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
if (currentDistance < distance || currentDistance == distance && p.length < nextAnnotationPosition.length) {
						distance= currentDistance;
						nextAnnotation= a;
						nextAnnotationPosition= p;
					}
				}
			}
		}
		if (containingAnnotationPosition != null && (!currentAnnotation || nextAnnotation == null)) {
			annotationPosition.setOffset(containingAnnotationPosition.getOffset());
			annotationPosition.setLength(containingAnnotationPosition.getLength());
			return containingAnnotation;
		}
		if (nextAnnotationPosition != null) {
			annotationPosition.setOffset(nextAnnotationPosition.getOffset());
			annotationPosition.setLength(nextAnnotationPosition.getLength());
		}
		
		return nextAnnotation;
	}
	
	/**
	 * Returns the annotation overlapping with the given range or <code>null</code>.
	 * 
	 * @param offset the region offset
	 * @param length the region length
	 * @return the found annotation or <code>null</code>
	 * @since 3.0
	 */