A snap to grid constraint implementation for the good old Object Handles v2.0 open-source framework.

SnapToGridConstraint.as

/**
 *  Latest information on this project can be found at http://www.rogue-development.com/objectHandles.html
 * 
 *  Copyright (c) 2009 Marc Hughes 
 * 
 *  Permission is hereby granted, free of charge, to any person obtaining a 
 *  copy of this software and associated documentation files (the "Software"), 
 *  to deal in the Software without restriction, including without limitation 
 *  the rights to use, copy, modify, merge, publish, distribute, sublicense, 
 *  and/or sell copies of the Software, and to permit persons to whom the Software 
 *  is furnished to do so, subject to the following conditions:
 * 
 *  The above copyright notice and this permission notice shall be included in all 
 *  copies or substantial portions of the Software.
 * 
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
 *  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 
 *  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 
 *  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 
 *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 
 *  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 
 * 
 *  See README for more information.
 * 
 **/
 
package com.roguedevelopment.objecthandles.constraints
{
	import com.roguedevelopment.objecthandles.DragGeometry;
	import com.roguedevelopment.objecthandles.IConstraint;
	
	/**
	 * This is a constraint that makes an object snap to a certain grid space.
	 * This can be turned on and off.
	 * 
	 **/
	public class SnapToGridConstraint implements IConstraint
	{
		public var gridSpaceX:int = 50;
		public var gridSpaceY:int = 50;
		public var enabled : Boolean = true;

		public function applyConstraint( original:DragGeometry, translation:DragGeometry, resizeHandleRole:uint ) : void
		{
			// Both are required for the logic to work
			if(!original || !translation || !enabled) return;
			
			//Reset back onto grid if the original object has been moved with the snapping disabled.
			if(Math.round(original.x)%gridSpaceX != 0)
				original.x = Math.round( original.x ) - Math.round( original.x )%gridSpaceX;
			if(Math.round(original.y)%gridSpaceY != 0)
				original.y = Math.round( original.y ) - Math.round( original.y )%gridSpaceY;
			
			translation.x = Math.round( translation.x - (translation.x%gridSpaceX) );
			translation.y = Math.round( translation.y - (translation.y%gridSpaceY) );
		}
	}
}