CD ROM Paradise Collection 4/CD ROM Paradise Collection 4 1995 Nov.iso/ghostscr/gsview07.zip/gsview.doc

Text File | 1993-05-10 | 29KB | 730 lines

1Overview
?Overview
 `Ghostview for Windows` is a graphical interface for MS-Windows `Ghostscript`.
 Ghostscript is an interpreter for the PostScript page description language
 used by laser printers.
 For documents following the Adobe PostScript Document Structuring
 Conventions, Ghostview for Windows allows selected pages to be viewed or
 printed.
 Ghostview for Windows can be used with Windows Ghostscript 2.6 or later.
 Ghostview for Windows was inspired by Tim Theisen's X11 Ghostview
 program.
 The ability to understand `DSC` comments comes from X11 Ghostview.

2Document Structuring Conventions
?Document Structuring Conventions
?DSC
?Encapsulated PostScript
?EPSF
?EPS
 Adobe has defined a set of extended comment conventions that provide
 additional information about the page structure and resource
 requirements of a postscript file.
 If a file contains these Document Structuring Convention (DSC) comments,
 Ghostview can display pages in random order using `Goto` and display pages
 in reverse order using `Prev`.  Selected pages can be extracted to
 another file or printed.

 If a file does not contain DSC comments, Ghostview can only
 display the pages in the original order.

 DSC conforming files start with the comment line:
  %!PS-Adobe-3.0
 where the number 3.0 may change and is the DSC version number.
 Some programs write postscript files with a control-D as the first
 character of the file, followed by the comment line mentioned above.
 Ghostview will correctly report that these files are not DSC conforming,
 but will still display them with page selection features available.
 Complain to the author of the program that produced the postscript file.
 To make the file DSC conforming, edit it to remove the control-D character.

 DSC conforming files contain lines such as:
  %%Pages: 24
  %%Page: 1 1
 These lines tell Ghostview how many pages a document contains and
 where they start.  Ghostview uses this information to select
 individual pages.

 Encapsulated PostScript Files (EPSF) are single page documents
 that contain a subset of the `DSC` comments and PostScript commands.
 EPS files start with the comment line:
  %!PS-Adobe-3.0 EPSF-3.0
 EPS files are commonly used for inclusion in other documents and
 for this reason require the bounding box comment:
   %%BoundingBox: llx lly urx ury
 where llx, lly, urx and ury are integers giving the x and y coordinates
 of the lower left and upper right corners of a bounding box which encloses
 all marks made on the page.

 Some EPS files contain a preview of the postscript document.
 This preview can be a Windows Metafile, a TIFF file, or an Interchange
 preview (EPSI format).
 For the Windows Metafile or TIFF file preview, the EPS file under DOS
 contains a binary header which specifies the location and lengths of
 the preview and postscript language sections of the EPS file.
 For the Interchange format, the preview is contained in DSC comments
 starting with
  %%BeginPreview: width height depth lines
 An EPS file with a preview can be created from an EPS file without a
 preview using `Add EPS Preview`
2Opening a Document
?File
?Open
?Select File
 The `Open` command on the `File` menu opens a file and displays
 the first page.

 If the file contains `DSC` comments, pages can be selected using
 `Next`, `Prev` and `Goto`.

 If the file does not contain `DSC` comments, `Prev` and `Goto` will
 not work.  Another file should not be selected until a last page of
 the file has been displayed.

 When a file is open, Ghostview will display the document filename,
 the current page (if available) and while the cursor is over
 the image, the location of the cursor in default user coordinates
 (1/72 inch).
 The cursor location is useful for calculating bounding boxes.

 The `Select File` command is similar to `Open` but it does not display
 the document.
 This command is useful for opening a document prior to printing it.

 See also `Print`.
2Page Selection
?Page Selection
?Next
?Prev
?Redisplay
?Goto
 `Next` moves to the next page of a document.
 This works even if the document does not contain `DSC` comments.

