AS3 lineTo method alternative

Question

This is more of a logical question than just looking for code, although it might be needed.

So i'm creating a drawing application and the first thing to do is use the lineTo method to draw a line -- that's all fine. But I learned this is not what I want, it does draw fine etc. but I want a tool that wouldn't "draw a line". I want a tool that doesn't lay the line down as you let go of click, but it lays down right when you click.

Now I don't really have a clue how to create this; can someone explain how one would code such a thing? This would sort of be an alternative to lineTo -- sorry if this sounds confusing, it's hard to word.

Answer 1

Here are two examples:

• Drawing application that draws like a pen
• Drawing application that draws lines / arrows

Pen Drawing (SWF Example)

This draws lines as curve to match the input device, persisting the line as it's drawn:

Code:

package
{
    import flash.display.Graphics;
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.events.MouseEvent;
    import flash.geom.Point;

    [SWF(percentWidth = 100, percentHeight = 100, backgroundColor = 0xefefef, frameRate = 30)]
    public class DrawingExample extends Sprite
    {

        //------------------------------
        //  model
        //------------------------------

        protected var lastPoint:Point;


        //------------------------------
        //  lifecycle
        //------------------------------

        public function DrawingExample()
        {
            super();

            stage.scaleMode = StageScaleMode.NO_SCALE;
            stage.align = StageAlign.TOP_LEFT;

            beginDrawing();
        }

        protected function beginDrawing():void
        {
            stage.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);
        }

        protected function mouseDownHandler(event:MouseEvent):void
        {
            stage.removeEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);

            // mark mouse down location
            lastPoint = new Point(mouseX, mouseY);

            // listen for movement or up/out
            stage.addEventListener(MouseEvent.MOUSE_MOVE, mouseMoveHandler);
            stage.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);
            stage.addEventListener(MouseEvent.MOUSE_OUT, mouseUpHandler);
        }

        protected function mouseMoveHandler(event:MouseEvent):void
        {
            var g:Graphics = graphics;
            g.lineStyle(1, 0x0000ff);

            // draw line segment
            g.moveTo(lastPoint.x, lastPoint.y);
            g.lineTo(mouseX, mouseY);

            // mark end of line segment
            lastPoint = new Point(mouseX, mouseY);
        }

        protected function mouseUpHandler(event:MouseEvent):void
        {
            stage.removeEventListener(MouseEvent.MOUSE_MOVE, mouseMoveHandler);
            stage.removeEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);
            stage.removeEventListener(MouseEvent.MOUSE_OUT, mouseUpHandler);

            beginDrawing();
        }

    }
}

Line Drawing (SWF Example)

Although tuned for arrow heads, the concept is the same for lines. When the input device is down, a line / arrow is staged but not persisted until the input device is up. Once drawn, the line persists.

Code:

package
{
    import flash.display.CapsStyle;
    import flash.display.Graphics;
    import flash.display.JointStyle;
    import flash.display.LineScaleMode;
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.events.Event;
    import flash.events.MouseEvent;
    import flash.geom.Point;

    [SWF(percentWidth = 100, percentHeight = 100, backgroundColor = 0xefefef, frameRate = 30)]
    public class Arrows extends Sprite
    {

        public var arrows:Vector.<Sprite> = new Vector.<Sprite>();

        public var canvas:Sprite;

        public var lineColor:uint = Math.random() * 0xffffff;

        public var lineWeight:Number = 5;

        private var startPoint:Point;


        public function Arrows()
        {
            super();

            addEventListener(Event.ADDED_TO_STAGE, addedToStageHandler);
        }

        protected function addedToStageHandler(event:Event):void
        {
            stage.scaleMode = StageScaleMode.NO_SCALE;
            stage.align = StageAlign.TOP_LEFT;

            addCanvas();
        }

        protected function addCanvas():void
        {
            canvas = new Sprite();
            addChild(canvas);

            lineColor = Math.random() * 0xffffff;

            // give alpha for interaction
            var g:Graphics = canvas.graphics;
            g.beginFill(0x0, 0.0);
            g.drawRect(0, 0, stage.stageWidth, stage.stageHeight);
            g.endFill();

            // listen for mouse down
            canvas.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);
        }

        protected function mouseDownHandler(event:MouseEvent):void
        {
            canvas.removeEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);

            // mark start point
            startPoint = new Point(event.localX, event.localY);

            // start rendering
            canvas.addEventListener(Event.ENTER_FRAME, enterFrameHandler);

            // listen for mouse up / out to end arrow
            canvas.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);
            canvas.addEventListener(MouseEvent.MOUSE_OUT, mouseUpHandler);
        }

        protected function enterFrameHandler(event:Event):void
        {
            var angle:Number = polarAngle(new Point(mouseX, mouseY), new Point(startPoint.x, startPoint.y));

            // draw line
            var g:Graphics = canvas.graphics;
            g.clear();

            // give alpha for interaction
            g.beginFill(0x0, 0.0);
            g.drawRect(0, 0, stage.stageWidth, stage.stageHeight);
            g.endFill();

            g.lineStyle(lineWeight, lineColor, 1, true, LineScaleMode.NORMAL, CapsStyle.SQUARE, JointStyle.MITER);
            g.moveTo(startPoint.x, startPoint.y);
            g.lineTo(mouseX, mouseY);

            // draw arrow head
            g.moveTo(mouseX - (20 * Math.cos((angle - 45) * Math.PI / 180)),
                     mouseY - (20 * Math.sin((angle - 45) * Math.PI / 180)));

            g.lineTo(mouseX + (5 * Math.cos((angle) * Math.PI / 180)),
                     mouseY + (5 * Math.sin((angle) * Math.PI / 180)));

            g.lineTo(mouseX - (20 * Math.cos((angle + 45) * Math.PI / 180)),
                     mouseY - (20 * Math.sin((angle + 45) * Math.PI / 180)));
        }

        protected function polarAngle(point:Point, center:Point=null):Number
        {
            if (!center)
                center = new Point(0, 0);

            return Math.atan2(point.y - center.y, point.x - center.x) * 180 / Math.PI;
        }

        protected function mouseUpHandler(event:MouseEvent):void
        {
            canvas.removeEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);
            canvas.removeEventListener(MouseEvent.MOUSE_OUT, mouseUpHandler);

            // stop rendering
            canvas.removeEventListener(Event.ENTER_FRAME, enterFrameHandler);

            // push canvas to arrows collection
            arrows.push(canvas);

            // add a fresh canvas
            addCanvas();
        }

    }
}