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Flash runtime tasks and system printing

Because Flash runtimes dispatch pages to the operating system's printing interface, be aware of the tasks managed by Flash runtimes and the tasks managed by an operating system's own printing interface. Flash runtimes can initiate a print job, read some of a printer's page settings, pass the content for a print job to the operating system, and verify if the user or system has canceled a print job. Other processes, such as displaying printer specific dialog boxes, canceling a spooled print job, or reporting on the printer's status, are all handled by the operating system. Flash runtimes are able to respond if there is a problem initiating or formatting a print job, but can report back only on certain properties or conditions from the operating system's printing interface. As a developer, your code needs to respond to these properties or conditions.

Working with exceptions and returns​

Check to see if the PrintJob.start() method returns true before executing addPage() and send() calls, in case the user has canceled the print job. A simple way to check whether these methods have been canceled before continuing is to wrap them in an if statement, as follows:

if (myPrintJob.start())
{
    // addPage() and send() statements here
}

If PrintJob.start() is true, the user selected Print (or a Flash runtime, such as Flash Player or AIR, has initiated a Print command). So, the addPage() and send() methods can be called.

Also, to help manage the printing process, Flash runtimes throw exceptions for the PrintJob.addPage() method, so that you can catch errors and provide information and options to the user. If a PrintJob.addPage() method fails, you can also call another function or stop the current print job. You catch these exceptions by embedding addPage() calls within a try..catch statement, as in the following example. In the example, [params] is a placeholder for the parameters specifying the actual content you want to print:

if (myPrintJob.start())
{
    try
    {
        myPrintJob.addPage([params]);
    }
    catch (error:Error)
    {
        // Handle error,
    }
    myPrintJob.send();
}

After the print job starts, you can add the content using PrintJob.addPage() and see if that generates an exception (for example, if the user has canceled the print job). If it does, you can add logic to the catch statement to provide the user (or the Flash runtime) with information and options, or you can stop the current print job. If you add the page successfully, you can proceed to send the pages to the printer using PrintJob.send().

If the Flash runtime encounters a problem sending the print job to the printer (for example, if the printer is offline), you can catch that exception, too, and provide more information or more options (such as displaying message text or providing an alert within an animation). For example, you can assign new text to a text field in an if..else statement, as the following code shows:

if (myPrintJob.start())
{
    try
    {
        myPrintJob.addPage([params]);
    }
    catch (error:Error)
    {
        // Handle error.
    }
    myPrintJob.send();
}
else
{
    myAlert.text = "Print job canceled";
}

For a working example, see Printing example: Scaling, cropping, and responding.

Working with page properties​

Once the user clicks OK in the Print dialog box and PrintJob.start() returns true, you can access the properties defined by the printer's settings. These settings include the paper width, paper height ( pageHeight and pageWidth), and content orientation on the paper. Because these are printer settings, not controlled by the Flash runtime, you cannot alter these settings; however, you can use them to align the content you send to the printer to match the current settings. For more information, see Setting size, scale, and orientation.

Setting vector or bitmap rendering​

You can manually set the print job to spool each page as vector graphics or a bitmap image. In some cases, vector printing produces a smaller spool file, and a better image than bitmap printing. However, if your content includes a bitmap image, and you want to preserve any alpha transparency or color effects, print the page as a bitmap image. Also, a non-PostScript printer automatically converts any vector graphics to bitmap images.

You specify bitmap printing by passing a PrintJobOptions object as the third parameter of PrintJob.addPage().

For Flash Player and AIR prior to AIR 2, set the PrintJobOptions object's printAsBitmap parameter set to true, as follows:

var options:PrintJobOptions = new PrintJobOptions();
options.printAsBitmap = true;
myPrintJob.addPage(mySprite, null, options);

If you don't specify a value for the third parameter, the print job uses the default, which is vector printing.

For AIR 2 and later, use the PrintJobOptions object's printMethod property to specify the print method. This property accepts three values, which are defined as constants in the PrintMethod class:

  • PrintMethod.AUTO: Automatically chooses the best print method based on the content being printed. For example, if a page consists of text, the vector print method is chosen. However, if a watermark image with alpha transparency is overlaid on the text, bitmap printing is chosen to preserve the transparency.

  • PrintMethod.BITMAP: Forces bitmap printing regardless of the content

  • PrintMethod.VECTOR: Forces vector printing regardless of the content

Timing print job statements​

ActionScript 3.0 does not restrict a PrintJob object to a single frame (as did previous versions of ActionScript). However, because the operating system displays print status information to the user once the user has clicked the OK button in the Print dialog box, call PrintJob.addPage() and PrintJob.send() as soon as possible to send pages to the spooler. A delay reaching the frame containing the PrintJob.send() call delays the printing process.

In ActionScript 3.0, there is a script time-out limit of 15 seconds. Therefore, the time between each major statement in a print job sequence cannot exceed 15 seconds. In other words, the 15-second script time-out limit applies to the following intervals:

  • Between PrintJob.start() and the first PrintJob.addPage()

  • Between PrintJob.addPage() and the next PrintJob.addPage()

  • Between the last PrintJob.addPage() and PrintJob.send()

If any of these intervals spans more than 15 seconds, the next call to PrintJob.start() on the PrintJob instance returns false, and the next PrintJob.addPage() on the PrintJob instance causes Flash Player or AIR to throw a run-time exception.