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HEWLETT-PACKARD

GPL/260
Programming Manual

HP 260 Computer Systems

GPL

Programming Manual

HEWLETT
PACKARD

HERRENBERGER STRASSE 130, D-7030 BOEBLINGEN

Part No. 45261-90064 Printed in Federal Republic of Germany 09/86

E0986

FEDERAL COMMUNICATION COMMISSION RADIO
FREQUENCY INTERFERENCE STATEMENT

(for U.S.A. only)

This equipment generates, uses, and can radiate radio frequency energy and if not installed and used in
accordance with the instructions manual, may cause interference to radio communications. It has been
tested and found to comply with the limits for a Class A computing device pursuant to Subpart J of Part
15 of FCC Rules, which are designed to provide reasonable protection against such interference when
operated in a commercial environment. Operation of this equipment in a residential area is likely to
cause interference in which case the user at his own expense will be required to take whatever measures
may be required to correct the interference.

NOTICE

The information contained in this document is subject to change without notice.

HEWLETT-PACKARD MAKES NO WARRANTY OF ANY KIND WITH REGARD TO THIS
MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Hewlett-Packard shall not
be liable for errors contained herein or for incidental or consequential damages in connection with the
furnishing, performance or use of this material.

Hewlett -Packard assumes no responsibility for the use or reliability of its software on equipment that
is not furnished by Hewlett-Packard.

This document contains proprietary information which is protected by copyright. All rights are
reserved. No part of this document may be photocopied, reproduced or translated to another language
without the prior written consent of Hewlett-Packard Company.

CONTENTS

Section 1
INTRODUCTION TO GPL

What is GPL? 1-1

What is Computer Graphics? 1-1

Payoff of Computer Graphics 1-2

Capabilities of GPL 1-2

Section 2

CONFIGURING THE PLOTTER

Software Configuration 2-1

Hardware Connection 2-1

Load the Graphics Software from Disc 2-2

Section 3

PROGRAMMING GUIDELINES

Naming Conventions 3-1

Gpl$ String 3-1

Parameters in GPL Subprograms 3-1

Use of REQUEST and RELEASE 3-1

Loading and Deleting the GPL Library Files 3-1

Sample Program 3-3

List and Study the Program 3-4

Troubleshooting 3-4

Nothing Happens When Program is Run 3-4

Program Halts on Error Condition 3-5

Picture Different Than Expected 3-5

Summary 3-5

Section 4

PLOT INITIALIZATION AND TERMINATION

GPL_plotteris 4-1

Gpl terminate 4-4

FNGpl_errm$ 4-5

Gpl_abortplot 4-5

Gpl clear 4-7

Gpl transmit 4-8

Summary 4-8

SEP 86
3

CONTENTS (continued)

Section 5

DEVICE SELECTION

Gpl config 5-1

Gpl_devident 5-2

Summary 5-4

Section 6

ESTABLISHING YOUR COORDINATE SYSTEM

Logical Units versus Physical Units 6-1

Scaling and Placement on Physical Device. 6-1

Physical Plotter Characteristics 6-2

Paper Size , 6-3

Gpl physarea 6-3

Gpl devorigin 6-4

Paper Placement 6-5

Logical Device Coordinates (LDC units) 6-5

Gpl_defldc 6-6

Helpful Hints 6-7

Gpl physviewp 6-7

Gpl_physrotate 6-8

Summary 6-8

Section 7

DRAWING STRAIGHT LINES

Current Position (CP) 7-1

Gpl move, Gpl imove 7-1

Gpl where 7-2

STRAIGHT LINES 7-2

Gpl frame 7-2

Gpl draw, Gpl idraw 7-3

LIMITS of CP 7-3

Gpl__linestyle 7-4

Summary 7-5

Section 8

PEN CONTROL

Gpl pen 8-1

Gpl penspeed 8-1

SEP 86
4

CONTENTS (continued)

Section 9

DRAWING TEXT STRINGS

Plotter Firmware Characters and Software -Generated Characters 9-1

Gpl_text 9-1

Use of CR and LF Control Characters with Gpl_text 9-2

Text Clipping 9-2

Drawing European Characters with Gpl_text 9-2

Gpl tsize 9-3

Specifying Character Size and Placement with Gpl__tsize 9-4

Gpl_lorg . 9-4

Gpl textrotate 9-6

Gpl itextwidth 9-6

Software -Generated Characters 9-8

Gpl__cset. 9-8

Summary 9-9

Section 10

USING SOFTWARE CHARACTERS

Width of Plotter Firmware Fonts 10-1

Width of Software -Generated Fonts 10-1

Underlining Plotter Firmware Characters 10-1

Underlining Proportional Software Characters 10-2

Creating a Character Set File 10-2

Character File Format 10-2

Section 11

VIEWING TRANSFORMATIONS

Definitions

World Coordinates

Logical Device Coordinates

Viewing Transformation . .

Window

Viewport

Clipping (or Scissoring) . . .

Gpl window

Gpl viewport

Gpl useldc .

Gpl usewc .

Summary

1-1
1-1
1-1
1-2
1-2
1-3
1-3
1-3
1-3
1-5
1-5
1-5

SEP 86

CONTENTS (continued)

Section 12
PICTURE FILES

Gpl_fileis 12-1

Gpl message 12-2

GPLFIL Utility Program 12-2

Section 13

PLOTTING AN ACETATE

Overhead Transparency Kit 13-1

Special Considerations 13-1

Ink Transfer and Drying 13-1

Viewing Area 13-1

Programming Guidelines 1 3-2

Viewing Area 13-2

Centering . 1 3-2

Pen Velocity 1 3-2

Multiple Passes 1 3-2

Avoiding Ink Run 13-2

Section 14

PROGRAM DESIGN TIPS

Simple Applications 14-1

Complex Applications 14-2

Memory Usage 1 4-4

SEP 86
6

CONTENTS (continued)

Appendix A
CHART DESIGN

Graphics Considerations A-l

Simplicity A-l

Select the Right Chart Type A-l

Plot Sizes A-2

Text A-2

Appendix B
GLOSSARY

Appendix C

GPL SUBPROGRAM FILES AND FONTS

Subprogram Files C-l

Font Files C-l

Other GPL Files C-l

Appendix D
GPL ERRORS

General Philosophy

Soft Errors

Hard Errors

Parameter Reference Errors.
Miscellaneous Errors

D-l
D-l
D-2
D-3
D-4

SEP 86

CONTENTS (continued)

