Bug 496249: Tags for disabling/enabling CDT code formatter

Change-Id: I4389c61612da6a4ee0011a49d6aeed7b52152436
Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>

11 files changed, 484 insertions, 7 deletions

diff --git a/core/org.eclipse.cdt.core/META-INF/MANIFEST.MF b/core/org.eclipse.cdt.core/META-INF/MANIFEST.MF
index 3d146697542..84147ef8242 100644
--- a/core/org.eclipse.cdt.core/META-INF/MANIFEST.MF
+++ b/core/org.eclipse.cdt.core/META-INF/MANIFEST.MF
@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.cdt.core; singleton:=true
-Bundle-Version: 6.6.100.qualifier
+Bundle-Version: 6.7.0.qualifier
 Bundle-Activator: org.eclipse.cdt.core.CCorePlugin
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin
diff --git a/core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/formatter/DefaultCodeFormatterConstants.java b/core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/formatter/DefaultCodeFormatterConstants.java
index 9b0f72a7a95..d4bec0effd5 100644
--- a/core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/formatter/DefaultCodeFormatterConstants.java
+++ b/core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/formatter/DefaultCodeFormatterConstants.java
@@ -91,6 +91,38 @@ public class DefaultCodeFormatterConstants {
 	 */
 	public static final String FALSE = "false"; //$NON-NLS-1$
 
+	/**
+	 * <pre>
+	 * FORMATTER / Formatter on tag format option
+	 *     - option id:         "org.eclipse.cdt.core.formatter.comment_formatter_on_tag"
+	 *     - default:           @formatter:on
+	 * </pre>
+	 * @see CCorePlugin#FORMAT_ON_TAG
+	 * @since 6.7
+	 */
+	public static final String FORMATTER_COMMENT_ON_TAG = CCorePlugin.PLUGIN_ID + ".formatter.comment_formatter_on_tag"; //$NON-NLS-1$
+	/**
+	 * <pre>
+	 * FORMATTER / Formatter off tag format option
+	 *     - option id:         "org.eclipse.cdt.core.formatter.comment_formatter_off_tag"
+	 *     - default:           @formatter:off
+	 * </pre>
+	 * @see CCorePlugin#FORMAT_OFF_TAG
+	 * @since 6.7
+	 */
+	public static final String FORMATTER_COMMENT_OFF_TAG = CCorePlugin.PLUGIN_ID
+			+ ".formatter.comment_formatter_off_tag"; //$NON-NLS-1$
+	/**
+	 * <pre>
+	 * FORMATTER / Formatter on tag format option
+	 *     - option id:         "org.eclipse.cdt.core.formatter.use_comment_formatter_tag"
+	 *     - default:           true
+	 * </pre>
+	 * @since 6.7
+	 */
+	public static final String FORMATTER_USE_COMMENT_TAG = CCorePlugin.PLUGIN_ID
+			+ ".formatter.use_comment_formatter_tag"; //$NON-NLS-1$
+
 	//	/**
 	//	 * <pre>
 	//	 * FORMATTER / Option to align type members of a type declaration on column
@@ -2484,6 +2516,21 @@ public class DefaultCodeFormatterConstants {
 	 */
 	public static final int WRAP_ONE_PER_LINE = 3;
 
+	/**
+	 * <pre>
+	 * FORMATTER / Default formatter on tag
+	 * </pre>
+	 * @since 6.7
+	 */
+	public static final String FORMATTER_ON_TAG = "@formatter:on"; //$NON-NLS-1$
+	/**
+	 * <pre>
+	 * FORMATTER / Default formatter off tag
+	 * </pre>
+	 * @since 6.7
+	 */
+	public static final String FORMATTER_OFF_TAG = "@formatter:off"; //$NON-NLS-1$
+
 	/*
 	 * Private constants.
 	 */
diff --git a/core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/formatter/DefaultCodeFormatterOptions.java b/core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/formatter/DefaultCodeFormatterOptions.java
index 6aac8f17204..65d4101d39a 100644
--- a/core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/formatter/DefaultCodeFormatterOptions.java
+++ b/core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/formatter/DefaultCodeFormatterOptions.java
@@ -264,6 +264,12 @@ public class DefaultCodeFormatterOptions {
 	public boolean use_tabs_only_for_leading_indentations;
 	public int initial_indentation_level;
 	public String line_separator;
+	/** @since 6.7 */
+	public String comment_formatter_on_tag;
+	/** @since 6.7 */
+	public String comment_formatter_off_tag;
+	/** @since 6.7 */
+	public boolean use_fomatter_comment_tag;
 
