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Plug-in developer's guide

Introduction
Installing development tools
Programming a plug-in
Going further

Introduction

From version 1.5, it's possible to add new features to Sweet Home 3D with plug-in files placed in your plug-ins folder. This allows Java programmers to develop and distribute new features for Sweet Home 3D without modifying the source files of the current version (which is good for upward compatibility), and without delivering a full version of the program (which is good for delivery size).
This document describes the tools required to create plug-ins, then shows how to program a plug-in that computes the maximum volume of the movable furniture added to a home, and finally gives some additional information that will help you to go further.

Installing development tools

If Sweet Home 3D targets a general audience, developing plug-ins requires special skills, and you should know how to program in Java with an IDE, before going further. This guide shows how to build a plug-in with Eclipse, but you can use the IDE of your choice, or no IDE at all.

Download and install Eclipse

First download Eclipse from http://www.eclipse.org/. The version named Eclipse IDE for Java Developers is enough to develop a plug-in, but you  can download any version for Java development.
Once downloaded, installing Eclipse is very simple: just uncompress the archive you'll get, open the eclipse folder and depending on your system, run the file named eclipse.exe (under Windows), eclipse.app (under Mac OS X) or eclipse (under Linux).
At the first run, Eclipse will require you to choose a workspace folder, where will be stored plug-in projects.
Once done, choose File > New > Project out of the menu to create a new project, select Java > Java project in the New project wizard that will be displayed, enter VolumePlugin as project name and click on Finish button. Finally, close the Welcome tab to discover your workspace as shown in figure 1.

Figure 1. Eclipse workspace

Download and install Sweet Home 3D library

The development of a plug-in is based on some classes of Sweet Home 3D that Eclipse must know to be able to build your project. The easiest way to add Sweet Home 3D classes to Eclipse is to download the JAR executable version of Sweet Home 3D available at http://prdownloads.sourceforge.net/sweethome3d/SweetHome3D-2.6.jar. Once downloaded, drag and drop the file SweetHome3D-2.6.jar on the VolumePlugin project icon in the Package Explorer view of Eclipse, and choose the item Build Path > Add to Build Path in the contextual menu of SweetHome3D-2.6.jar file, as shown in figure 2.

Figure 2. Adding SweetHome3D-2.6.jar to Build Path

Programming a plug-in

Now that you installed the required tools, let's see how you can program your first plug-in for Sweet Home 3D.

Creating the plug-in class

First, create a new subclass of com.eteks.sweethome3d.plugin.Plugin by choosing File > New > Class menu item in Eclipse.

Figure 3. Creating a new class

In the New Java Class dialog, enter VolumePlugin as the class name, enter a package (here the chosen package was com.eteks.test), and choose com.eteks.sweethome3d.plugin.Plugin as the super class of VolumePlugin. Once done, click on Finish. Eclipse will create the file of the new class with the following content:

package com.eteks.test;

import com.eteks.sweethome3d.plugin.Plugin;
import com.eteks.sweethome3d.plugin.PluginAction;

public class VolumePlugin extends Plugin {
    @Override
    public PluginAction[] getActions() {
        // TODO Auto-generated method stub
        return null;
    }
}

As you can guess from the TODO comment, you must now change the implementation of the getActions method to return a plug-in action able to compute the volume of the movable furniture. Replace return null; by the following statement:

        return new PluginAction [] {new VolumeAction()}; 

and choose Edition > Quick Fix out of Eclipse menu to create the missing class VolumeAction, as shown in figure 4.

Figure 4. Using Quick fix to generate a missing class

In the New Java Class dialog that appears, select the Enclosing type check box to create an inner class of VolumePlugin and click on Finish. This will create the class VolumeAction that inherits from com.eteks.sweethome3d.plugin.PluginAction class and contains an empty execute method:

    public class VolumeAction extends PluginAction {
        @Override
        public void execute() {
            // TODO Auto-generated method stub
        }
    }

This method is the one that Sweet Home 3D will call when the user will launch the plug-in action ; thus this is the place where you must implement how to compute the volume of the furniture and display it:

    public class VolumeAction extends PluginAction {
        @Override
        public void execute() {
            float volumeInCm3 = 0;
            // Compute the sum of the volume of the bounding box of 
            // each movable piece of furniture in home
            for (PieceOfFurniture piece : getHome().getFurniture()) {
                if (piece.isMovable()) {
                    volumeInCm3 += piece.getWidth() 
                                   * piece.getDepth() 
                                   * piece.getHeight();
                }
            }
            
