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GEF/Contributor Guide


Prepare your development environment

Download IDE

To develop against GEF or GEF4 we recommend to download an 'Eclipse IDE for Eclipse Committers' for Luna SR2 or Mars and to prepare it as outlined in the following sections.

Specify Execution Environment for J2SE-1.7 (and optionally J2SE-1.8)

All GEF4 bundles with JavaFX dependencies are compatible to JavaFX 2.2 (or higher) and thus specify a J2SE-1.7 BREE (bundle required execution environment). In order to resolve the JavaFX dependencies, you will have to ensure that a Java 7 JVM, which provides JavaFX 2.2 (e.g. an Oracle JVM), is used to resolve the J2SE-1.7 execution environment. This is important, because the e(fx)clipse JavaFX-PDE integration (which we needed to resolve JavaFX dependencies; JavaFX will not be visible on the OSGi classpath by default) will only be able to resolve JavaFX dependencies (of a bundle with J2SE-1.7 BREE), if the respective jfxrt.jar (which bundles the JavaFX 2.2 classes) can be located in the installation location of the JVM that is used to resolve the J2SE-1.7 execution environment.

In order to ensure that this is the case, go to "Windows -> Preferences -> Java -> Installed JREs" and ensure a compatible Java SE 7, which provides JavaFX 2.2, is installed. Eclipse will automatically detect the jar libraries provided by the JVM and add it to the registration. Note that the jfxrt.jar will actually not be added to the JVM definition, and that it does not have to be manually added to it either, because the contained JavaFX classes will be added to the classpath of all bundles with javafx.* package imports (and J2SE-1.7 BREE) by the e(fx)clipse JavaFX-PDE-integration automatically (see below). To ensure that the respective JVM is used to resolve the J2SE-1.7 execution environment, go to "Windows -> Preferences -> Java -> Installed JREs -> Execution Environments" and select it there.

While all GEF4 bundles are compatible with JavaFX 2.2 and Java 7, you may decide to use JavaFX 8.0 and Java 8 in your client code. In this case, you will have to ensure that in addition to the Java SE 7 JVM, a compatible Java SE 8 JVM, which bundles JavaFX 8.0, is registered as installed JRE and specified to resolve the J2SE-1.8 execution environment. Note that here, the jfxrt.jar will be automatically added to the JRE definition when registering the Java 8 JVM. However, the jfxswt.jar will not be added (it contains the javax.embed.swt.* classes), and it also does not have to be manually added to the JVM definition as well, as it will be added to the classpath of all bundles that have JavaFX dependencies (and J2SE-1.8 BREE) by the e(fx)clipse JavaFX-PDE-integration.

Install e(fx)clipse JavaFX-PDE-integration

When developing against those GEF4 components that are dependent on JavaFX, it is required to install the e(fx)clipse JavaFX-PDE-integration (org.eclipse.fx.ide.pde.feature) version 2.0.0 into your Eclipse development environment to properly resolve JavaFX dependencies within your workspace. It is needed because JavaFX is not included on any of the default OSGi classpaths, so JavaFX dependencies of the GEF4 bundles will otherwise not be properly resolved (unless you manually add the respective jars to your classpath, which is not recommended).

You can up to now install the required JavaFX-PDE-integration version 2.0.0 from the e(fx)clipse Mars M7 preview update-site or the e(fx)clipse IDE nightly update-site, where it is provided as the e(fx)clipse - IDE - PDE feature (org.eclipse.fx.ide.pde.feature.feature.group). e(fx)clipse JavaFX-PDE-integration integration will work with a Luna as well as a Mars development environment.

Having installed the e(fx)clipse JavaFX-PDE-integration in your development environment, it will automatically add additional classpath entries for those bundles that contain classes with javafx.* imports. However, it requires that a JVM, which provides JavaFX, is registered as an installed JRE and is used to resolve the execution environment matching that of the respective bundle (as outlined above).

