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The Microsoft Windows PostScript printer driver supports a wide variety of
PostScript printers and fonts. This topic provides a brief overview of the
features for the driver and in particular those features new for Windows
3.1.
 
External Printer Installation
 
The PostScript driver can support printers that are not listed in its
default list of the supported printers. Such "external" printers must have
accompanying Windows printer description (WPD) files that provide the
information the PostScript driver needs to access the printer correctly.
Typically, printer vendors create the WPD files for and distribute them with
their printers.
 
In Windows 3.1, the PostScript driver uses the same process to install both
internal and external printers. If a printer vendor supplies a WPD file and
an OEMSETUP.INF file for the external printer, the user can use the Printers
dialog box in Control Panel to install the printer. In this case, the
OEMSETUP.INF file must have a statement having the same form as the
following example:
 
1:PSCRIPT.DRV,1:NEWPRN.WPD,"New PostScript printer","DEVICESPECIFIC"
 
In this example, 1 represents a logical disk and is previously defined in a
[Disks] section. Control Panel automatically installs both the PostScript
driver (if necessary) and the WPD file to the SYSTEM directory. The first
time the printer is used to print a document, the driver scans all the
installed WPD files, and adds the new external printer to the list of
installed external printers.
 
In Windows 3.1, the maximum number of external printers a user can install
depends on the available space in WIN.INI. The theoretical limit is 32,000
printers.
 
Printer Font Metrics Support
 
For printers that have hard disks or resident fonts from some other source,
external PFM files can be added to the WIN.INI file to make the driver aware
of these fonts. This is similar to the way soft fonts are installed.
 
Printer Selection by Model Name
 
Windows 3.1 uses model names to identify printers. This means, for example,
that applications create printer device contexts by passing a model name,
such as "Apple LaserWriter IINT," instead of the generic driver name,
"PostScript."
 
This use of model name also affects printer selection. When installing a
printer, the driver searches the list of installed internal and external
printers and installed WPD files for the requested model name. This means
the model name stored in the WPD file must exactly match the model name in
the initialization file. If the driver is unable to find the requested
model, it will use the default printer (Apple LaserWriter Plus).
 
Device Initialization
 
The PostScript driver supports the Windows device-initialization functions.
This means that applications can maintain private, device-independent
initialization data that is separate from the default configurations set
using Control Panel. For more information about device-independent
initialization data, see the ExtDeviceMode and DeviceCapabilities functions
in the Microsoft Windows Device Driver Adaptation Guide.
 
Initialization File Entries for PostScript Printers
 
The PostScript printer driver uses global and per-port initialization
sections in the WIN.INI file. These sections specify information about the
PostScript printer.
 
Global Initialization Section
 
The global-initialization section, [Pscript], contains data that is not
associated with a particular port. In particular, this section defines the
installed external printers and the corresponding WPD files. The section has
the following form:
 
[PSCRIPT]
External Printers=2
printer1=abc_ps
printer2=xyz_ps
 
The External Printers setting indicates how many external printers there
are. The printern setting indicates the base filename of a given WPD file
associated with the external printer.
 
Per-Port Initialization Section
 
The per-port initialization section contains data that is specific to each
port connection. In particular, it defines the printer settings for the
printer connected to the given port. In Windows 3.1, each printer is
identified by model name, so the heading for the per-port initialization
section has the following form:
 
[ModelName,port]
 
The ModelName defines the printer (for example, Apple LaserWriter Plus) and
the port specifies the communication port, such as COM1 or LPT1. The
following is an example of a per-page initialization section:
 
[Apple LaserWriter Plus,COM1]
feed2=1
feed15=5
 
Windows saves the state of printer connections on a per-port basis. The
printer number is no longer stored in the section. The number is derived
from the model name.
 
Advanced Options Dialog Box
 
The Windows 3.1 PostScript driver provides an Advanced Options dialog box
that gives the user control of most of the driver's advanced features, such
as duplex printing, font management, TrueType support, and error handling.
The driver displays the dialog box whenever the user chooses the Options
button in the driver's Setup dialog box. Descriptions of the various
advanced options are given in the following sections of this topic.
 
