
          value: null
        },

        /**
         * The z-depth of the card, from 0-5.
         */
        elevation: {
          type: Number,
          value: 1,
          reflectToAttribute: true
        },

        /**
         * Set this to true to animate the card shadow when setting a new
         * `z` value.
         */
        animatedShadow: {
          type: Boolean,
          value: false
        },

        /**
         * Read-only property used to pass down the `animatedShadow` value to
         * the underlying paper-material style (since they have different names).
         */
        animated: {
          type: Boolean,
          reflectToAttribute: true,
          readOnly: true,
          computed: '_computeAnimated(animatedShadow)'
        }
      },
      
      /**
       * Format function for aria-hidden. Use the ! operator results in the
       * empty string when given a falsy value.
       */
      _isHidden: function(image) {
        return image ? 'false' : 'true';
      },

      _headingChanged: function(heading) {
        var label = this.getAttribute('aria-label');
        this.setAttribute('aria-label', heading);
      },

      _computeHeadingClass: function(image) {
        return image ? ' over-image' : '';
      },

      _computeAnimated: function(animatedShadow) {
        return animatedShadow;
      }
    });
  </script>
</dom-module>