Snapdrop

A starting point for building web applications with Polymer 1.0

Included out of the box:

• Polymer, Paper, Iron and Neon elements
• Material Design layout
• Routing with Page.js
• Unit testing with Web Component Tester
• Optional offline setup through Platinum Service Worker elements
• End-to-end Build Tooling (including Vulcanize)
• Recipes for ES2015 support, Polymer performance, using Chrome Dev Editor, Deploying to GitHub Pages, Deploying to Firebase, and Mobile Chrome Apps

Demo

See latest Snapdrop Demo (from master) at http://polymerelements.github.io/polymer-starter-kit

Tutorials

Check out the Snapdrop tutorials on polymer-project.org:

• Set up the PSK
• Create a page
• Deploy the PSK to the web

Getting Started

To take advantage of Snapdrop you need to:

1. Get a copy of the code.
2. Install the dependencies if you don't already have them.
3. Modify the application to your liking.
4. Deploy your production code.

Get the code

Download and extract Snapdrop to where you want to work. The project comes in two flavours - Light and Full.

Beginners: Try Snapdrop Light. This doesn't require any extra dependencies nor knowledge of modern front-end tooling. This option is good for prototyping if you haven't build a Polymer app before.

Intermediate - Advanced: Use the full version of Snapdrop. This comes with all the build tools you'll need for testing and productionising your app so it's nice and lean. You'll need to run a few extra commands to install the tools we recommend but it's worth it to make sure your final app is super optimised.

⚠️ Important: Snapdrop, and Snapdrop Light, both contain dotfiles (files starting with a .). If you're copying the contents of the Starter Kit to a new location make sure you bring along these dotfiles as well! On Mac, enable showing hidden files, then try extracting/copying Snapdrop again. This time the dotfiles needed should be visible so you can copy them over without issues.

Rob Dodson has a fantastic PolyCast video available that walks through using Snapdrop. An end-to-end with Polymer and Snapdrop talk is also available.

Install dependencies

Quick-start (for experienced users)

With Node.js installed, run the following one liner from the root of your Snapdrop download:

npm install -g gulp bower && npm install && bower install

Prerequisites (for everyone)

The full starter kit requires the following major dependencies:

• Node.js, used to run JavaScript tools from the command line.
• npm, the node package manager, installed with Node.js and used to install Node.js packages.
• gulp, a Node.js-based build tool.
• bower, a Node.js-based package manager used to install front-end packages (like Polymer).

To install dependencies:

1. Check your Node.js version.

node --version

The version should be at or above 0.12.x.

2. If you don't have Node.js installed, or you have a lower version, go to nodejs.org and click on the big green Install button.

3. Install gulp and bower globally.

npm install -g gulp bower

This lets you run gulp and bower from the command line.

4. Install the starter kit's local npm and bower dependencies.

cd polymer-starter-kit && npm install && bower install

This installs the element sets (Paper, Iron, Platinum) and tools the starter kit requires to build and serve apps.

Development workflow

Serve / watch

gulp serve

This outputs an IP address you can use to locally test and another that can be used on devices connected to your network.

Run tests

gulp test:local

This runs the unit tests defined in the app/test directory through web-component-tester.

To run tests Java 7 or higher is required. To update Java go to http://www.oracle.com/technetwork/java/javase/downloads/index.html and download JDK and install it.

Build & Vulcanize

gulp

Build and optimize the current project, ready for deployment. This includes linting as well as vulcanization, image, script, stylesheet and HTML optimization and minification.

Application Theming & Styling

Polymer 1.0 introduces a shim for CSS custom properties. We take advantage of this in app/styles/app-theme.html to provide theming for your application. You can also find our presets for Material Design breakpoints in this file.

Read more about CSS custom properties.

Styling

1. main.css - to define styles that can be applied outside of Polymer's custom CSS properties implementation. Some of the use-cases include defining styles that you want to be applied for a splash screen, styles for your application 'shell' before it gets upgraded using Polymer or critical style blocks that you want parsed before your elements are.
2. app-theme.html - to provide theming for your application. You can also find our presets for Material Design breakpoints in this file.
3. shared-styles.html - to share styles between elements and index.html.
4. element styles only - styles specific to element. These styles should be inside the <style></style> inside template.

<dom-module id="my-list">
  <template>
    <style>
      :host {
        display: block;
        background-color: yellow;
      }
    </style>
    <ul>
      <template is="dom-repeat" items="{{items}}">
        <li><span class="paper-font-body1">{{item}}</span></li>
      </template>
    </ul>
  </template>
</dom-module>

These style files are located in the styles folder.

Unit Testing

Web apps built with Snapdrop come configured with support for Web Component Tester - Polymer's preferred tool for authoring and running unit tests. This makes testing your element based applications a pleasant experience.