 	private DefaultCodeFormatterOptions() {
 		// cannot be instantiated
@@ -282,6 +288,11 @@ public class DefaultCodeFormatterOptions {
 
 	public Map<String, String> getMap() {
 		Map<String, String> options = new HashMap<>();
+		options.put(DefaultCodeFormatterConstants.FORMATTER_COMMENT_ON_TAG, comment_formatter_on_tag);
+		options.put(DefaultCodeFormatterConstants.FORMATTER_COMMENT_OFF_TAG, comment_formatter_off_tag);
+		options.put(DefaultCodeFormatterConstants.FORMATTER_USE_COMMENT_TAG,
+				this.use_fomatter_comment_tag ? DefaultCodeFormatterConstants.TRUE
+						: DefaultCodeFormatterConstants.FALSE);
 		//		options.put(DefaultCodeFormatterConstants.FORMATTER_ALIGNMENT_FOR_ARGUMENTS_IN_ALLOCATION_EXPRESSION, getAlignment(this.alignment_for_arguments_in_allocation_expression));
 		options.put(DefaultCodeFormatterConstants.FORMATTER_ALIGNMENT_FOR_ARGUMENTS_IN_METHOD_INVOCATION,
 				getAlignment(this.alignment_for_arguments_in_method_invocation));
@@ -2025,10 +2036,25 @@ public class DefaultCodeFormatterOptions {
 				this.tab_char = MIXED;
 			}
 		}
+		final Object formatterCommentOnTag = settings.get(DefaultCodeFormatterConstants.FORMATTER_COMMENT_ON_TAG);
+		if (formatterCommentOnTag != null) {
+			this.comment_formatter_on_tag = (String) formatterCommentOnTag;
+		}
+		final Object formatterCommentOffTag = settings.get(DefaultCodeFormatterConstants.FORMATTER_COMMENT_OFF_TAG);
+		if (formatterCommentOffTag != null) {
+			this.comment_formatter_off_tag = (String) formatterCommentOffTag;
+		}
+		final Object useFormatterCommentTag = settings.get(DefaultCodeFormatterConstants.FORMATTER_USE_COMMENT_TAG);
+		if (useFormatterCommentTag != null) {
+			this.use_fomatter_comment_tag = DefaultCodeFormatterConstants.TRUE.equals(useFormatterCommentTag);
+		}
 	}
 
