How to dynamically set print page margins in Flash CS3

//I can get the right margins by defining a rectangle and giving it the following dimensions:

var rect1:Rectangle = new Rectangle(0, 0, 792,612); 

//When the print button is pressed the following code executes using the dimensions defined by rect1:

prntCover_btn.addEventListener(MouseEvent.CLICK, printCover);

function printCover(evt:MouseEvent):void {
    front_mc.visible = false;
        var myPrintJob:PrintJob = new PrintJob();
        var options:PrintJobOptions = new PrintJobOptions();
        options.printAsBitmap = true;
        front_mc.scaleX = 1;
        front_mc.scaleY = 1;
        myPrintJob.start();
        myPrintJob.addPage(front_mc, rect1, options);
        myPrintJob.send();

    } 

//U.S.paper is 792 = 11.5 inch wide paper. Would like to use A3 size so I did this after the line myPrintJob.start();

var margin_height:Number = (myPrintJob.paperHeight - myPrintJob.pageHeight)/2;
var margin_width:Number = (myPrintJob.paperWidth - myPrintJob.pageWidth)/2;

This is not working to place the mc correctly on the page. This i开发者_如何学Gos all the Adobe help provides. Also Googled and tried different variations but no success. Can anyone help?

Thanks in advance for any insight into this.

Annie

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You could clarify the question a bit because it is a bit unclear what you're trying to achieve... if I understood correctly, you probably want to print something in the middle of a larger paper.

You can get the paper size the user chose only after calling PrintJob.start() so you'll have to define the printArea parameter after that. As the printArea defines a rectangle relative to the DisplayObject being printed, in order to center the DisplayObject you'll have to make sure that the DisplayObject is in the center of the rectangle;

var myPrintJob:PrintJob = new PrintJob();
var options:PrintJobOptions = new PrintJobOptions();
options.printAsBitmap = true;
front_mc.scaleX = 1;
front_mc.scaleY = 1;
myPrintJob.start();

var marginWidth:Number = (myPrintJob.pageWidth - front_mc.width) / 2;
var marginHeight:Number = (myPrintJob.pageHeight- front_mc.height) / 2;
var rect:Rectangle = new Rectangle(-marginWidth, -marginHeight, myPrintJob.pageWidth, myPrintJob.pageHeight);

myPrintJob.addPage(front_mc, rect1, options);
myPrintJob.send();