CompositionCompleteEvent  - AS3

package flashx.textLayout.events.examples
{
    import flash.display.Graphics;
    import flash.display.Sprite;
    import flash.geom.Rectangle;
    import flash.text.engine.TextLine;
    
    import flashx.textLayout.compose.StandardFlowComposer;
    import flashx.textLayout.compose.TextFlowLine;
    import flashx.textLayout.container.ContainerController;
    import flashx.textLayout.conversion.TextConverter;
    import flashx.textLayout.elements.FlowLeafElement;
    import flashx.textLayout.elements.ParagraphElement;
    import flashx.textLayout.elements.TextFlow;
    import flashx.textLayout.events.CompositionCompleteEvent;

    public class CompositionCompleteEvent_example extends Sprite
    {
        private var wordToHighlight:String = "shall";
        private var poemContainer:Sprite;
        private var txtFlow:TextFlow;
        private var controller:ContainerController;
        private const poem:String = "Sonnet 18\n" +
        "Shall I compare thee to a summer's day?\n" +
        "Thou art more lovely and more temperate:\n" +
        "Rough winds do shake the darling buds of May,\n" +
        "And summer's lease hath all too short a date:\n" +
        "Sometime too hot the eye of heaven shines,\n" +
        "And often is his gold complexion dimmed,\n" +
        "And every fair from fair sometime declines,\n" +
        "By chance, or nature's changing course untrimmed:\n" +
        "But thy eternal summer shall not fade,\n" +
        "Nor lose possession of that fair thou ow'st,\n" +
        "Nor shall death brag thou wand'rest in his shade,\n" +
        "When in eternal lines to time thou grow'st,\n" +
        "So long as men can breathe or eyes can see,\n" +
        "So long lives this, and this gives life to thee.\n" +
        "William Shakespeare\n";
        
        public function CompositionCompleteEvent_example()
        {
                 poemContainer = new Sprite();
                 txtFlow = new TextFlow();
                            
            poemContainer.x = 30;
            poemContainer.y = 30;
            this.stage.addChild( poemContainer );
            
            controller = new ContainerController(poemContainer, 300, 230);
            controller.verticalScrollPolicy = flashx.textLayout.container.ScrollPolicy.OFF;
            txtFlow = TextConverter.importToFlow( poem, TextConverter.PLAIN_TEXT_FORMAT );
            txtFlow.flowComposer = new StandardFlowComposer();

            txtFlow.addEventListener(CompositionCompleteEvent.COMPOSITION_COMPLETE, compositionCompleteHandler);
            txtFlow.flowComposer.addController( controller );

            txtFlow.flowComposer.updateAllControllers();
        }
        
        private function compositionCompleteHandler(event:CompositionCompleteEvent):void {
            if (event.textFlow == txtFlow) {
                checkForMatchingWord();
            }
        }
        
        private function checkForMatchingWord():void {
            var currentLeaf:FlowLeafElement = txtFlow.getFirstLeaf();
            var currentParagraph:ParagraphElement = currentLeaf ? currentLeaf.getParagraph() : null;
            
            while (currentParagraph) { // iterate over all paragraphs in the text flow
                var paraStart:uint = currentParagraph.getAbsoluteStart();
                var currWordBoundary:int = 0;
                var nextWordBoundary:int = 0;
                var pattern:RegExp = new RegExp(wordToHighlight, "i");
                
                while (true) { // iterate over letters in a word
                    nextWordBoundary = currentParagraph.findNextWordBoundary(currWordBoundary);
                    if (nextWordBoundary == currWordBoundary) {
                        break; // end of paragraph; break of inner while loop
                    }
                    var word:String = '';
                    var indexInLeaf:int = currWordBoundary + paraStart - currentLeaf.getAbsoluteStart();
                    var wordLen:uint = nextWordBoundary - currWordBoundary; 

                    while (true){ // traverse consecutive leaf elements looking for 'wordLen' characters
                                                        
                        // Take as many characters from the current leaf as possible to meet the quota of 'wordLen'
                        var consumeCount:uint = indexInLeaf + wordLen <= currentLeaf.textLength ? wordLen : currentLeaf.textLength - indexInLeaf; 
                        word += currentLeaf.text.substr (indexInLeaf, consumeCount);
                                                                        
                        wordLen -= consumeCount;
                        if (!wordLen)
                            break;
                            
                        // Quota not met; move to the next leaf
                        // Also reset the index where the next leaf will be scanned
                        currentLeaf = currentLeaf.getNextLeaf();
                        indexInLeaf = 0;
                    }
                    if (pattern.test(word)) {                                    
                        highlightWord(currWordBoundary, nextWordBoundary, word, paraStart);
                    }
                    currWordBoundary = nextWordBoundary;
                }
                                        
                // At this point, currentLeaf is the last leaf in currentParagraph. Move to the next paragraph.
                currentLeaf = currentLeaf.getNextLeaf();
                currentParagraph = currentLeaf ? currentLeaf.getParagraph() : null;                    
            }
        }
        
        private function highlightWord(begin:int, end:int, word:String, paraStart:int):void {
            
            var absoluteBegin:int = paraStart + begin;
            var absoluteEnd:int = paraStart + end;
            
            var startTextFlowLineIndex:int = txtFlow.flowComposer.findLineIndexAtPosition(absoluteBegin);
            var endTextFlowLineIndex:int = txtFlow.flowComposer.findLineIndexAtPosition(absoluteEnd);
            var txtFlowLine:TextFlowLine = txtFlow.flowComposer.getLineAt(startTextFlowLineIndex);
            var txtLine:TextLine = txtFlowLine.getTextLine();
            
            // get the bounds of the first and last Atom of the textLine
            var startbounds:Rectangle = txtLine.getAtomBounds(txtLine.getAtomIndexAtCharIndex(begin));
            var endbounds:Rectangle = txtLine.getAtomBounds(txtLine.getAtomIndexAtCharIndex(end));
            
            var box:Sprite = new Sprite();
            var g:Graphics = box.graphics;
            
            g.lineStyle(1, 0xFFFF00, 0.5); // set line style
            g.beginFill(0xFFFF00, 0.3); // set fill style
            // draw a rectangle around the specified boundaries
            g.drawRect(startbounds.left, startbounds.top, (endbounds.x - startbounds.x), startbounds.height);
            txtLine.addChild(box);
        }
    }
}