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/*
 * Copyright 2009 Google Inc.
 * 
 * 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.gwt.user.client.ui;

import com.google.gwt.core.client.Scheduler;
import com.google.gwt.core.client.Scheduler.ScheduledCommand;
import com.google.gwt.layout.client.Layout;
import com.google.gwt.layout.client.Layout.AnimationCallback;
import com.google.gwt.layout.client.Layout.Layer;

/**
 * A scheduled command used by animated layouts to ensure that only layout is
 * ever performed for a panel within a given user event.
 * 
 * 

* Note: This class assumes that {@link com.google.gwt.layout.client.Layout.Layer#getUserObject Layer.getUserObject()} will * return the widget associated with a given layer. *

*/ public class LayoutCommand implements ScheduledCommand { private boolean scheduled, canceled; private int duration; private Layout.AnimationCallback callback; private final Layout layout; /** * Creates a new command for the given layout object. * * @param layout */ public LayoutCommand(Layout layout) { this.layout = layout; } /** * Cancels this command. A subsequent call to * {@link #schedule(int, Layout.AnimationCallback)} will re-enable it. */ public void cancel() { // There's no way to "unschedule" a command, so we use a canceled flag. canceled = true; } public final void execute() { scheduled = false; if (canceled) { return; } doBeforeLayout(); layout.layout(duration, new Layout.AnimationCallback() { public void onAnimationComplete() { // Chain to the passed callback. if (callback != null) { callback.onAnimationComplete(); } } public void onLayout(Layer layer, double progress) { // Inform the child associated with this layer that its size may // have changed. Widget child = (Widget) layer.getUserObject(); if (child instanceof RequiresResize) { ((RequiresResize) child).onResize(); } // Chain to the passed callback. if (callback != null) { callback.onLayout(layer, progress); } } }); } /** * Schedules a layout. The duration and callback passed to this method will * supercede any previous call that has not yet been executed. * * @param duration * @param callback */ public void schedule(int duration, AnimationCallback callback) { this.duration = duration; this.callback = callback; canceled = false; if (!scheduled) { scheduled = true; Scheduler.get().scheduleFinally(this); } } /** * Called before the layout is executed. Override this method to perform any * work that needs to happen just before it. */ protected void doBeforeLayout() { } }




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