Appendix E

SUMMARY OF GPL SUBPROGRAMS

Gpl abortplot E-2

Gpl_clear E-2

Gpl_config E-3

Gpl cset E-3

Gpl_defldc E-3

Gpl_devident , E-4

Gpl devorigin E-4

Gpl draw E-6

FNGpl_errm$ E-6

Gpl_fileis E-7

Gpl frame E-7

Gpl_idraw E-8

Gpl imove E-8

Gpl_itextwidth E-8

Gpl__linestyle E-8

Gpl_lorg E-9

Gpl message E-10

Gpl move E- 1 1

Gpl_pen E- 1 1

Gpl penspeed E- 1 2

Gpl physarea E- 1 2

Gpl_physrotate E- 1 3

Gpl physviewp E- 1 3

Gpl_plotteris E-14

Gpl terminate E-14

Gpl_text E- 1 5

Gpl textrotate E- 1 6

Gpl transmit E- 1 6

Gpl_tsize E- 1 6

Gpl_useldc E- 1 6

Gpl usewc E- 1 7

Gpl viewport E- 1 7

Gpl_where E- 1 7

Gpl_window E-17

SEP 86
8

PRINTING HISTORY

New editions are complete revisions of the manual. Update packages, which are issued between editions,
contain additional and replacement pages to be merged into the manual by the customer. The dates on
the title page change only when a new edition or a new update is published. No information is
incorporated into a reprinting unless it appears as a prior update; the edition does not change when an
update is incorporated.

The software code printed alongside the date indicates the version level of the software product at the
time the manual or update was issued. Many product updates and fixes do not require manual changes
and, conversely, manual corrections may be done without accompanying product changes. Therefore, do
not expect a one to one correspondence between product updates and manual updates.

First Edition Jul 1985 B. 07. 00

Second Edition Sep 1986 B. 08.00

LIST OF EFFECTIVE PAGES

The List of Effective Pages gives the date of the most recent version of each page in the manual. To
verify that your manual contains the most current information, check the dates printed at the bottom of
each page with those listed below. The date on the bottom of each page reflects the edition or subsequent
update in which that page was printed.

Effective Pages Date

all Sep 1986

j NOTE

Graphics Plotter Library system software is included with the operating
system and system software of the following computer systems:

• all HP 250 Business Computer Systems

• all HP 260 Business Computer Systems

This manual describes the operation of GPL system software supplied with
the most recent version operating system and system software of the
previously mentioned computer systems. (At this edition of the GPL
Programmer's Manual, B. 08 is the most recent version of operating system
and system software for these computer systems. )

Note that not every plotting device is supported on each computer system.
To find out if a particular plotting device is supported on your computer
system contact your third party representative or your local HP Sales
Office.

In this manual, the phrase "your computer system" refers to the HP 250 and
HP 260 Business Computer Systems.

WHAT IS GPL?

GPL is a BASIC -language subprogram library callable from BASIC for drawing pictures on HP Graphic
Plotters. The library is intended for the application programmer who wants to include simple plotter
graphics in his application and wants easy access to the plotters. GPL is implemented in BASIC and
therefore uses some application program memory space.

WHAT IS COMPUTER GRAPHICS?

In the simplest case, "Computer Graphics" is the output of pictures on certain computer peripherals. You
may view these pictures on CRT's (graphics terminals) or graphics plotters. In business applications, output
computer graphics may be used to produce graphs, charts, maps, floor plans, and engineering drawings.

In more complicated applications, sophisticated peripherals may be used for interactive, real time input
and output of pictures. This is called "Interactive Computer Graphics".

GPL is oriented to the output of hardcopy pictures on HP Graphics Plotters. Facilities for storing pictures
in files for later output on a device are included.

SEP 86
1-1

Introduction to GPL

GPL is not intended to support interactive computer graphics and does not contain facilities for graphics
input.

PAYOFF OF COMPUTER GRAPHICS

Computer graphics is a good tool for displaying and analyzing data. For example, you can spot trends and
problem areas with a chart much faster than with a list of numbers. The analysis is also more easily
communicated to others in graphical form. For large audiences, you can draw charts on overhead slide
acetates and use an overhead projector to view the charts.

GPL is ideal for producing charts and overhead acetate slides in typical business situations.

CAPABILITIES OF GPL

Key features include:

• Easy to use, mnemonic syntax

CALL Gpl_move(G$,X,Y) —moves pen to (X,Y)

CALL Gpl_draw(G$,X,Y) —draws a straight line to (X,Y)

CALL Gpl_text(G$, "HELLO") —draws HELLO at pen location

In the above calls, G$ is a string which contains all temporary parameters passed between GPL calls.

• Device -independent programs and application manuals

• Oriented towards business applications

Emphasis on charts, graphs, and overhead slides

• Is compatible with HP RS-232-C Graphics Plotters

• Powerful

Nine line styles, selection of multi-colored pens, control of pen velocity

Numerous decorative character fonts, control of character width, height, and rotation

Device -independent coordinate system - world (problem) coordinates, logical plotter

Rotation, translation, and scaling of entire plots

File storage of pictures - convenient for multiple copies of pictures

• First Day Productivity

It's easy to get started. Instructions are complete.

SEP 86

1-2

Introduction to GPL

GPL was designed for the business environment. It may not work for all applications because extra
computer memory is occupied by extensive code to make GPL easy to use.

SEP 86
1-3

SEP 86
1-4

Before learning how to program with GPL, connect the plotter to your computer system. Instructions
appear in "Operating and Managing"(part number 45260-900020). Plotter installation includes hardware
connection and software configuration.

SOFTWARE CONFIGURATION

Run the CONFIG utility program, described in the "Utilities Manual" (part number 4526-90061). GPL
requires configuration of the PACK and TIO DROM's. In the "Asynchronous Port Configuration"
function, configure the plotter as a 26xx terminal, format 8N1.

HARDWARE CONNECTION

See "Operating and Managing" for hardware configuration. Be sure to perform a plotter self-test and
system confidence test.

