Change classes with shortcut eclipse-platform#2413

Tab change can now handle the chevron. And after reaching the last tab,
it jumps to the first, if chevron doesn´t exist

Author: jannisCode

bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/handlers/TraversePageHandler.java

@@ -0,0 +1,127 @@
+/*******************************************************************************
+ * Copyright (c) 2004, 2015 IBM Corporation 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:
+ *     IBM Corporation - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.ui.internal.handlers;
+import java.lang.reflect.Method;
+import org.eclipse.core.commands.ExecutionEvent;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.custom.CTabFolder;
+import org.eclipse.swt.custom.CTabItem;
+import org.eclipse.swt.widgets.Control;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Shell;
+/**
+ * This handler is an adaptation of the widget method handler that implements
+ * page traversal via {@link SWT#TRAVERSE_PAGE_NEXT} and
+ * {@link SWT#TRAVERSE_PAGE_PREVIOUS} events.
+ *
+ * @since 3.5
+ */
+public class TraversePageHandler extends WidgetMethodHandler {
+	/**
+	 * The parameters for traverse(int).
+	 */
+	private static final Class<?>[] METHOD_PARAMETERS = { int.class };
+	@Override
+	public final Object execute(final ExecutionEvent event) {
+		Control focusControl = Display.getCurrent().getFocusControl();
+		if (focusControl != null) {
+			boolean forward = "next".equals(methodName); //$NON-NLS-1$
+			int traversal = getTraversalDirection(forward);
+			Control control = focusControl;
+
+			do {
+				if (control instanceof CTabFolder folder && isFinalItemInCTabFolder(folder, forward)
+						&& !areHiddenItems(folder)) {
+					loopToSecondToFirstItemInCTabFolder(folder, forward);
+					traversal = getTraversalDirection(!forward); // we are in the second-to-last item in the given
+					// direction. Now, use the Traverse-event to move back by one
+				}
+				if (control.traverse(traversal))
+					return null;
+				if (control instanceof Shell)
+					return null;
+				control = control.getParent();
+			} while (control != null);
+		}
+		return null;
+	}
+
+	private boolean areHiddenItems(CTabFolder folder) {
+		CTabItem[] items = folder.getItems();
+		for (CTabItem i : items) {
+			if (!i.isShowing()) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+	private int getTraversalDirection(boolean direction) {
+		return direction ? SWT.TRAVERSE_PAGE_NEXT : SWT.TRAVERSE_PAGE_PREVIOUS;
+	}
+
+	/**
+	 * Sets the current selection to the second-to-last item in the given direction.
+	 *
+	 * @param folder  the CTabFolder which we want to inspect
+	 * @param forward whether we want to traverse forwards of backwards
+	 */
+	private void loopToSecondToFirstItemInCTabFolder(CTabFolder folder, boolean forward) {
+		if (forward) {
+			folder.showItem(folder.getItem(0));
+			folder.setSelection(1);
+		} else {
+			int itemCount = folder.getItemCount();
+			folder.setSelection(itemCount - 2);
+		}
+	}
+
+	/**https://github.com/jannisCode/eclipse.jdt.ui.git
+	 * {@return Returns whether the folder has currently selected the final item in
+	 * the given direction.}
+	 *
+	 * @param folder  the CTabFolder which we want to inspect
+	 * @param forward whether we want to traverse forwards of backwards
+	 */
+	private boolean isFinalItemInCTabFolder(CTabFolder folder, boolean forward) {
+		CTabItem currentFolder = folder.getSelection();
+		CTabItem lastFolder = null;
+		if (forward) {
+			int itemCount = folder.getItemCount();
+			lastFolder = folder.getItem(itemCount - 1);
+		} else {
+			lastFolder = folder.getItem(0);
+		}
+		return currentFolder.equals(lastFolder);
+	}
+
+	/**
+	 * Looks up the traverse(int) method on the given focus control.
+	 *
+	 * @return The method on the focus control; <code>null</code> if none.
+	 */
+	@Override
+	protected Method getMethodToExecute() {
+		final Control focusControl = Display.getCurrent().getFocusControl();
+		if (focusControl != null) {
+			try {
+				return focusControl.getClass().getMethod("traverse", //$NON-NLS-1$
+						METHOD_PARAMETERS);
+			} catch (NoSuchMethodException e) {
+				// Do nothing.
+			}
+		}
+		return null;
+	}
+}