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/*
 * Copyright 2008 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.impl;

import com.google.gwt.core.client.JavaScriptObject;
import com.google.gwt.dom.client.Element;
import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.EventListener;

/**
 * Native implementation associated with {@link com.google.gwt.user.client.DOM}.
 */
public abstract class DOMImpl {

  protected static boolean eventSystemIsInitialized;

  public static native EventListener getEventListener(Element elem) /*-{
    // Return elem.__listener if and only if it was assigned from our module
    var maybeListener = elem.__listener;
    return @DOMImpl::isMyListener(*)(maybeListener) ? maybeListener : null;
  }-*/;

  public static native void setEventListener(Element elem, EventListener listener) /*-{
    elem.__listener = listener;
  }-*/;

  /**
   * Returns trueif the object is an instance of EventListener and
   * the object belongs to this module.
   * 
   * Note that this method should only be called from JSNI, otherwise it can be inlined and compiler
   * can remove instanceOf checks. E.g.
   * 
   * EventListener listener = getEventListenerFromSomeJsniCode();
   * if (isMyListener(listener)) {
   *   // This block will always be executed because the compiler proves that the instance of checks
   *   // are not required after inlining isMyListener.
   * }
   * 
   */
  private static boolean isMyListener(Object object) {
    /*
     * The first test ensures the Object belongs to this module in Production
     * Mode by ensuring this is not a JavaScriptObject. In Production Mode,
     * foreign Java objects appear to be JavaScriptObject. See
     * Cast.isJavaScriptObject().
     * 
     * The second test then checks the exact type.
     * 
     * TODO: make the generated code smaller!
     */
    return !(object instanceof JavaScriptObject)
        && (object instanceof com.google.gwt.user.client.EventListener);
  }

  public native void eventCancelBubble(Event evt, boolean cancel) /*-{
    evt.cancelBubble = cancel;
  }-*/;

  public abstract Element eventGetFromElement(Event evt);
  
  public native boolean eventGetRepeat(Event evt) /*-{
    return !!evt.repeat;
  }-*/; 
 
  public abstract Element eventGetToElement(Event evt);

  public final int eventGetTypeInt(Event evt) {
    return eventGetTypeInt(evt.getType());
  }
  
  public native int eventGetTypeInt(String eventType) /*-{
    switch (eventType) {
    case "blur": return 0x01000;
    case "change": return 0x00400;
    case "click": return 0x00001;
    case "dblclick": return 0x00002;
    case "focus": return 0x00800;
    case "keydown": return 0x00080;
    case "keypress": return 0x00100;
    case "keyup": return 0x00200;
    case "load": return 0x08000;
    case "losecapture": return 0x02000;
    case "mousedown": return 0x00004;
    case "mousemove": return 0x00040;
    case "mouseout": return 0x00020;
    case "mouseover": return 0x00010;
    case "mouseup": return 0x00008;
    case "scroll": return 0x04000;
    case "error": return 0x10000;
    case "mousewheel": return 0x20000;
    case "DOMMouseScroll": return 0x20000;
    case "contextmenu": return 0x40000;
    case "paste": return 0x80000;
    case "touchstart": return 0x100000;
    case "touchmove": return 0x200000;
    case "touchend": return 0x400000;
    case "touchcancel": return 0x800000;
    case "gesturestart": return 0x1000000;
    case "gesturechange": return 0x2000000;
    case "gestureend": return 0x4000000;
    default: return -1;
    }
  }-*/; 
  
  public native void eventSetKeyCode(Event evt, char key) /*-{
    evt.keyCode = key;
  }-*/;
 
  public abstract Element getChild(Element elem, int index);

  public abstract int getChildCount(Element elem);

  public abstract int getChildIndex(Element parent, Element child);

  public native int getEventsSunk(Element elem) /*-{
    return elem.__eventBits || 0;
  }-*/;

  public abstract void insertChild(Element parent, Element child, int index);

  public void maybeInitializeEventSystem() {
    if (!eventSystemIsInitialized) {
      initEventSystem();
      eventSystemIsInitialized = true;
    }
  }

  public abstract void releaseCapture(Element elem);

  public abstract void setCapture(Element elem);

  public abstract void sinkBitlessEvent(Element elem, String eventTypeName);

  public abstract void sinkEvents(Element elem, int eventBits);

  /**
   * Initializes the event dispatch system.
   */
  protected abstract void initEventSystem();
}