GPLCFT - GRAPHICS

DEVICE/SYSTEM

CONFIDENCE

TEST

Slowest, velocity

test -,

10/13/86

Run* 1

7475A

Deviice addness-14

NINE HNESTYX.es SIX PENS g

M
¥

Buffer s:ize=1024 bytes

2 1

3 3

s s

e - - e

§ .

TEST

COMPLETED

!-N0im(W 1X31

! "#$%S" () *+. -./

0123456789: ; <=>?

" *" 9 Rn iia£TS

@ABCDEFGHIJKLMN0

ad6Ci6666dddCiHiil5U

PQRSTUVWXYZ [\] *_

Ai8£a*0»XidUEYp

"abcdefghi jklmno

pqrstuvwxyz (1 } ~

Revision HP260.7.C

SEP 86

2-1

Configuring the Plotter

LOAD THE GRAPHICS SOFTWARE FROM DISC

The GPLLOD program transfers GPL files from one medium to another. GPL is supplied on one of the
following types of distribution medium:

• the Operating System Tape Cartridge

• the 8 -inch floppy labeled GPL

• the two 3. 5 -inch microfloppies labeled GPL LIBRARY and GPL TEXT

Use the following procedure to copy the GPL files from your distribution medium to your fixed disc.

RUN "GPLLOD"

Press the softkey corresponding to the device from which the files are to be transferred. Then press the
softkey corresponding to the device on which the files will be stored.

GPLLOD asks what should be transferred:

GPL25X LIBRARY — All GPL files except those for software -generated

character sets.

SOFTWARE TEXT — The files required to plot software -generated characters.

ALL — Both of the above.

Now press the softkey corresponding to the group of files you want to transfer.

"Operating and Managing" contains some troubleshooting suggestions. Follow these suggestions when a
problem occurs.

SEP 86

2-2

Before learning how to program with GPL, you must understand several concepts relating to the way it
works. The disc contains a sample program to help you understand the structure of a GPL program.

NAMING CONVENTIONS

The names of all GPL calls begin with the prefix "Gpl_". The names of all GPL internal (nonuser)
subprograms and functions begin with the prefix "Gpli". You should name all of your application
subprograms and functions with a prefix other than "Gpl_" or "Gpli".

GPL$ STRING

The first parameter in most GPL calls is a 1 200 character string that contains all parameters that are
passed between the GPL subprogram calls. In all of the examples in this manual, the string will be called
Gpl$. To dimension the string, use the command:

DIM Gpl$[1200]

This variable name must be passed between all modules that use GPL subprograms. It is important that
this string variable be dimensioned to be exactly 1200 characters. Attempting to pass a string of length
other than 1200 between GPL subprograms will result in an error.

PARAMETERS IN GPL SUBPROGRAMS

All numeric parameters in the GPL subprograms parameter list must be of type REAL.

USE OF REQUEST AND RELEASE

GPL uses TIO whenever the device address is in the range 1 1 to 20. Each time data is to be sent to the
plotter, GPL inquires about available plotter buffer space. If the buffer is almost full, GPL waits until
buffer space is available. TIO requires that the device be REQUEST'ed before a Gpl_plotteris call, and

RELEASE'd after a Gpl terminate call. This lets other users access the device. It is the responsibility of

the application program, not GPL, to perform REQUEST and RELEASE operations.

LOADING AND DELETING THE GPL LIBRARY FILES

The GPL library occupies a large block of user memory. It is necessary to load and delete several GPL
subprogram files during the execution of a program. This can all be done under program control. For
example, you could use statements of the form:

SEP 86

3-1

Programming Guidelines

DEL 5001,9999

LOAD SUB "GPL252", 5001,1

at the beginning of your program to load the GPL initialization subprograms.

Clear the entire subprogram library from the user memory at the end of your program with the
statement:

DEL 5001,9999

The GPL library is organized into logical subprogram files as follows:

FILE

GPL251
GPL252
GPL253
GPL254
GPL255
GPL256
GPL257
GPL258

Contains subprograms for:

Device selection

Initialization and plotting area specifications

Plot setup and specifications

Text and straight lines

Straight lines

Text

Plot termination

Determining width of text strings

SEP 86

3-2

Programming Guidelines

SAMPLE PROGRAM

A sample application program, GPLE01, has been included in the GPL library for use with this chapter.
The sample program draws a typical business line chart on any of the supported plotters. Extensive
comments are included to help you read the program.

To run the program, perform the following steps:

1) MSI ":<volume-spec for the disc containing the GPL files>"

2) RUN "GPLE01 " and follow the instructions on the screen.

The program will ask for the plotter model number and device address. The address is 8 or 1 1 through

20.

Device address 8 will send the plotter protocol to the CRT display. First, run the program using 8 and
compare the display with a listing of the program.

Now run the program, giving the address to which the plotter is connected. The picture that is generated
should be similar to that shown below.

3500

TOTAL

DOLLARS IN MILLIONS

3000 -

3500

2000

1500 -

1000

500 -

XYZ COMPANY

ORDERS

DOMESTIC

INTERNATIONAL

PLOTTED ON HP 7<79A GRAPHICS PLOTTER USING PHOflBAM 8PLE01

SEP 86
3-3

Programming Guidelines

List and Study the Program

List the program named "GPLE01". Study the listing of GPLE01 and try to understand the meaning of

the GPL calls from mnemonic names and comments. All GPL calls start with the prefix "Gpl ". Try to

understand how the plot was generated. These calls will be explained in the following chapters.

GPL is divided into several modules. The desired subprogram must be loaded before it can be used.

DEL 7000,9999

LOAD SUB "GPL252", 7000,1 ! for device initialization

DEL 7000,9999

LOAD SUB "GPL253", 7000,1 ! for setting plotting coordinates

DEL 7000,9999

LOAD SUB "GPL254", 7000,1 f for plotting

DEL 7000,9999

LOAD SUB "GPL257", 7000,1 ! for termination

The library is deleted at the end of execution by the statement

DEL 7000,9999

The LOAD SUB statements require either that files "GPL252", "GPL253", "GPL254" and "GPL257" reside
on the MSI disc or that the LOAD SUB statements contain a device specifier. In addition, execution
requires a 64K partition.