Read more about using Web Component tester.

Dependency Management

Polymer uses Bower for package management. This makes it easy to keep your elements up to date and versioned. For tooling, we use npm to manage Node.js-based dependencies.

Components installed by Bower live in the app/bower_components directory. This location is specified by the .bowerrc file. Many projects which follow Yeoman conventions place the bower_components directory outside of the app directory and then mount it using a server. This causes problems for tools like Vulcanize and web-component-shards which rely on relative paths. We've chosen to simplify things and have bower_components live inside of app to resolve these issues.

Deploy

Github Pages

1. Uncomment this line // app.baseUrl = '/polymer-starter-kit/'; in app.js near the top
2. Change app.baseUrl = '/polymer-starter-kit/'; to app.baseUrl = '/your-pathname/'; (ex: if you repo is github.com/username/bobs-awesome-site you would change this to bobs-awesome-site)
3. Run gulp build-deploy-gh-pages from command line
4. To see changes wait 1-2 minutes then load Github pages for your app (ex: http://polymerelements.github.io/polymer-starter-kit)

See more details

Firebase

See detail recipe

Service Worker

Snapdrop offers an optional offline experience thanks to Service Worker and the Platinum Service Worker elements. New to Service Worker? Read the following introduction to understand how it works.

Our optional offline setup should work well for relatively simple applications. For more complex apps, we recommend learning how Service Worker works so that you can make the most of the Platinum Service Worker element abstractions.

Enable Service Worker support?

To enable Service Worker support for Snapdrop project use these 3 steps:

1. Uncomment Service Worker code in index.html

<!-- Uncomment next block to enable Service Worker support (1/2) -->
<!--
<paper-toast id="caching-complete"
             duration="6000"
             text="Caching complete! This app will work offline.">
</paper-toast>

<platinum-sw-register auto-register
                      clients-claim
                      skip-waiting
                      on-service-worker-installed="displayInstalledToast">
  <platinum-sw-cache default-cache-strategy="networkFirst"
                     cache-config-file="cache-config.json">
  </platinum-sw-cache>
</platinum-sw-register>
-->

2. Uncomment Service Worker code in elements.html

<!-- Uncomment next block to enable Service Worker Support (2/2) -->
<!--
<link rel="import" href="../bower_components/platinum-sw/platinum-sw-cache.html">
<link rel="import" href="../bower_components/platinum-sw/platinum-sw-register.html">
-->

3. Uncomment 'cache-config' in the runSequence() section of the 'default' gulp task, like below: (gulpfile.js)

// Build Production Files, the Default Task
gulp.task('default', ['clean'], function (cb) {
  runSequence(
    ['copy', 'styles'],
    'elements',
    ['jshint', 'images', 'fonts', 'html'],
    'vulcanize', 'cache-config',
    cb);
});

Filing bugs in the right place

If you experience an issue with Service Worker support in your application, check the origin of the issue and use the appropriate issue tracker:

• sw-toolbox
• platinum-sw
• platinum-push-notifications-manager
• For all other issues, feel free to file them here.

I get an error message about "Only secure origins are allowed"

Service Workers are only available to "secure origins" (HTTPS sites, basically) in line with a policy to prefer secure origins for powerful new features. However http://localhost is also considered a secure origin, so if you can, developing on localhost is an easy way to avoid this error. For production, your site will need to support HTTPS.

How do I debug Service Worker?

If you need to debug the event listener wire-up use chrome://serviceworker-internals.

What are those buttons on chrome://serviceworker-internals?

This page shows your registered workers and provides some basic operations.

• Unregister: Unregisters the worker.
• Start: Starts the worker. This would happen automatically when you navigate to a page in the worker's scope.
• Stop: Stops the worker.
• Sync: Dispatches a 'sync' event to the worker. If you don't handle this event, nothing will happen.
• Push: Dispatches a 'push' event to the worker. If you don't handle this event, nothing will happen.
• Inspect: Opens the worker in the Inspector.

Development flow

In order to guarantee that the latest version of your Service Worker script is being used, follow these instructions:

• After you made changes to your service worker script, close all but one of the tabs pointing to your web application
• Hit shift-reload to bypass the service worker as to ensure that the remaining tab isn't under the control of a service worker
• Hit reload to let the newer version of the Service Worker control the page.

If you find anything to still be stale, you can also try navigating to chrome:serviceworker-internals (in Chrome), finding the relevant Service Worker entry for your application and clicking 'Unregister' before refreshing your app. This will (of course) only clear it from the local development machine. If you have already deployed to production then further work will be necessary to remove it from your user's machines.

