Bug 81983 [preferences] Disabling and enabling folding on small file takes forever
3.1 M4 Using enable/disable folding on a small CU takes forever. This is caused by the recent change to apply the preference to all Java editors. In another (hidden) window (Debug) I had StyledText open which (understandably) took long to react on the preference change. Non-visible editor's should not react to this change until they become visible.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
fMarkExceptions= store.getBoolean(PreferenceConstants.EDITOR_MARK_EXCEPTION_OCCURRENCES);
		fMarkImplementors= store.getBoolean(PreferenceConstants.EDITOR_MARK_IMPLEMENTORS);
		fMarkMethodExitPoints= store.getBoolean(PreferenceConstants.EDITOR_MARK_METHOD_EXIT_POINTS);
	}
	
	/*
	 * @see AbstractTextEditor#createSourceViewer(Composite, IVerticalRuler, int)
	 */
	protected final ISourceViewer createSourceViewer(Composite parent, IVerticalRuler verticalRuler, int styles) {
		
		ISourceViewer viewer= createJavaSourceViewer(parent, verticalRuler, getOverviewRuler(), isOverviewRulerVisible(), styles, getPreferenceStore());
		
		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);
		
		getSourceViewerDecorationSupport(viewer);				
		
		return viewer;
	}
	
	public final ISourceViewer getViewer() {
		return getSourceViewer();
	}