 `Prev` moves to the previous page.

 `Redisplay` redisplays the current page.

 `Goto` shows a dialog box which allows selection of the next page
 number to display.  The `Select Page` dialog box shows page labels
 since these are likely to be more useful than a sequential page number.

 The `Prev`, `Redisplay` and `Goto` commands work only if the
 document contains `DSC` comments.
2Document Information
?Info
 A brief information area at the top of the window is used by
 Ghostview to display the document filename, the current page number
 and label (if available) and while the cursor is over the image, the
 location of the cursor in default user coordinates (1/72 inch).
 The cursor location is useful for calculating bounding boxes.

 The `Info` command on the `File `menu shows a dialog box with the
 following information about the `DSC` comments in the current document.

 `File `is the full pathname to the document.

 `Type` is` DSC`,` EPS` or `No DSC comments`.
 `EPS` is an Encapsulated PostScript File - a single page document
 that contains a subset of the `DSC` comments and PostScript commands.
 `EPS `files are commonly used for inclusion in other documents.

 `Title` is a text title that can be used when printing banner
 pages and for routing or recognising documents.

 `Date` is the time the document was created.

 `BoundingBox` specifies a box that encloses all the marks painted
 on the page.  The four values are the coordinates of the lower left
 and upper right corners of the bounding box in default user
 coordinates (1/72 inch).

 `Orientation `is either `Portrait `or` Landscape`.

 `Default Media` gives the media name followed by the width and
 height of that media in default user coordinates (1/72 inch).

 `Page Order` is either `Ascending`, `Descending` or `Special`

 `Pages` is the total number of pages in the document.

 `Page` gives the page label and page number.

 `Bitmap `is the size of the display bitmap in pixels which may be
 useful if you are copying the displayed image to the clipboard.
2Printing
?Print
?Print To File
?Print File
?Extract
 The `Print` command on the `File `menu allows printing of the document
 using Ghostscript.
 The Ghostscript printer driver and resolution are selected using the
 `Select Device` dialog box.   Pages are selected using the `Select Pages`
 dialog box.  The `All`, `Odd` and `Even` buttons provide quick selection
 of pages.

 The `mswinprn` printer driver uses the windows printer drivers
 and should work with any printer with raster capabilities.
 Printer resolution cannot be selected from within Ghostview; use
 the Control Panel instead.  This driver is very slow.

 With all other printer drivers, Ghostscript sends the output direct
 to the printer, without passing through a Windows printer driver.
 If you have trouble printing you may have to `Print To File`
 and then `Print File` or use the DOS command `COPY /B FILENAME PRN`.

 This list of available devices and resolutions is stored in the
 [Devices] section of gsview.ini.  The default list of devices
 and resolutions is taken from the standard distribution version
 of Ghostscript for Windows 2.6 and may not be complete.

 To print a document without displaying it, open the document
 using `Select File`.

 `Print To File` is similar to the `Print` command except that Ghostscript
 will write the output to a file instead of sending it to a printer.

 If you want to produce a bitmap, some useful drivers are
 `bmpmono`, `bmp16`, `bmp16m` and `bmp256`.

 `Print File` sends a file to a local port, bypassing the Windows
 printer drivers.
 This is useful for sending a document to a PostScript printer,
 or for sending an output file produced by Ghostscript to a printer.

 `Extract` allows a range of pages to be copied from the current
 document to a new document.  For example, ten pages can be extracted
 from the middle of the current document and written to another file,
 which will later be sent to a printer.

