Eclipse plugin development: how to open two parallel editors programmatically

5 minute read


Depends on the Eclipse version on which your plugin is developed, the methods of opening two editors in an eclipse plugin programmatically are quite different due to the evolvement of the Eclipse SWT. I tried many solutions provided by others online, but none of them work perfectly on my environment. Finally, I reused some source code of the “New Editor (Side by side)” feature of Eclipse fulfill the requirement for my own plug-in.

My Requirement

My plugin is for trace analysis of two interacting software. So I need two traces to be shown in the editors at the same time for easy access and synchronization. A side by side editors is what I am looking for.

Solution Option 1: Programmatically split an editor area to show two editors side by side

This solution only works for Eclipse 4. However, my plugin project has a long history and is still using eclipse 3. It would be a great amount of effort to upgrade my whole plugin project, which is a big one, to Eclipse 4 in order to adapt to this solution.

Solution Option 2: Splits an editor by inserting one editor into another

This option can split the editor perfectly, however, I failed to get the parallel editors back, but only the active one. This limits my requirement to analysis both files opened in the parallel editors later on.

Solution Option 3: use the content merge extension

Another optional solution is to use Merge extension. Merge extension allow user to view two different files side by side and compare the difference of them. However, this is way more complicated than I need. Merge extension provides many features which I don’t need in the solution and they make the implementation for my needed feature difficult.

Selected Solution: extension bundle for split-editors

This is an official feature released by Eclipse. The source code for this feature can be downloaded online. My solution used the interfaces of this solution. This work perfectly in my environment.

  • The editor area split handler
public class OpenDualEditorsHandler extends AbstractHandler {
	EModelService ms;
	EPartService ps;
	WorkbenchPage page;

    public Object execute(ExecutionEvent event) throws ExecutionException {
		IEditorPart editorPart = HandlerUtil.getActiveEditor(event);
		if (editorPart == null) {
			Throwable throwable = new Throwable("No active editor");
			BigFileApplication.showErrorDialog("No active editor", "Please open one file first", throwable);
			return null;

		MPart container = (MPart) editorPart.getSite().getService(MPart.class);
		MElementContainer m = container.getParent();
		if (m instanceof PartSashContainerImpl) {
			Throwable throwable = new Throwable("The active file is already opened in one of the parallel editors");
			BigFileApplication.showErrorDialog("TThe active file is already opened in one of the parallel editors",
					"The active file is already opened in one of the parallel editors", throwable);
			return null;
		IFile file = getPathOfSelectedFile(event);

		IEditorDescriptor desc = PlatformUI.getWorkbench().getEditorRegistry().getDefaultEditor(file.getName());
		try {
			IFileUtils fileUtil = RegistryUtils.getFileUtils();
			File f = BfvFileUtils.convertFileIFile(file);
			f = fileUtil.convertFileToBlankFile(f);
			IFile convertedFile = ResourcesPlugin.getWorkspace().getRoot().getFileForLocation(Path.fromOSString(f.getAbsolutePath()));
			convertedFile.getProject().refreshLocal(IResource.DEPTH_INFINITE, null);
			if (!convertedFile.exists()) {

			IEditorPart containerEditor = HandlerUtil.getActiveEditorChecked(event);
			IWorkbenchWindow window = HandlerUtil.getActiveWorkbenchWindowChecked(event);
			ms = window.getService(EModelService.class);
			ps = window.getService(EPartService.class);
			page = (WorkbenchPage) window.getActivePage();
			IEditorPart editorToInsert = page.openEditor(new FileEditorInput(convertedFile), desc.getId());
			splitEditor(0.5f, 3, editorToInsert, containerEditor, new FileEditorInput(convertedFile));
			window.getShell().layout(true, true);

		} catch (CoreException e) {

		return null;

    private void createEmptyFile(IFile file) {
		byte[] emptyBytes = "".getBytes();
		InputStream source = new ByteArrayInputStream(emptyBytes);
		try {
				file.create(source, false, null);
		} catch (CoreException e) {
			try {
			} catch (IOException e) {
				// Don't care

	private void splitEditor(float ratio, int where, IEditorPart editorToInsert, IEditorPart containerEditor,
			FileEditorInput newEditorInput) {
		MPart container = (MPart) containerEditor.getSite().getService(MPart.class);
		if (container == null) {

		MPart toInsert = (MPart) editorToInsert.getSite().getService(MPart.class);
		if (toInsert == null) {

		MPartStack stackContainer = getStackFor(container);
		MElementContainer<MUIElement> parent = container.getParent();
		int index = parent.getChildren().indexOf(container);
		MStackElement stackSelElement = stackContainer.getChildren().get(index);

		MPartSashContainer psc = ms.createModelElement(MPartSashContainer.class);
		psc.getChildren().add((MPartSashContainerElement) stackSelElement);
		psc.setSelectedElement((MPartSashContainerElement) stackSelElement);

		MCompositePart compPart = ms.createModelElement(MCompositePart.class);
		compPart.setLabel("dual-trace:" + containerEditor.getTitle() + " and " + editorToInsert.getTitle());

		parent.getChildren().add(index, compPart);


	private MPartStack getStackFor(MPart part) {
		MUIElement presentationElement = part.getCurSharedRef() == null ? part : part.getCurSharedRef();
		MUIElement parent = presentationElement.getParent();
		while (parent != null && !(parent instanceof MPartStack))
			parent = parent.getParent();

		return (MPartStack) parent;

	private IFile getPathOfSelectedFile(ExecutionEvent event) {
		IWorkbenchWindow window = PlatformUI.getWorkbench().getActiveWorkbenchWindow();
		if (window != null) {
			window = HandlerUtil.getActiveWorkbenchWindow(event);
			IStructuredSelection selection = (IStructuredSelection) window.getSelectionService().getSelection();
			Object firstElement = selection.getFirstElement();
			if (firstElement instanceof IFile) {
				return (IFile) firstElement;
			if (firstElement instanceof IFolder) {
				IFolder folder = (IFolder) firstElement;
				AtlantisBinaryFormat binaryFormat = new AtlantisBinaryFormat(
				// arbitrary, just any file in the binary set is needed
				return AtlantisFileUtils.convertFileIFile(binaryFormat.getExecVtableFile());
		return null;
  • Get the active parallel editors programmatically

        IEditorPart editorPart = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage().getActiveEditor();
		MPart container = (MPart) editorPart.getSite().getService(MPart.class);
		MElementContainer m = container.getParent();
		if (!(m instanceof PartSashContainerImpl)) {
			Throwable throwable = new Throwable("This is not a dual-trace");
			BigFileApplication.showErrorDialog("This is not a dual-trace!", "Open a dual-trace First", throwable);

		MPart editorPart1 = (MPart) m.getChildren().get(0);
		MPart editorPart2 = (MPart) m.getChildren().get(1);

The parallel editors

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