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
int stateMask= stateMasks[j];
						ITextHover textHover= configuration.getTextHover(sourceViewer, t, stateMask);
						((ITextViewerExtension2)sourceViewer).setTextHover(textHover, t, stateMask);
					}
				} else {
					ITextHover textHover= configuration.getTextHover(sourceViewer, t);
					((ITextViewerExtension2)sourceViewer).setTextHover(textHover, t, ITextViewerExtension2.DEFAULT_HOVER_STATE_MASK);
				}
			} else
				sourceViewer.setTextHover(configuration.getTextHover(sourceViewer, t), t);
		}
	}
	
	/*
	 * @see org.eclipse.jdt.internal.ui.viewsupport.IViewPartInputProvider#getViewPartInput()
	 */
	public Object getViewPartInput() {
		return getEditorInput().getAdapter(IJavaElement.class);
	}
	
	/*
	 * @see org.eclipse.ui.texteditor.AbstractTextEditor#doSetSelection(ISelection)
	 */
	protected void doSetSelection(ISelection selection) {
		super.doSetSelection(selection);
		synchronizeOutlinePageSelection();
	}
	
	boolean isFoldingEnabled() {
		return JavaPlugin.getDefault().getPreferenceStore().getBoolean(PreferenceConstants.EDITOR_FOLDING_ENABLED);