Almathera Ten Pack 3: CDPD 3/Almathera Ten on Ten - Disc 3: CDPD3.iso/scope/101-125/scopedisk105/plt13/plt.doc

Text File | 1995-03-19 | 15KB | 354 lines

                                PLT:
                             Version 1.3
                          November 16, 1989

                           Rich Champeaux
                             Jim Miller


NOTICE:  PLT: is not in the public domain.  We reserve all rights to both the
         executable and the source.  PLT: may not be sold without expressed,
         written permission of either Rich Champeaux or Jim Miller.  PLT: is
         however, freely distributable provided that this file accompanies it.


PLT: is a file-handler that emulates a plotter by accepting HP-GL commands,
creating a raster image, and then dumping it to any Preferences supported
graphics printer.  The current resolution set with preferences is used,
allowing PLT: to make full use of a printer's capability.

PLT: accepts virtually all of the standard HP-GL commands, including scaling
and text.  The commands that were not implemented are those which are
generally contained in an extended graphics cartridge, such as: circles,
arcs, filled regions, etc.


PLT: Features:

   - Lines are stored in a tree/linked list structure untill the handler is
     closed or the command AF or PG is recieved.  The plot is then rasterized
     and dumped to the printer in strips.  This allows plots to be printed
     with resolutions and page sizes for which a raster for the entire page
     would not fit in memory.

   - Pens can be assigned colors and thicknesses.  The pen colors are defined
     by RGB values, and thicknesses are defined in pixel widths.  The pens
     can be defined in an environment variable or when the handler is opened.
     The number of bit planes used for the raster depends on the number of
     different colors requested, not the number of pens.  Therefore, 7 black
     pens and 5 red pens of various thicknesses, would only take 2 bit planes.

   - PLT: supports variable paper sizes.  It knows the standard paper sizes,
     A, B, C, D, and E, and can also use the paper size defined by the limits
     fields of Preference's Graphic 2 screen.  The entire width of any dot
     matrix printer supported by Preferences can be used, including wide
     carriage printers.  If the requested page size is too large to be
     printed, a requester is displayed, giving the option to reduce the size
     of the plot (keeping the aspect ratio) to the maximum size of the
     printer.  The plot can also be reduced to the page size specified by
     Preferences.

   - PLT: has a preview mode that displays the plot on the screen.  The
     aspect ratio of the requested page is preserved.  This allows the plot
     to be displayed on the screen the way it will appear on paper.
     A 640 x 400 screen is used to provide maximum resolution.

   - PLT: v1.3 supports multiple, disk-resident fonts.  The fonts can be
     changed or created by the user.  An included program, 'cf', is used to
     convert the fonts from a text representation of the vectors to a
     format usable by PLT:.  Fonts are loaded in only when needed, and
     fonts can be changed durring a plot with the CS, CA, SS, and SA HP-GL
     commands.  A standard ascii font and a math-greek font are included
     with this release.

   - PLT: can also be used by programs that assume that a plotter is
     connected to the serial port by using the CMD command.  For example:
        CMD serial.device PLT:

   - PLT: has two memory usage modes that it can run in: memory-squander and
     memory-conserve.  The memory-squander mode sits a tree structure on top
     of the linked list to speed up inserts.  The memory-conserve mode uses
     only a linked list.  The memory-squander mode is much faster than the
     memory-conserve mode since it's insert time is O(log2(n)), but it
     requires twice as much memory per line.  The memory-conserve mode's
     insert time is O(n), and becomes unbearably slow as the number of lines
     becomes greater than about 8000.  The memory-conserve mode does, however,
     allow twice as many lines to be plotted.  PLT: v1.3 defaults to the
     memory-squander mode and will automatically remove the tree and switch to
     the memory-conserve mode when availble memory is less than 2k.

-----------------------------------------------------------------------------

Installing PLT:

   1) Copy the file 'plt-handler' to the L: directory.
   2) Create a directory and assign "PLTDATA:" to it.
   3) copy the files 'ascii', 'math-greek', and 'pltfontnames' to the
      directory 'PLTDATA:'
   4) Add the following to the mountlist:

      PLT:        Handler   = L:plt-handler
                  StartUp   = P/000-1
                  StackSize = 5000
                  Priority  = 5
                  GlobVec   = 1
      #


      (Note: the StartUp field is used to pass default parameters to the
       handler.  It is explained below.)

