com.allen_sauer.gwt.dnd.client.drop.GridConstrainedDropController.java Source code

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Here is the source code for com.allen_sauer.gwt.dnd.client.drop.GridConstrainedDropController.java

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/*
 * Copyright 2009 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.drop;

import com.google.gwt.user.client.ui.AbsolutePanel;
import com.google.gwt.user.client.ui.Widget;

import com.allen_sauer.gwt.dnd.client.DragContext;

/**
 * A {@link DropController} which constrains the placement of draggable widgets the grid specified
 * in the constructor.
 */
public class GridConstrainedDropController extends AbsolutePositionDropController {

    private int gridX;

    private int gridY;

    public GridConstrainedDropController(AbsolutePanel dropTarget, int gridX, int gridY) {
        super(dropTarget);
        this.gridX = gridX;
        this.gridY = gridY;
    }

    @Override
    public void drop(Widget widget, int left, int top) {
        left = Math.max(0, Math.min(left, dropTarget.getOffsetWidth() - widget.getOffsetWidth()));
        top = Math.max(0, Math.min(top, dropTarget.getOffsetHeight() - widget.getOffsetHeight()));
        left = Math.round((float) left / gridX) * gridX;
        top = Math.round((float) top / gridY) * gridY;
        dropTarget.add(widget, left, top);
    }

    @Override
    public void onMove(DragContext context) {
        super.onMove(context);
        for (Draggable draggable : draggableList) {
            draggable.desiredX = context.desiredDraggableX - dropTargetOffsetX + draggable.relativeX;
            draggable.desiredY = context.desiredDraggableY - dropTargetOffsetY + draggable.relativeY;
            draggable.desiredX = Math.max(0,
                    Math.min(draggable.desiredX, dropTargetClientWidth - draggable.offsetWidth));
            draggable.desiredY = Math.max(0,
                    Math.min(draggable.desiredY, dropTargetClientHeight - draggable.offsetHeight));
            draggable.desiredX = Math.round((float) draggable.desiredX / gridX) * gridX;
            draggable.desiredY = Math.round((float) draggable.desiredY / gridY) * gridY;
            dropTarget.add(draggable.positioner, draggable.desiredX, draggable.desiredY);
        }
    }
}