Voici un bout de code permettant de créer/dessiner un bouton en Actionscript 3, plus particulièrement une croix pour un bouton "Fermer"/"Close".

var closeButton:MovieClip= new MovieClip();

closeButton.graphics.beginFill(0xC2012D, 0.95);
closeButton.graphics.drawRoundRect(0, 0, 15, 15, 3, 3);
closeButton.graphics.moveTo(3, 3);
closeButton.graphics.lineTo(12, 12);
closeButton.graphics.lineStyle(2, 0xFFFFFF);
closeButton.graphics.endFill();
closeButton.graphics.moveTo(3, 12);
closeButton.graphics.lineTo(12, 3);
closeButton.graphics.lineStyle(2, 0xFFFFFF);
closeButton.graphics.endFill();
closeButton.x = 155;
closeButton.y = -45;

closeButton.addEventListener(MouseEvent.CLICK, onClickClose);

addChild(closeButton);