3Properties
?Properties
 Some printer drivers allow extra properties to be specified.
 If two sections are added to the gsview.ini file for these printer
 drivers, Ghostview will enable the `Properties` button which will
 display the `Edit Properties` dialog box.
 The following example shows how to add property information
 for the cdjcolor driver.
 First add a section which gives the current values.
 This section, after the first character is removed, gives the options
 that will appear in the `Property` list box.
 The first character is `s` for string or `d` for number.
  [cdjcolor]
  dBitsPerPixel=24
  dDepletion=1
  dShingling=2
  dBlackCorrect=4

 Next add a section which gives the values to display in the
 `Value` list box.
  [cdjcolor values]
  dBitsPerPixel=1,3,8,16,24
  dDepletion=1,2,3
  dShingling=0,1,2
  dBlackCorrect=0,1,2,3,4,5,6,7,8,9
 Ghostview will also add the value `[Not defined]` to the listbox.

 When you press the `OK` button in the `Edit Properties` dialog
 box, the current settings are written to the gsview.ini file.

 When Ghostview prints a file, it will give Ghostscript the contents
 of the [cdjcolor] section of gsview.ini as follows:
  -dBitsPerPixel=24 -dDepletion=1 -dShingling=2 -dBlackCorrect=3
 If the value of a property is `[Not defined]`, that property will
 not be sent to Ghostscript.

 Some entries for the cdj family of drivers are supplied in the
 property.ini file that comes with Ghostview.
3PS to EPS
?PS to EPS
 In general, it is not possible to convert a PostScript file to `EPS`.
 However, many single page PostScript files can be converted to `EPS`
 by changing the first line of the file to
  %!PS-Adobe-3.0 EPSF-3.0
 and then adding or fixing up the `%%BoundingBox` comment.

 To convert a PostScript file to `EPS`, the original file `must` be
 `single page` document.  If the document contains `DSC` comments
 and is multi page, extract the desired page with `File` | `Extract`.
 If the document does not contain `DSC` comments, you will need to
 edit the file by hand to extract the desired page.

 `EPS` documents `must not` use any of the following operators:
  banddevice   clear         cleardictstack  copypage
  erasepage    exitserver    framedevice     grestoreall
  initclip     initgraphics  initmatrix      quit
  renderbands  setglobal     setpagedevice   setpageparams
  setshared    startjob      letter          note
  legal        a3            a4              a5

 The following operators should be used with care:
  nulldevice   setgstate     sethalftone    setmatrix
  setscreen    settransfer   setcolortransfer

 It is `your` responsibility to make sure that the above requirements
 are met.

 To test if a document contains any of the above operators, select
 `Options` | `EPS Warn` and then `Open` the desired document.
 After the page has been displayed, look in the Ghostscript text window.
 If any of the above operators have been used you should see lines like:
  Warning: EPS files must not use ...
 If you find these warnings then do `not` use `PS to EPS`.
 Remember to turn off `EPS Warn` afterwards.

 A document must be displayed before `PS to EPS` is used.
 The document must contain a `showpage`.
 This is required so that the bounding box can be measured.

 For documents without `DSC` comments, `PS to EPS` allows a bounding
 box to be specified, then writes out an `EPS` file consisting of
 an `EPS` wrapper around the original document.

 For documents with `DSC` comments, `PS to EPS` will change the
 first line of the file to
  %!PS-Adobe-3.0 EPSF-3.0
 then allows the `%%BoundingBox` comment to be changed or added.

 For `EPS` documents, `PS to EPS` allows the `%%BoundingBox` comment to
 be changed.

 See also `Add EPS Preview`, `Extract`, `EPS Warn`.
2Clipboard
?Clipboard
?Edit
?Copy
?Paste To
?Convert Bitmap
?Bitmap
?Add EPS Preview
?Extract EPS
 The Ghostview window can be copied to the Clipboard as a bitmap
 by selecting `Copy` from the `Edit` menu.
 The bitmap may be a Device Independent Bitmap or it may be a Device
 Dependent Bitmap, depending on how Ghostscript was compiled.
 The default for Ghostscript 2.6 is a Device Independent Bitmap
 (BMP format).

 An alternative way to get a bitmap output from Ghostscript is
 to use one of the BMP drivers.  See `Print`.

 `Paste To` copies a Device Independent Bitmap from the Clipboard
 (if available) to a BMP file.