Multiple-Resolution Printer Support
 
In Windows 3.1, the user can set the resolution of the output by selecting
the Resolution option in the Advanced Options dialog box. Some printers are
capable of printing in multiple resolutions and all printers can emulate
certain resolutions (without changing the physical size of the dots). The
list of hardware-supported resolutions can be viewed by moving the scroll
arrow. Items can be selected from the list or an arbitrary value can be
entered.
 
The halftone parameters (angle and frequency) do not update automatically
when changing the hardware resolution. You must enter the correct values
manually. Printers that only have one hardware resolution are acceptable.
 
Duplex Support
 
The Windows 3.1 driver supports duplex PostScript printers. If duplex
printing is enabled (by the printer's WPD file), the driver expands the
Options dialog box to give user control of duplex settings.
 
PostScript Header Support
 
The size of the PostScript header is less than 8K. Most header functions are
efficient and compact. This minimizes the overhead of print jobs that
include the header to just a few seconds.
 
Users who want to reduce printing times as much as possible should download
the header to their printer using the Print Options dialog to make all the
functions used be resident in the printer. With the header in place,
printing times are reduced by about 10 seconds. However, for sending files
to service bureaus, the header must be included in the print job and not
downloaded previously.
 
Automatic Error Handler
 
The Windows 3.1 driver automatically downloads an error handler that exists
for the life of a job. The error handler provides valuable feedback for the
user. If an error occurs, the handler prints a brief message telling the
user what happened and what to do about it, followed by the command and a
trace of the stack at the time of the error. This information can be used to
correct the problem, or give the support staff help in determining the
problem.
 
Automatic Handshaking
 
A common error is mismatched protocol settings between Control Panel and the
PostScript driver. The Windows 3.1 driver will automatically download code
to the printer to select the appropriate handshaking if the printer is
connected to a serial port. If the printer is connected to a parallel port
hardware, standard handshaking is used; network connections do not require
handshaking. Consequently, the Handshake button has been removed.
 
EPS Printing
 
Users can produce an Encapsulated PostScript (EPS) file that can be imported
into applications such as Aldus PageMaker with any Windows application that
prints using the PostScript driver. This is done by selecting the Print to
EPS File option from the PostScript Options dialog box, and then printing.
The output of the print job is redirected into the PostScript-only EPS file
specified in the Options dialog box. No alternate representation of the
image (for example, metafile or TIFF image) is produced by the driver.
 
By default, the bounding rectangle is the whole page (that is, the imageable
area of the page). If the printing application issues a SET_BOUNDS escape,
that rectangle will be used instead of the whole page. Therefore, before
printing a page, every application that might possibly have its output sent
to an EPS file should issue a SET_BOUNDS escape with the bounding rectangle
of all the output.
 
Detectable Start of Page
 
In Windows 3.1, the PostScript driver calls the StartPage function at the
beginning of each page. Users can define their own StartPage function to
carry out any per-page processing.
 
Document-Structuring Convention Support
 
The Windows 3.1 PostScript driver can generate output that conforms to the
document-structuring conventions defined by Adobe. These conventions make it
easier for applications to parse and rearrange PostScript output to perform
special operations, or print more efficiently. Users should request
conforming output if they plan on using the PostScript output as input to
another program that processes PostScript files. (This option does not need
to be checked for EPS files.)
 
The driver creates output that conforms to the Document-Structuring
Convention (DSC) only if the user chooses the Generate Conforming Output
option in the Advanced Setup dialog box. If this option is not explicitly
set, the driver may optimize output for printing efficiency and therefore
cannot guarantee conformance with DSC. In particular, the optimized output
may not be "page independent" as specified by the conventions. That is,
pages may need to be printed in a specific order, relying on fonts or other
resources loaded from previous pages. For more information about
DSC-conforming output, see version 3.0 of Adobe's Document Structuring
Conventions.
 
Color
 
The PostScript driver is a one bit-per-pixel device. However, this does not
mean it can represent only black and white. Bitmaps in a one bit-per-pixel
format can use any color for the foreground and background.
 
On black and white devices, colors are converted to gray levels by the
PostScript color machinery. For example, when a bitmap is transferred to the
printer, the foreground and background colors are examined to determine the
two colors to use for the transfer.
 
