// Copyright 2012 Google Inc. All Rights Reserved.
//
// 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.google.collide.client.util.dom;
import com.google.collide.client.util.dom.eventcapture.MouseCaptureListener;
import com.google.collide.shared.util.ListenerRegistrar.Remover;
import com.google.gwt.user.client.Timer;
import elemental.events.Event;
import elemental.events.EventListener;
import elemental.events.EventRemover;
import elemental.events.MouseEvent;
import elemental.html.Element;
/**
* An {@link EventListener} implementation that parses the low-level events and
* produces high-level gestures, such as triple-click.
*
* This class differs subtly from the native {@link Event#CLICK} and
* {@link Event#DBLCLICK} events by dispatching the respective callback on mouse
* down instead of mouse up. This API difference allows clients to easily handle
* for example the double-click-and-drag case.
*/
public class MouseGestureListener {
/*
* TODO: When we have time, look into learning the native OS's
* delay by checking timing between CLICK and DBLCLICK events
*/
/**
* The maximum time in milliseconds between clicks to consider the latter
* click to be part of the same gesture as the previous click.
*/
public static final int MAX_CLICK_TIMEOUT_MS = 250;
public static Remover createAndAttach(Element element, Callback callback) {
MouseGestureListener instance = new MouseGestureListener(callback);
final EventRemover eventRemover = element.addEventListener(
Event.MOUSEDOWN, instance.captureListener, false);
return new Remover() {
@Override
public void remove() {
eventRemover.remove();
}
};
}
/**
* An interface that receives callbacks from the {@link MouseGestureListener}
* when gestures occur.
*/
public interface Callback {
/**
* @return false to abort any handling of subsequent mouse events in this
* gesture
*/
boolean onClick(int clickCount, MouseEvent event);
void onDrag(MouseEvent event);
void onDragRelease(MouseEvent event);
}
private final Callback callback;
private final MouseCaptureListener captureListener = new MouseCaptureListener() {
@Override
protected boolean onMouseDown(MouseEvent evt) {
return handleNativeMouseDown(evt);
}
@Override
protected void onMouseMove(MouseEvent evt) {
handleNativeMouseMove(evt);
}
@Override
protected void onMouseUp(MouseEvent evt) {
handleNativeMouseUp(evt);
}
};
private boolean hasDragInThisGesture;
private int numberOfClicks;
private final Timer resetClickStateTimer = new Timer() {
@Override
public void run() {
resetClickState();
}
};
private MouseGestureListener(Callback callback) {
this.callback = callback;
}
private boolean handleNativeMouseDown(MouseEvent event) {
numberOfClicks++;
if (!callback.onClick(numberOfClicks, event)) {
resetClickState();
return false;
}
/*
* If the user does not click again within this timeout, we will revert
* back to a clean state
*/
resetClickStateTimer.schedule(MAX_CLICK_TIMEOUT_MS);
return true;
}
private void handleNativeMouseMove(MouseEvent event) {
if (!hasDragInThisGesture) {
// Dragging the mouse resets the click state
resetClickState();
hasDragInThisGesture = true;
}
callback.onDrag(event);
}
private void handleNativeMouseUp(MouseEvent event) {
if (hasDragInThisGesture) {
callback.onDragRelease(event);
hasDragInThisGesture = false;
}
}
private void resetClickState() {
numberOfClicks = 0;
resetClickStateTimer.cancel();
}
}