TROUBLESHOOTING

Nothing Happens When Program is Run

a. Check to see that the device is on and that status lights are correct.

b. Run GPLCFT to make sure that the plotter is properly connected. If this fails, follow the
troubleshooting steps for GPLCFT.

The above checks should turn up most possible problems.

SEP 86

3-4

Programming Guidelines

Program Halts on Error Condition

No ON ERROR control is supplied in this simple example. If an error message comes up with a program
halt, consult an "Operating and Managing" or "Syntax Reference Guide". Some errors may be difficult to
interpret. Typical errors include:

Error # Probable Cause

2 Memory Overflow (occurs in a 32K partition, but should

not happen on a 64K partition)

56 The GPL library was not found on the MSI disc.

1 30 Invalid device address for your hardware configuration.

1 3 1 The device REQUEST'd was not available because somebody

else reserved the device.

1 32 The wrong type of device was REQUEST'ed, such as a workstation.

1 3 3 Selected device is down.

Picture Different Than Expected

a. Run the program to verify that the error is repeatable.

b. Run program GPLCFT to check for system and device problems.

If test (a) shows that the error is not repeatable, then it may be an intermittent problem. Check the entire
configuration. If the problem still exists, then you may have to contact your Hewlett-Packard service
representative for further help.

If test (a) shows a repeatable problem and GPLCFT uncovers no problem, there may be a problem
somewhere in the system software or hardware. Recheck the configuration.

SUMMARY

In this chapter you have been exposed to a typical graphics application progxam. Operations performed
include loading the GPL library with the application and plotting on one of the supported plotters. After
completing these tasks, you are ready to learn how to program a graphics application.

SEP 86
3-5

SEP 86
3-6

PLOT INITIALIZATION AND
TERMINATION

SECTION

In this chapter, you will learn the basic concepts of plotting with GPL, as well as the routines necessary to
start and stop plotting. Several subprograms are available to initialize the plotter and to terminate
plotting. A plot may terminate in one of three ways: normal completion of the program, an error
condition, or a user initiated exit.

These subprograms are introduced in this chapter:

Gpl plotteris

Gpl terminate

FNGpl_.errm$
Gpl abortplot

Gpl clear

Gpl transmit

Initializes a specified plotter and the
data stored in Gpl$.

Terminates plotting and processes all
data in the software and plotter buffers.

Displays error message for GPL errors.

Terminates plotting immediately and
flushes all data in the buffers.

Advances paper on chart advance plotters
and moves pen stable to the upper right
position.

Processes all data in the GPL buffer
and brings plot to its current state.

GPL PLOTTERIS

This is the first call to make when actually plotting. The subprogram initializes the device and the
parameters in the Gpl$ string. The syntax is:

Gpl plotter is(Gpl $,Model $ ,Dev add,Mess add,Er ror)

The parameters are:

Model$: Model number of graphics device stored in a string. ModelS can also contain the paper size

appended to the model name (as is returned by a call to the Gpl devident subprogram). For example ,the

parameter ModelS might now contain a string similar to "7550A/A3" when calling Gpl plotteris. If a

paper code is explicitly specified, it must match the actual plotter setting. If only the model name is given,
the Gpl$ string is initialized with the actual plotter setting.

SEP 86

4-1

Plot Initialization and Termination

The following are allowed values:

7220A

7220C

7220S
7220T

7221A
7221B
7221C

7221S
722 IT

7225A/3
7225A/3V

7225A/4

7225A/4V

7225B/3
7225B/3V

7225B/4

7225B/4V

7470A
7440A

7475A

7550A

The HP 7221A plotter is supported on all HP 250 and HP 260 models except Model 35. A hardware
incompatibility prevents the HP 7221 A from being initialized on the Model 35.

NOTE

"7 22 5 A/ 3" means that you have an HP 7 22 5 A Graphics Plotter equipped
with option 17603A Personality Module. "7225A/4" means option
17604A Personality Module. The "V" is associated with plotters that have
velocity select capability. A similar set of conventions holds for the 7225B
Graphic Plotters.

Dev add: This is the system address to which the graphics device is connected. Allowed values are in the

ranges 8-9 or 1 1-20. Send the data to your CRT (address 8) or the bit bucket (address 9) when you first
test a program to verify that the program will execute with no errors. A real device is assumed to be there
only when 1 1-20 is specified . Gpl__plotteris checks to see if the device that you specified is the device
that is there.

Mess add: This is the system address for operator messages for a plotter. Usually this is 8, the workstation

from which your application is running. Allowed values are in the range 8-9.

SEP 86

4-2

Plot Initialization and Termination

Error: This is an error return parameter to signal whether the initialization was successful. The currently
supported error returns include:

-No hard error encountered

1 - 1 099 -ERRN for system errors not explicitly

handled by Gpl plotteris.

1151 -Invalid Gpl$ (probably insufficient length)

1152 -Invalid Model$ (not one of the supported devices)

1153 -Invalid Device_address (Must be 8-9 or 1 1 -20)

1154 -Invalid Message__address (must be in range 8-20)

1161 -Plotter ownership error - must do REQUEST before

calling Gpl_plotteris

1162 -No response from plotter (when the

devices address ranges from 1 1 to 20)

1163 -Device is not the specified model (for

device address ranging from 11 to 20)

1164 -Plotter could no be initialized

(for a variety of reasons)

1165 -Unsupported plotter response during identify sequence

1 166 -Invalid plotter response during identify sequence
1181 -Plotter responded initially but later did not.

All further sending of data to plotter stopped.

This error parameter should be checked in all applications. If non-zero, then unpredictable results can
occur with further program execution. The function FNGpl_errm$, described in a later section and
shown in the above example, may be used to display the error message.

To use Gpl plotteris, follow this sequence:

DIM Gpl $[12 00]

! Assign values to Model $,Dev add,Mess add

ON ERROR GOTO Request_error
REQUEST Dev_ add
OFF ERROR

CALL Gpl_plotteris(Gpl $,Model $,Dev_add,Mess_add,Error)
IF Error<>0 THEN Init error

! Case where REQUEST fails

! ERRN is typically in the range from 1 30 to 139

Request_error:OFF ERROR

BEEP

DISP "Error in attempting to REQUEST plotter."

