Bug 318363 [UI] Closing Perspectives changes others
If you open the Debug perspective and then close it the Package Explorer disappears. Root cause was that I opened the second perspective using the perspective switcher which performed the operation 'locally' rather than going through the WorkbenchPage#setPerspective code. This meant that the 'openPerspectives' list wasn't updated which meant that the 'closePerspective' call delegated to 'closeAllPerspectives' since it thought there was only one open.
bundles/org.eclipse.e4.ui.workbench.addons.swt/src/org/eclipse/e4/ui/workbench/addons/perspectiveswitcher/PerspectiveSwitcher.java
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.graphics.Region;
import org.eclipse.swt.layout.RowLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.MenuItem;
import org.eclipse.swt.widgets.ToolBar;
import org.eclipse.swt.widgets.ToolItem;
import org.eclipse.ui.IPerspectiveDescriptor;
import org.eclipse.ui.IPerspectiveFactory;
import org.eclipse.ui.IWorkbenchPage;
import org.eclipse.ui.IWorkbenchPreferenceConstants;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.internal.IPreferenceConstants;
import org.eclipse.ui.internal.PerspectiveExtensionReader;
import org.eclipse.ui.internal.PerspectiveTagger;
import org.eclipse.ui.internal.WorkbenchPage;
import org.eclipse.ui.internal.dialogs.SelectPerspectiveDialog;
import org.eclipse.ui.internal.e4.compatibility.E4Util;
import org.eclipse.ui.internal.e4.compatibility.ModeledPageLayout;
import org.eclipse.ui.internal.registry.PerspectiveDescriptor;
import org.eclipse.ui.internal.util.PrefUtil;
import org.osgi.service.event.Event;
import org.osgi.service.event.EventHandler;
public class PerspectiveSwitcher {