/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.waveprotocol.wave.client.scroll;
import com.google.common.annotations.VisibleForTesting;
import com.google.gwt.core.client.Duration;
import org.waveprotocol.wave.client.common.util.MathUtil;
import org.waveprotocol.wave.client.scheduler.Scheduler.Task;
import org.waveprotocol.wave.client.scheduler.SchedulerInstance;
import org.waveprotocol.wave.client.scheduler.TimerService;
/**
* Decorates a scroller, providing a layer of animated scroll movement.
*
* @author hearnden@google.com (David Hearnden)
*/
public final class AnimatedScrollPanel<T> implements ScrollPanel<T>, Task {
/** Time period for the animation. */
private final static int ANIMATION_DURATION_MS = 300;
private final ScrollPanel<? super T> target;
private final TimerService scheduler;
// Animation state.
private Duration counter;
private double startLocation;
private double endLocation;
/**
* Creates an animating scroller.
*
* @param scheduler scheduler for running animations
* @param target underlying scroller
*/
@VisibleForTesting
AnimatedScrollPanel(TimerService scheduler, ScrollPanel<? super T> target) {
this.scheduler = scheduler;
this.target = target;
}
/**
* Creates an animation layer over a scroller.
*/
public static <T> AnimatedScrollPanel<T> create(ScrollPanel<? super T> target) {
return new AnimatedScrollPanel<T>(SchedulerInstance.getHighPriorityTimer(), target);
}
@Override
public void moveTo(double location) {
startLocation = getViewport().getStart();
endLocation = location;
counter = new Duration();
execute();
scheduler.scheduleDelayed(this, 0);
}
/**
* Sets the underlying target's scroll location to the current animation
* location.
*/
@Override
public void execute() {
int time = counter.elapsedMillis();
target.moveTo(location(time));
if (time < ANIMATION_DURATION_MS) {
// Run again, but delayed so that paint can occur first.
scheduler.scheduleDelayed(this, 0);
}
}
/** @return the animation's scroll location at a particular time. */
private double location(int time) {
// Clip current time to start/end bounds.
double ctime = MathUtil.clip(0, ANIMATION_DURATION_MS, time);
// Follow first quadrant of sine.
double t = (ctime / ANIMATION_DURATION_MS) * (Math.PI / 2);
double x = Math.sin(t);
return startLocation + x * (endLocation - startLocation);
}
@Override
public Extent getViewport() {
return target.getViewport();
}
@Override
public Extent getContent() {
return target.getContent();
}
@Override
public Extent extentOf(T measurable) {
return target.extentOf(measurable);
}
}