对齐到格子与锁定到网格

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
                width="700" height="450" applicationComplete="applicationCompleteHandler(event)"
                backgroundColor="0xFFFFFF" backgroundGradientColors="[0xFFFFFF,0xFFFFFF]"
                fontSize="12" layout="absolute"
                viewSourceURL="http://img.l4cd.net/attachment/snap-to-grid/srcview/"
                >
    
    <mx:Script>
        <![CDATA[
            import mx.events.FlexEvent;
            protected var hGap:Number;
            protected var vGap:Number;
            protected function clickHandler(event:MouseEvent):void
            {
                hGap = h.value * 10;
                vGap = v.value * 10;
                drawGrid();
            }
            
            private function drawGrid():void
            {
                content.graphics.clear();
                content.graphics.lineStyle(2,0xFF0000);
                var pos:Number = 0;
                while(pos < content.width)
                {
                    pos += vGap;
                    content.graphics.moveTo(pos,0);
                    content.graphics.lineTo(pos,content.height);
                }
                pos = 0;
                while(pos < content.height)
                {
                    pos += hGap;
                    content.graphics.moveTo(0,pos);
                    content.graphics.lineTo(content.width,pos);
                }
            }
            
            protected function applicationCompleteHandler(event:FlexEvent):void
            {
                clickHandler(null);
                dot = new Sprite();
                dot.graphics.beginFill(0xFF6600,0.75);
                dot.graphics.drawCircle(0,0,10);
                dot.graphics.endFill();
                content.addChild(dot);
                dot.x = dot.y = 40;
                dot.addEventListener(MouseEvent.MOUSE_DOWN,onSpriteDown);
            }
            protected var dot:Sprite;
            
            protected function onSpriteDown(event:MouseEvent):void
            {
                stage.addEventListener(MouseEvent.MOUSE_MOVE,onDragMove);
                stage.addEventListener(MouseEvent.MOUSE_UP,onDragStop);
                onDragMove(event);
            }
            
            protected function onDragMove(event:MouseEvent):void
            {
                var targetX:int = event.stageX;
                var targetY:int = event.stageY;
                var distanceX:Number = 0;
                var distanceY:Number = 0;
                if(snap.selected)
                {
                    distanceX = 10;
                    distanceY = 10;
                }
                if(lock.selected)
                {
                    distanceX = hGap / 2;
                    distanceY = vGap / 2;
                }
                
                //最主要代码,判断当前位置是否在网格的上下左右指定像素内
                var value:int;
                if(distanceX > 0)
                {
                    value = targetX % hGap;
                    if(value < distanceX)
                    {
                        targetX -= value;
                    }else if(value >= hGap - distanceX)
                    {
                        targetX += hGap - value;
                    }
                }
                if(distanceY)
                {
                    value = targetY % vGap;
                    if(value < distanceY)
                    {
                        targetY -= value;
                    }else if(value >= vGap - distanceY)
                    {
                        targetY += vGap - value;
                    }
                }
                dot.x = targetX;
                dot.y = targetY;
                event.updateAfterEvent();
            }
            
            protected function onDragStop(event:MouseEvent):void
            {
                stage.removeEventListener(MouseEvent.MOUSE_MOVE,onDragMove);
                stage.removeEventListener(MouseEvent.MOUSE_UP,onDragStop);
            }
            
        ]]>
    </mx:Script>
    <mx:UIComponent id="content" left="0" right="0" top="0" bottom="0">
        
    </mx:UIComponent>
    <mx:NumericStepper id="h" x="10" y="418" maximum="10" minimum="1" value="4"/>
    <mx:NumericStepper id="v" x="75" y="418" maximum="10" minimum="1" value="4"/>
    <mx:Button x="140" y="418" label="生成网格" click="clickHandler(event)"/>
    <mx:CheckBox id="snap" x="222" y="418" label="Snap To Grid" selected="true"/>
    <mx:CheckBox id="lock" x="333" y="418" label="Lock To Grid"/>
</mx:Application>