1 files changed, 218 insertions, 0 deletions
diff --git a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/contentmergeviewer/MirrorManager.java b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/contentmergeviewer/MirrorManager.java
new file mode 100644
index 000000000..72dddd4ae
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/contentmergeviewer/MirrorManager.java
@@ -0,0 +1,218 @@
+/*******************************************************************************
+ * Copyright (c) 2018 EclipseSource and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Philip Langer - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.ide.ui.internal.contentmergeviewer;
+
+import org.eclipse.compare.CompareConfiguration;
+import org.eclipse.compare.contentmergeviewer.ContentMergeViewer;
+import org.eclipse.compare.contentmergeviewer.IMergeViewerContentProvider;
+import org.eclipse.compare.contentmergeviewer.TextMergeViewer;
+import org.eclipse.compare.internal.CompareUIPlugin;
+import org.eclipse.compare.internal.MergeViewerContentProvider;
+import org.eclipse.core.runtime.Assert;
+import org.eclipse.emf.compare.ide.ui.internal.configuration.EMFCompareConfiguration;
+import org.eclipse.jface.util.PropertyChangeEvent;
+import org.eclipse.jface.viewers.IContentProvider;
+import org.eclipse.swt.graphics.Image;
+import org.eclipse.swt.widgets.Composite;
+
+/**
+ * A manager class for handling the switching of the mirrored mode for each specialized
+ * {@link ContentMergeViewer} and {@link TextMergeViewer} in EMF Compare,
+ */
+public class MirrorManager {
+	/**
+	 * The compare configuration used by the merge viewer.
+	 */
+	private final EMFCompareConfiguration configuration;
+
+	/**
+	 * The first content provider that's set while this manager is managing the content providers. We keep
+	 * track of this because org.eclipse.compare.contentmergeviewer.ContentMergeViewer.updateContentProvider()
+	 * replace our content provider with a default one.
+	 */
+	private IContentProvider managedContentProvider;
+
+	/**
+	 * The mirror of the first content provider that's set while this manager is managing the content
+	 * providers.
+	 */
+	private IContentProvider mirroredManagedContentProvider;
+
+	/**
+	 * Creates an instance for this confirmation.
+	 * 
+	 * @param configuration
+	 *            the EMF compare configuration.
+	 */
+	public MirrorManager(EMFCompareConfiguration configuration) {
+		this.configuration = configuration;
+	}
+
+	/**
+	 * Returns the appropriate content provider based on the current state of
+	 * {@link EMFCompareConfiguration#isMirrored()}.
+	 * <p>
+	 * This method should be used in overrides of
+	 * {@link ContentMergeViewer#setContentProvider(IContentProvider)} to automatically set the correctly
+	 * mirrored content provider.
+	 * </p>
+	 * 
+	 * @param contentProvider
+	 *            the current content provider.
+	 * @return the appropriate content provider based on the current mirroring state.
+	 */
+	public IContentProvider getContentProvider(IContentProvider contentProvider) {
+		Assert.isTrue(contentProvider instanceof IMergeViewerContentProvider);
+		if (managedContentProvider == null) {
+			managedContentProvider = contentProvider;
+		}
+
+		if (configuration.isMirrored()) {
+			if (mirroredManagedContentProvider == null) {
+				mirroredManagedContentProvider = new MirroredContentProvider(configuration,
+						(IMergeViewerContentProvider)managedContentProvider);
+			}
+			return mirroredManagedContentProvider;
+		} else {
+			return managedContentProvider;
+		}
+	}
+
+	/**
+	 * Called from a derived {@link ContentMergeViewer#handlePropertyChangeEvent(PropertyChangeEvent)} method
+	 * to intercept the preference change for swapping, i.e., mirroring the sides.
+	 * <p>
+	 * If this method returns true, the caller should not call
+	 * <code>super.handlePropertyChangeEvent(event)</code> but rather should do the processing themselves to
+	 * avoid calls to {@link ContentMergeViewer#updateContentProvider()} which will set the bogus default
+	 * content provider. The method sets the MIRRORED property of the configuration as is normally done when
+	 * calling super.
+	 * </p>
+	 * 
+	 * @param event
+	 *            the event to handle.
+	 * @return true, if the property change is the property for the preference switching of sides, false
+	 *         otherwise.
+	 */
+	public boolean handlePropertyChangeEvent(PropertyChangeEvent event) {
+		// For backward compatibility, instead of using ComparePreferencePage.SWAPPED,
+		// we compute the value.
+		if (event.getProperty().equals(CompareUIPlugin.PLUGIN_ID + ".Swapped")) { //$NON-NLS-1$
+			configuration.setProperty(EMFCompareConfiguration.MIRRORED, event.getNewValue());
+			return true;
+		} else {
+			return false;
+		}
+	}
+
+	/**
+	 * A merge viewer content provider that mirrors all the directional methods. It's implemented by extending
+	 * MergeViewerContentProvider because {@link TextMergeViewer#isUsingDefaultContentProvider()} tests for
+	 * that. If that's false, the viewer created by
+	 * {@link TextFallbackCompareViewerCreator#createViewer(Composite, CompareConfiguration)} will not be able
+	 * to use shared documents while mirrored.
+	 */
+	private static class MirroredContentProvider extends MergeViewerContentProvider {
+		private final IMergeViewerContentProvider delegate;
+
+		public MirroredContentProvider(EMFCompareConfiguration configuration,
+				IMergeViewerContentProvider delegate) {
+			super(configuration);
+			this.delegate = delegate;
+		}
+
+		@Override
+		public boolean showAncestor(Object input) {
+			return delegate.showAncestor(input);
+		}
+
+		@Override
+		public void saveRightContent(Object input, byte[] bytes) {
+			delegate.saveLeftContent(input, bytes);
+		}
+
+		@Override
+		public void saveLeftContent(Object input, byte[] bytes) {
+			delegate.saveRightContent(input, bytes);
+		}
+
+		@Override
+		public boolean isRightEditable(Object input) {
+			return delegate.isLeftEditable(input);
+		}
+
+		@Override
+		public boolean isLeftEditable(Object input) {
+			return delegate.isRightEditable(input);
+		}
+
+		@Override
+		public String getRightLabel(Object input) {
+			return delegate.getLeftLabel(input);
+		}
+
+		@Override
+		public Image getRightImage(Object input) {
+			return delegate.getLeftImage(input);
+		}
+
+		@Override
+		public Object getRightContent(Object input) {
+			return delegate.getLeftContent(input);
+		}
+
+		@Override
+		public String getLeftLabel(Object input) {
+			return delegate.getRightLabel(input);
+		}
+
+		@Override
+		public Image getLeftImage(Object input) {
+			return delegate.getRightImage(input);
+		}
+
+		@Override
+		public Object getLeftContent(Object input) {
+			return delegate.getRightContent(input);
+		}
+
+		@Override
+		public String getAncestorLabel(Object input) {
+			return delegate.getAncestorLabel(input);
+		}
+
+		@Override
+		public Image getAncestorImage(Object input) {
+			return delegate.getAncestorImage(input);
+		}
+
+		@Override
+		public Object getAncestorContent(Object input) {
+			return delegate.getAncestorContent(input);
+		}
+
+		@Override
+		public void setLeftError(String errorMessage) {
+			super.setRightError(errorMessage);
+		}
+
+		@Override
+		public void setRightError(String errorMessage) {
+			super.setLeftError(errorMessage);
+		}
+
+		@Override
+		public void dispose() {
+			super.dispose();
+			delegate.dispose();
+		}
+	}
+}