 	public void setDefaultSettings() {
 		//		this.alignment_for_arguments_in_allocation_expression = Alignment.M_COMPACT_SPLIT;
+		this.comment_formatter_on_tag = DefaultCodeFormatterConstants.FORMATTER_ON_TAG;
+		this.comment_formatter_off_tag = DefaultCodeFormatterConstants.FORMATTER_OFF_TAG;
+		this.use_fomatter_comment_tag = true;
 		this.alignment_for_arguments_in_method_invocation = Alignment.M_COMPACT_SPLIT;
 		this.alignment_for_assignment = Alignment.M_COMPACT_SPLIT;
 		this.alignment_for_base_clause_in_type_declaration = Alignment.M_NEXT_PER_LINE_SPLIT;
diff --git a/core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/formatter/CodeFormatterVisitor.java b/core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/formatter/CodeFormatterVisitor.java
index 22ae42e2b46..4ed22399500 100644
--- a/core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/formatter/CodeFormatterVisitor.java
+++ b/core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/formatter/CodeFormatterVisitor.java
@@ -35,6 +35,7 @@ import org.eclipse.cdt.core.dom.ast.IASTBinaryExpression;
 import org.eclipse.cdt.core.dom.ast.IASTBreakStatement;
 import org.eclipse.cdt.core.dom.ast.IASTCaseStatement;
 import org.eclipse.cdt.core.dom.ast.IASTCastExpression;
+import org.eclipse.cdt.core.dom.ast.IASTComment;
 import org.eclipse.cdt.core.dom.ast.IASTCompositeTypeSpecifier;
 import org.eclipse.cdt.core.dom.ast.IASTCompoundStatement;
 import org.eclipse.cdt.core.dom.ast.IASTConditionalExpression;
@@ -438,7 +439,8 @@ public class CodeFormatterVisitor extends ASTVisitor implements ICPPASTVisitor,
 
 		localScanner.setSource(compilationUnitSource);
 		scribe.initializeScanner(compilationUnitSource);
-		scribe.setSkipPositions(collectInactiveCodePositions(unit));
+		scribe.setSkipInactivePositions(collectInactiveCodePositions(unit));
+		scribe.setSkipForbiddenPositions(collectNoFormatCodePositions(unit));
 
 		fStatus = new MultiStatus(CCorePlugin.PLUGIN_ID, 0, "Formatting problem(s) in '" + unit.getFilePath() + "'", //$NON-NLS-1$//$NON-NLS-2$
 				null);
@@ -4466,6 +4468,64 @@ public class CodeFormatterVisitor extends ASTVisitor implements ICPPASTVisitor,
 	}
 
 	/**
+	 * Collect source positions of no-format sections in the given translation unit.
+	 *
+	 * @param translationUnit  the {@link IASTTranslationUnit}, may be <code>null</code>
+	 * @return a {@link List} of {@link Position}s
+	 */
+	private List<Position> collectNoFormatCodePositions(IASTTranslationUnit translationUnit) {
+		if (translationUnit == null || !this.preferences.use_fomatter_comment_tag) {
+			return Collections.emptyList();
+		}
+		String fileName = translationUnit.getFilePath();
+		if (fileName == null) {
+			return Collections.emptyList();
+		}
+		List<Position> positions = new ArrayList<>();
+		int inactiveCodeStart = -1;
+		boolean inInactiveCode = false;
+
+		IASTComment[] commentsStmts = translationUnit.getComments();
+
+		for (IASTComment commentStmt : commentsStmts) {
+			IASTComment statement = commentStmt;
+			if (!statement.isPartOfTranslationUnitFile()) {
+				// comment is from a different file
+				continue;
+			}
+			IASTNodeLocation nodeLocation = statement.getFileLocation();
+			if (nodeLocation == null) {
+				continue;
+			}
+
+			String comment = new String(statement.getComment());
+			/**
+			 * According to JDT formatter rules, we need to evaluate the latest tag if both
+			 * are defined at the same time in the comment.
+			 */
+			int offPos = comment.lastIndexOf(this.preferences.comment_formatter_off_tag);
+			int onPos = comment.lastIndexOf(this.preferences.comment_formatter_on_tag);
+			if (offPos != -1 && offPos > onPos) {
+				if (!inInactiveCode) {
+					inactiveCodeStart = nodeLocation.getNodeOffset();
+					inInactiveCode = true;
+				}
+			} else if (onPos != -1 && onPos > offPos) {
+				if (inInactiveCode) {
+					int inactiveCodeEnd = nodeLocation.getNodeOffset();
+					positions.add(new Position(inactiveCodeStart, inactiveCodeEnd - inactiveCodeStart));
+				}
+				inInactiveCode = false;
+			}
+		}
+		if (inInactiveCode) {
+			positions.add(new Position(inactiveCodeStart, translationUnit.getFileLocation().getNodeLength()));
+			inInactiveCode = false;
+		}
+		return positions;
+	}
+
+	/**
 	 * Collect source positions of preprocessor-hidden branches
 	 * in the given translation unit.
 	 *
diff --git a/core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/formatter/Scribe.java b/core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/formatter/Scribe.java
index 2b34203f45b..4bdc4a57ebb 100644
--- a/core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/formatter/Scribe.java
+++ b/core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/formatter/Scribe.java
@@ -88,7 +88,14 @@ public class Scribe {
 	private int textRegionStart;
 	public int scannerEndPosition;
 
