Java org eclipse swt

SWT/Beginners

This page is useful for beginners who would like to develop SWT. All of the information here is cross-platform, general knowledge. Please note the page is under construction.

Contents

Getting started

Please note this article is still being written and is not final.

Prerequisites

This guide assumes basic knowledge of Java, git, and general Eclipse development. Nothing in this guide covers any platform specific development knowledge — for this documentation please see further reading.

Eclipse plugins

Download and install SWT tools. Other than that, you may find the following plugins useful (not mandatory for SWT development):

Download/import sources and binaries

SWT works using two code repositories:

1. The source code, which contains Java and JNI source code for all widgets. This where 99% of all changes belong.
2. The binaries, which contain the platform specific library objects. These allow the Java source code to call the operating system’s toolkit.

Start by cloning both of git repos above. From the sources repo, import the following projects:

• org.eclipse.swt
• org.eclipse.swt.snippets
• org.eclipse.swt.examples
• org.eclipse.swt.tests

This will add the SWT source code, snippets, example applications, and test cases to your workspace.

Now import the binaries project. This will depend on your platform and architecture of your machine — choose accordingly. For example, on 64-bit Linux GTK I would be importing:

Modify the .classpath

After importing the SWT sources and binaries, you will see lots of errors. This is normal, as the SWT sources have not yet been linked to the binary matching your platform and can be resolved by modifying the .classpath file.

1. Open the «Navigator» view (not Package Explorer).
2. In the org.eclipse.swt folder you will see a collection of .classpath files corresponding to various platforms (GTK, Win32, Cocoa, etc.).
3. Copy the desired .classpath_* file.
4. Paste it in the same folder, except rename it to .classpath
5. Go to Project -> Clean, and clean the org.eclipse.swt project and the project matching your platform’s binaries.

Gerrit configuration

Eclipse/SWT uses a code review tool called Gerrit. It’s quite easy to configure if you have the EGit plugin installed.

1. Open the «Git Repositories» view
2. Expand the «org.eclipse.swt» item (assuming you have the org.eclipse.platform.swt project in your EGit repositories view)
3. Expand the «Remotes» item
4. Right click the «origin» item, and select «Gerrit configuration»
5. Fill in your information from Gerrit (username).

For more information about using Gerrit, see the more comprehensive SWT Gerrit page.

Writing a patch

Commit messages

The goal of a commit message is to clarify any ambiguities for the reviewer(s) and any developer who may read the message later. It should be comprehensive and avoid skipping information that was exchanged verbally or via chat. Do not write empty commit messages.

Configuration

All commit messages must be signed off by your first and last name. Please configure your git settings to reflect as such. Additionally when committing, ensure that EGit has generated a change ID, which goes at the bottom of the commit message. It can be generated by clicking one of the buttons at the top right area of the «Commit window».

Structure

An SWT commit message should follow this format:

Bug ID : The bug description should be the same as that in Bugzilla (maybe slightly trimmed)

Change-ID: xxxxxxxxxxx (auto generated)

Signed-off-by: Firstname Lastname (auto generated)

• Test strategy: steps outlining how to reproduce the issue. Link to a snippet, steps to follow, or a pointer to where to find such instructions.
• JUnit tests performed: you should mention if you ran the relevant SWT JUnit tests. For example «Ran AllNonBrowserTests on Wayland» and related results. If they don’t need to be ran, mention why there is no need to run the tests.

How SWT interacts with native code: native and non-native changes

Before writing an SWT patch, it’s important to have a crash course on how SWT interacts with native code. Earlier we mentioned the SWT sources (org.eclipse.swt) and the binaries (such as org.eclipse.swt.gtk.linux.x86_64, as an example). The binaries project in your workspace contains library objects, such as .SO files on Linux, .dll on Windows, etc. Modifying the .classpath allows the SWT sources project to load these library objects and run the SWT from your workspace.

How does this work? Well the SWT sources use Java code to interact with native libraries through JNI. This is done by adding boilerplate JNI function signatures in files like OS.java, for example. SWT Tools then generates the JNI C code which links the Java JNI functions to the actual native calls. The generated code and the JNI function signatures (as well any other Java code) are then merged as one change under the org.eclipse.swt project. This type of patch is considered a native change.

After such a change is merged, the JNI C code does not need to be generated again. Changes that do not modify the JNI code are considered non-native changes, as no additional changes beyond «pure» Java code needs to be made. However SWT does not load every function possible from native libraries, only those that are actually called/needed by SWT. It is not uncommon that a bug fix will require a new native function to be available for use in SWT, in which case its method signature needs to be added to SWT. And thus the process repeats itself.

