/*
 * Copyright 2011 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.animation.client;

import com.google.gwt.core.client.GWT;

/**
 * Base class for animation implementations.
 */
abstract class AnimationSchedulerImpl extends AnimationScheduler {

  /**
   * The singleton instance of animation scheduler.
   */
  static final AnimationScheduler INSTANCE;

  static {
    AnimationScheduler impl = GWT.create(AnimationScheduler.class);

    /*
     * If the implementation isn't natively supported, revert back to the timer
     * based implementation.
     * 
     * If impl==null (such as with GWTMockUitlities.disarm()), use null. We
     * don't want to create a new AnimationSchedulerImplTimer in this case.
     */
    if (impl instanceof AnimationSchedulerImpl) {
      if (!((AnimationSchedulerImpl) impl).isNativelySupported()) {
        impl = new AnimationSchedulerImplTimer();
      }
    }

    INSTANCE = impl;
  }

  /**
   * Check if the implementation is natively supported.
   * 
   * @return true if natively supported, false if not
   */
  protected abstract boolean isNativelySupported();
}