Windows uses brushes to fill objects. Patterned brushes are defined by an
8x8 bitmap that is used to tile a region that is to be filled. However,
since the PostScript driver is a one bit-per-pixel device, there is no color
information stored in its brushes. When a brush is used to fill an object,
the current text and background colors are used.
 
In Windows 3.1, the user can force all colors (other than white) to print as
black by setting the All Colors to Black option in the Advanced Options
dialog box. This option is useful if a printout loses detail from thin,
light-colored areas.
 
Color-Separation Support
 
To provide minimal support for color separation, the Windows 3.1 PostScript
driver recognizes the scignore variable in the PostScript header. Setting
this variable to True disables all color change commands allowing the
application to perform multiple passes over the input, setting the current
color to be the correct process color.
 
Before starting color separation, an application must set the scignore
variable using the PASSTHROUGH escape and the following string:
 
/scignore true def
 
Device-Independent Bitmaps
 
Device-independent bitmaps (DIBs) are used to deal with more than one
bit-per-pixel bitmaps. The implementation in the PostScript driver uses the
PostScript image operator on black and white devices and the colorimage
operator on color devices to render multiple bit-per-pixel images. (Notice,
however, that this makes the output printer dependent.)
 
Applications that want to print multiple bit-per-pixel images should use the
SetDIBitsToDevice or StretchDIBitsToDevice function to render these images.
GDI will simulate these if the driver does not support them.
 
StretchBlt Support
 
The PostScript driver supports arbitrary scaling of bitmap images. This
means applications can call the StretchBlt function without GDI intercepting
the call and carrying out the scaling on its own. With StretchBlt
implemented in the PostScript driver, the source bitmap is transferred
directly to the printer and stretched using the PostScript imagemask
operator. A run-length encoding (RLE) compression scheme has also been
implemented to reduce the amount of data that needs to be transferred to the
printer.
 
Compressed Bitmaps
 
The user can direct the PostScript driver to compress bitmaps before sending
them to the printer by setting the Compress Bitmap option in the Advanced
Options dialog box. Compressing bitmaps speeds up the generation of the
PostScript output but slows down the printer itself (PostScript printers
need more time to decompress the bitmaps). This option is recommended only
if the user is more concerned about having the printing application finish
quickly than with how long it takes to get the printout.
 
Font Management
 
The Windows 3.1 PostScript driver encloses each page in a gsave/grestore
pair to restore the graphics state (reclaim memory) without deleting
downloaded fonts. Also, the driver now calculates memory consumption during
the course of a print job, and will flush downloaded fonts at the start of
any page if memory is low.
 
Users can modify this behavior by setting the Printer VM and the Per Page
Font Downloading options in the Advanced Options dialog box. The Printer VM
option specifies how much available memory is in the printer. The driver
uses this setting when calculating memory usage. The Per Page Font
Downloading option directs the driver to flush printer memory at the end of
every page regardless of how much free memory exists. Essentially, this
option forces the driver to downloaded fonts with each page.
 
TrueType Support
 
The Windows 3.1 PostScript driver supports TrueType fonts allowing users to
create and print document containing TrueType fonts on PostScript printers.
The driver also provides a variety of advanced options that let the user
determine how TrueType fonts are to be used with the printer. Depending on
the capabilities of the printer, the user may want to convert TrueType fonts
to an Abode format, or substitute the TrueType font with a printer-resident
font.
 
The PostScript driver may need to convert the fonts to PostScript
device-font format before downloading to the printer. This is true if the
printer does not support the TrueType font format itself. If the driver must
convert TrueType fonts, it can convert them to either Adobe Type 3 bitmap
fonts or Type 1 outline fonts. The user sets the type in the TrueType option
in the Advanced Options dialog box. The TrueType to Type 1 conversion is not
exact and may produce fonts of slightly inferior quality to the original
TrueType font. However, using this conversion will reduce print time and
require much less printer memory for documents containing lots of TrueType
fonts at large point sizes.
 
The user can direct the PostScript driver to substitute PostScript
printer-resident fonts for TrueType fonts by using the Substitution option
in the Advanced Options dialog box. This option displays another dialog box
that lists the TrueType fonts and lets the user choose the substitution
font. Using substitution fonts reduces print time and requires less printer
memory.
 
