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Q74704: INFO: Supporting PostScript Features in Windows

Article: Q74704
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1
Operating System(s): 
Keyword(s): _IK kbSDKWin16
Last Modified: 04-JUL-1999

3.00 3.10
WINDOWS
kbprg

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1 
-------------------------------------------------------------------------------

SUMMARY
=======

There are some issues involved when designing an application to provide support
for PostScript printers. The application must determine if the PostScript driver
is available by using an accurate detection system. If an application generates
PostScript directly, the PASSTHROUGH escape can be used to send the file. This
must be done with care because the application is communicating directly with
the printer.

MORE INFORMATION
================

The first issue is how to determine if a PostScript driver is an installed
printer driver under Windows. An application cannot assume the PostScript driver
is named PSCRIPT.drv because this forces PostScript driver vendors to use the
same filename. The correct method is to run code similar to the following
pseudocode:

     bFound = FALSE;
     for (each device in [Devices] section of win.ini) {

       /* extract the necessary fields from the ini line */ 
       szDriverName = driver name extracted from ini line
       szModelName = left side of ini line (the key)
       szPort = port name extracted from ini line.

       hIC = CreateIC(szDriverName, szModelName, szPort, NULL);
       if (hIC) {
               /* see if driver supports GETTECHNOLOGY escape */ 
               wEscape = GETTECHNOLOGY;
           if (Escape(hIC, QUERYESCSUPPORT, sizeof(WORD), &wEscape, NULL))

     {

                         Escape(hIC, GETTECHNOLOGY, 0, NULL,

     &szTechnology);

                           /* Check that the string starts with PostScript
                            * by doing a case-insensitive search. Allow
                            * for the possibility that the string could be
                            * longer, like "PostScript level 2" or some other
                            * extension.
                            */ 
                           if (beginning of string is "PostScript")
                                   bFound = TRUE;
                  }
                  DeleteDC(hIC);
          }

          /* if the driver has been found break out */ 
          if (bFound)
                  break;
     }

     if (bFound) {

          PostScript driver is szDriverName, model is szModelName, port is
          szPort.

     }

NOTE: In the event that GETTECHNOLOGY is not supported by some printer drivers,
another method need to be used to determine if the printer is a PostScript
printer. One possible method is to use QUERYESCSUPPORT on escapes that are only
implemented by PostScript printers. For example:

     EPSPRINTING
     SETLINEJOIN
     SETMITERLIMIT
     SET_POLY_MODE

Similarly, you can determine a PCL printer by calling QUERYESCSUPPORT on the
following escape:

     DRAWPATTERNRECT

The second issue is how to print application-generated PostScript code. The
mechanism from a Windows-based application is through the PASSTHROUGH escape.
The PASSTHROUGH escape is documented in the "Microsoft Windows Software
Development Kit Reference Volume 2," Chapter 12. In addition to the
documentation, one requirement on the buffer passed is easy to miss; the first
word must contain the length of the buffer. The contents of the data sent by
PASSTHROUGH can alter the state of the printer.

To be safe, obey the following rules:

1. Surround PASSTHROUGH data by save/restore PostScript operators.

2. Do not embed GDI calls between PASSTHROUGH escapes. For example:

     PASSTHROUGH(save)
     Rectangle
     OtherGDIRoutines
     PASSTHROUGH(restore)

  Some driver code and software fonts are downloaded to the printer under
  certain conditions. The above operations could cause the driver and printer
  to lose synchronization, and potentially cause the job to fail. In general,
  no assumptions should be made concerning the code generated by a given GDI
  call.

3. Do not send a command to cause a page ejection.

Additional query words: 3.00 3.10

======================================================================
Keywords          : _IK kbSDKWin16 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1
Issue type        : kbinfo

=============================================================================

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