DISP ERRM$

! Initialization error

Init_error: DISP FNGpl_errm$(Error)

SEP 86

4-3

Plot Initialization and Termination

GPL TERMINATE

This is the last call to make when actually plotting. It processes data in the buffers, leaves the device in a
friendly state, and cleans up any picture files. The syntax is:

CALL Gpl_terminate(Gpl$, Error)

The Error return parameter gives a code for the last GPL call in which invalid parameters were
encountered. means no such errors.

1101 -Gp

1102 -Gp

1103 -Gp

1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115

Gp
Gp
Gp
Gp
Gp
Gp
Gp
Gp
Gp
Gp
Gp

g p :

1116 -Gp

1 1 1 7 - Gp

1 1 1 8 - Gp:

1119 -Gp
1120-Gp

1121 -Gp

1122 -Gp:

1123
1124
1125
1126
1127

Gp
Gp
Gp
Gp
Gp

clear
"defldc

draw

frame
jdraw

imove

linestyle
_lorg

message

move

penspeed

physarea

devorigin

pen

physrotate

physviewp

terminate
Jext

transmit

textrotate

tsize

useldc

usewc
_viewport
_ where

window

cset

In addition, the following error return parameters signify that data was lost during plotting. These errors
take precedence over the "soft errors" reported above.

1 1 8 1 - Plotter responded initially but later stopped.
Further plotting to device terminated.

1 1 82 - Invalid plotter response.

Further plotting to device terminated.

1 1 83 - Picture file could not be opened during plotting.
Sending plot data to file terminated.

SEP 86
4-4

Plot Initialization and Termination

FNGPL_ERRM$

As an aid to handling errors and debugging simple programs, an error reporting function, FNGpl errm$,

has been included in the GPL library.

Whenever an error is returned by:

Gpl_plotteris
Gpl_terminate

and any other GPL subprograms with an error to return parameter, an error message may be displayed.
Use the statement

DISP FNGpl_errm$(Error)

to display it on the screen.

GPL ABORTPLOT

CALL Gpl_abortplot(Gpl$)

aborts the current plot. This call flushes the software and plotter buffers of all data and terminates
plotting immediately. Use Gpl terminate after Gpl abortplot to leave the plotter in a friendly state.

SEP 86

4-5

Plot Initialization and Termination

A common way to use the abort feature is to allow the user to push a softkey labeled "ABORT PLOT" or
"STOP PLOTTING" when actually plotting.

DIM Gpl$[ 1200]

ON ERROR GOTO Request_error

REQUEST 12

OFF ERROR

DEL 7001,9999

LOAD SUB "GPL252",7001,1

CALL Gpl_plotteris(Gpl$,"7220A",l 2,8,Error)

IF Error>0 THEN Init_error

ON KEY #8,#16,#24 :"STOP PLOTTING" GOTO Abort_plot

DEL 7001,9999

LOAD SUB "GPL254",7001,1

Abort-0

GOTO Terminate

Abort_plot: DEL 7001,9999

LOAD SUB "GPL257",7001,1

CALL Gpl_abortplot(Gpl$)
DISP "Plot aborted."
Abort" 1
Terminate: DEL 7001,9999

LOAD SUB "GPL257",7001,1

CALL Gpl_terminate(Gpl$,Error)
RELEASE 1 2

IF Abort-0 THEN DISP "Plot terminated normally."
IF Error>0 THEN DISP FNGpl_errm$(Error)
GOTO End_message

Request error: BEEP

OFF ERROR

IF ERRN-1 30 THEN DISP "Device address out of allowed range."

IF ERRN-1 3 1 THEN DISP "Device is already reserved."

IF ERRN-1 32 THEN DISP "Invalid device type."

IF ERRN<1 30 OR ERRN>1 32 THEN DISP ERRM$

GOTO End_message

Init_error:DISP FNGpl_errm $(Error )

End message: DISP "Program terminated."

DEL 7001,9999
END

The HALT key should not be programmed to abort the plot because a HALT is immediate. The
application may be in one of the GPL subprograms when HALT is pushed. This latter case would cause
the application program to stop executing. Any data left in the device buffer is NOT flushed and will be
plotted.

SEP 86

4-6

Plot Initialization and Termination

GPL._CLEAR

Gpl clear performs a variety of functions; it should be called at the end of every plot.

a) Advances the paper for chart advance plotters when roll paper is loaded in the plotter.

b) Puts the pen away (for 7220 and 7221 series plotters).

c) Moves the pen stable to the upper right position so that paper may be easily changed.

d) Places a special code in picture files for controlling the clear function and the aborting of plots. (This
last function is used only when Gpl fileis has been called).

To execute the clear function

CALL Gpl_clear (Gpl$,Crt ,Hardcopy)

Two parameters (besides Gpl$) must be supplied:

Crt - PLeserved for future use. must be used at this time. Hardcopy - Allowed values are 0, 1, 3, and 4.

No operation (NOP)

1 Moves pen out of way

3* Causes half page (ISO A4) paper advance
4* Causes full page (ISO A3) paper advance

For example, CALL Gpl clear(Gpl$,0,3) causes an ISO A4 (or English A) size paper advance. The actual

advance distance is controlled by the ENGLISH/METRIC switch setting on the plotter.

* When used with the new HP 7550A plotter, this parameter can also be used to feed a full page of paper
from the plotter's paper magazine. Setting the hardcopy parameter to either "3" or "4" causes a full page
of paper to be fed to the HP 7550A plotter from the plotter's paper magazine.

SEP 86

4-7

Plot Initialization and Termination

GPL__TRANSMIT

Graphic data is buffered internally in the GPL software. This data is stored in the Gpl$ string, and is
cleared automatically when it gets full. The amount of buffer space allows about 33 separate or 65
contiguous straight lines to be stored. About 300 characters of text can also be stored in the buffer.
Usually a mixture has been stored.

The Gpl_transmit function may be used to clear this buffer. The function is useful for performance
optimization and for synchronizing a plot with user interactions. The syntax for Gpl transmit is:

Gpl_transmit (Gpl$, Option)

For example, you may wish to ask a question in the middle of a plot. The Gpl_transmit function will
cause the plot to be updated so that the user can see the current state of the plot at the same time that the
question is asked.

In another case, you may notice that there are pauses in the plotting due to the time it takes to compute
points (Gpl does consume significant computation time). You can minimize such delays by calling

Gpl transmit at judiciously selected places in your program. A good place to call Gpl transmit is after

CALL Gpl text with a long string of text supplied.

