changed the error message so that the ^ is always pointing to the right

character

bundles/org.eclipse.ui/src/org/eclipse/ui/internal/SearchDecoration.java

@@ -14,11 +14,13 @@
 
 package org.eclipse.ui.internal;
 
+
 import java.util.regex.Pattern;
 import java.util.regex.PatternSyntaxException;
 
 import org.eclipse.jface.fieldassist.ControlDecoration;
 import org.eclipse.jface.fieldassist.FieldDecorationRegistry;
+import org.eclipse.swt.graphics.GC;
 import org.eclipse.swt.graphics.Image;
 
 /**
@@ -41,7 +43,9 @@ private SearchDecoration() {
 	 *                         the validation.
 	 */
 	public static boolean validateRegex(String regex, ControlDecoration targetDecoration) {
-		String errorMessage = getValidationError(regex);
+		GC gc = new GC(targetDecoration.getControl());
+
+		String errorMessage = getValidationError(regex, gc);
 		if (errorMessage.isEmpty()) {
 			targetDecoration.hide();
 			return true;
@@ -53,6 +57,7 @@ public static boolean validateRegex(String regex, ControlDecoration targetDecora
 		targetDecoration.setImage(decorationImage);
 		targetDecoration.setDescriptionText(errorMessage);
 		targetDecoration.show();
+		gc.dispose();
 		return false;
 	}
 
@@ -62,20 +67,33 @@ public static boolean validateRegex(String regex, ControlDecoration targetDecora
 	 * @return The appropriate error message if the regex is invalid or an empty
 	 *         string if the regex is valid.
 	 */
-	private static String getValidationError(String regex) {
+	private static String getValidationError(String regex, GC gc) {
 		try {
 			Pattern.compile(regex);
 			return ""; //$NON-NLS-1$
 		} catch (PatternSyntaxException e) {
-			String message = e.getLocalizedMessage();
+			String description = e.getDescription();
+			int errorIndex = e.getIndex();
+			String pattern = e.getPattern();
+
+			StringBuilder sBuilder = new StringBuilder();
+
+			sBuilder.append(description + " at index " + errorIndex); //$NON-NLS-1$
+			sBuilder.append(System.lineSeparator());
+			sBuilder.append(pattern);
+			sBuilder.append(System.lineSeparator());
+
+			String stringToIndexString = pattern.substring(0, errorIndex);
+			String buildString = ""; //$NON-NLS-1$
+			String thinSpace = "\u2009"; //$NON-NLS-1$
 
-			// Only preserve the first line of the original error message.
-			int i = 0;
-			while (i < message.length() && "\n\r".indexOf(message.charAt(i)) == -1) { //$NON-NLS-1$
-				i++;
+			while (gc.stringExtent(buildString).x < gc.stringExtent(stringToIndexString).x - 1) {
+				buildString += thinSpace; // $NON-NLS-1$
 			}
+			sBuilder.append(buildString);
 
-			return message.substring(0, i);
+			sBuilder.append("^"); //$NON-NLS-1$
+			return sBuilder.toString();
 		}
 	}