 `Convert Bitmap` converts between a Device Independent Bitmap and
 a Device Dependent Bitmap.
 If the clipboard contains a Device Independent Bitmap (BMP format),
 this is converted to a Device Dependent Bitmap and added to the clipboard.
 If the clipboard does not contain a colour palette, one is created
 from the Device Independent Bitmap and added to the clipboard.
 This option is present because some applications (notably Windows
 Paintbrush) won't recognise a Device Independent Bitmap in the clipboard.

 `Add EPS Preview` takes a bitmap from the clipboard and uses it to add
 a preview to an EPS file.
 `Add EPS Preview` can create a DOS EPS file with a Windows Metafile or
 TIFF preview, or an EPSI file with an Interchange preview.
 To use the `Add EPS Preview` command the following steps must be followed.
 Select `Orientation` | `Portrait`.  Select `Options` | `EPS Clip`.
 Select `Media` | `Resolution` and set a suitable resolution for the preview.
 `Open` an EPS file that does not contain a preview.  Select `Edit` | `Copy`.
 Select `Edit` | `Add EPS Preview`, then the preview format,
 then the new EPS filename.
 If adding an Interchange preview, the document must have an `%%EndComments`
 line, otherwise Ghostview may put the preview in the wrong place.

 To extract the PostScript or Preview section from a DOS EPS
 file, use `File` | `Select File` followed by `Edit` | `Extract EPS`
 then `PostScript` or `Preview`.

 See also `PS to EPS`.
2Options
?Options
 The `Options` menu has the following selections
3Ghostscript Command
?Ghostscript Command
 The `Ghostscript Command` option allows selection of the command
 to use when executing Ghostscript.  The default is `gswin`.
 If Ghostscript is not in the Ghostview directory, or not on the
 PATH, use this option to set the full pathname to Ghostscript.
 If you wish to specify that Ghostscript should look for its
 initialisation files in a different place, add a -I option to
 the command as in the following example:
  c:\gs\gswin -Ic:\gs;d:\psfonts
 Try to keep the command length short, otherwise Ghostview will
 have trouble printing files with Ghostscript.
 Only the Ghostscript EXE and include path may be specified -
 other items will confuse Ghostview.
3Sounds
?Sounds
 The `Sounds` option assigns sounds to various events.
 For each event the sound can be set to `None`, a `Speaker Beep` or
 a `Wave` file.

 You must have a sound driver loaded before using Wave files.
 Wave file sounds are not available under Windows 3.0.

 The events are:

 `Output Page`: the PostScript showpage operator was executed.

 `No Page`: an invalid page was selected.
 For example, pressing `Prev` while on the first page of a document
 with `DSC` comments.

 `No Number`: a command required page numbering and the document did
 not have page numbering.
 For example, pressing `Goto` when viewing a document without
 `DSC` comments.

 `Not Open`:  a command required a document to be open and this was
 not the case.
 For example, pressing `Goto` when no document is open.

 `Error`: many types of errors.

 `Timeout`: no response from Ghostscript within a timeout period.
 For example, display snowflak.ps on a PC with a 286-12 CPU.

 `Start`: Ghostview opened.

 `Exit`: Ghostview closed.

 The defaults are for `No Page` and `Error` to be a `Speaker Beep`
 and all other events to be `None`.
3Save Settings
?Save Settings
?Settings
?INI file
?Save Settings on Exit
 The `Save Settings` option saves the Ghostview window position,
 window size, last used printer, `User Defined`, `Ghostscript Command`,
 `Button Bar`, `Quick Open`, `Auto Redisplay`, `EPS Clip`, `EPS Warn`,
 `Sounds`, `Orientation`, `Media` and `Resolution` options to the file
 gsview.ini in the windows directory.
 Ghostview reads gsview.ini during startup.