This function is called automatically when the following are called:

Gpl_clear
Gpl_terminate

The option parameter is reserved for future use. It should be set to at all times.

SUMMARY

In this chapter you have learned how to initialize and terminate plotting. Special care must be taken to
terminate a plot with one of the termination calls defined by GPL, as an abnormal exit may leave the
plotter in an unfriendly state. GPL includes an error routine to handle those errors that occur most
frequently in graphics plotting.

SEP 86
4-8

To enable the programmer to write device -independent code, GPL includes two subprograms which can be
called to determine what devices are available and the characteristics of each device. It is also possible to
maintain a configuration file specifying which plotters are available on a particular system.

The following subprograms are covered in this chapter:

Gpl__config Reads the device configuration from a data file and returns the model numbers and

addresses of devices configured into your system.

Gpl_devident Attempts to identify the device at a specified address and returns information about
any device (if any) found at that address.

Gpl__config

This subprogram reads the device configuration file GPL%CF (or an alternate file name if you supply it)
and returns the model numbers and system addresses of graphics devices connected to your system.

To read the default file GPL%CF, use the following call sequence:

DIM Model$(10),Dev_add(10),Mess_add(10)
CALL Gpl_config("","",No_devices,Model$(*),Dev_add(»),
Mess_add(*) , Error)

The number of devices in your system will be returned in the parameter No_devices. If 0, an error
occurred, and the Error parameter should be checked. The above dimension statements allow up to 10
devices to be returned. If the file contains more than 10 devices, adjust the dimension statements
accordingly.

To read from another configuration file, for example "ABCDEF", just supply the file name as the first
parameter in the call.

CALL Gpl_config("ABCDEF"," ", No_of_dev ices, Mode 1$ (*) ,
Dev_add(«) ,Mess_add (*), Error)

The second parameter is the protect code for the configuration file.

The array parameters (Model$(*), Dev_add(*), and Mess_add(*)) are arrays containing the model number,
graphics device address, and message device address.

The Error parameter is only if no errors occurred. Typical errors include:

1191 - ASSIGN Return- 1: Configuration file not found.

1 192 - ASSIGN Return- 2: Configuration file protected.

1193 - ASSIGN Return- 3: Specified file is of wrong type.

1194 — ASSIGN Return-4: Access violation.

1 195 - ASSIGN Return- 5: Other error.

SEP 86

5-1

Device Selection

1 196 - Invalid configuration file data format

1 197 - Invalid model number in configuration file
1 1 9 8 - Invalid device address in configuration file

1 199 - Invalid message address in configuration file

The GPL error reporting function FNGpl errm$ may be used to display the error. Gpl_config is in file

"GPL 2 51". To load Gpl_config in a program module, use:

LOAD SUB "GPL251", line_start, line_increment

Gpl_devident

This subprogram attempts to identify the device at the supplied device address. If the identification is
unsuccessful, or the device is not a supported plotter, then an error is returned. During the identification
process, the plotter RS-232-C handshake is configured to communicate with your computer system.

Gpl_devident is contained in files "GPL 2 51" and "GPL 2 5 2". It is also used by Gpl plotteris during the

initialization sequence.

To use the function, you must first REQUEST the device address, then supply the device address to
Gpl devident.

REQUEST Device_address

CALL Gpl_dev iden t (Device_address, Mode 1$, Advance, Buffer, Pens, Error)

The returned parameters include:

Model$ - Model number of the plotter at this address. The returned value is not always exact, but is close
enough for GPL to be aware of the plotter's capabilities.

Returned

Possible

7220A

7220A.7220S single sheet mode

7220C

7220C.7220T (single sheet mode)

7220S

7220S (auto advance mode)

7220T

7220T (auto advance mode)

7221A

7221B

7221B.7221S (single sheet mode)

722 1C

7221C.7221T (single sheet mode)

7221S

7 22 IS (auto advance mode)

7221T

7 22 IT (auto advance mode)

7225A/3

7225A/3V,7225A/3,7225B/3V,7225B/3

7225A/4

7225A/4V,7225B/4,7225B/4V,7225B/4

7470A/size

7470A

747 5 A/size

7475A

7550A/size

7550A

7440A/size

7440A

For the 7470A, HP ColorPro(7440A), 7475A and 7550A plotters, a call to Gpl_devident returns the
paper size for which the plotter is set. Model $ contains information of the form:
model number/paper size. For example, a call to Gpl devident might return:

SEP 86

5-2

Device Selection

"7470A/A" (an HP 7470A Plotter with ANSI A size paper)
"7475A/B" (an HP 7475A Plotter with ANSI B size paper)
"75S0A/A3" (an HP 7550A Plotter with ISO A3 size paper)
"7440A/A" (an HP 7440A plotter with ANSI A size paper)
"7440A/A4" (an HP 7440A plotter with ISO A4 size paper)

NOTE

The source of the paper size information varies with the plotting device.
With the HP 7470A, HP ColorPro (7440A) and HP 7475A plotters, the
maximum plot-surface (paper size) depends on the position of the plotter's
paper size switch. With the HP 7550A the paper size if! determined
automatically by the plotter.

Advance - Parameter (redundant) specifying whether automatic chart advance capability is present.

- No advance

1 - Auto advance present and enabled

Buffer - Buffer size for the plotter is in bytes
Buffer Size

600

630

928 or 2976

11 10 or 3038

1128 or 3056

1158 or 3086

255

1024

1024 (programmable to 1974)

1024 (programmable to 12000)

Plotter

Device address 8 or 9

7225A/4,7225A/4V,7225B/4,7225B/4V

7225A/3,7225A/3V,7225B/3 > 7225B/3V

7220A/C/S/T

7221C/T

7221B/S

7221A

7470A

HP ColorPro (7440A)

7475A

HP ColorPro (7440A) with GEC

7550A

In the above table "GEC" stands for "Graphics Enhancement Cartridge".

Pens - Number of pens on the plotter (1, 2, 4, 6, or 8).

Error - Error return parameter of the initialization or the identification is not successful.