-	private List<Position> fSkipPositions = Collections.emptyList();
+	/**
+	 * It keeps the list of inactive region.
+	 */
+	private List<Position> fSkipInactivePositions = Collections.emptyList();
+	/**
+	 * It keeps the list of no-format region.
+	 */
+	private List<Position> fSkipForbiddenPositions = Collections.emptyList();
 
 	private boolean skipOverInactive;
 
@@ -668,10 +675,19 @@ public class Scribe {
 	}
 
 	/**
+	 * Set the positions where we don't want to perform any check
+	 * @param list The list of positions
+	 */
+	public void setSkipForbiddenPositions(List<Position> list) {
+		if (list != null)
+			fSkipForbiddenPositions = list;
+	}
+
+	/**
 	 * @param list
 	 */
-	public void setSkipPositions(List<Position> list) {
-		fSkipPositions = list;
+	public void setSkipInactivePositions(List<Position> list) {
+		fSkipInactivePositions = list;
 		skipOverInactive = !list.isEmpty();
 	}
 
@@ -1287,8 +1303,22 @@ public class Scribe {
 	 * @param offset
 	 * @return
 	 */
+	private boolean isForbidden(int offset) {
+		for (Iterator<Position> iter = fSkipForbiddenPositions.iterator(); iter.hasNext();) {
+			Position pos = iter.next();
+			if (pos.includes(offset)) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * @param offset
+	 * @return
+	 */
 	private Position getInactivePosAt(int offset) {
-		for (Iterator<Position> iter = fSkipPositions.iterator(); iter.hasNext();) {
+		for (Iterator<Position> iter = fSkipInactivePositions.iterator(); iter.hasNext();) {
 			Position pos = iter.next();
 			if (pos.includes(offset)) {
 				return pos;
@@ -2037,7 +2067,7 @@ public class Scribe {
 	}
 
 	boolean shouldSkip(int offset) {
-		return offset >= fSkipStartOffset && offset < fSkipEndOffset;
+		return ((offset >= fSkipStartOffset && offset < fSkipEndOffset) || isForbidden(offset));
 	}
 
