G-Earth supports console & GUI extensions, this page is focused on extension structure and development.
## Features
* Packet hash/name support
* Interception of incoming/outgoing packets
* Full chat console support for I/O
## Console extensions
Console extensions are the most basic kind of extensions, a few lines of code can get us started.
A console extension is made of a Java class that extends _Extension_.
Let's start a sample extension creating a maven project:
Since G-Earth is built using maven, once we've compiled G-Earth, it's possible to add it as a project dependency:
```xml
4.0.0G-EarthGangSampleExtension1.0-SNAPSHOTorg.apache.maven.pluginsmaven-jar-plugin2.5${project.build.directory}/bintruetruelib/SampleExtensionfalsemaven-assembly-plugin2.5packagesingle${project.build.directory}/binSampleExtensionjar-with-dependenciesSampleExtensionfalseorg.apache.maven.pluginsmaven-compiler-plugin88G-EarthG-Earth0.2
```
That should be enough to configure maven. Now let's move on to the code.
Every extension needs to include an _ExtensionInfo_ annotation in order to identify the extension, our ExtensionInfo would look like this:
```java
@ExtensionInfo(
Title = "Sample Extension",
Description = "Used for the wiki",
Version = "1.0",
Author = "G-Earth"
)
```
The extension constitutes a standalone jar, so we'll need to include a main method to start it up like this:
```java
public class SampleExtension extends Extension {
private SampleExtension(String[] args) {
super(args);
}
public static void main(String[] args) {
new SampleExtension(args).run();
}
}
```
That would be a bare minimum to get it loaded into G-Earth, now let's have a look at the API to improve our little extension
## A quick look to the extensions API
In this section we'll build upon the previous example with the functionality provided by G-Earth's API
### Initializing our extension
_initExtension_ is called whenever G-Earth loads the extension, it's specially useful to init the _HashSupport_ and other features, we'll use it in the following examples
### Intercepting packets
The _intercept_ method lets us intercept a packet from its id and modify it if we want to. Typically, we use this function call inside _initExtension_.
```java
intercept(HMessage.Side.TOCLIENT, 4000, hMessage -> {
// oops we got disconnected
});
```
### Sending packets
G-Earth includes the sendTo[Client/Server] method in order to send packets.
```java
sendToClient(new HPacket("{l}{u:1234}"));
// or
sendToClient(new HPacket(1234));
```
### Doing stuff upon client connection
```java
@Override
protected void onStartConnection() {
// we're connected to habbo
}
```
### Minimalistic interaction; onClick
If (and only if) the _onClick_ method is overridden by your extension, G-Earth will display a green "Start" button next to your extension and the function will get called on-click. For form extensions, this option is automatically used to open the GUI. For non-gui extensions, this is an additional feature you could use.
```java
@Override
protected void onClick() {
// the user clicked this extension! I must do something relevant here
}
```
### HashSupport
_HashSupport_ allows us to use hashes/names in order to intercept and send packets, using the aforementioned methods.
```java
private HashSupport mHashSupport;
@Override
protected void initExtension() {
// This is called when G-Earth loads the extension
mHashSupport = new HashSupport(this);
mHashSupport.intercept(HMessage.Side.TOCLIENT, "RoomUserStartTyping", hMessage -> {
mHashSupport.sendToServer("RoomUserStopTyping");
});
}
```
### ChatConsole
_ChatConsole_ is a new G-Earth feature that allows us to use the in-game chat in order to easily communicate with the extension, it can read your input and write messages, you can also set a welcome message, we'll add it to our example.
(side note: the implementation of ChatConsole hides the whole thing from the Habbo servers, so all interaction stays local)
```java
private HashSupport mHashSupport;
private ChatConsole mChatConsole;
@Override
protected void initExtension() {
// This is called when G-Earth loads the extension
mHashSupport = new HashSupport(this);
mChatConsole = new ChatConsole(mHashSupport, this, "I'm a welcome message!");
mChatConsole.onInput(input -> {
if (input.equals("ping"))
mChatConsole.writeOutput("pong", false);
});
}
```
Once loaded it will appear to your friend's list
It will show the welcome message after typing _:info_
If used correctly it can be pretty powerful.
## GUI extensions
We'll build a simple GUI based extension using the concepts we learnt on the console extension part.
The main difference is that instead of extending from _Extension_ we'll extend from _ExtensionForm_. This introduces some changes, for example, in order to call to our extension in _main_, we'll call _runExtensionForm_ instead of the constructor.
```java
public class SampleExtension extends ExtensionForm {
public static void main(String[] args) {
runExtensionForm(args, SampleExtension.class);
}
}
```
Since _ExtensionForm_ is an abstract class, we'll have to implement _launchForm_ in order to setup the javafx components
```java
public ExtensionForm launchForm(Stage primaryStage) throws Exception {
FXMLLoader loader = new FXMLLoader(getClass().getResource("sampleextension.fxml"));
Parent root = loader.load();
primaryStage.setTitle("Sample extension");
primaryStage.setScene(new Scene(root));
primaryStage.setResizable(false);
return loader.getController();
}
```
Assuming you've created the .fxml file, this code would be enough for G-Earth to load your extension.
From there, you can design your own UI and use the API to create a fully functional extension.