            // Display the result in a message box (\u00b3 is for 3 in supercript)
            String message = String.format(
                "The maximum volume of the movable furniture in home is %.2f m\u00b3.", 
                volumeInCm3 / 1000000);
            JOptionPane.showMessageDialog(null, message);
        }
    }

Now that you specified what you want the plug-in to do, you must describe how the user will launch this new action. You have the choice between adding a new menu item to a menu, and/or a new button to the tools bar. This choice is done by setting the appropriate properties of the plug-in action at its creation. For example, if you want the users to launch the volume action with the menu item Compute volume found in the Tools menu, you'll add the following constructor to VolumnAction class:

        public VolumeAction() {
           putPropertyValue(Property.NAME, "Compute volume");
           putPropertyValue(Property.MENU, "Tools");
           // Enables the action by default
           setEnabled(true);
        }

The VolumePlugin plug-in class is now programmed, and almost ready to work as a plug-in in Sweet Home 3D. The two last things to do are:

• creating an ApplicationPlugin.properties description file,
• putting the files together in a JAR file.

Creating the plug-in description file

An ApplicationPlugin.properties file describes the plug-in name, its class, the Sweet Home 3D and Java minimum versions under which it is supported, and legal stuff. Choose File > New > File from Eclipse menu, enter the file name ApplicationPlugin.properties and click on Finish, as shown in figure 5.

Figure 5. Creating a new file

Then enter the following description in the new file and save it:

name=Movable furniture volume
class=com.eteks.test.VolumePlugin
description=Computes the volume of the movable furniture in home
version=1.0
license=GNU GPL
provider=(C) Copyrights 2008 eTeks
applicationMinimumVersion=1.5
javaMinimumVersion=1.5

Creating the plug-in JAR

The plug-in JAR contains the class files created from the compilation of the VolumePlugin.java file, and the ApplicationPlugin.properties file. As Eclipse compiles a Java file as soon as you save it, you just have to choose File > Export... from the menu and select Java > JAR file in the Export dialog that will be displayed. In the Jar Export wizard that appears as shown in figure 6, select the project check box and enter the path of a JAR file placed in the Sweet Home 3D plug-ins folder. This appropriate folder depends on your system as follows:

• under Windows Vista / 7, this folder is C:\Users\user\AppData\Roaming\eTeks\Sweet Home 3D\plugins,
• under Windows XP and previous versions of Windows, this folder is C:\Documents and Settings\user\Application Data\eTeks\Sweet Home 3D\plugins,
• under Mac OS X, it's the subfolder Library/Application Support/eTeks/Sweet Home 3D/plugins of your user folder,
• under Linux and other Unix, it's the subfolder .eteks/sweethome3d/plugins of your user folder.

Figure 6. Exporting to a JAR file

Testing the plug-in

The plug-in you developed will run in Sweet Home 3D, either with the Java Web Start version, the installers version, or the SweetHome3D-2.6.jar you downloaded previously. As the latest one is an executable JAR, you can run it by double-clicking on it or with the following command:

java -jar /path/to/SweetHome3D-2.6.jar

As long as you're debugging, you will probably prefer to run Sweet Home 3D with this command, to be able to read in the console the stack trace of the exceptions thrown during the execution of your plug-in.

Once Sweet Home 3D is launched, you'll see the new menu and its item appear as shown in figure 7:

Figure 7. Plug-in menu

If you choose the new menu item for the home example created in user's guide, you'll get the following result:

Figure 8. Plug-in in action

Deploying the plug-in

Once ready, your plug-in may be deployed on the computer of other Sweet Home 3D users by simply copying it in their plug-ins folder. From version 1.6, a plug-in file may be also installed in the plug-ins folder of Sweet Home 3D by double-clicking on it, if its extension is SH3P (simply change the file extension from .zip to .sh3p). This may not work under Linux.
To stop using a plug-in, remove its file from the plug-ins folder and relaunch Sweet Home 3D.

Installing/uninstalling a plug-in by copying it in Sweet Home 3D plug-ins folder isn't very user-friendly. This will be probably improved In future versions of Sweet Home 3D with a pane dedicated to the management of plug-ins.

Going further

The programming of the first plug-in showed you the big picture. Here's some additional information that will help you to go further.

Sweet Home 3D API - Javadoc

The most useful documentation to develop a new plug-in is the Sweet Home 3D API (Application Programming Interface), generated with javadoc tool.
Use only the classes of com.eteks.sweethome3d.plugin, com.eteks.sweethome3d.model and com.eteks.sweethome3d.tools packages in your plug-in if you want it to be upward compatible with future versions of Sweet Home 3D. This will be largely enough to program any plug-in that works on the home data available in Sweet Home 3D.
The packages matching the other layers of the program are included in the Javadoc for information purpose only. Don't rely on their API, as it may still change in the future with no guarantee of upward compatibility (anyway you'll see no reference to a class of com.eteks.sweethome3d.viewcontroller, com.eteks.sweethome3d.swing or com.eteks.sweethome3d.io packages in the aforementioned packages).