   5) Mount the handler using the command 'mount PLT:'

-----------------------------------------------------------------------------

Switches and Pen Definitions:

   PLT:'s mode switches and pen definitions are recieved from three sources:
the mountlist entry, an environment variable, and the file name path.  All
three sources use the following format:

      SWITCHES/RGB-t/RGB-t/RGB-t...

      where:
         SWITCHES could be:  A..E  Selects standard page sizes A,B,C,D, or E.
                                   (default is A)

                                P  Selects the page size specified by the
                                   limits fields of Preferences' Graphics 2
                                   screen.

                                R  Reduces the plot (keeping the aspect ratio)
                                   to the size specified by the limits fields
                                   of Preferences' Graphics 2 screen.

                                S  Draws plot on preview screen.

                                W  Displays a status window when plotting to
                                   printer. (default)

                                M  Forces PLT: to use the memory-conserve
                                   mode.

                                L  Makes the label command do a carriage
                                   return when it receives a line feed.
                                   This switch allows copatability with the
                                   Amiga since the newline character on the
                                   amiga is a linefeed.

                     (A '-' can be prefixed to a switch to negate it.)

         Pens are described as: RGB-t
            where:
                                RGB is the color of the pen in hex.
                                t   is the pen thickness in pixels. (optional,
                                    defaults to 1).

      Ex.
         SB/000-1/f00-3/0c3-2
         -WP/0f0/000-2/f30
         /000-1/0f0-1/f00-2
         DRM
         C-R/000-1

   The switches and pen definitions defined in the mountlist or the
environment variable "pltinfo" are used as the defaults for PLT:.  If the
environment variable exists, the entry in the mountlist is ignored.  These
defaults can be temparily overridden by the switches and pen definitions
passed to PLT: as the file path (Ex. PLT:SB/000-1/f00-2).  The switches
specified with the file path selectively override the defaults.  For
example, if the defaults were 'SBWR' and the switches specified in the file
path were '-S-R' then the S and R switches would be negated, but the other
switches would be unaffected.  Defining pens in the file path, however,
completly replaces the default pen definitions.  A maximum of 15 pens can
be defined.  If a pen is selected whose number is greater than the total
number of defined pens, then the pen number is MODed with the total number
of defined pens.

   To define the switches and pen definitions in the mountlist, use the field
'StartUp'.

   Ex.      StartUp = P/000-1/f00-1/0f0-1/00f-1

The StartUp field appears to be limited to 39 characters and cannot start
with a '-'.  If you require more characters or a leading '-', use the
environment variable.

   The enviroment variable used is "pltinfo".  It is set in the following
manner:

   setenv pltinfo P/000-1/f00-1/0f0-1/00f-1

The enviroment variable has the advantage of being easily changed after PLT:
has been mounted.

-----------------------------------------------------------------------------

Fonts:

   The fonts of PLT: are disk resident and user modifiable.  The fonts are
stored in the directory PLTDATA:.  A file in that directory, 'pltfontnames',
contains the names of the fonts accessible to PLT:.  The file contains a list
of font names, one name per line, that are to be associated with the font
numbers 0 thru 50.  The fonts are selected using the HP-GL character set
commands: CS, CA, SS, SA.  CS and CA designate the standard and alternate
fonts, respectively.  SS is then used to make the standard font the current
font, and SA is used to make the alternate font the standard font.  The
default font is font 0, which is the first font listed in the file
'pltfontnames'.

   The fonts are described by a text file, whose name ends with the extension
'.fnt', and then must be compiled with the program 'cf' before they can be
used by PLT:.  The characters consist of 1 or more strokes of the pen.  Each
character in the font has an entry which specifies the value of the character
and a list of end points describing each stroke of the pen.

   The first 2 numbers in the file contain the width and height of the
character cell.  Large characters, such as capital letters should completely
fill the cell, however, the characters are allowed to have end points that
lie outside of the cell.

