Diagnosing Printing Problems in Your Application

• Microsoft Windows Software Development Kit (SDK) version 3.1

SUMMARY

When you are in the midst of development and concentrating on coding, it is easy to lose sight of problem areas external to your application. When diagnosing a printing problem in your application, there are three major areas to be aware of:

• Environment/network issues
• Printer and printer driver issues
• Application coding issues

MORE INFORMATION

Environment/Network Issues

Check List:

1. Do other applications print correctly?

Do other Windows-based applications such as Paintbrush or Microsoft Write print successfully? If they do not, then the problem probably isn't with your application. You should try a clean boot (starting your computer after all unnecessary commands have been removed from your CONFIG.SYS and AUTOEXEC.BAT files) to help narrow down the problem.

Try printing to a local printer to ensure that the problem isn't related to your network. If your application prints correctly to a local printer and not to the network printer, the problem could be with incorrect network settings.

Is Print Manager enabled? If not, try enabling Print Manager. Try turning off the Fast Printing Direct To Port option if it's on. For more information about how these settings affect printing in Windows, please see the following articles in the Microsoft Knowledge Base:

   ARTICLE-ID: Q82746
   TITLE     : General Information About Print Manager and Windows 3.1

   ARTICLE-ID: Q82747
   TITLE     : How Windows Prints to a Network

Printer and Driver Issues

Check List:

1. Test with various printer drivers.

It is important to test with several different printers to determine whether the problem happens only on a specific printer. If so, be sure to check the WDL to determine whether there's an updated driver for the printer.

Be sure to test printing on machines with different display drivers. Printer drivers normally do not support all output functions and rely on GDI to assist. In many cases, GDI in turn calls into the display driver to do the actual work. So, a bug in the display driver could show up during printing. For example, test with the standard VGA driver that shipped with Windows 3.1 and another display driver with more capabilities such as the 8514/a.

Check for incorrect settings on the printer. Make sure the printer is set up correctly in Print Manager. Check that the correct properties, printer port, and so on, have been specified. It's possible the printer driver file is corrupt. Try removing the printer driver through Control Panel, deleting the printer driver file (along with deleting UNIDRIV.DLL if appropriate) and reinstalling the driver through Control Panel.

Application Coding Issues

Check List:

1. Compare your code to PRNTFILE and/or DIBVIEW.

Do the Windows Software Development Kit (SDK) sample programs PRNTFILE and DIBVIEW print correctly on your system? If so, comparing your code to these samples will be useful. Note that there is a minor bug in PRNTFILE. To fix it, move to where the bAbort flag in PRNTFILE.C is initialized to right after the IDM_PRINT case, before any calls to escape. Without this fix, with some printers, if you begin printing, cancel, and try to print again, you will receive an error on the STARTDOC escape. This is because some printer drivers call your application's abort procedure during STARTDOC, and the bAbort flag has not been reinitialized after canceling the previous print job.

Do you do banding (using the NEXTBAND and BANDINFO escapes) in your application? This is particularly important if you are doing a lot of graphics output or you are making calls to the SDK region functions. There have been problem reports concerning the region functions consuming GDI resources in nonbanding applications, and at this time the only known resolution is to implement banding in your application.

If you don't do banding in your application then Windows does it for you by creating a disk-based metafile and then playing back the entire metafile into each printer band. Using the NEXTBAND escape eliminates the disk-based metafile so the printing process is greatly simplified. As an added benefit, you should notice an increase in performance. After adding the NEXTBAND escape, try optimizing your code even more using the BANDINFO escape.

The sample program DIBVIEW demonstrates the correct usage of both the NEXTBAND and BANDINFO escapes. If you need more information on banding, query on the following word in the Microsoft Knowledge Base:

   GdiPrnBanding

If you are just learning about printing under Windows, or if you are considering implementing banding in your application, the Printing Self-Study Module has a great deal of information and sample code ready for your use. For more information about the Printing Self-Study Module, see the following application note in the Microsoft Knowledge Base:

   Appnote: PW0778: Printing Self-Study Module

• The escapes NEXTBAND and NEWFRAME and the EndPage function reset the printer HDC to default values. If you've made any changes to the printer HDC such as selecting in GDI objects (fonts, pens, brushes, and so forth) or changing the mapping mode, then you must set up the printer HDC again. The symptom here is that the first page prints fine and subsequent pages do not.
• Make sure each call to EndPage() has a matching StartPage(). EndPage() fails (return -1) if StartPage() has not been called.
• Have you set an Abort procedure and is it properly exported? The Windows 3.0 PostScript driver version 3.3 causes an unrecoverable application error (UAE) if there isn't an Abort procedure. With all the hundreds of Windows printer drivers available, it is best to avoid unnecessary complications and just set a simple Abort procedure.
• If you're trying to mix the PASSTHROUGH escape with calls to GDI functions then you must do banding and use the PASSTHROUGH escape on the first band only.
• Use QUERYESCSUPPORT before calling printer escapes to make sure that the printer driver supports the escape you want to call next.
• If you are printing bitmaps, always use DIBs (device independent bitmaps). Use the sample program WINCAP or DIBVIEW as a model for printing DIBs. Query the Microsoft Knowledge Base for more information about these samples.