/*
* Copyright 2000-2016 Vaadin Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.vaadin.client;
import static com.vaadin.shared.EventId.BLUR;
import static com.vaadin.shared.EventId.FOCUS;
import java.util.function.Supplier;
import com.google.gwt.event.dom.client.BlurEvent;
import com.google.gwt.event.dom.client.BlurHandler;
import com.google.gwt.event.dom.client.DomEvent.Type;
import com.google.gwt.event.dom.client.FocusEvent;
import com.google.gwt.event.dom.client.FocusHandler;
import com.google.gwt.event.shared.EventHandler;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.ui.Widget;
/**
* Helper class for attaching/detaching handlers for Vaadin client side
* components, based on identifiers in UIDL. Helpers expect Paintables to be
* both listeners and sources for events. This helper cannot be used for more
* complex widgets.
* <p>
* Possible current registration is given as parameter. The returned
* registration (possibly the same as given, should be store for next update.
* <p>
* Pseudocode what helpers do:
*
* <pre>
*
* if paintable has event listener in UIDL
* if registration is null
* register paintable as as handler for event
* return the registration
* else
* if registration is not null
* remove the handler from paintable
* return null
*
*
* </pre>
*/
public class EventHelper {
/**
* Adds or removes a focus handler depending on if the connector has focus
* listeners on the server side or not.
*
* @param connector
* The connector to update. Must implement focusHandler.
* @param handlerRegistration
* The old registration reference or null if no handler has been
* registered previously
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static <T extends ComponentConnector & FocusHandler> HandlerRegistration updateFocusHandler(
T connector, HandlerRegistration handlerRegistration) {
return updateHandler(connector, connector, FOCUS, handlerRegistration,
FocusEvent.getType(), connector.getWidget());
}
/**
* Adds or removes a focus handler depending on if the connector has focus
* listeners on the server side or not.
*
* @param connector
* The connector to update. Must implement focusHandler.
* @param handlerRegistration
* The old registration reference or null if no handler has been
* registered previously
* @param widget
* The widget which emits focus events
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static <T extends ComponentConnector & FocusHandler> HandlerRegistration updateFocusHandler(
T connector, HandlerRegistration handlerRegistration,
Widget widget) {
return updateHandler(connector, connector, FOCUS, handlerRegistration,
FocusEvent.getType(), widget);
}
/**
* Adds or removes a blur handler depending on if the connector has blur
* listeners on the server side or not.
*
* @param connector
* The connector to update. Must implement BlurHandler.
* @param handlerRegistration
* The old registration reference or null if no handler has been
* registered previously
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static <T extends ComponentConnector & BlurHandler> HandlerRegistration updateBlurHandler(
T connector, HandlerRegistration handlerRegistration) {
return updateHandler(connector, connector, BLUR, handlerRegistration,
BlurEvent.getType(), connector.getWidget());
}
/**
* Adds or removes a blur handler depending on if the connector has blur
* listeners on the server side or not.
*
* @param connector
* The connector to update. Must implement BlurHandler.
* @param handlerRegistration
* The old registration reference or null if no handler has been
* registered previously
* @param widget
* The widget which emits blur events
*
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static <T extends ComponentConnector & BlurHandler> HandlerRegistration updateBlurHandler(
T connector, HandlerRegistration handlerRegistration,
Widget widget) {
return updateHandler(connector, connector, BLUR, handlerRegistration,
BlurEvent.getType(), widget);
}
public static <H extends EventHandler> HandlerRegistration updateHandler(
ComponentConnector connector, H handler, String eventIdentifier,
HandlerRegistration handlerRegistration, Type<H> type,
Widget widget) {
return updateHandler(connector, eventIdentifier, handlerRegistration,
() -> widget.addDomHandler(handler, type));
}
/**
* Updates handler registered using {@code handlerProvider}: removes it if
* connector doesn't have anymore {@code eventIdentifier} using provided
* {@code handlerRegistration} and adds it via provided
* {@code handlerProvider} if connector has event listener with
* {@code eventIdentifier}.
*
* @param connector
* connector to check event listener presence
* @param eventIdentifier
* event identifier whose presence in the connector is checked
* @param handlerRegistration
* resulting handler registration to remove added handler in case
* of absence event listener
* @param handlerProvider
* the strategy to register handler
* @return handlerRegistration which should be used to remove registered
* handler via {@code handlerProvider}
*/
public static <H extends EventHandler, W extends Widget> HandlerRegistration updateHandler(
ComponentConnector connector, String eventIdentifier,
HandlerRegistration handlerRegistration,
Supplier<HandlerRegistration> handlerProvider) {
if (connector.hasEventListener(eventIdentifier)) {
if (handlerRegistration == null) {
handlerRegistration = handlerProvider.get();
}
} else if (handlerRegistration != null) {
handlerRegistration.removeHandler();
handlerRegistration = null;
}
return handlerRegistration;
}
}