Model classes architecture

Sweet Home 3D is based on a MVC (Model View Controller) architecture, so understanding how is organized its Model layer is essential. The figure 9 (available also at PDF format) presents almost all the classes and interfaces available in the version 1.5 of com.eteks.sweethome3d.model package that matches this Model layer.

Figure 9. UML diagram of com.eteks.sweethome3d.model package
(click on a class to view its javadoc)

The central class in the Model layer is the HomeApplication class (10), the abstract super class of SweetHome3D application main class. The instance of this class gives access to the Home instances (7) currently edited, and to the UserPreferences object (11) that stores the length unit in use (12), the furniture catalog (14) and the textures catalog (15) from which the user chooses pieces of furniture (17) and textures (18).
A Home instance (7) stores all the objects the user created in the home plan:

• the list of HomePieceOfFurniture objects (13) which implement the interface PieceOfFurniture (16),
• the collection of Wall objects (9),
• the list of Room objects (5),
• the collection of DimensionLine objects (2),
• the collection of Label objects (3).

These objects implement the Selectable interface (1) as well as the ObserverCamera object (4), that stores the location of the camera in the Virtual visitor mode. All the external information managed by Model objects, like the icon and the 3D model of a piece of furniture (16), or the image of a texture (20) is accessed through the Content interface (19), implemented by the URLContent class and other classes of the com.eteks.sweethome3d.tools package.

This UML diagram should help you understand which classes are available in the Sweet Home 3D model and how you can access to them, but you'll probably notice that no constructors and no mutators (or setters if you prefer) are cited in it. It's just by lack of room but you can use them with no problem in a plug-in class. Note also that any modification of an existing object of the model will be notified to the displayed components either with PropertyChangeEvents, with CollectionEvents (8) or with SelectionEvents (6), thus allowing all changes to be reflected immediately on screen.

Sweet Home 3D model isn't thread safe for performance reasons. All modifications of an object belonging to the model should be done in the Event Dispatch Thread.

Plug-in classes architecture

The architecture of plug-in classes is much more simple to understand than the Model layer's one. The com.eteks.sweethome3d.plugin package contains only three classes among which you're supposed to use only Plugin and PluginAction classes, as shown in figure 10 (also available at PDF format).

Figure 10. UML diagram of com.eteks.sweethome3d.plugin package
(click on a class to view its javadoc)

A PluginManager instance (1) is created at application launch and searchs the plug-ins installed in user's plug-ins folder. Each time a new home is edited, this manager instanciates and configures a Plugin object (3) for each plug-in found at launch time. Then, it calls the getActions method to retrieve all the actions (4) that will be added as menu items and/or tool bar buttons in the home window. Each action is an instance of PluginAction, which looks like Action class, with its execute method and its modifiable properties (2).

Note that the Plugin class gives you access to an UndoableEditSupport instance through its getUndoableEditSupport method. As soon as you modify a home or its objects (furniture, walls...) in the execute method of a PluginAction instance, you should also post an UndoableEdit object to the undoable edit support returned by getUndoableEditSupport method, otherwise users won't be able to undo/redo correctly the changes you made.

Localization

If you plan to develop a plug-in for Sweet Home 3D users community, try to localize the strings it displays either in actions name and menu or in dialogs you'll create (or at least prepare its localization). Two constructors of the PluginAction class will help you to organize the translation of actions properties with .properties files, and if you need to translate other strings in your plug-in (like the one in the dialog shown by the tested plug-in) reuse these .properties files with ResourceBundle Java class.
If you prefer to limit the number of properties files, you might even write the values of the action properties and other strings in the ApplicationPlugin.properties description file of your plug-in.

If you want an example that uses this architecture, download the Export to SH3F plug-in available at http://sweethome3d.com/plugins/ExportToSH3F-1.0.sh3p, and unzip it (this plug-in file contains also the source code of the plug-in).
As described in Help forum, this plug-in creates a SH3F file that contains all the furniture you imported in the furniture catalog of Sweet Home 3D.

Contributing plug-ins

You can post the plug-ins you programmed in Plug-ins Contributions Tracking System to share them with Sweet Home 3D users community.
Many features can be added to Sweet Home 3D thanks to plug-ins, from importers to exporters, but also plug-ins able to modify the data of a home like the Home Rotator Plug-in developed by Michel Mbem.

 

Last update : August 24, 2010

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