 	void skipRange(int offset, int endOffset) {
diff --git a/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/CodeFormatterTest.java b/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/CodeFormatterTest.java
index 4c2a10cc35a..f959926efae 100644
--- a/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/CodeFormatterTest.java
+++ b/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/CodeFormatterTest.java
@@ -3563,4 +3563,44 @@ public class CodeFormatterTest extends BaseUITestCase {
 	public void testAttributedNamedScopedEnumDeclaration_Bug535256_4() throws Exception {
 		assertFormatterResult();
 	}
+
+	////@formatter:off
+	//int
+	//main(){
+	//return
+	//0
+	//;}
+	////@formatter:on
+
+	////@formatter:off
+	//int
+	//main(){
+	//return
+	//0
+	//;}
+	////@formatter:on
+	public void testOnOffTags() throws Exception {
+		fOptions.put(DefaultCodeFormatterConstants.FORMATTER_USE_COMMENT_TAG, true);
+		fOptions.put(DefaultCodeFormatterConstants.FORMATTER_COMMENT_ON_TAG, "@formatter:on");
+		fOptions.put(DefaultCodeFormatterConstants.FORMATTER_COMMENT_OFF_TAG, "@formatter:off");
+		assertFormatterResult();
+	}
+
+	////@formatter:off
+	//    void this_line_intentionally_indented() {
+	// int x;
+	// }
+	////@formatter:on
+
+	////@formatter:off
+	//    void this_line_intentionally_indented() {
+	// int x;
+	// }
+	////@formatter:on
+	public void testOnOffTagsDoesNotChangeFirstLineIndent() throws Exception {
+		fOptions.put(DefaultCodeFormatterConstants.FORMATTER_USE_COMMENT_TAG, true);
+		fOptions.put(DefaultCodeFormatterConstants.FORMATTER_COMMENT_ON_TAG, "@formatter:on");
+		fOptions.put(DefaultCodeFormatterConstants.FORMATTER_COMMENT_OFF_TAG, "@formatter:off");
+		assertFormatterResult();
+	}
 }
diff --git a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterMessages.java b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterMessages.java
index 6deaa290f1b..39eb4f6a6c8 100644
--- a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterMessages.java
+++ b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterMessages.java
@@ -369,6 +369,7 @@ final class FormatterMessages extends NLS {
 	public static String ModifyDialog_tabpage_braces_title;
 	public static String ModifyDialog_tabpage_indentation_title;
 	public static String ModifyDialog_tabpage_whitespace_title;
+	public static String ModifyDialog_tabpage_formatter_tag_title;
 	//	public static String ModifyDialog_tabpage_blank_lines_title;
 	public static String ModifyDialog_tabpage_new_lines_title;
 	public static String ModifyDialog_tabpage_control_statements_title;
@@ -402,6 +403,15 @@ final class FormatterMessages extends NLS {
 
 	public static String CPreview_formatter_exception;
 
+	public static String FormatterModifyDialog_offOn_preview_header;
+	public static String FormatterModifyDialog_offOn_description;
+	public static String FormatterModifyDialog_offOn_pref_enable;
+	public static String FormatterModifyDialog_offOn_pref_off_tag;
+	public static String FormatterModifyDialog_offOn_pref_on_tag;
+	public static String FormatterModifyDialog_offOn_error_startsWithWhitespace;
+	public static String FormatterModifyDialog_offOn_error_endsWithWhitespace;
+	public static String FormatterModifyDialog_offOn_error_empty;
+
 	private FormatterMessages() {
 		// Do not instantiate
 	}
diff --git a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterMessages.properties b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterMessages.properties
index e03b4ad3646..c879b3ae186 100644
--- a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterMessages.properties
+++ b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterMessages.properties
@@ -433,6 +433,7 @@ ModifyDialog_tabpage_new_lines_title=New &Lines
 ModifyDialog_tabpage_control_statements_title=Con&trol Statements
 ModifyDialog_tabpage_line_wrapping_title=Line Wra&pping
 ModifyDialog_tabpage_comments_title=Co&mments
+ModifyDialog_tabpage_formatter_tag_title=Off/On Tags
 
 ModifyDialog_dialog_title=Profile ''{0}''
 ModifyDialog_apply_button=Apply
@@ -476,3 +477,12 @@ CPreview_formatter_exception=The formatter threw an unhandled exception while fo
 