 When the `Save Settings on Exit` option is checked, Ghostview will
 automatically save the above settings when you quit Ghostview.
3Save Last Directory
?Save Last Directory
 When the `Save Last Directory` option is `checked`, Ghostview will
 save the current directory when you quit Ghostview.  When Ghostview
 is started next, this will be made the current directory.
 This is the default.

 When `Save Last Directory` option is `unchecked`, the current
 directory when Ghostview is started will be the directory where
 Ghostview is located, or the working directory specified by
 the Program Manager.
3Button Bar
?Button Bar
 When the `Button Bar` option is `checked`, Ghostview will display
 a Button Bar down the left side of the window.  This is the default.
 The Button Bar contains the following items:

 `File` | `Open`

 `File` | `Print`

 `File` | `Info`

 `Help` | `Contents`

 `File` | `Goto`

 `File` | `Next`

 `File` | `Prev`

 `Go forward 5 pages`

 `Go back 5 pages`

 When the `Button Bar` option is `unchecked`, Ghostview will not
 display the Button Bar.
3Quick Open
?Quick Open
 When the `Quick Open` option is `checked`, Ghostview will not reload
 Ghostscript before every document, making opening of documents quicker.

 Ghostview tries to preserve the Ghostscript state between documents,
 but a document may still leave the Ghostscript interpreter in an unusual
 state or cause an error.  If an error occurs, Ghostscript will close.
 Error messages are displayed in the Ghostscript window.
 Select `Redisplay` to reopen the document.

 If `Quick Open` is `unchecked`, Ghostview will close Ghostscript and
 restart it before each new document or whenever the page orientation,
 resolution or size is changed.
3Auto Redisplay
?Auto Redisplay
 When the `Auto Redisplay` option is `checked`, Ghostview will
 redisplay `DSC` documents when the `Orientation`, `Resolution`
 or `Media` are changed.

 If `Auto Redisplay` is `unchecked`, the `File` | `Redisplay` command
 must be used to redisplay a document after changing the
 `Orientation`, `Resolution` or `Media`.  This is the default.
3EPS Clip
?EPS Clip
 When the `EPS Clip` option is `checked`, Ghostview will clip the
 display bitmap to the bounding box of an EPS file instead of using the
 page size specified on the `Media` menu.  This is useful when
 adding a bitmap preview to an EPS file.

 If `EPS Clip` is `unchecked`, Ghostview will use the page size
 specified on the `Media` menu for EPS files.  This is the default.

 See also `Clipboard` | `Add EPS Preview`
3EPS Warn
?EPS Warn
 When the `EPS Warn` option is `checked`, Ghostview will write a
 prolog to Ghostscript when each file is opened.  This prolog will
 produce warning messages in the Ghostscript text window if any
 PostScript operators that should not be used in `EPS` files
 are used.  An example warning message is:
  Warning: EPS files must not use /initgraphics
 `EPS Warn` is not infallible.  It is possible to access restricted
 operators without `EPS Warn` producing a warning.

 The default for `EPS Warn` is `unchecked`.

 See also `PS to EPS`.
2Page Orientation
?Orientation
?Portrait
?Landscape
?Upside-down
?Seascape
?Swap Landscape
 The `Portrait`, `Landscape`, `Upside-down` and `Seascape`
 (reverse Landscape) commands on the `Orientation `Menu select
 the page orientation used by the display.
 `Landscape` implies a clockwise rotation of the paper by 90 degrees.
 `Seascape` implies an anti-clockwise rotation of the paper by 90 degrees.
 These orientation options only affect the display and do not affect
 the print commands.
 If a `DSC` page orientation comment is found, the orientation will be
 selected automatically.

 When the `Swap Landscape` option is `checked`, Ghostview swaps the
 meaning of Landscape and Seascape.
 Most of the Landscape documents that I have encountered require a 90
 clockwise rotation of the paper to view.
 However, there is no standard and some documents need to be rotated
 the other way.
 The `Swap Landscape` button allows Ghostview to automatically rotate the
 document the right way in response to the `%%Orientation` comment in the
 PostScript file.
2Page Size and Display Resolution
?Resolution
?Media
?Page Size
?User Defined
 The `Resolution` command on the `Media` menu selects the display
 resolution in dots per inch.
 The default for a VGA display is 96 dots per inch.