Typical values for the error include:

1153 - Invalid device address

1 1 6 1 - Device address must be REQUEST'd

1 162 - No response from plotter

1 164 - Plotter responded, but attempts to initialize failed

1165 - Unsupported plotter

SEP 86

5-3

Device Selection

1 166 - Invalid response from plotter

1 1 8 1 - Plotter responded then stopped responding

Again, the function FNGpl errm$ may be used to display the error.

SUMMARY

In determining the device to be used for a particular plot, you can either rely on the default configuration
file, or inquire about which devices are at addresses 11-20. If your plotter configuration is relatively
stable, it is much faster to simply read the configuration file.

SEP 86

5-4

ESTABLISHING YOUR
COORDINATE SYSTEM

SECTION

This chapter deals with the characteristics of individual plotters, and the logical coordinate system used by
GPL. GPL allows the programmer to write device -independent code by specifying the logical units to be
mapped onto the physical plotting surface.

The following subprogram calls are introduced in this chapter:

Gpl physarea Specifies the physical dimensions of the area within which the plot will be

drawn.

Gpl devorigin

Gpl_defldc
Gpl physviewp

Gpl physrotate

Defines the origin point of the physical plotting area on the available plotting
surface.

Defines the logical coordinate system in user units,

Specifies the location of the logical device coordinate (LDC) space on the
physical area.

Determines the orientation of the plot on the plotter. The default value
allows GPL to rotate the plot to best fit the device being used.

LOGICAL UNITS VERSUS PHYSICAL UNITS

To plot on a device, you need to have the coordinates of a specific plotter. In GPL, you specify your own
coordinates. You may choose any units that are convenient to your application. These coordinates may be
independent of any particular plotter, which allows you to write device independent graphics programs.

SCALING AND PLACEMENT ON PHYSICAL DEVICE

In order to take full advantage of GPL's capabilities, you need to take into account some important device
differences, such as different plotting areas and aspect ratios.

SEP 86

6-1

Establishing Your Coordinate System

PHYSICAL PLOTTER CHARACTERISTICS

The supported plotters have the following plotting surface capabilities:

Origin Offset

Maximum Plotting Area

Series

Width

Height

7220A/C 7221A/B/C

400

285

7220S/T 7221S/T

400

285

7225A/B

285.5

203.5

7470A(US)

10.2

259.1

190.2

7470A(A4)

9.5

274.2

190.2

7440A(US)

7.0

8.0

191.5

257.3

7440A(A4)

9.2

5.6

191.5

272.3

7475A(US-A)

14.5

198.2

257.9

7475AOJS-B)

3.5

4.9

257.9

414.2

7475A(A4)

13.5

11.5

192.2

274.7

7 47 5 A( A 3)

0.6

13.1

274.7

402.2

7550A(US-A)

2.2

15.3

196

254.2

7550A(US-B)

0.8

1.9

254.2

411.2

7550A(A4)

10.7

9.8

190

271.7

7550A(A3)

10.2

271.7

399.2

The origin offset denotes how far the plotting origin differs from the lower left corner of the paper. (See
DEVORIGIN in Appendix D.)

Several calls, including Gpl physarea, Gpl_devorigin, Gpl_physrotate, and Gpl_

control the placement of the plot on your particular plotter.

_physviewp, exist to

SEP 86

6-2

Establishing Your Coordinate System

PAPER SIZE

Typical paper sizes used in plotting include the following:
Sheets

ISO A3 - 297 mm by 420 mm

ISO A4 - 210 mm by 297 mm

US/English "B size" - 1 1 inches (279 mm) by 17 inches (432 mm)

US/English "A size" - 8-1/2 inches (216 mm) by 1 1 inches (279 mm)

Rolls (for chart advantage plotters)

Metric (317 mm high, 10mm perforation widths)
US/English (315 mm high, 1 8 mm perforation widths)

Acetate (Hewlett-Packard supplied)

8. 5 in (216 mm) by 10. 5 in (267 mm)

8. 5 in (216 mm) by 1 1 in (279 mm) for 7470A paper-backed acetate.

GPL___PHYSAREA

CALL Gpl_physarea(Gpl $, Width_pamm,Height_pamm)

Gpl_physarea is used to specify the WIDTH and HEIGHT of your plot in mm. The defaults are:

Width- 2 5 0mm
Height* 180mm

Other values may be set as in the following example:

CALL Gpl_physarea(Gpl$, 160,220)
sets the physical area to a WIDTH of 1 60mm and a HEIGHT of 220mm.

CALL Gpl_physarea(Gpl$,254, 177.8)

sets the physical plotting area to a WIDTH of 254 mm (10 inches) and a HEIGHT of 177. 8 mm (exactly 7
inches).

This physical plotting area may or may not be rotated to fit on the selected plotter, depending on the
physical characteristics of the plotter. The optional rotation may be made explicit by using
Gpl_physrotate, as described later in this chapter. It is important that the paper be oriented according to
the paper loading instructions given in "Operating and Managing".

SEP 86

6-3

Establishing Your Coordinate System

GPL DEVORIGIN

CALL Gpl_devorigin(Gpl$,X_lower_left_plmm,Y_lower_left_plmm)

The physical plotting area is placed on the plotting surface with the Gpl_devorigin subprogram. The
parameters are the X and Y position in mm of the bottom and left edges of the plot on the plotting
surface relative to the plotter's addressable plotting origin.

For example,

CALL Gpl_devorigin(Gpl$,0,0)

starts the plotting area at the plotting surface origin (regardless of whether or not the plot is rotated).

It is important to note that the devorigin parameters refer to the lower left of the plotting surface (which
is never rotated) and not the plot (which may or may not be rotated).

OUTER RECTANGLE REPRESENTS ENTIRE 400 Bly » ■ PLOTTING SURFACE FOR 7220 AMU 7221 SERIES PLOTTERS

i-J

CALL 6pl_phyiare»(6pl*,250. 160}

CALL 6pI_0flVOrlglMGplt. 10. 10)

CALL SpIJlBvorloln (Gpl*. 20. 20)

CALL GpljtevorlglnCGplS. 40, 40)

The following default values are used if Gpl_devorigin is not explicitly called.

