Writing Printer-Independent Reports

This chapter provides an overview of printer-independent reports and discusses the sample program for selecting the printer type at runtime.

Understanding Printer-Independent Reports

To create a printer-independent report, you must write a program that avoids using any characteristics that are unique to a specific printer. Although complete printer independence may be too restrictive, make your report as printer-independent as you can by following these guidelines:

• Your program should be free of the following commands:

  • GRAPHIC FONT (use ALTER-PRINTER instead).

  • PRINTER-INIT, PRINTER-DEINIT, and USE-PRINTER-TYPE (except for using this command to select a printer at runtime, as demonstrated in the sample program that follows).

  • CODE-PRINTER and CODE qualifiers of the PRINT command.

  • DECLARE-PRINTER and PRINT-DIRECT.

  • The SYMBOL-SET argument of the ALTER-PRINTER command.

• The report should be readable if printed on a line printer. Graphics or solid lines printed with the graphic command are not printed on a line printer. Test your graphical report on a line printer.

• Use only a small set of fonts. Font numbers 3, 4, and 5 and their boldface versions are the same regardless of the type of printer that you use (except for a line printer). Font 3 is Courier, font 4 is Helvetica, and font 5 is Times Roman. Note that on some HP printers, Helvetica may not be available. This reduces the common fonts to fonts 3 and 5 only.

• Be aware of certain limitations. EPS-file images can be printed only on PostScript printers. HPGL-file images can be printed only on HP LaserJet Series 3 or higher or printers that emulate HP PCL at that level. BMP-file images can be printed using Microsoft Windows only. GIF-file and JPEG-file images are suitable only for HTML output. PRINT-IMAGE and PRINT-CHART may not work with old printers that use PostScript Level 1 or HP LaserJet Series II.

If your report is printer-neutral and does not specify a printer, you can specify the printer at runtime in two ways.

The first method is to use the -PRINTER:xx command-line flag, which specifies the output type for your report. Use the following commands:

• -PRINTER:LP for line-printer output.

• -PRINTER:PS for PostScript output.

• -PRINTER:HP for HP LaserJet output.

• -PRINTER:WP for Microsoft Windows output.

• -PRINTER:HT for HTML output.

If you are using the system shell, enter this command on the command line:

sqr test ​username/password ​-printer:ps

Note. Currently, PRINTER:WP sends output to the default Microsoft Windows printer. To specify a nondefault Microsoft Windows printer, enter the following command: -PRINTER:WP:{Printer Name}. The {Printer Name} is the name assigned to your printer. For example, to send output to a Microsoft Windows printer named NewPrinter, you would use -PRINTER:WP:NewPrinter. If your printer name has spaces, enclose the entire command in double quotes.

The second method of specifying the printer type is by using the USE-PRINTER-TYPE command.

See USE-PRINTER-TYPE.

Reviewing the Sample Program for Selecting the Printer Type at Runtime

In the following example, the PROGRAM section prompts the user to select the printer type at runtime. The relevant lines are shown like this:

begin-program
  input $p 'Printer type'    ! Prompt user for printer type
  let $p = lower($p)         ! Convert type to lowercase
  evaluate $p                ! Case statement
  when = 'hp'
  when = 'hplaserjet'        ! HP LaserJet
    ​use-printer-type hp
    ​break
  when = 'lp'
  when = 'lineprinter'       ! Line Printer
    ​use-printer-type lp
    ​break
 when = 'ps'
  when = 'postscript'        ! PostScript
    ​use-printer-type ps
    ​break
  when-other
    display 'Invalid printer type.'
    stop
  end-evaluate
  do list_customers
end-program

In this code, the INPUT command prompts the user to enter the printer type. Because the USE-PRINTER-TYPE command does not accept a variable as an argument, the EVALUATE command is used to test for the six possible values and set the printer type accordingly.

The EVALUATE command is similar to a switch statement in the C language. It compares a variable to multiple constants and carries out the appropriate code.