 The `Media` menu also allows selection of page size.
 Available page sizes are:
  Letter          8.5 x 11   inch
  Tabloid        11   x 17   inch
  Ledger         17   x 11   inch
  Legal           8.5 x 14   inch
  Statement       5.5 x  8.5 inch
  Executive       7.5 x 10   inch
  A3              297 x 420  mm
  A4              210 x 297  mm
  A5              148 x 210  mm
  B4              257 x 364  mm
  B5              182 x 257  mm
  Folio           8.5 x 13   inch
  Quarto          8.5 x 10.8 inch
  10x14          10   x 14   inch

 A user defined size can be specified in PostScript points (1/72 inch)
 with the `User Defined` command.  A size of 480x360 points at 96 dpi
 will give an image size of 640x480 pixels.

 If a `DSC` media comment is found, the page type will be selected
 automatically.  If the media specification is not one of the above
 page types, the `User Defined` size will be set.
2Running Ghostview from the File Manager
?Registration Info Editor
?File Manager
 To run Ghostview when a PostScript file is double clicked in the
 File Manager, the following sequence must be followed to teach
 File Manager about PostScript files.

 From the `Program Manager`, run the Registration Info Editor using
 `File `| `Run...` then type `regedit`.
 From the `Registration Info Editor` select `Edit `| `Add File Type...`
 then enter the following fields:
  Identifier = psfile
  Filetype = PostScript
  Action = Open
  Command = gsview %1
  Uses DDE = unchecked
  Action = Print
  Command = gsview /p %1
  Uses DDE = unchecked
 Then press `OK`.

 From the `File Manager`, select `File `| `Associate` then
 enter the following fields:
  Files with Extension = ps
  Associate With = PostScript (gsview)
 Then press `OK`.

 That's it!  Now when you double click on a PostScript file,
 the `File Manager` will run Ghostview.  When you drop a PostScript
 file on the `Print Manager`, Ghostview will print the file.
2Copyright
?Copyright
 The `About` menu item shows the Ghostview copyright message
 and Ghostview version number.

  GSVIEW.EXE - A Ghostscript graphical interface
  Copyright (C) 1993  Russell Lang

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

     Author: Russell Lang
   Internet: [e-mail]

 ps.c module Copyright (C) 1992 Tim Theisen ([e-mail]).
2Common Problems
?Problems
 `Problem:` Ghostview can't run gswin.

 From the Ghostview menu select `Options` | `Ghostscript Command`
 and enter the correct executable path and include path for Ghostscript.
 For example:
  c:\gs\gswin.exe -Ic:\gs

 The default Ghostscript Command is `gswin`.  This will work if
 Ghostscript is in the same directory as Ghostview, or if the
 Ghostscript directory is on the PATH.

 Make sure you don't already have Windows Ghostscript running.
 Only one copy of Windows Ghostscript can be running at a time.
 Only one copy of Ghostview can be running at a time.

 `Problem:` Ghostscript starts and then immediately exits with error code 1.

 Read the error message in the Ghostscript window before pressing OK
 in the message box.

 Ghostscript probably couldn't find its initialisation files.
 Set the environment variable GS_LIB to the directory containing
 the Ghostscript initialisation files, or add -Idirectory to the command
 in `Options` | `Ghostscript Command`.

 Read the file use.doc that comes with Ghostscript.

 `Problem:` Message Box says `Incompatible Ghostscript`

 You probably have an earlier version of Ghostscript.
 Make sure you have Ghostscript version 2.6 or later.

 `Problem:` Ghostview says 'wait' and shows an hourglass cursor.
 When the cursor is moved off the Ghostview window it changes to a
 normal arrow.

