/*
* Copyright 2008 Fred Sauer
*
* 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.allen_sauer.gwt.dnd.client;
import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Element;
import com.google.gwt.user.client.ui.Panel;
import com.google.gwt.user.client.ui.Widget;
import com.allen_sauer.gwt.dnd.client.drop.DropController;
import com.allen_sauer.gwt.dnd.client.util.Area;
import com.allen_sauer.gwt.dnd.client.util.CoordinateLocation;
import com.allen_sauer.gwt.dnd.client.util.DOMUtil;
import com.allen_sauer.gwt.dnd.client.util.Location;
import com.allen_sauer.gwt.dnd.client.util.WidgetArea;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
/**
* Package private helper implementation class for {@link AbstractDragController}
* to track all relevant {@link DropController DropControllers}.
*/
class DropControllerCollection {
protected static class Candidate implements Comparable {
private final DropController dropController;
private Area targetArea;
Candidate(DropController dropController) {
this.dropController = dropController;
Widget target = dropController.getDropTarget();
if (!target.isAttached()) {
throw new IllegalStateException(
"Unattached drop target. You must call DragController#unregisterDropController for all drop targets not attached to the DOM.");
}
targetArea = new WidgetArea(target, null);
}
public int compareTo(Object arg0) {
Candidate other = (Candidate) arg0;
Element myElement = getDropTarget().getElement();
Element otherElement = other.getDropTarget().getElement();
if (DOM.compare(myElement, otherElement)) {
return 0;
} else if (DOM.isOrHasChild(myElement, otherElement)) {
return -1;
} else if (DOM.isOrHasChild(otherElement, myElement)) {
return 1;
} else {
return 0;
}
}
DropController getDropController() {
return dropController;
}
Widget getDropTarget() {
return dropController.getDropTarget();
}
Area getTargetArea() {
return targetArea;
}
}
private final ArrayList dropControllerList;
private Candidate[] sortedCandidates = null;
/**
* Default constructor.
*/
DropControllerCollection(ArrayList dropControllerList) {
this.dropControllerList = dropControllerList;
}
/**
* Determines which DropController represents the deepest DOM descendant
* drop target located at the provided location <code>(x, y)</code>.
*
* @param x offset left relative to document body
* @param y offset top relative to document body
* @return a drop controller for the intersecting drop target or <code>null</code> if none
* are applicable
*/
DropController getIntersectDropController(int x, int y) {
Location location = new CoordinateLocation(x, y);
for (int i = sortedCandidates.length - 1; i >= 0; i--) {
Candidate candidate = sortedCandidates[i];
Area targetArea = candidate.getTargetArea();
if (targetArea.intersects(location)) {
return candidate.getDropController();
}
}
return null;
}
/**
* Cache a list of eligible drop controllers, sorted by relative DOM positions
* of their respective drop targets. Called at the beginning of each drag operation,
* or whenever drop target eligibility has changed while dragging.
*
* @param boundaryPanel boundary area for drop target eligibility considerations
* @param context the current drag context
*/
void resetCache(Panel boundaryPanel, DragContext context) {
ArrayList list = new ArrayList();
if (context.draggable != null) {
WidgetArea boundaryArea = new WidgetArea(boundaryPanel, null);
for (Iterator iterator = dropControllerList.iterator(); iterator.hasNext();) {
DropController dropController = (DropController) iterator.next();
Candidate candidate = new Candidate(dropController);
if (DOMUtil.isOrContains(context.draggable.getElement(),
candidate.getDropTarget().getElement())) {
continue;
}
if (candidate.getTargetArea().intersects(boundaryArea)) {
list.add(candidate);
}
}
}
sortedCandidates = (Candidate[]) list.toArray(new Candidate[list.size()]);
Arrays.sort(sortedCandidates);
}
}