 ProfileConfigurationBlock_load_profile_wrong_profile_message=Import failed. This is not a valid profile: Expected ''{0}'' but encountered ''{1}''.
 FormatterTabPage_ShowInvisibleCharacters_label=Show &invisible characters
+
+FormatterModifyDialog_offOn_preview_header=Off/On tags
+FormatterModifyDialog_offOn_description=Off/On tags can be used in any comments to turn the formatter off and on in a source file.\n- At the beginning of each file, the formatter is enabled.\n- Each time the formatter sees an off tag, it disables formatting for that comment and the source after it.\n- Each time the formatter sees an on tag, it enables formatting for the source after that comment.\n
+FormatterModifyDialog_offOn_pref_enable=Enable Off/On tags
+FormatterModifyDialog_offOn_pref_off_tag=Off tag:
+FormatterModifyDialog_offOn_pref_on_tag=On tag:
+FormatterModifyDialog_offOn_error_startsWithWhitespace=This value must not start with a white space.
+FormatterModifyDialog_offOn_error_endsWithWhitespace=This value must not end with a white space.
+FormatterModifyDialog_offOn_error_empty=This value must not be empty.
diff --git a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterModifyDialog.java b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterModifyDialog.java
index 5838b0bc7b9..e0b242a5260 100644
--- a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterModifyDialog.java
+++ b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterModifyDialog.java
@@ -38,5 +38,6 @@ public class FormatterModifyDialog extends ModifyDialog {
 				new ControlStatementsTabPage(this, values));
 		addTabPage(FormatterMessages.ModifyDialog_tabpage_line_wrapping_title, new LineWrappingTabPage(this, values));
 		addTabPage(FormatterMessages.ModifyDialog_tabpage_comments_title, new CommentsTabPage(this, values));
+		addTabPage(FormatterMessages.ModifyDialog_tabpage_formatter_tag_title, new FormatterTagTabPage(this, values));
 	}
 }
diff --git a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterTagTabPage.java b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterTagTabPage.java
new file mode 100644
index 00000000000..4b4f39eb152
--- /dev/null
+++ b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/FormatterTagTabPage.java
@@ -0,0 +1,93 @@
+/*******************************************************************************
+ * Copyright (c) 2019 Marco Stornelli
+ *
+ * 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
+ *
+ *******************************************************************************/
+package org.eclipse.cdt.internal.ui.preferences.formatter;
+
+import java.util.Map;
+import java.util.Observable;
+import java.util.Observer;
+
+import org.eclipse.cdt.core.formatter.DefaultCodeFormatterConstants;
+import org.eclipse.swt.widgets.Composite;
+import org.eclipse.swt.widgets.Group;
+
+public class FormatterTagTabPage extends FormatterTabPage {
+
+	private final String PREVIEW = createPreviewHeader(FormatterMessages.FormatterModifyDialog_offOn_preview_header)
+			+ "void method1()   {  doSomething();  }\n\n// @formatter:off\n" //$NON-NLS-1$
+			+ "void method2()   {  doSomething();  }\n// @formatter:on\n\n" //$NON-NLS-1$
+			+ "void method3()   {  doSomething();  }\n\n" //$NON-NLS-1$
+			+ "/* @formatter:off                                           */\n\nvoid\nfoo()\n;"; //$NON-NLS-1$
+
+	private StringPreference fOnTag;
+	private StringPreference fOffTag;
+	private CheckboxPreference fUseTag;
+	private TranslationUnitPreview fPreview;
+
+	public FormatterTagTabPage(IModificationListener modifyListener, Map<String, String> workingValues) {
+		super(modifyListener, workingValues);
+	}
+
+	@Override
+	protected void initializePage() {
+		fPreview.setPreviewText(PREVIEW);
+	}
+
+	@Override
+	protected void doUpdatePreview() {
+		super.doUpdatePreview();
+		fPreview.update();
+	}
+
+	@Override
+	protected void doCreatePreferences(Composite composite, int numColumns) {
+		final Group generalGroup = createGroup(numColumns, composite,
+				FormatterMessages.ModifyDialog_tabpage_formatter_tag_title);
+		createLabel(numColumns, generalGroup, FormatterMessages.FormatterModifyDialog_offOn_description);
+		fUseTag = createCheckboxPref(generalGroup, numColumns,
+				FormatterMessages.FormatterModifyDialog_offOn_pref_enable,
+				DefaultCodeFormatterConstants.FORMATTER_USE_COMMENT_TAG, FALSE_TRUE);
+		fUseTag.addObserver(new Observer() {
+			@Override
+			public void update(Observable arg0, Object arg1) {
+				fOnTag.setEnabled(fUseTag.getChecked());
+				fOffTag.setEnabled(fUseTag.getChecked());
+			}
+		});
+		PreferenceValidator validator = new PreferenceValidator() {
+			@Override
+			public String validate(String value) {
+				if (value != null && !value.isEmpty()) {
+					if (Character.isWhitespace(value.charAt(0))) {
+						return FormatterMessages.FormatterModifyDialog_offOn_error_startsWithWhitespace;
+					} else if (Character.isWhitespace(value.charAt(value.length() - 1))) {
+						return FormatterMessages.FormatterModifyDialog_offOn_error_endsWithWhitespace;
+					}
+					return null;
+				}
+				return FormatterMessages.FormatterModifyDialog_offOn_error_empty;
+			}
+		};
+		fOffTag = createStringPref(generalGroup, numColumns, FormatterMessages.FormatterModifyDialog_offOn_pref_off_tag,
+				DefaultCodeFormatterConstants.FORMATTER_COMMENT_OFF_TAG);
+		fOffTag.setValidator(validator);
+		fOnTag = createStringPref(generalGroup, numColumns, FormatterMessages.FormatterModifyDialog_offOn_pref_on_tag,
+				DefaultCodeFormatterConstants.FORMATTER_COMMENT_ON_TAG);
+		fOnTag.setValidator(validator);
+	}
+
+	@Override
+	protected CPreview doCreateCPreview(Composite parent) {
+		fPreview = new TranslationUnitPreview(fWorkingValues, parent);
+		return fPreview;
+	}
+
+}
diff --git a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/ModifyDialogTabPage.java b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/ModifyDialogTabPage.java
index 4401c3080c0..65101096722 100644
--- a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/ModifyDialogTabPage.java
+++ b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/preferences/formatter/ModifyDialogTabPage.java
@@ -69,6 +69,18 @@ public abstract class ModifyDialogTabPage implements IModifyDialogTabPage {
 	};
 