Please note that from Mars M7 onwards (or more precisely beginning with gef4-master build #2316, 2015-04-25), GEF4 will require e(fx)clipse 2.0.0 explicitly and will not work with earlier versions of e(fx)clipse. This is because GEF4 bundles no longer specify javafx.* package imports, and JavaFX dependencies will thus not be resolved with earlier e(fx)clipse versions.

Install API Tools Execution Environment Descriptions

All production code GEF and GEF4 bundles (i.e. excluding doc and test bundles) are configured to have API tooling enabled. The API checks, which are configured on a project-specific basis, include checks for references that do not exist in the specified execution environment (as all GEF4 API is still provisional, this is the only aspect it is used for in GEF4). As API tooling requires execution environment descriptions to perform the respective checks, these should be installed (you will see warnings for missing execution environment descriptions otherwise otherwise), as outline under Execution_Environments#Installing Execution Environment Descriptions.

Install Oomph Version Management Tool

In addition to the API Tools, for the GEF and GEF4 bundles we make use of the Oomph Version Management tool to ensure service revision increments are performed as needed (the tool will provide indications of which bundle and feature versions to update when performing changes on the service level). Please install it from the Oomph update site.

Install Maven Integration (m2e)

In case you want to run a headless build locally in your workspace, you should install the Maven Integration (m2e), as GEF and GEF4 builds are based on Maven/Tycho.

Obtaining Source Code

The complete source code of the GEF project (with the exception of the web-site) is hosted at http://git.eclipse.org:

Check out the code (Committers and Contributors) using EGit

To check out the code within your local workspace, perform the following steps:

  1. Copy the URI of the repository you want to clone (following the links provided above, the URIs are listed under the Clone section). Note that committers will have to use the ssh protocol URI, whereas consumers and contributors are encouraged to use the git protocol URI.
  2. Clone the Git repository
    1. Open the Git Repository Exploring Perspective (provided by EGit) within Eclipse, and from the toolbar of the Git Repositories Browser view select to Clone a Git Repository and add the clone to this view.
    2. If the repository URL was copied to clipboard before, the upcoming Clone Git Repository dialog should already provide the necessary entries for URI, Host, and Repository path, so you may simple forward by pressing Next >.
    3. Select the branches you want to clone from remote. The master branch is the one used for the current development stream. Development in maintenance releases is performed in respective maintenance branches. After having selected all branches of interest, press Next > to continue.
    4. Choose a local directory to store the cloned repository (the default will be located under your home directory) and select the Initial branch to check out.
  3. Checkout the projects
    1. Right-click the Working directory entry, located under the org.eclipse.gef (resp. org.eclipse.gef4) repository within the Git Repositories Browser view and from the context menu select to Import Projects....
    2. In the upcoming Import Projects from Git Repository dialog, select to Import existing projects and press Next >.
    3. Choose the projects you want to import (by default all are selected) and press Finish to conclude.

Setting up the workspace

Set up the Target Platform

A target definition file is provided by the org.eclipse.gef.target (as well as the org.eclipse.gef4.target) project. To specify the target platform, simply open the respective target definition (e.g. MARS.target) within the Target Editor, let is fully resolve (i.e. wait until the Resolving Target Definition background task has finished and the installable units are listed under the respective Locations), then choose to "Set as Target Platform).

In case the target editor does not properly resolve the target definition, an invalid target cache may be the cause. In such cases, opening the target definition file with a text editor and incrementing the sequence number manually, will invalidate the cache when reopening it with the target editor again. After the cache has been invalidated, the sequence number can be restored.

Set up API Tooling

GEF (proper) uses PDE API tooling to guarantee proper handling of version numbering as well as API compatibility, so without definition of an API baseline you will see compile problems after having checked out the code. API-baselines are provided by the org.eclipse.gef.baseline project. You may define them by going to Preferences -> Plug-in Development -> API Baselines, then choose to select "Add Baseline..." and point to the plugins sub-folder of an API baseline located in the baselines project (note that the dialog browses the file system instead of the workspace, so you will have to point into the respective folder in your local Git repository).