If the printer supports the TrueType font format, the user can also direct
the driver to download TrueType fonts to the printer by using the
Substitution option in the Advanced Options dialog box. In this case, the
user sets the Download as a SoftFont option for a TrueType font instead of
choosing a printer-resident font. The driver converts the TrueType font to a
soft font and downloads it to the printer. This is the default for any
TrueType font that hasn't been assigned a printer font in the substitution
table.
 
Rotated Text
 
The PostScript driver can support printing text at any angle. Applications
may create fonts using any Escapement value (that is, by specifying the
angle of the baseline). The only limitation is that the Orientation (that
is, the angle of individual characters) is ignored.
 
Escapes
 
There are four PostScript-related printer escapes: EPSPRINTING,
POSTSCRIPT_DATA, POSTSCRIPT_IGNORE, and GETSETSCREENPARAMS.
 
The EPSPRINTING escape is intended for applications that produce their own
PostScript. It suppresses the Windows PostScript header. With this option
on, no GDI output functions will work.
 
The POSTSCRIPT_DATA escape is just like the PASSTHROUGH (also known as
DEVICE_DATA) escape except that it is recognized only by PostScript devices.
This escape is intended for applications that produce two representations of
the output: one intended for PostScript devices and the other for
non-PostScript devices. It should be used in conjunction with
POSTSCRIPT_IGNORE to make the PostScript driver ignore the GDI
representation.
 
The POSTSCRIPT_IGNORE escape is used to make the PostScript driver ignore or
accept all the output. The lpInData parameter points to a Boolean value that
indicates whether the GDI functions should be ignored (TRUE) or not (FALSE,
the default).
 
The GETSETSCREENPARAMS escape, new for Windows 3.1, sets and retrieves the
current screen parameters, such as angle and frequency, for halftoning. The
user can also set these parameters by using the Halftone Frequency and
Halftone Angle options in the Advanced Options dialog box.
 
Detailed descriptions of other escapes are available in the Microsoft
Windows Device Driver Adaptation Guide which has driver-oriented
descriptions.
 
PostScript Printer Communications
 
Most PostScript printers support both serial and parallel ports. The fastest
and most efficient way to connect your printer to your computer is usually
with a parallel port (LPTx). If your printer has both a parallel and a
serial port, the parallel port should be used.
 
If you are using serial communications and have a newer PostScript printer,
you may be able to increase the transmission rate from the standard 9600
baud. Many printers support communications of 19,200 baud.
 
The following is a PostScript program that can be sent to the printer to set
it up for 19,200-baud communications. Save the following in a file called
19200.PS and then use the MS-DOS copy command (COPY 19200.PS COM1:) to send
it to the printer.
 
% set laserwriter for 19200 baud
%   set up hardware handshaking
%   see page 121-122 of apple manual for details
%   use ETX/ACK (cts/rts)
serverdict begin 0 exitserver
statusdict begin 25 19200 7 setsccbatch end
% a ^D should be appended to this file in most cases
 
Note:  This will set the speed permanently (even after a power cycle). Use
       the following PostScript program to reset the communications channel
       to the default 9600 baud.
 
% set laserwriter for 9600 baud
%   set up hardware handshaking
%   see page 121-122 of apple manual for details
%   use ETX/ACK (cts/rts)
serverdict begin 0 exitserver
statusdict begin 25 9600 0 setsccbatch end
% a ^D should be appended to this file in most cases
 
You will also have to set the port on the computer to this speed by issuing
the following command, which should go in your AUTOEXEC.BAT file:
 
MODE COM1:,19200,n,8,1
 
Driver Limitations
 
The following are limitations placed on the driver by PostScript:
 
♦  PostScript does not support most raster operations (Rops). However, it
   does support BLACKNESS, WHITENESS, and SRCCOPY.
 
♦  PostScript has a 750-point polygon limit. This number is reduced by two
   when filling with a hatch or pattern. This is because a clipping path
   must be built as well as the path to fill and stroke. In cases where this
   limit is reached, the driver will request that GDI simulate the polygon.
   This is very slow. Applications should avoid generating large polygons.
 
 
                                      ♦