v0.2.1

<zero-list-hero>

It's hero time! A Polymer 1.1+ web component that hero-animates and layouts a sequence of elements. I do this so you don't have to.

Featuring:

• Automatic transitions.
• NEW! Automatic responsive layout - masonry using first-fit algorithm à la Pinterest.
• Bespoke cascaded entry-exit effects à la Google Play Newsstand App.
• Built-in debouncer.
• Configurable animations.
• Almost entirely declarative - works by itself!

Let's get this money

1. Import web-components-lite polyfill.

<script src="bower_components/webcomponentsjs/webcomponents-lite.js"></script>

2. Import zero-list-hero web component.

<link rel="import" href="bower_components/zero-list-hero/zero-list-hero.html">

3. Profit!

Basic usage:

<zero-list-hero>
<!-- Dynamically append/remove elements inside here -->
...
<div hero-id="hero1">I'm Tom</div>
<div hero-id="hero3">I'm Mary</div>
<div hero-id="hero2">I'm John</div>
...
</zero-list-hero>

With Polymer's dom-repeat:

<zero-list-hero>
<template is="dom-repeat" items="[[list]]">
  <my-card hero-id$="[[item.foo]]" foo$="[[item.foo]]" bar$="[[item.bar]]"></my-card>
</template>
</zero-list-hero>

Using built-in responsive masonry layout:

<zero-list-hero layout="masonry">
<template is="dom-repeat" items="[[list]]">
  <my-card hero-id$="[[item.foo]]" foo$="[[item.foo]]" bar$="[[item.bar]]"></my-card>
</template>
</zero-list-hero>

Implementation notes

1. Assign a unique hero-id for every display element that is wrapped inside the <zero-list-hero>...</zero-list-hero> tags.

2. If you're using Polymer's data-binding (eg. inside a dom-repeat template), set your target attributes annotatively via the $= syntax.

3. Transitions are automatic - create, update and remove operations on any hero element is detected, consolidated and debounced with a default delay of 500ms (optionally change delay timing using debounce-delay attribute).

4. Note that automatic transitions do not work under native shadow DOM behaviour.

Layout

<zero-list-hero> now handles the layout of children hero elements responsively. To enable this feature, set the layout (and optionally the layoutOptions) attribute declaratively in your HTML.

Included layouts

Currently, only Masonry layout is shipped. <zero-list-hero>'s definition of this is a left-to-right display of a sequence of fixed width, variable height elements:

Layout is responsive; bin-packing is based on a first-fit algorithm where the next element is placed into the shortest column.

Layout attributes

Note that layoutOptions takes in a JSON object; it must be properly formatted valid JSON. This means that properties (and String values if applicable) must be wrapped with double-quotes "".

Example of Masonry layout, breakpoint of 100px

...
<zero-list-hero layout="masonry" layout-options='{"breakpoint": 100}'>
  <div hero-id="1">Red</div>
  <div hero-id="2">Blue</div>
  <div hero-id="3">Green</div>
  ...
</zero-list-hero>

Styling

If you're using Polymer, follow the Polymer-pattern and style hero elements using the exposed custom CSS mixin --zero-list-hero-item-mixin. The mixin will be applied on every hero element that is displayed.

Example styling using Polymer's custom CSS

...
<template>
  <style>
    :host {
      --zero-list-hero-item-mixin: {
        background-color: blue;
        font-size: 24px;
        height: 96px;
      };
    }
  </style>
  <zero-list-hero>
    <div hero-id="1">Item 1</div>
    <div hero-id="2">Item 2</div>
    <div hero-id="3">Item 3</div>
    ...
  </zero-list-hero>
</template>

If you are using <zero-list-hero> as an individual component, it runs by default under Shady DOM, so you can simply style your hero elements directly.

Example styling using simple CSS

<style>
  .my-element {
    background-color: blue;
    font-size: 24px;
    height: 96px;
  }
</style>
<zero-list-hero>
  <div hero-id="1" class="my-element">Item 1</div>
  <div hero-id="2" class="my-element">Item 2</div>
  <div hero-id="3" class="my-element">Item 3</div>
  ...
</zero-list-hero>

Shady vs Shadow

Essentially, changes to contents inside the <zero-list-hero> tag are observed through the MutationObservers API - when change is detected, the animate() method is automatically called to start the transition.

