Bug 54900 [rulers] Java Editor does not show ruler on external Java files
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitDocumentProvider.java
import org.eclipse.jface.util.PropertyChangeEvent;
import org.eclipse.jface.text.Assert;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DefaultLineTracker;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.ILineTracker;
import org.eclipse.jface.text.ISynchronizable;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.source.Annotation;
import org.eclipse.jface.text.source.AnnotationModelEvent;
import org.eclipse.jface.text.source.IAnnotationAccessExtension;
import org.eclipse.jface.text.source.IAnnotationModel;
import org.eclipse.jface.text.source.IAnnotationModelListener;
import org.eclipse.jface.text.source.IAnnotationModelListenerExtension;
import org.eclipse.jface.text.source.IAnnotationPresentation;
import org.eclipse.jface.text.source.ImageUtilities;
import org.eclipse.ui.IFileEditorInput;
import org.eclipse.ui.IStorageEditorInput;
import org.eclipse.ui.texteditor.AbstractMarkerAnnotationModel;
import org.eclipse.ui.texteditor.AnnotationPreference;
import org.eclipse.ui.texteditor.AnnotationPreferenceLookup;
import org.eclipse.ui.texteditor.IDocumentProvider;
import org.eclipse.ui.texteditor.MarkerAnnotation;
import org.eclipse.ui.texteditor.MarkerUtilities;
import org.eclipse.ui.texteditor.ResourceMarkerAnnotationModel;
import org.eclipse.ui.editors.text.EditorsUI;
import org.eclipse.ui.editors.text.ForwardingDocumentProvider;
import org.eclipse.ui.editors.text.TextFileDocumentProvider;
import org.eclipse.jdt.core.IBuffer;
import org.eclipse.jdt.core.ICompilationUnit;