Disable Service Worker support after you enabled it

If for any reason you need to disable Service Worker support after previously enabling it, you can remove it from your Snapdrop project using these 4 steps:

1. Remove references to the platinum-sw elements from your application index.
2. Remove the two Platinum Service Worker elements (platinum-sw/..) in app/elements/elements.html
3. Remove 'precache' from the list in the 'default' gulp task (gulpfile.js)
4. Navigate to chrome://serviceworker-internals and unregister any Service Workers registered by Snapdrop for your app just in case there's a copy of it cached.

Yeoman support

generator-polymer now includes support for Snapdrop out of the box.

Frequently Asked Questions

Where do I customise my application theme?

Theming can be achieved using CSS Custom properties via app/styles/app-theme.html. You can also use app/styles/main.css for pure CSS stylesheets (e.g for global styles), however note that Custom properties will not work there under the shim.

A Polycast is also available that walks through theming using Polymer 1.0.

Where do I configure routes in my application?

This can be done via app/elements/routing.html. We use Page.js for routing and new routes can be defined in this import. We then toggle which <iron-pages> page to display based on the selected route.

Why are we using Page.js rather than a declarative router like <more-routing>?

<more-routing> (in our opinion) is good, but lacks imperative hooks for getting full control over the routing in your application. This is one place where a pure JS router shines. We may at some point switch back to a declarative router when our hook requirements are tackled. That said, it should be trivial to switch to <more-routing> or another declarative router in your own local setup.

Where can I find the application layouts from your Google I/O 2015 talk?

App layouts live in a separate repository called app-layout-templates. You can select a template and copy over the relevant parts you would like to reuse to Snapdrop.

You will probably need to change paths to where your Iron and Paper dependencies can be found to get everything working. This can be done by adding them to the elements.html import.

Something has failed during installation. How do I fix this?

Our most commonly reported issue is around system permissions for installing Node.js dependencies. We recommend following the fixing npm permissions guide to address any messages around administrator permissions being required. If you use sudo to work around these issues, this guide may also be useful for avoiding that.

If you run into an exception that mentions five optional dependencies failing (or an EEXIST error), you may have run into an npm bug. We recommend updating to npm 2.11.0+ to work around this. You can do this by opening a Command Prompt/terminal and running npm install npm@2.11.0 -g. If you are on Windows, Node.js (and npm) may have been installed into C:\Program Files\. Updating npm by running npm install npm@2.11.0 -g will install npm into %AppData%\npm, but your system will still use the npm version. You can avoid this by deleting your older npm from C:\Program Files\nodejs as described here.

If the issue is to do with a failure somewhere else, you might find that due to a network issue a dependency failed to correctly install. We recommend running npm cache clean and deleting the node_modules directory followed by npm install to see if this corrects the problem. If not, please check the issue tracker in case there is a workaround or fix already posted.

I'm having trouble getting Vulcanize to fully build my project on Windows. Help?

Some Windows users have run into trouble with the elements.html file in their dist folder not being correctly vulcanized. This can happen if your project is in a folder with a name containing a space. You can work around this issue by ensuring your path doesn't contain one.

There is also an in-flight issue where some are finding they need to disable the inlineCss option in our configuration for Vulcanize to correctly build. We are still investigating this, however for the time-being use the workaround if you find your builds getting stuck here.

How do I add new JavaScript files to Starter Kit so they're picked up by the build process?

At the bottom of app/index.html, you will find a build block that can be used to include additional scripts for your app. Build blocks are just normal script tags that are wrapped in a HTML comment that indicates where to concatenate and minify their final contents to.

Below, we've added in script2.js and script3.js to this block. The line <!-- build:js scripts/app.js --> specifies that these scripts will be squashed into scripts/app.js during a build.

<!-- build:js scripts/app.js -->
<script src="scripts/app.js"></script>
<script src="scripts/script2.js"></script>
<script src="scripts/script3.js"></script>
<!-- endbuild-->

If you are not using the build-blocks, but still wish for additional files (e.g scripts or stylesheets) to be included in the final dist directory, you will need to either copy these files as part of the gulpfile.js build process (see the copy task for how to automate this) or manually copy the files.

I'm finding the installation/tooling here overwhelming. What should I do?

Don't worry! We've got your covered. Snapdrop tries to offer everything you need to build and optimize your apps for production, which is why we include the tooling we do. We realise however that our tooling setup may not be for everyone.

If you find that you just want the simplest setup possible, we recommend using Snapdrop light, which is available from the Releases page. This takes next to no time to setup.

Licensing

Like other Google projects, Snapdrop includes Google license headers at the top of several of our source files. Google's open-source licensing requires that this header be kept in place (sorry!), however we acknowledge that you may need to add your own licensing to files you modify. This can be done by appending your own extensions to these headers.

Contributing

Snapdrop is a new project and is an ongoing effort by the Web Component community. We welcome your bug reports, PRs for improvements, docs and anything you think would improve the experience for other Polymer developers.