Adjust Java and Plug-in Compiler Preferences (Discouraged access errors/warnings caused by provisional API)

As all GEF4 API is currently released as provisional, all GEF4 API package exports are guarded with the x-internal directive (see Marking stable, provisional, and non-API for details). Dependent on your workspace settings, this may lead to a lot of Java compiler warnings/errors, which result from discouraged API access. You may want to adjust your workspace-wide Java and Plug-in compiler preferences to get rid of them.

  • Go to "Preferences -> Java -> Compiler -> Warnings/Errors", then select the respective severity ("Warning", "Ignore") for the "Deprecated and restricted API -> Discouraged reference (access rule)" entry.
  • Go to "Preferences -> Plug-in Development -> Compilers", then select the respective severity ("Warning", "Ignore") for the "References ->References to discouraged classes" entry.

Coding conventions

Marking stable, provisional, and non-API

According to the Eclipse Provisional API Guidelines and the Naming Conventions, the following conventions are followed to differentiate between stable, provisional, and non-API (see also bug #438900):

  • Stable API: All stable API packages do not contain 'internal' in their package names and are exposed via 'Export-Package' in the plug-in MANIFEST.MF, unguarded by 'x-friends' or 'x-internal' directives.
  • Provisional API: All provisional API packages do not contain 'internal' in their package names and are exposed via 'Export-Package' in the plug-in MANIFEST.MF, guarded by an 'x-internal' directive.
  • Non-API: All non-API packages contain 'internal' in their package names , e.g. org.eclipse.gef4.internal.geometry.utils. These packages should only be exposed via 'Expose-Package' in the plug-in MANIFEST.MF, if this is guarded by an 'x-friends' directive.

Please note that for the Mars release, all of the GEF4 API will still be provisional (i.e. all API packages are provisional API packages). This will cause a lot of warnings/errors in your workspace, unless you follow the guidance given Adjust Java and Plug-in Compiler Preferences.

Starting an (Eclipse Application) runtime, resolving JavaFX runtime dependencies

When launching an Eclipse runtime that contains GEF4 bundles with JavaFX dependencies, the e(fx)clipse org.eclipse.fx.javafx bundle org.eclipse.fx.osgi fragment have to be included in the runtime configuration (they are already included in the GEF4 target). Also, -Dosgi.framework.extensions=org.eclipse.fx.osgi has to be added to the VM arguments in the runtime configuration's Arguments tab. If you are having problems with the e(fx)clipse runtime resolution you can add -Defxclipse.osgi.hook.debug=true to the VM arguments to enable debugging output. We noticed that e(fx)clipse does not seem to work correctly when running SWT on GTK 3 on older GTK versions. In this case, you can enforce SWT to use GTK 2 by setting the environment variable SWT_GTK3=0 or adding --launcher.GTK_version 2 to your eclipse.ini.

Running a headless build locally

GEF (as well as GEF4) uses a Maven/Tycho-based build infrastructure. With the Maven Integration installed, the headless build that is executed by the gef-master and gef4-master Hudson build jobs can also be executed in the local workspace. Make sure you have checked out all projects of a respective git repository (GEF and GEF4 are independent). Then easily run the build by right-clicking the pom.xml file located within the org.eclipse.gef.releng or org.eclipse.gef4.releng project respectively, and selecting 'Run As -> Maven build...'.

In the configuration wizard you have to specify the goals ("clean verify") and the profiles ("Mars.target") for the build. Note that without setting the target profile the build will not run successfully.


You should select a Java-8 JVM in the "JRE" tab, to ensure that you run with a configuration comparable to that of the CI-server (hudson.eclipse.org). Otherwise your local build might behave differently compared to the continuous CI build. For example, javadoc errors are will not lead to a build failure when running with Java-7, while the build will fail if using Java-8 (as done in the CI server build jobs).