 	/**
+	 * Preference validator
+	 */
+	interface PreferenceValidator {
+		/**
+		 * Validate callback
+		 * @param value The value to be checked
+		 * @return String error or null otherwise
+		 */
+		String validate(String value);
+	}
+
+	/**
 	 * The base class of all Preference classes. A preference class provides a wrapper
 	 * around one or more SWT widgets and handles the input of values for some key.
 	 * On each change, the new value is written to the map and the listeners are notified.
@@ -77,6 +89,7 @@ public abstract class ModifyDialogTabPage implements IModifyDialogTabPage {
 		private final Map<String, String> fPreferences;
 		private boolean fEnabled;
 		private String fKey;
+		private PreferenceValidator fValidator;
 
 		/**
 		 * Create a new Preference.
@@ -143,6 +156,22 @@ public abstract class ModifyDialogTabPage implements IModifyDialogTabPage {
 		 * of this object has changed (enabled, key, ...).
 		 */
 		protected abstract void updateWidget();
+
+		public void setValidator(PreferenceValidator validator) {
+			fValidator = validator;
+		}
+
+		/**
+		 * Check if preference is valid according to its validator
+		 * @param value The preference value
+		 * @return Null if valid, the error string otherwise
+		 */
+		protected String isValid(String value) {
+			if (fValidator != null) {
+				return fValidator.validate(value);
+			}
+			return null;
+		}
 	}
 
 	/**
@@ -319,6 +348,126 @@ public abstract class ModifyDialogTabPage implements IModifyDialogTabPage {
 	}
 
