Dibujar con el ratón en Flash

this.createEmptyMovieClip("canvas_mc", 999);
var isDrawing:Boolean = false;
//
clear_btn.onRelease = function() {
    canvas_mc.clear();
};
//
var mouseListener:Object = new Object();
mouseListener.onMouseDown = function() {
    canvas_mc.lineStyle(5, 0xFF0000, 100);
    canvas_mc.moveTo(_xmouse, _ymouse);
    isDrawing = true;
};
mouseListener.onMouseMove = function() {
    if (isDrawing) {
        canvas_mc.lineTo(_xmouse, _ymouse);
        updateAfterEvent();
    }
};
mouseListener.onMouseUp = function() {
    isDrawing = false;
};
Mouse.addListener(mouseListener);