As a result of the build, an update-site will be created in the target sub-folder of the org.eclipse.gef.repository respectively org.eclipse.gef4.repository project. Please note that you need to have a JDK installed (and used by Tycho) rather than a JRE, because the Tycho builds rely on the availability of a javadoc executable for the generation of API documentation in the doc bundles.

Creating a Contribution

You can contribute to GEF either by producing a patch, or via GitHub. In either case, your contribution should be related to a corresponding Bugzilla entry (you can search for existing bugs, or file a new one).

We can easily consume your contribution (compare Contributing a Patch), if:

If your contribution does not exceed the contribution limit (currently 1000 LOC) this will allow us to simply consume it. If your contribution was not developed from scratch or contains content from other authors, please indicate this on the related Bugzilla entry. As in cases where the contribution exceeds the limit, we will have to open a contribution questionnaire (and may have to ask for additional information via the related Bugzilla) to handle such cases (see Eclipse Legal Process).

Produce a Patch

To contribute a patch, create a branch in your local Git repository for working on your changes, e.g. a fix for bug 321775:

git checkout -b fix-321775

Test, fix, and commit until you're done. Run the Maven build to make sure everything works. Then create a patch including all commits on your branch against master, like this:

git format-patch master --stdout > fix-321775.patch

Finally, attach your patch to the corresponding bug, in this case bug 321775.

Fork via GitHub

To contribute via GitHub, fork the GitHub repository you'd like to contribute to from https://github.com/eclipse (i.e. the GEF or GEF4. Commit, test, and push your contribution to your fork. When you're done, add a link to the Github commit you want to contribute to a comment in the corresponding bugzilla entry, e.g.:


For details, see Development_Resources/Handling_Git_Contributions.

Commiting code


When committing code, the following format should be used:

 '[' ( <bug-id> | 'NONE' ) ']' <one-line-summary-or-single-line-commit-message> (  '(' 'CQ' <cq-number> ')' )?
 ( <wrapped-detailed-commit-message> )?


 [355997] Add support for calculating bezier curve intersections. (CQ 5976)
 [NONE] Update target definition to Eclipse SDK 4.2.0.I20120222-0915.

Furthermore, the following constraints should be regarded:

  • The bug id of the bug, which is used to track the changes should always be provided, or NONE to indicate that the changes are made without any directly related bug.
  • The commit message should be specified using present tense, declaring why the changes were made.
  • If a commit message is longer than one short line, it should be formatted to have a short, one-line summary, a blank line, and a wrapped longer description (see [1].
  • If the committer is not the contributor of the changes, the Git author field should be used to specify the full name of the contributor (see Development_Resources/Handling_Git_Contributions). In case the changes were approved by means of a contribution questionnaire, the CQ number should be specified in round brackets after the one line summary.

Handling Bugs

When working with bugzillas, the following guidelines should be regarded.

Classifying Bugs

For GEF4, components are pretty fine-grained, so selection of a bugzilla component is usually sufficient to identify the part of the API that is concerned.

For Draw2d/GEF (MVC) 3.x this may not be sufficient. We thus use categories for this issue, which will be stated as a [<category_name>] prefix within the bugzilla's summary. The list of currently used categories is:

  • General
    • [TVT] - Translation Verification Tests
  • Draw2d
    • [GraphLayout]
    • [Geometry]
    • [Text]
  • GEF
    • [Command]
    • [DnD]
    • [EditPart]
    • [EditPolicy]
    • [Palette]
    • [Print]
    • [Tool]

Resolving Policy

When resolving bugzillas, it should be stated how the bug is verified. Preferably this is a JUnit test. Alternatively, the bugzilla will say that the defect can be reproduced in the Logic example and you can demonstrate the fix working in the logic example (or other examples using GEF). If the bug is trivial or obvious and does not require a test, we can just state this in the Bugzilla too.