Best Practices in Widget Development - Examples and Counterexamples

Best Practices in Widget Development
Examples and Counterexamples

Daniel Dahrendorf (IMC)

ROLE Developer Camp,
Lausanne, Switzerland
August 23, 2010

© www.role-project.eu

Dr Stephen Dann from flickr.com jbvkoos from flickr.com

23.08.2010 © www.role-project.eu

DESIGN AND USABILITY


In General

• Focus on a single task
– Give your end user a single functionality
• Own added Value
– Do not create a Widget which requires a second widget
• Self explanatory interface
– There should be no need for help text or support


Size of Widgets

• Use a standard height
• The widget should scale between 250px and 500px
– Use a width of 100% for the main elements of the widget
– Center elements
• Use views
– Canvas, home and profile views


Customization

• Let the user customize the widget
– Color
– Background
– Content
• Provide always default or sample values
and include a “welcome mode”
• Use the user preferences feature
of Google Gadgets


Use Space effectively

• Avoid scrollbars
• Use tabs
• Use paging


User Account

• Content should be interesting even the user is not logged in
• State the benefits of creating an account
• Use OAuth if possible


DEVELOPMENT


Development Environment

• Own Apache Shindig Server
– A web application which can be run e.g.
in a Apache Tomcat

• OSDE
– Eclipse plugin with built in Apache
Shindig server

• Google Gadget Editor
– A Google gadget which provides an editor
and the possibility to save the widgets at
iGoogle


Development Environment

• Own Apache Shindig Server
– A web application which can be run e.g.
in a Apache Tomcat

– Comfortable way to create complex
interacting widgets


Using the features provided by the gadget API

• The Gadget and OpenSocial API provides a lot of useful
features:
– fetch social data
– provide UI element
– Get data from external sources

• Only available for type=“html’’ widgets


Selected Features:

• Tabs
– Creates customizable tabs

• Setprefs
– Allows setting of user preferences

• Pubsub (OpenSocial 0.8 only)
– Inter-widget-communication
– Use OpenApp instead
(http://code.google.com/p/open-app/)

• Internationalization
– Provides a mechanism to
translate widgets


makeRequest and the Same Origin Policy

• The gadget API provides a function to fetch
HTML/XML/JSON content (OpenSocial 0.8):

gadgets.io.makeRequest(url, callback, opt_params)

• As widgets run in iFrames this proxy approach allows to
fetch data from other domains (same origin policy)
• Other approaches to solve cross domain problems are:
– JSONP (retrieving JSON via Script Tags)
– PMRPC (http://code.google.com/p/pmrpc/)


Caching Problems

• If you are using makeRequest() to fetch content that is
updated more than once an hour, such as feed data, you
might not get the latest updates


Refreshing the Content Cache

• Solution: create a wrapper with a refresh interval

function makeCachedRequest(url, callback, params,
refreshInterval) {

var timestamp = new Date().getTime();
var sep = "?";
if (refreshInterval && refreshInterval > 0) {
timestamp =
Math.floor(timestamp / (refreshInterval * 1000));
}
if (url.indexOf("?") > -1) {
sep = "&";
}
url = [ url, sep, "nocache=", timestamp ].join("");
gadgets.io.makeRequest(url, callback, params);
}


Caching of external files

• Container caches:
– JavaScript added with <script>
– CSS added with <link>
– Content got using the gadget API
• Further because of the widget infrastructure only absolute
links are allowed

• External files are needed if the widget becomes more
complex


Loading JavaScript / CSS dynamically
http://www.bitsbythepound.com/include-
1. Determine the location of the xml external-javascript-and-css-files-with-a-
google-wave-gadget-249.html
function getModuleBase() {
if (window.__moduleBase)
return window.__moduleBase;
if (_args){
var moduleBase = _args()['url'];
moduleBase = moduleBase.substring(0, moduleBase.lastIndexOf('/') + 1);
window.__moduleBase = moduleBase;
return window.__moduleBase;
}
alert('Can not find module base. Gadget may not work properly.');
return '';
};

2. Create mechanism for loading JS and CSS
jQuery provides a cross-browser require script plugin (requireScript)
3. Load the js/css in gadget init
function init() {
var useCaching = false;
addScript("js/default.js",useCaching);
addStylesheet("css/style.css",useCaching);
};
gadgets.util.registerOnLoadHandler(init);


Performance

• Goal: Reduce size of the files and number of HTTP requests

• Minify JavaScript code
– E.g. http://www.crockford.com/javascript/jsmin.html
• Pack all stuff in one XML file
– Suggestion of Google
• Use the containers’ cache
– gadgets.io.getProxyUrl
• More sources for optimization:
– http://code.google.com/intl/de-DE/apis/gadgets/docs/publish.html
– http://wiki.opensocial.org/index.php?title=OpenSocial_Latency_Meas
urement

Maintainability VS. Performance?

Performance Testing and debugging

• Use e.g. the Firebug extension of Firefox for debugging and
measuring the performance


Conclusions

• Guidelines are helping to provide a user friendly interface
• Customizations allows users to personalize their widgets
• An own Apache Shindig server can be used to develop
interacting widgets
• Using the Gadget API prevents to “reinvent the wheel”
• Caching and cross domain problems can be handled with
several methods
• A widget can be optimized regarding its performance
• Tools are available for debugging and performance
measuring


ROLE ALLIANCE PROGRAM

What is the Alliance Program?
A partner network of strategic users, vendors and other
stakeholder

Why should I become a member?
As a member you have a lot of benefits e.g., access to our
showcase platform, free visit of specific workshops, test
of prototypes or attendance at Alliance Partner meetings

How can I become part of the Alliance Program?
Please register under
http://www.roleproject.eu/AllianceProgram


References

• http://www.google.com/webmasters/gadgets/guidelines.html
• http://www.seoish.com/how-to-internationalize-google-
gadgets/
• Lal, R. and Chava, L. C. 2010 Developing Web Widget with
Html, Css, JSON and Ajax: a Complete Guide to Web
Widget. CreateSpace.
• http://www.bitsbythepound.com/include-external-javascript-
and-css-files-with-a-google-wave-gadget-249.html
• http://code.google.com/intl/de/apis/gadgets/docs/remote-
content.html


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