Simple example of a dummy e4 editor addition, which is contributed via a Model Fragment

examples/org.eclipse.e4.ui.examples.e4editor/.classpath

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+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-21"/>
+	<classpathentry kind="con" path="org.eclipse.pde.core.requiredPlugins"/>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

examples/org.eclipse.e4.ui.examples.e4editor/.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>org.eclipse.e4.ui.examples.e4editor</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.pde.ManifestBuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.pde.SchemaBuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.pde.PluginNature</nature>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

examples/org.eclipse.e4.ui.examples.e4editor/.settings/org.eclipse.core.resources.prefs

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+eclipse.preferences.version=1
+encoding/<project>=UTF-8

examples/org.eclipse.e4.ui.examples.e4editor/.settings/org.eclipse.jdt.core.prefs

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+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=21
+org.eclipse.jdt.core.compiler.compliance=21
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enablePreviewFeatures=disabled
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.problem.reportPreviewFeatures=warning
+org.eclipse.jdt.core.compiler.release=enabled
+org.eclipse.jdt.core.compiler.source=21

examples/org.eclipse.e4.ui.examples.e4editor/META-INF/MANIFEST.MF

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+Manifest-Version: 1.0
+Bundle-ManifestVersion: 2
+Bundle-Name: DummyEditor
+Bundle-SymbolicName: org.eclipse.e4.ui.examples.e4editor;singleton:=true
+Bundle-Version: 1.0.0.qualifier
+Require-Bundle: org.eclipse.swt,
+ org.eclipse.jface,
+ org.eclipse.e4.core.contexts;bundle-version="1.13.0",
+ org.eclipse.e4.core.di;bundle-version="1.9.500",
+ org.eclipse.e4.ui.workbench;bundle-version="1.16.0",
+ org.eclipse.e4.ui.model.workbench;bundle-version="2.4.400",
+ jakarta.annotation-api,
+ org.eclipse.ui.workbench;bundle-version="3.133.100"
+Automatic-Module-Name: org.eclipse.e4.ui.examples.dummyeditor
+Bundle-ActivationPolicy: lazy
+Bundle-RequiredExecutionEnvironment: JavaSE-21
+Model-Fragment: fragment.e4xmi

examples/org.eclipse.e4.ui.examples.e4editor/build.properties

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+bin.includes = META-INF/,\
+               .,\
+               fragment.e4xmi
+source.. = src/
+output.. = bin/

examples/org.eclipse.e4.ui.examples.e4editor/fragment.e4xmi

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+<?xml version="1.0" encoding="ASCII"?>
+<fragment:ModelFragments xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:basic="http://www.eclipse.org/ui/2010/UIModel/application/descriptor/basic" xmlns:commands="http://www.eclipse.org/ui/2010/UIModel/application/commands" xmlns:fragment="http://www.eclipse.org/ui/2010/UIModel/fragment" xmlns:menu="http://www.eclipse.org/ui/2010/UIModel/application/ui/menu" xmi:id="_6pcn8N7gEe-4ibwCH2r47g">
+  <fragments xsi:type="fragment:StringModelFragment" xmi:id="_Bzi3IN7hEe-4ibwCH2r47g" featurename="menuContributions" parentElementId="org.eclipse.e4.legacy.ide.application">
+    <elements xsi:type="menu:MenuContribution" xmi:id="_JtwUoN7hEe-4ibwCH2r47g" elementId="org.eclipse.e4.ui.examples.e4editor.menucontribution.0" positionInParent="after=additions" parentId="window">
+      <children xsi:type="menu:HandledMenuItem" xmi:id="_XMBQkN7hEe-4ibwCH2r47g" elementId="org.eclipse.e4.ui.examples.e4editor.handledmenuitem.opene4editor" label="Open E4 Editor" command="_e-OBkN7hEe-4ibwCH2r47g"/>
+    </elements>
+  </fragments>
+  <fragments xsi:type="fragment:StringModelFragment" xmi:id="_c1D8sN7hEe-4ibwCH2r47g" featurename="commands" parentElementId="org.eclipse.e4.legacy.ide.application">
+    <elements xsi:type="commands:Command" xmi:id="_e-OBkN7hEe-4ibwCH2r47g" elementId="org.eclipse.e4.ui.examples.e4editor.command.opene4editor" commandName="Open E4 Editor"/>
+  </fragments>
+  <fragments xsi:type="fragment:StringModelFragment" xmi:id="__zpxEN7iEe-4ibwCH2r47g" featurename="handlers" parentElementId="org.eclipse.e4.legacy.ide.application">
+    <elements xsi:type="commands:Handler" xmi:id="_DRaRYN7jEe-4ibwCH2r47g" elementId="org.eclipse.e4.ui.examples.e4editor.handler.0" contributionURI="bundleclass://org.eclipse.e4.ui.examples.e4editor/org.eclipse.e4.ui.examples.e4editor.OpenEditorHandler" command="_e-OBkN7hEe-4ibwCH2r47g"/>
+  </fragments>
+  <fragments xsi:type="fragment:StringModelFragment" xmi:id="_WJS9YN7jEe-4ibwCH2r47g" featurename="descriptors" parentElementId="org.eclipse.e4.legacy.ide.application">
+    <elements xsi:type="basic:PartDescriptor" xmi:id="_YIdYwN7jEe-4ibwCH2r47g" elementId="org.eclipse.e4.ui.examples.e4editor.partdescriptor.e4editor" label="E4 Editor" closeable="true" contributionURI="bundleclass://org.eclipse.e4.ui.examples.e4editor/org.eclipse.e4.ui.examples.e4editor.E4Editor">
+      <tags>Editor</tags>
+      <tags>removeOnHide</tags>
+    </elements>
+  </fragments>
+</fragment:ModelFragments>

examples/org.eclipse.e4.ui.examples.e4editor/src/org/eclipse/e4/ui/examples/e4editor/E4Editor.java

