Writing an interface for JavaScript Addons

Tutorial Series	Plasma Tutorial
Previous	None
What's Next	Writing a JavaScript Addon
Further Reading	Introduction to Writing Plasmoids with JavaScript

Introduction

This is a tutorial on how to write an interface for JavaScript addons for Plasma. Since the interface can be anything from a plasmoid to a dataengine and all the way to a service, this tutorial uses a plasmoid to write an interface for addons. Please note that this tutorial does not cover the whole plasmoid tutorial. To whole plasmoid tutorial can be found here.

Setting up

Before we start to program the little interface we need to do some setup. First of all, we create a directory called MyJSInterface, where our interface will be located, with the following directory structure:

MyJSInterface/

contents/

code/

metadata.desktop

In the root directory of our addon, we create a file metadata.desktop with the following content:

[Desktop Entry] Name=MyJSInterface Name[x-test]=xxMyJSInterfacexx

Comment=My first JavaScript interface

X-KDE-ServiceTypes=Plasma/Applet Type=Service X-Plasma-API=javascript X-Plasma-MainScript=code/main.js

X-KDE-Library= X-KDE-PluginInfo-Author=<Your name here> X-KDE-PluginInfo-Email=<Your email here> X-KDE-PluginInfo-Name=org.myorg.myJSInterface X-KDE-PluginInfo-Version=0.1 X-KDE-PluginInfo-Website=http://plasma.kde.org/ X-KDE-PluginInfo-Depends= X-KDE-PluginInfo-License=LGPL X-KDE-PluginInfo-EnabledByDefault=true

Important are the X-KDE-PluginInfo-Name. This section is important for the addons to attach themselfs.

The plasmoid

The plasmoid will have a simple interface, that has a textbox and an output area. Firstly we build the interface. The following code looks like this:

!screenshot!

var linearLayout = new LinearLayout(plasmoid); var textBox = new TextEdit(); var button = new PushButton(); var label = new Label();

linearLayout.addItem(textBox); linearLayout.addItem(button); linearLayout.addItem(label);

Now we insert the code that "grabs" the addons.

// we want to hold on to the addons var addons = new Array()

// callback function when an addon has been located function addonCreated(addon) {

 print("new addon: " + addon)
 addons.push(addon);
 setData(addonsObject[i].name, 'text', );
 print(addons.length);

First of all we will define a constructor. In this case we name it MyJavaScriptAddon

function MyJavaScriptAddon() {

   print("Hello World");

}

This constructor gets called, when this addon is loaded by another JavaScript instance. In there we will get a console output with "Hello World".

The next step is to provide our Addon a method, which print out our input.

MyJavaScriptAddon.prototype.echo = function(text) {

   print(text);

}

In this part, the actual method is called echo, however having MyJavaScriptAddon.prototype prefixed is important for JavaScript to make sure that echo is a member of this class. To understand the concept of object orienting in JavaScript see this tutorial .

At the end of your Addon it is also important that you "publish" your class for other instances that would like to use it.

registerAddon(MyJavaScriptAddon)

Now, we should save our written code into MyFirstJSAddon/contents/code and name it main.js.

Installing

To install this addon, simply navigate to the root directory of our addon and type this into the console:

plasmapkg -t Plasma/JavascriptAddon -i MyJavaScriptAddon/