if(syntaxDiagramTab.isEnabled()) {
ElementRule r = editorRules.getEnclosingRuleAtPosition(getCaretPosition());
if(r == null) {
syntaxDiagramTab.setPlaceholder("Select a rule to display its syntax diagram");
} else {
if(r.hasErrors() && r.needsToBuildErrors()) {
grammarEngine.computeRuleErrors(r);
try {
syntaxDiagramTab.createGraphsForRule(r);
} catch (Exception e) {
// ignore