   The first line of each character entry consists of an '*' followed by the
value of the character.  The remaining part of the line is a comment.
Following that are the pen strokes that make up the character.  Each stroke
consists of a number indicating the number of end points in the stroke,
followed by the the starting location of the stroke, followed by the end
points of the lines in the stroke.  Below is an example of a character entry.
The comments on the right are only for the documentation and should not be
in the actual font file.


*  48 '0'      Below are comments that should not be in the actual file
8              <- number of end points (lines) in the first stroke.
12 3           <- starting point of the first stroke
12 18          <- end point of the first line in the stroke
9 21           <-|
3 21           <-|
0 18           <-|
0 3            <-|- more end points
3 0            <-|
9 0            <-|
12 3           <-|
1              <- number of end points (lines) in the next stroke
10 20          <- starting point of next stroke
2 1            <- end point of the only line in the second stroke

   The character entry is ended by the occurance of the '*' marking the next
character entry.

   The font file is compiled and placed in the PLTDATA: directory by the
program 'cf'.

   Ex.   cf ascii

The font file is assumed to end with the extension '.fnt'.

   The cf program is only a simple state machine, so it does not handle errors
very well.  It merely tells you what the character it discovered the error at
was and the position of that character in the file.  Source to the cf program
is included with this release.

-----------------------------------------------------------------------------

Specifing the Raster Height:

   The maximum height of the raster that PLT: uses when it prints a strip of
the plot can be specified by the user.  The user specifies the maximum number
of lines in the raster using the enviroment variable 'PltMaxRasHgt'.

   Ex.   setenv PltMaxRasHgt 100

   Specifing the maximum raster height is a way of controlling the amount of
memory that PLT: uses for the raster.  The actual raster height that is used
is always a multiple of the number of lines that the printer driver can print
in one "strip" at the specified resolution.  The minimum raster height, and
the default, is the height of one "strip".

-----------------------------------------------------------------------------

Specifing the Left Margin:

   The left margin of the plot can be specified in inches using the environment
variable 'PltXOffset'.

   Ex.   setenv PltXOffset 0.5

   The value is only accurate to one tenth of an inch.

-----------------------------------------------------------------------------

Operation:

PLT: can be used in a variety of manners.

1.      You can copy files containing HP-GL commands to the handler.
            Ex.  copy <filename> PLT:

2.      You can direct a CAD package to plot to a file and give the
        filaname as "PLT:"

3.      You can redirect output from a CAD package heading towards
        the serial port to the handler.
            Ex.  cmd serial.device PLT:

4.      You can write your own applications that write directly to the
        handler PLT:.
            Ex.   file=fopen("PLT:","w");

-----------------------------------------------------------------------------

Memory:

PLT: does take up quite a bit of memory.  Not as much as a full raster image,
but still quite alot.

PLT: code needs      35K
printer.device needs 49K
raster varies from    5K - 14K
each lines takes     28 bytes  (or 16 in the Memory Conserve mode)


Before data is read, PLT: removes about 90K - 100K from your system.

An average plot will usually require an additional 30-50k.
A complex plot will usually require about 180K or more.

-----------------------------------------------------------------------------


QUESTIONS or BUG REPORTS

   Since there have been so many changes to PLT: from v1.2, there are sure to
be numerous bugs lurking in the code.  Any questions or bug reports should be
sent to the following addresses:

Rich Champeaux
[e-mail]

or

Jim Miller
[e-mail]

or send US mail to:

Rich Champeaux
11 Mansfield Dr.
Chelmsford, MA  01824

(Sending US mail to the above address will be slow, since that is my home
 address, not my school address)

   Every attempt will be made to solve your problems within a reasonable
amount of time.


| It would be appreciated if anyone using PLT: would email or US mail your
| comments to one of the above addresses.  Even an "I am using PLT:" message
| is welcome.  We have put a lot of effort into PLT: and since we did not
| write PLT: for a profit, but merely for the ego boost, we would like to
| know approximately how many people are using it, and what they think about
| it.  Thank you.
|
| Rich Champeaux