Bug 40788 [plan item] Configurable Next/Previous actions
Toolbar drop down, or editor specific control. Needs to be coordinated with Platform UI.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
StyledText text= viewer.getTextWidget();
		text.addBidiSegmentListener(new  BidiSegmentListener() {
			public void lineGetSegments(BidiSegmentEvent event) {
				event.segments= getBidiLineSegments(event.lineOffset, event.lineText);
			}
		});
		
		JavaUIHelp.setHelp(this, text, IJavaHelpContextIds.JAVA_EDITOR);
				
		fSourceViewerDecorationSupport= new SourceViewerDecorationSupport(viewer, fOverviewRuler, fAnnotationAccess, sharedColors);
		configureSourceViewerDecorationSupport();
		
		return viewer;
	}
	
	public final ISourceViewer getViewer() {
		return getSourceViewer();
	}
	
	/*
	 * @see AbstractTextEditor#createSourceViewer(Composite, IVerticalRuler, int)
	 */
	protected ISourceViewer createJavaSourceViewer(Composite parent, IVerticalRuler verticalRuler, IOverviewRuler overviewRuler, boolean isOverviewRulerVisible, int styles) {
			return new JavaSourceViewer(parent, verticalRuler, fOverviewRuler, isOverviewRulerVisible(), styles);
	}
	
	/*
	 * @see AbstractTextEditor#affectsTextPresentation(PropertyChangeEvent)
	 */
	protected boolean affectsTextPresentation(PropertyChangeEvent event) {