/*
* 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.ui;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.event.dom.client.ContextMenuEvent;
import com.google.gwt.event.dom.client.ContextMenuHandler;
import com.google.gwt.event.dom.client.DomEvent;
import com.google.gwt.event.dom.client.DoubleClickEvent;
import com.google.gwt.event.dom.client.DoubleClickHandler;
import com.google.gwt.event.dom.client.MouseDownEvent;
import com.google.gwt.event.dom.client.MouseDownHandler;
import com.google.gwt.event.dom.client.MouseUpEvent;
import com.google.gwt.event.dom.client.MouseUpHandler;
import com.google.gwt.event.shared.EventHandler;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.Event.NativePreviewEvent;
import com.google.gwt.user.client.Event.NativePreviewHandler;
import com.vaadin.client.ComponentConnector;
import com.vaadin.client.VConsole;
import com.vaadin.client.WidgetUtil;
public abstract class AbstractClickEventHandler implements MouseDownHandler,
MouseUpHandler, DoubleClickHandler, ContextMenuHandler {
private HandlerRegistration mouseDownHandlerRegistration;
private HandlerRegistration mouseUpHandlerRegistration;
private HandlerRegistration doubleClickHandlerRegistration;
private HandlerRegistration contextMenuHandlerRegistration;
protected ComponentConnector connector;
private String clickEventIdentifier;
/**
* The element where the last mouse down event was registered.
*/
private Element lastMouseDownTarget;
/**
* Set to true by {@link #mouseUpPreviewHandler} if it gets a mouseup at the
* same element as {@link #lastMouseDownTarget}.
*/
private boolean mouseUpPreviewMatched = false;
private HandlerRegistration mouseUpEventPreviewRegistration;
/**
* Previews events after a mousedown to detect where the following mouseup
* hits.
*/
private final NativePreviewHandler mouseUpPreviewHandler = new NativePreviewHandler() {
@Override
public void onPreviewNativeEvent(NativePreviewEvent event) {
if (event.getTypeInt() == Event.ONMOUSEUP) {
mouseUpEventPreviewRegistration.removeHandler();
// Event's reported target not always correct if event
// capture is in use
Element elementUnderMouse = WidgetUtil
.getElementUnderMouse(event.getNativeEvent());
if (lastMouseDownTarget != null
&& elementUnderMouse == lastMouseDownTarget) {
mouseUpPreviewMatched = true;
} else {
VConsole.log("Ignoring mouseup from " + elementUnderMouse
+ " when mousedown was on " + lastMouseDownTarget);
}
}
}
};
public AbstractClickEventHandler(ComponentConnector connector,
String clickEventIdentifier) {
this.connector = connector;
this.clickEventIdentifier = clickEventIdentifier;
}
public void handleEventHandlerRegistration() {
// Handle registering/unregistering of click handler depending on if
// server side listeners have been added or removed.
if (hasEventListener()) {
if (mouseDownHandlerRegistration == null) {
mouseDownHandlerRegistration = registerHandler(this,
MouseDownEvent.getType());
mouseUpHandlerRegistration = registerHandler(this,
MouseUpEvent.getType());
doubleClickHandlerRegistration = registerHandler(this,
DoubleClickEvent.getType());
contextMenuHandlerRegistration = registerHandler(this,
ContextMenuEvent.getType());
}
} else {
if (mouseDownHandlerRegistration != null) {
// Remove existing handlers
mouseDownHandlerRegistration.removeHandler();
mouseUpHandlerRegistration.removeHandler();
doubleClickHandlerRegistration.removeHandler();
contextMenuHandlerRegistration.removeHandler();
mouseDownHandlerRegistration = null;
mouseUpHandlerRegistration = null;
doubleClickHandlerRegistration = null;
contextMenuHandlerRegistration = null;
}
}
}
/**
* Registers the given handler to the widget so that the necessary events
* are passed to this {@link ClickEventHandler}.
* <p>
* By default registers the handler with the connector root widget.
* </p>
*
* @param <H>
* @param handler
* The handler to register
* @param type
* The type of the handler.
* @return A reference for the registration of the handler.
*/
protected <H extends EventHandler> HandlerRegistration registerHandler(
final H handler, DomEvent.Type<H> type) {
return connector.getWidget().addDomHandler(handler, type);
}
/**
* Checks if there is a server side event listener registered for clicks
*
* @return true if there is a server side event listener registered, false
* otherwise
*/
public boolean hasEventListener() {
return connector.hasEventListener(clickEventIdentifier);
}
/**
* Event handler for context menu. Prevents the browser context menu from
* popping up if there is a listener for right clicks.
*/
@Override
public void onContextMenu(ContextMenuEvent event) {
if (hasEventListener() && shouldFireEvent(event)) {
// Prevent showing the browser's context menu when there is a right
// click listener.
event.preventDefault();
}
}
@Override
public void onMouseDown(MouseDownEvent event) {
/*
* When getting a mousedown event, we must detect where the
* corresponding mouseup event if it's on a different part of the page.
*/
lastMouseDownTarget = WidgetUtil
.getElementUnderMouse(event.getNativeEvent());
mouseUpPreviewMatched = false;
mouseUpEventPreviewRegistration = Event
.addNativePreviewHandler(mouseUpPreviewHandler);
}
@Override
public void onMouseUp(MouseUpEvent event) {
/*
* Only fire a click if the mouseup hits the same element as the
* corresponding mousedown. This is first checked in the event preview
* but we can't fire the even there as the event might get canceled
* before it gets here.
*/
if (hasEventListener() && mouseUpPreviewMatched
&& lastMouseDownTarget != null
&& WidgetUtil.getElementUnderMouse(
event.getNativeEvent()) == lastMouseDownTarget
&& shouldFireEvent(event)) {
// "Click" with left, right or middle button
fireClick(event.getNativeEvent());
}
mouseUpPreviewMatched = false;
lastMouseDownTarget = null;
}
/**
* Sends the click event based on the given native event.
*
* @param event
* The native event that caused this click event
*/
protected abstract void fireClick(NativeEvent event);
/**
* Called before firing a click event. Allows sub classes to decide if this
* in an event that should cause an event or not.
*
* @param event
* The user event
* @return true if the event should be fired, false otherwise
*/
protected boolean shouldFireEvent(DomEvent<?> event) {
return true;
}
/**
* Event handler for double clicks. Used to fire double click events. Note
* that browsers typically fail to prevent the second click event so a
* double click will result in two click events and one double click event.
*/
@Override
public void onDoubleClick(DoubleClickEvent event) {
if (hasEventListener() && shouldFireEvent(event)) {
fireClick(event.getNativeEvent());
}
}
/**
* Click event calculates and returns coordinates relative to the element
* returned by this method. Default implementation uses the root element of
* the widget. Override to provide a different relative element.
*
* @return The Element used for calculating relative coordinates for a click
* or null if no relative coordinates can be calculated.
*/
protected com.google.gwt.user.client.Element getRelativeToElement() {
return connector.getWidget().getElement();
}
}