Writing a non-native change

Non-native changes require no special action — submit the patch by right clicking the org.eclipse.swt project in the «Git repositories» view and select «Push to Gerrit».

Writing a native change

Native changes are trickier because they require you to rebuild the native bindings. The aforementioned library objects now have to be generated manually in order for SWT to run with local changes. While the library objects do not need to be submitted in your Gerrit change, they do have to be built for testing purposes (otherwise SWT won’t run and will complain about library link errors). For instructions on building the library objects, check for a README file in binaries project folder for your platform.

After testing your patch, follow the steps below to submit a native change:

1. Prepare all Java code, including function signatures in OS.java
2. Go to Project -> Clean. Clean the SWT sources and binaries projects. Make sure «Build Automatically» is checked in the Project menu.
3. After cleaning, some *.c and *.h files will show up in the Git staging area. Usually these are files like os.c, os_stats.c, os_stats.h, etc.
4. Commit these, as well as the Java files (or any other changes relating to your patch) Submit the patch by right clicking the org.eclipse.swt project in the «Git repositories» view and select «Push to Gerrit».

Further reading

Outside of the basics contained in this tutorial, there is additional documentation that provides further insight into development on each platform.

Additionally, there are some workflow tasks which are platform agnostic. You can find these at the SWT workflow documentation.

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Developing SWT applications using Eclipse

While SWT is integrated as part of the Eclipse plug-in API, for standalone application development it is best to develop against the SWT standalone download. This document will help you get set up.

First, download the .zip of SWT for your platform from the SWT homepage.

The SWT .zip file can then be imported into your workspace. In the File menu, choose Import and select the Existing Projects Into Workspace wizard. (In newer versions of eclipse, you can find Existing Projects Into Workspace in the General category).

Direct the wizard to the location where you downloaded the .zip file. This will create a project called org.eclipse.swt in your workspace.

Your Java projects can then add the SWT project as a dependency. Open the properties dialog of your Java project, and on the Java Build Path page, include the org.eclipse.swt project.

With the SWT project as a dependency, you can now benefit from Eclipse features such as the Javadoc view and code assist.

Now you can run any main class in your project by selecting the class and then selecting Run > Run As > Java Application

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SWT: The Standard Widget Toolkit

SWT is an open source widget toolkit for Java designed to provide efficient, portable access to the user-interface facilities of the operating systems on which it is implemented.

Welcome

Welcome to SWT! You may have come to this page looking for snippets (little code examples) or examples (big code examples like ControlExample); widget snapshots or documentation. Or maybe you want to request a feature, report a bug, or ask a question. Whatever the reason, you will find many resources here. Enjoy!

Downloads

Latest Release
Download page
For links to latest released version of the SWT Binary and Source for all platforms, select the entry for the latest official release and then click on SWT Binary and Source from the menu on the left.

Stable Builds
Download page
For links to stable milestone builds of the SWT Binary and Source for all platforms, select the entry for the latest milestone build and then click on SWT Binary and Source from the menu on the left.

Integration Builds
Download page
For links to daily Integration builds of SWT Binary and Source for all platforms, select a current integration build (select entry starting with I in the Integration builds) and then click on SWT Binary and Source from the menu on the left.

Maven Artifacts
SWT fragments for all the supported platforms are published to Maven Central for every release. The table below contains the links to the artifacts.

Windows

Mac/Cocoa

Linux/GTK (x86 64-bit)

Linux/GTK (ppcle 64-bit)

How to contribute

Articles

• How to develop SWT applications in Eclipse
• How to run the ControlExample and other SWT examples
• How to deploy SWT applications on Mac OS X
• How to generate the SWT JNI Code
• How to generate the SWT JNI Code for Cocoa
• Using OpenGL in SWT Applications
• Many more articles about SWT on Eclipse Corner at eclipse.org
• Full list of articles and documentation

Resources

• SWT wiki
• Widget screenshots with links to documentation
• Snippets, helpful little code examples
• Examples, helpful big code examples
• The SWT FAQ answers many common questions
• Tools and Plug-ins for SWT developers
• Online Javadoc
• Books and additional documentation
• Test Plan for SWT
• SWT Community Page
• SWTBot, UI/functional testing tool for SWT and Eclipse based applications.
• Eclipse/SWT Accessibility wiki

Contact Us

SWT development is discussed and tracked in the Eclipse bugzilla under the Platform/SWT component. You can subscribe to the new bug inbox by watching platform-swt-inbox@eclipse.org from your bugzilla email preferences.

If you are modifying or porting SWT and have questions, try the SWT developer mailing list [archive, search].

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