throws UnableToCompleteException {
if (!uiWriter.isWidgetElement(elem)) {
return null;
}
FieldManager fieldManager = uiWriter.getFieldManager();
FieldWriter fieldWriter = fieldManager.require(fieldName);
// Allocate a local variable to hold the dom id for this widget. Note
// that idHolder is a local variable reference, not a string id. We
// have to generate the ids at runtime, not compile time, or else
// we'll reuse ids for any template rendered more than once.
String idHolder = uiWriter.declareDomIdHolder(null);
uiWriter.ensureCurrentFieldAttached();
FieldWriter childFieldWriter = uiWriter.parseElementToField(elem);
String elementPointer = idHolder + "Element";
uiWriter.addInitStatement(
"Element %s = com.google.gwt.dom.client.Document.get().getElementById(%s);",
elementPointer, idHolder);
if (uiWriter.useLazyWidgetBuilders()) {
// Register a DOM id field.
String lazyDomElementPath = LazyDomElement.class.getCanonicalName();
FieldWriter elementWriter = fieldManager.registerField(lazyDomElementPath, elementPointer);
elementWriter.setInitializer(String.format("new %s<Element>(%s)",
lazyDomElementPath, fieldManager.convertFieldToGetter(idHolder)));
// Add attach/detach sections for this element.
fieldWriter.addAttachStatement("%s.get();",
fieldManager.convertFieldToGetter(elementPointer));
fieldWriter.addDetachStatement(
"%s.addAndReplaceElement(%s, %s.get());",
fieldName,
fieldManager.convertFieldToGetter(childFieldWriter.getName()),
fieldManager.convertFieldToGetter(elementPointer));
} else {
// Delay replacing the placeholders with the widgets until after
// detachment so as not to end up attaching the widget to the DOM
// unnecessarily
uiWriter.addDetachStatement(
"%1$s.addAndReplaceElement(%2$s, %3$s);",
fieldName,
childFieldWriter.getName(),
elementPointer);
}
// Create an element to hold the widget.
String tag = getLegalPlaceholderTag(elem);
idHolder = fieldManager.convertFieldToGetter(idHolder);
if (uiWriter.useSafeHtmlTemplates()) {
idHolder = uiWriter.tokenForStringExpression(elem, idHolder);
} else {
idHolder = "\" + " + idHolder + " + \"";
}