Build Widgets

Anatomy of a Widget
• Config.xml <- W3C Widgets P&C Spec
• icon.png
• index.html <- HTML start file
• JavaScript code, CSS

• Zip it up, change ext to .wgt, and you’re
done

Widget metadata
• Id
• Height, Width
• Name
• Description
• Version
• Features
• Author info
• License

A Silly Example: config.xml
<?xml version="1.0" encoding="utf-8"?>
<widget xmlns="http://www.w3.org/ns/widgets"
id="http://www.getwookie.org/widgets/tea"
version="1.0” height="150” width="125">
<name>Tea</name>
<description>A silly Tea widget</description>
<author>Scott Wilson</author>
</widget>

A Silly Example: index.html
<html>
<body>
<img src="tea.jpg" />
<p>Time for a break, mate</p>
</body>
</html>

Make your own basic widget
1. Make an index.html file
2. Make a config.xml file
3. Zip them up, and change suffix to “.wgt”
4. Upload to a wookie server

Uploading
• Go to http://192.168.2.161/wookie
• Click “admin”
• Login with java/java
• Click “add new widget”
• Find your .wgt file
• OK!

Previewing a widget
• Go to 192.168.2.161:8080/wookie
• Click “View Widget Gallery”
• Click the “demo” link under your widget
• Your widget will show

Preferences
• You can store preferences for an instance of
a widget using:

widget.preferences.setItem(“key”, “value”)
widget.preferences.getItem(“key”)

Collaborative Widgets
• State and Participants

• State is shared across widgets with the same
IRI in the same shared context.
• State is propagated to related widgets using
an event callback
• State is set by submitting deltas

State example
wave.setStateCallback(stateUpdated);

stateUpdated = function(){
var keys = wave.getState().getKeys();
for (var i = 0; i < keys.length; i++) {
alert(wave.getState().get(keys[i]));
}
};

wave.getState().submitValue(“key”, “value”);

Participants
• Register callbacks with:
wave.setParticipantCallback(myfunction);

• Methods:
– getViewer() - get the current user
– getParticipants() - get map of all participants

• Model:
– getId(), getDisplayName(), getThumbnailUrl()

Making a collaborative app
• This requires some more planning

1. Draw up a design
2. Create a working test page
3. Implement models, action handlers and
event handlers
4. Create the config.xml, icon.png, zip it up
and run it

Design
• Start with the view - what the widget looks
like
• Create the model - what are the objects in
the state model?
• Add the actions - how you interact with it
• Wire it all up…

Prototyping
• Make a regular html page to test out your
view. Populate it with fake model, and don’t
wire up the actions yet
• You can reuse this for the real widget - just
take out your fake state info sections

Implementing
• Create a “Model” object for your state
model
• Create a “Controller” object, and a method
in it for each action
• Register the participant and state event
handlers with an “update view” method that
populates the view when running

Models
• Models can be implemented in typical “bean” fashion
• Save/Find methods need to access wave state
• Can use JSON (e.g. with json.js) or just plain strings for storage

function Task(id,name,status,assigned){
this.task_id = id;
this.name = name;
this.status = status;
this.assigned_to = assigned;
}
Task.prototype.save = function(){
wave.getState().submitValue(this.task_id, JSON.stringify(this));
}

Static model methods
Task.create = function(json){
var obj = JSON.parse(json);
var task = new Task(obj.task_id,
obj.name,obj.status,obj.assigned_to);
return task;
• Typically need
}
methods to turn state
Task.find = function(task_id){
for (var i = 0; i < keys.length; i++) {
strings back into
var key = keys[i];
if (key == task_id){
model instances
return Task.create(task_id, wave.getState().get(key));

}
} • Also finder methods to
}
return null;
get a particular model
Task.findAll = function(){ object
var tasks = {};
for (var i = 0; i < keys.length; i++) { • This isn’t the only way
var key = keys[i];
var task = Task.create(key, wave.getState().get(key));
tasks[key] = task;
to do this, but is an
}
return tasks;
OK pattern
}

Controllers
/**
* The Controller object
* This is used to wire up the view and model with actions
• Methods for each
*/
var Controller = {
action, making
// Action handlers changes to the model
// Toggle task state between completed and to-do
toggleTask: function(task_id){
• You usually don’t
},
need to do any code
// Create a new task
newTask: function(){
},
that interacts with
// Abandon task for someone else to do
HTML, as the event
abandonTask: function(task_id){
}, handlers should do
// Claim a task (assign to self)
claimTask: function(task_id){
that
}
}

Event Handlers
// Update the view when state has been updated These fire whenever the state or participants
stateUpdated: function(){ are updated (e.g. by another instance).
var tasks = Task.findAll();
if (tasks && tasks != null){
var tasklist = ""; Event handlers need to be registered like so:
for (key in tasks) {
var task = tasks[key]; wave.setStateCallback(Controller.stateUpdated);
wave.setParticipantCallback(Controller.participantsUpdated);
tasklist += // the task stuff to show
dwr.util.setValue("tasklist", tasklist, {
escapeHtml:false }); Also useful to have these methods called
var objDiv = document.getElementById("tasklist"); from onLoad() in an init() function to
objDiv.scrollTop = objDiv.scrollHeight; create initial view
}
},
participantsUpdated: function(){ You can import JQuery if you like for
Controller.updateUser(); setting the view content, or do it using
} DOM

Packaging
You need to add this to your config.xml to tell
Wookie to include the Wave Gadget API
methods:

<feature
name="http://wave.google.com"
required="true"/>

Uploading, debugging and testing
• You need a • I’ve set up a Moodle
collaborative instance at:
environment to test
your widget properly 192.168.2.XXX

Login as ws1,ws2,ws3,
or ws4

Other stuff…
• AJAX • Camera access
If you want to call If you want to access the
external sites from user’s camera from a
within the widget, call widget, there is an
myurl =
example of how to do
widget.proxify(url)
first to call it via proxy. this in the moodle
Also need to add the course (topic 3)
site to the server
whitelist.

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