Deleting from a textFlow with out a full recomposition

Here is an example:

http://theyrule.net/test/delete_from_top/SingleContainerTest.swf

Click the red rectangle at the bottom to start.

It adds a new divElement to the bottom of the textFlow every frame.

The bottom of the flow is always displayed.

When it gets 500 divElements added - it starts deleting one divElement from the top every frame.

This causes the performance to drop dramatically - I assume it is recomposing.

I would like to be able to do this without losing performance - I can do it using multiple textFlows - one for each div - but that results in having to mantain a lot of code in order to select across textFlows.

This is the source:

------------------------------

package

{

import flash.display.Sprite;

import flash.events.Event;

import flash.events.MouseEvent;

import flash.system.System;

import flash.text.TextField;

import flash.text.TextFormat;

import flashx.textLayout.container.ContainerController;

import flashx.textLayout.container.ScrollPolicy;

import flashx.textLayout.edit.EditManager;

import flashx.textLayout.elements.DivElement;

import flashx.textLayout.elements.ParagraphElement;

import flashx.textLayout.elements.SpanElement;

import flashx.textLayout.elements.TextFlow;

import flashx.textLayout.formats.TextLayoutFormat;

import flashx.textLayout.formats.VerticalAlign;

import flashx.undo.UndoManager;

[SWF (width="500", height="700", backgroundColor="#FFFFFF")]

public class SingleContainerTest extends Sprite

{

protected var tf:TextFlow;

protected var em:EditManager;

protected var um:flashx.undo.UndoManager

protected var _bg:Sprite;

protected var _spr:Sprite;

protected var _cc:ContainerController

protected var _init_fmt:TextLayoutFormat;

protected var _btn:Sprite;

protected var _playing:Boolean = false;

protected var _count:int = 0;

protected var _graph:Sprite;

protected var _print_out:TextField;

protected var _last_time:Date = new Date();

protected var _last_five:Array = [];

public function SingleContainerTest()

{

var cw:Number = 200; // the container width

var ch:Number = 600;  // the container height

_bg = new Sprite();

_bg.graphics.lineStyle(.25, 0);

_bg.graphics.drawRect(0,0,cw,ch);

addChild(_bg);

_spr = new Sprite();

addChild(_spr);

_graph = new Sprite();

_graph.x = cw + 10;

_graph.y = 250;

addChild(_graph);

_print_out = new TextField();

var fmt:TextFormat = _print_out.defaultTextFormat;

fmt.font = "_sans";

_print_out.wordWrap = true;

_print_out.multiline = true;

_print_out.width = stage.stageWidth - (10 + _graph.x);

_print_out.x = _graph.x;

_print_out.y = _graph.y + 10;

addChild(_print_out);

//define TextFlow and manager objects

tf = new TextFlow();

um = new UndoManager();

em = new EditManager(um);

tf.interactionManager = em;  

//compose TextFlow to display

_cc = new ContainerController(_spr,cw,ch);

//_cc.verticalAlign = VerticalAlign.BOTTOM;

//_cc.verticalScrollPolicy = ScrollPolicy.ON;

tf.flowComposer.addController(_cc);

tf.flowComposer.updateAllControllers();

//make a button to add Inline Graphic elements

_btn = new Sprite();

_btn.graphics.beginFill(0xFF0000,1);

_btn.graphics.drawRect(0,0,120,30);

addChild(_btn);

_btn.addEventListener(MouseEvent.CLICK, btnClicked);

_btn.y = 600;

addMessage("hjfhsdg");

}

public function addMessage(msg:String):void {

//define elements to contain text

var d:DivElement = new DivElement();

var p:ParagraphElement = new ParagraphElement();

var s:SpanElement = new SpanElement();

s.text = msg;

//add these elements to the TextFlow

p.addChild(s);

d.addChild(p);

tf.addChild(d);

tf.flowComposer.updateAllControllers();

_cc.verticalScrollPosition = _cc.getContentBounds().height;

tf.flowComposer.updateAllControllers();

}

protected function btnClicked(e:MouseEvent):void {

_playing = !_playing;

removeEventListener(Event.ENTER_FRAME, onEnterFrame);

if(_playing){

addEventListener(Event.ENTER_FRAME, onEnterFrame);

}

}

protected function onEnterFrame(e:Event):void {

_count++;

if(_count > 500){

tf.removeChildAt(0);

}

addMessage("Message Number: " + _count + " " + randomString());

printOut()

}

protected function printOut():void {

var now:Date = new Date();

var tm:Number = (now.getTime() - _last_time.getTime());

_last_five.push(tm);

if(_last_five.length > 10) _last_five.shift();

var avg_tm:Number = 0;

for(var i:int = 0; i < _last_five.length; i++) avg_tm += _last_five;

avg_tm = Math.round(avg_tm/_last_five.length);

var elapsed_str:String = "message: \t\t\t"+_count

+ "\ntime: \t\t\t\t" + tm + "ms"

+ "\navg of last 10:\t\t" + avg_tm +"ms";

//trace(elapsed_str );

_print_out.text = elapsed_str;

_last_time = now;

drawGraph(tm);

}

protected function drawGraph(tm:Number):void {

if(_count % 5 == 0){

_graph.graphics.beginFill(0x0);

_graph.graphics.drawRect(_count/10,-Math.round(tm/10),1,1);

_graph.graphics.beginFill(0xFF0000);

_graph.graphics.drawRect(_count/10,-Math.round(System.totalMemory/1000000),1,1);

}

}

protected function randomString():String {

var chars:String = "abcdefghijklmnopqrstuvwzyz                    ";

var chars_len:Number = chars.length;

var random_str:String = "";

var num_chars:Number = Math.round(Math.random() * 100);

for (var i:int =0; i < num_chars; i++){

random_str = random_str + chars.charAt(Math.round(Math.random() * chars_len));

}

return random_str;

}

}

}