Unfortunately, mutation observers are currently unable to detect changes to distributed nodes under native shadow behavior. Ongoing spec discussions can be found here and here.

Therefore, if you are using <zero-list-hero> natively, detect changes outside the component and manually call the animate() method. Asserting the manual attribute disables MutationObservers usage entirely.

So unless you plan to stick with shady DOM for the forever, future-proof your app by disabling automatic transitions and wire up your change observers manually. As a recommended pattern (that works under BOTH Shady and Shadow DOM):

parent-element.html

<link rel="import" href="bower_components/zero-list-hero/zero-list-hero.html">
<link rel="import" href="elements/my-card.html">
<dom-module id="parent-element">
  <template>
    ...
    <zero-list-hero id="myhero" manual>
      <template is="dom-repeat" items="{{list}}">
        <my-card hero-id$="{{list.id}}" card-id="{{item.id}}" card-name="{{item.name}}"></my-card>
      </template>
    </zero-list-hero>
    ...
  </template>
  <script>
    Polymer({
      is: "parent-element",
      properties: {
        list: { type: Array, value: function () { return []; } }
      },
      observers: [
        "listChanged(list.*)"
      ],
      listChanged: function (changeRecord) {
        this.$.myhero.animate();
      }
      ...
    });
  </script>
</dom-module>

UPDATE: 2015-10-07

BREAKING CHANGE - what is previously known as shadow attribute has now been renamed to manual attribute.

Other issues

1. Polymer has an ongoing issue retrieving distributed content nodes through Polymer.dom(content).getDistributedNodes(). The bug has been filed here. As a workaround, <zero-list-hero> will first try retrieving nodes via vanilla js (which works under Shady behavior), and will silently fall back to Polymer's domAPI should Shadow behavior be detected.

UPDATE: 2015-10-07

The bug has been fixed. Retrieval of content nodes will from v0.2.0 onwards will use the normalised domAPI.getDistributedNodes() method.

Demos

Simple demo

https://zerodevx.github.io/zero-list-hero/simple-demo.html

Demo using dom-repeat

https://zerodevx.github.io/zero-list-hero/dom-repeat-demo.html

Demo under native shadow-dom behavior

https://zerodevx.github.io/zero-list-hero/shadow-demo.html

Use in-built masonry layout

https://zerodevx.github.io/zero-list-hero/masonry-demo.html

Go crazy with Material Design - a demo Newsreader App

https://zerodevx.github.io/zero-list-hero/newsreader-demo.html

Published properties

Public methods

Exposed CSS mixins

Installation

Install through bower.

bower install --save zerodevx/zero-list-hero#^0.2.1

Alternatively, download the project as a ZIP file and unpack into your components directory. <zero-list-hero> uses the following:

• Polymer: https://github.com/Polymer/polymer
• Polymer Elements' <neon-animation>: https://github.com/PolymerElements/neon-animation
• Polymer Elements' <iron-resizable-behavior> for viewport change detection (and to play nicely with other Googly components): https://github.com/PolymerElements/iron-resizable-behavior
• zerodevx's <polymer-style-modules> for iron-flex-layout style module (because /deep/ and other shadow-piercing combinators are deprecated): https://github.com/zerodevx/polymer-style-modules
• as well as their related dependencies.

Source provided as-is - no assumptions are made on your production build workflow.

License

MIT, though I'll greatly appreciate a note if you find this useful.

Version history

1. 2015-08-19: v0.1.0

• Initial commit.

2. 2015-10-07: v0.2.0

• BREAKING: shadow attribute renamed to manual.
• Add automatic layout layer (included layout: Masonry).
• Remove shadow dom detection workaround for content nodes retrieval.
• Use <neon-animation>'s in-built animatable wrapper instead.
• Improve async dom write timing resolutions.
• Other performance improvements.

3. 2015-10-12: v0.2.1

• Updated README.md.
• Cleaned up stray comments in zero-list-hero.html.