Bug 96917 [implementation] If two editors use the 2.x-compatible API, one or both doesn't work
At least one problem is that 3.0 installs partitioners for every editor that might possibly edit a file, but each editor expects its own partitioner to be installed. Leading to the famous white screen with blue line.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitDocumentProvider.java
}
				return -1;
			}
			public void put(Position position,  Object value) {
				int index= getIndex(position);
				if (index == -1) {
					Entry entry= new Entry();
					entry.fPosition= position;
					entry.fValue= value;
					fList.add(entry);
				} else {
					Entry entry= (Entry) fList.get(index);
					entry.fValue= value;
				}
			}
			public void remove(Position position) {
				int index= getIndex(position);
				if (index > -1)
					fList.remove(index);
			}
			public void clear() {
				fList.clear();
			}
		}
		/**
		 * Annotation model dealing with java marker annotations and temporary problems.
		 * Also acts as problem requester for its compilation unit. Initially inactive. Must explicitly be
		 * activated.
		 */
		protected static class CompilationUnitAnnotationModel extends ResourceMarkerAnnotationModel implements IProblemRequestor, IProblemRequestorExtension {