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+/*******************************************************************************
+* Copyright (c) 2025 Feilim Breatnach and others.
+*
+* This program and the accompanying materials are made available under the
+* terms of the Eclipse Public License 2.0 which accompanies this distribution,
+* and is available at https://www.eclipse.org/legal/epl-2.0/
+*
+* SPDX-License-Identifier: EPL-2.0
+*
+* Contributors: Feilim Breatnach, Pilz Ireland
+*******************************************************************************/
+
+package org.eclipse.e4.ui.examples.e4editor;
+
+import jakarta.annotation.PostConstruct;
+
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.widgets.Composite;
+import org.eclipse.swt.widgets.Text;
+
+public class E4Editor {
+
+	@PostConstruct
+	public void postConstruct(Composite parent) {
+		Text label = new Text(parent, SWT.ITALIC);
+		label.setText("E4 Editor Content...");
+
+	}
+}

examples/org.eclipse.e4.ui.examples.e4editor/src/org/eclipse/e4/ui/examples/e4editor/OpenEditorHandler.java

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+/*******************************************************************************
+* Copyright (c) 2025 Feilim Breatnach and others.
+*
+* This program and the accompanying materials are made available under the
+* terms of the Eclipse Public License 2.0 which accompanies this distribution,
+* and is available at https://www.eclipse.org/legal/epl-2.0/
+*
+* SPDX-License-Identifier: EPL-2.0
+*
+* Contributors: Feilim Breatnach, Pilz Ireland
+*******************************************************************************/
+
+package org.eclipse.e4.ui.examples.e4editor;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.function.Predicate;
+
+import org.eclipse.e4.core.di.annotations.Execute;
+import org.eclipse.e4.ui.model.application.MApplication;
+import org.eclipse.e4.ui.model.application.ui.advanced.MArea;
+import org.eclipse.e4.ui.model.application.ui.basic.MPart;
+import org.eclipse.e4.ui.model.application.ui.basic.MPartSashContainer;
+import org.eclipse.e4.ui.model.application.ui.basic.MPartSashContainerElement;
+import org.eclipse.e4.ui.model.application.ui.basic.MPartStack;
+import org.eclipse.e4.ui.workbench.modeling.EModelService;
+import org.eclipse.e4.ui.workbench.modeling.EPartService;
+import org.eclipse.e4.ui.workbench.modeling.EPartService.PartState;
+
+public class OpenEditorHandler {
+
+	public static final String DUMMY_EDITOR_DESCRIPTOR_ID = "org.eclipse.e4.ui.examples.e4editor.partdescriptor.e4editor";
+
+	@Execute
+	public void execute(EModelService modelService, MApplication application, EPartService partService) {
+		Predicate<MPart> isEditorAlreadyOpenFilter = part -> DUMMY_EDITOR_DESCRIPTOR_ID.equals(part.getElementId());
+		Optional<MPart> alreadyOpenMatchingPart = partService.getParts().stream().filter(isEditorAlreadyOpenFilter)
+				.findFirst();
+
+		MPart dummyPart = alreadyOpenMatchingPart.orElse(partService.createPart(DUMMY_EDITOR_DESCRIPTOR_ID));
+		if (alreadyOpenMatchingPart.isEmpty()) {
+			dummyPart = partService.createPart(DUMMY_EDITOR_DESCRIPTOR_ID);
+
+			// not entirely necessary: but for consistency let's place our dummy editor
+			// where editor instances appear
+			Optional<MPartStack> primaryDataStack = findPrimaryConfiguationAreaPartStack(application, modelService);
+			if (primaryDataStack.isPresent()) {
+				primaryDataStack.get().getChildren().add(dummyPart);
+			}
+		} else {
+			dummyPart = alreadyOpenMatchingPart.get();
+		}
+
+		partService.showPart(DUMMY_EDITOR_DESCRIPTOR_ID, PartState.ACTIVATE);
+		partService.bringToTop(dummyPart);
+	}
+
+	private Optional<MPartStack> findPrimaryConfiguationAreaPartStack(MApplication application,
+			EModelService modelService) {
+		// find the part stack from the application model which represents the area
+		// where our main 'editors' appear, ie. the main workspace area
+		List<MArea> areaCandidates = modelService.findElements(application, org.eclipse.ui.IPageLayout.ID_EDITOR_AREA,
+				MArea.class, null, EModelService.IN_SHARED_ELEMENTS);
+		if (areaCandidates.size() == 1) {
+			MArea primaryArea = areaCandidates.get(0);
+			for (MPartSashContainerElement element : primaryArea.getChildren()) {
+				if (element instanceof MPartStack) {
+					return Optional.of((MPartStack) element);
+				} else if (element instanceof MPartSashContainer) {
+					return ((MPartSashContainer) element).getChildren().stream().filter(c -> c instanceof MPartStack)
+							.map(c -> (MPartStack) c).findFirst();
+				}
+			}
+		}
+
+		return Optional.empty();
+	}
+}