 	/**
+	 * Wrapper around a textfied
+	 */
+	protected final class StringPreference extends Preference {
+
+		private final Label fLabel;
+		private final Text fText;
+
+		protected String fSelected;
+		protected String fOldSelected;
+
+		/**
+		 * Create a new NumberPreference.
+		 * @param composite The composite on which the SWT widgets are added.
+		 * @param numColumns The number of columns in the composite's GridLayout.
+		 * @param preferences The map to store the values.
+		 * @param key The key to store the values.
+		 * @param text The label text for this Preference.
+		 */
+		public StringPreference(Composite composite, int numColumns, Map<String, String> preferences, String key,
+				String text) {
+			super(preferences, key);
+
+			fLabel = createLabel(numColumns - 1, composite, text, GridData.FILL_HORIZONTAL);
+			fText = new Text(composite, SWT.SINGLE | SWT.BORDER | SWT.LEFT);
+			fText.setFont(composite.getFont());
+
+			fText.setLayoutData(
+					createGridData(1, GridData.HORIZONTAL_ALIGN_END, fPixelConverter.convertWidthInCharsToPixels(20)));
+
+			updateWidget();
+
+			fText.addFocusListener(new FocusListener() {
+				@Override
+				public void focusGained(FocusEvent e) {
+					StringPreference.this.focusGained();
+				}
+
+				@Override
+				public void focusLost(FocusEvent e) {
+					StringPreference.this.focusLost();
+				}
+			});
+
+			fText.addModifyListener(new ModifyListener() {
+				@Override
+				public void modifyText(ModifyEvent e) {
+					fieldModified();
+				}
+			});
+		}
+
+		private IStatus createErrorStatus(String error) {
+			return new Status(IStatus.ERROR, CUIPlugin.getPluginId(), 0, Messages.format(error), null);
+		}
+
+		protected void focusGained() {
+			fOldSelected = fSelected;
+			fText.setSelection(0, fText.getCharCount());
+		}
+
+		protected void focusLost() {
+			updateStatus(null);
+			final String input = fText.getText();
+			if (validInput(input) != null)
+				fSelected = fOldSelected;
+			else
+				fSelected = input;
+			if (fSelected != fOldSelected) {
+				saveSelected();
+				fText.setText(fSelected);
+			}
+		}
+
+		protected void fieldModified() {
+			final String trimInput = fText.getText().trim();
+			final String error = validInput(fText.getText());
+
+			updateStatus(error == null ? null : createErrorStatus(error));
+
+			if (error == null) {
+				if (fSelected.equals(trimInput)) {
+					fSelected = trimInput;
+					saveSelected();
+				}
+			}
+		}
+
+		private String validInput(String input) {
+			return isValid(input);
+		}
+
+		private void saveSelected() {
+			getPreferences().put(getKey(), fSelected);
+			setChanged();
+			notifyObservers();
+		}
+
+		@Override
+		protected void updateWidget() {
+			final boolean hasKey = getKey() != null;
+
+			fLabel.setEnabled(hasKey && getEnabled());
+			fText.setEnabled(hasKey && getEnabled());
+
+			if (hasKey) {
+				String s = getPreferences().get(getKey());
+				fSelected = s;
+				fText.setText(s);
+			} else {
+				fText.setText(""); //$NON-NLS-1$
+			}
+		}
+
+		@Override
+		public Control getControl() {
+			return fText;
+		}
+	}
+
+	/**
 	 * Wrapper around a textfied which requests an integer input of a given range.
 	 */
 	protected final class NumberPreference extends Preference {
@@ -901,6 +1050,17 @@ public abstract class ModifyDialogTabPage implements IModifyDialogTabPage {
 	 * Convenience method to create a NumberPreference. The widget is registered as
 	 * a potential focus holder, and the default updater is added.
 	 */
+	protected StringPreference createStringPref(Composite composite, int numColumns, String name, String key) {
+		final StringPreference pref = new StringPreference(composite, numColumns, fWorkingValues, key, name);
+		fDefaultFocusManager.add(pref);
+		pref.addObserver(fUpdater);
+		return pref;
+	}
+
+	/*
+	 * Convenience method to create a NumberPreference. The widget is registered as
+	 * a potential focus holder, and the default updater is added.
+	 */
 	protected NumberPreference createNumberPref(Composite composite, int numColumns, String name, String key,
 			int minValue, int maxValue) {
 		final NumberPreference pref = new NumberPreference(composite, numColumns, fWorkingValues, key, minValue,