 The above state is normal while Ghostview is waiting for Ghostscript
 to do something.  It may be that the document is very complex and
 Ghostscript is just taking a long time.  In this state it is safe to
 resize or scroll the window, but do not select any menu commands.

 If this is not the case then Ghostview probably got no response
 from Ghostscript.
 Open the Ghostscript text window and look at the error message.
 Close Ghostscript using the Ghostscript system menu.
 If Ghostview is still waiting, press the Ghostview Open button
 (even though the cursor is still an hourglass).
 Press the 'Yes' button on the 'gsview is busy' message box.
 Ghostview should then revert to the non-waiting mode.
2Internals
?Internals
 The preferred method for driving Ghostscript would be to start it
 as a child process and then to send it postscript code through a pipe.
 Windows 3.1 supports neither child processes nor pipes.

 Ghostview interacts with Ghostscript by sending messages between
 the Ghostview and Ghostscript windows.
 Ghostview creates an imitation pipe to Ghostscript by writing
 into a shareable global memory block and then passing the handle
 to Ghostscript.

 Ghostview starts Ghostscript for displaying using
  gswin -rXDPIxYDPI -gWIDTHxHEIGHT -sGSVIEW=xxxx -
 where xxxx is the handle to the Ghostview window.
 Ghostscript then tells Ghostview the handle to the text window by sending
 a message WM_USER with wParam HWND_TEXT=0 to the Ghostview window.
 Instead of creating another window for the image, Ghostscript
 creates a child window of the Ghostview window for displaying
 the bitmap. Ghostscript tells Ghostview the handle to this child
 image window by sending a message WM_USER with wParam
 HWND_IMGCHILD=1.

 Ghostscript also sends WM_USER messages to Ghostview with wParam
 GSWIN_CLOSE=2 when it is exiting,
 SYNC_OUTPUT=3 when the image needs to be redrawn (win_sync_output),
 OUTPUT_PAGE=4 when a page is to be output (win_output_page),
 SCROLL_POSITION=5 when the window is scrolled and
 PIPE_DATA=6 for passing the handle to a global memory block (in
 lParam) for the imitation pipe.

 When Ghostscript sends the OUTPUT_PAGE command it waits until it
 receives a NEXT_PAGE command from Ghostview.

 Ghostview sends WM_USER messages to the Ghostscript Image window with
 wParam NEXT_PAGE=10 when it is time to move to the next page and
 COPY_CLIPBOARD=11 when the bitmap should be copied to the clipboard.
 Ghostview sends WM_USER messages to the Ghostscript Text window with
 wParam PIPE_REQUEST=12 when it wants more pipe data.

 Ghostview uses temporary files of the name gsviewXX.XXX in the
 directory given by the TEMP environment variable.
 Keep TEMP short to avoid the gswin command line exceeding 128 characters.

 Ghostview starts Ghostscript for printing using
  gswin -sGSVIEW=xxxx @optfile filename.ps quit.ps
 optfile contains
  -dNOPAUSE
  -sDEVICE=devname
  -rXDPIxYDPI
  -gWIDTHxHEIGHT
  -sOutputFile=filename

 To start Ghostview and display filename.ps use:
  gsview filename.ps
 To start Ghostview and print filename.ps using Ghostscript use:
  gsview /P filename.ps
 To start Ghostview and print filename.ps to a file using Ghostscript use:
  gsview /F filename.ps
 To start Ghostview in debug mode use:
  gsview /D
 In debug mode Ghostview will `not` remove its temporary files.
 This is to allow inspection of these files after Ghostview has finished.

 The ability to select individual pages for an Adobe Document
 Structuring Conventions conforming document is due to the inclusion of
 the ps.c module from X11 Ghostview by Tim Theisen ([e-mail]).
 Don't sent mail to Tim about Ghostview for Windows, unless it is about a
 bug in the ps.c module.