Plotter
Series

X origin

Y origin

7220A/C
7221A/B/C

7220S/T
7221S/T

7225A/B

SEP 86
6-4

Establishing Your Coordinate System

7470A(US)

10.2

7470A(A4)

9.5

7440A(US)

7.0

8.0

7440A(A4)

9.2

5.6

7475A(US-A)

14.5

7475A(US-B)

3.5

4.9

7475A(A4)

13.5

11.5

7475A(A3)

0.6

13.1

7550A(US-A)

2.2

15.3

7550A(US-B)

0.8

1.9

7550A(A4)

10.7

9.8

7550A(A3)

10.2

PAPER PLACEMENT

See "Operating and Managing" for uniform paper loading instructions. Most of your plotting will be done
on either US/English A size paper (8. 5 in by 11 in) or ISO A 4 size paper (210 mm by 297 mm).

In general, binder holes should be placed to the left for 7220 and 7221 series plotters, on the top for 7225,
7475A, and 7550A plotters, and on the right for 747 0A and 7440A plotters.

The defaults were chosen so that the plotting area attempts to cover the grid on 1 Ox 1 to the CM graph
paper. You may use this paper (or the metric paper equivalent) for measuring the placement of items on a
graph. The device origin may have to be adjusted slightly to compensate for individual plotter differences
and/or the use of metric paper sizes.

LOGICAL DEVICE COORDINATES (LDC UNITS)

Your plotter has a rectangular plotting area. You are limited to plotting within this rectangle at all times.

To specify the logical units you merely specify the coordinate range to be applied to your rectangular
plotting area. Four parameters are specified, the minimum and maximum X (horizontal direction)
coordinates, and the minimum and maximum Y (vertical direction) coordinates. All plotting should have
(X,Y) coordinates within these limits, and the limits define the "logical device coordinates", or "LDC units".
See the following figure for a diagram of a logical device coordinate rectangle. Note that the point
(Xmin,Ymin) corresponds to the lower left corner of your plot. The point (Xmax,Ymax) corresponds to the
upper right corner. Increasing X values causes the pen to move RIGHT. Increasing Y values causes the pen
to move UP.

SEP 86

6-5

Establishing Your Coordinate System

OUTER RECTANGLE REPRESENTS ENTIRE 400 a ll »9 ■ PL0TTIN6 SURFACE FOR 7220 AND 7221 SERIES PLOTTERS .

I pctn, Vjn)

CALL 6plJ«H*» (•fit. 0. HO. 0. MO] >
CALL Sol JlhyMTM Holt. ISO. MOI

CALL SoUovorlt In Hoi*. 10. 10)
CALL Sol-davorlglrt (loll 20, Ml
CALL Sol Jlevorlgln (Golf. 40. 40]

' "Bumx, YaaxTj

L — - «

-»*S-

GPL DEFLDC

CALL Gpl_defldc(Gpl$,X_min,X_max,Y_min,Y_max)

Gpl defldc defines logical device coordinates. The parameters X min and X max are the minimum

and maximum X coordinates, and Y_min and Y__max are the minimum and maximum Y coordinates.
X_min must be less that X_max, and Y_min must be less than Y_max.

Note: In all GPL calls in which a rectangle is specified, the boundaries are specified in the order X min,

X max, Y min, Y max.

The default values are:

Xmin ■
Xmax - 250
Ymin -
Ymax- 180

which is the same as would be set by the subprogram call:

CALL Gpl defldc(Gpl$, 0,250, 0,180)

SEP 86
6-6

Establishing Your Coordinate System

Helpful Hints

You should call Gpl_defldc soon after Gpl_plotteris and keep the logical device coordinate limits fixed
throughout the entire plot.

The best "logical device coordinates" are in units that reflect the final physical size of your plot. For
example, convenient physical size for charts and graphs are:

WIDTH HEIGHT FOR

250 mm 180 mm Metric Unit Charts and Graphs
1 in 7 in U.S. Unit Charts and Graphs

The placement of the plot in LDC coordinates is controlled by the other subprograms described in this
chapter (Gpl_physarea, Gpl_devorigin, Gpl_physviewp, Gp]_physrotate). The main advantage to the
Gpl_defldc subprogram is that it allows you to define any convenient coordinates; you are not restricted
to using millimeters.

GPL PHYSVIEWP

CALL Gpl_physviewp(Gpl$,X_min_pamm,X_max_pamm,Y_min_pamm,Y_max_painm)

Specifies the placement of the LDC (logical device coordinate) limits in the physical area (Gpl_physarea)
coordinate system. The default is a value which centers the LDC space in the physical area coordinate
system with maximum area. The default is set whenever Gpl_physarea or Gpl_defldc is called. Thus,
Gpl_physviewp should be called only after any calls to Gpl_defldc and Gpl_physarea.

This function is used whenever you wish to do one or more of the following:

(1) Stretch the plot in one direction, usually when you want to cover the entire physical area. Care
must be used, as circles on the logical plotter will be deformed into ellipses.

(2) Move the plot from the center of the physical area.

(3) Change the size of the plot to something other than determined by the LDC and physical area
coordinate limits.

X min pamm - Minimum x on physical area in millimeters

X max pamm - Maximum x on physical area in millimeters

Y min pamm - Minimum y on physical area in millimeters

Y max pamm - Maximum y on physical area in millimeters

SEP 86

6-7

Establishing Your Coordinate System

GPL_PHYSROTATE

CALL Gpl_Phys rotate (Gpl$, Rotation)

This function is used to control the rotation of a plot on all plotters. The plotting area specified by

Gpl physarea will be rotated according to the rotation parameter, which has 5 values: It is possible to

rotate a plot from to 270 degrees, in 90 degree increments (relative to the plotter axes).

No rotation on 7720, 7221, 7475A and 7550A plotters. 90 degree clockwise (CW) rotation on 7225,
747 0A and HP ColorPro(7440A) plotters. Used most often for ISO A4 (English A or US-A) size plots
that are oriented vertically.

1 90 degree counterclockwise (CCW) rotation on 7220, 7221, HP ColorPro(7440A), 7470A, and 7550A
plotters. No rotation on the 7225 plotter. Used most often for ISO A4 (English A or US-A) size plots
that are oriented horizontally.

2 (default) Software looks at Gpl_physarea parameters and attempts to fit on ISO A 4 (English A or
US-A) size sheet.

-1 90 degree clock-wise rotation (CW) on series HP ColorPro(7440A), 7470A, 7475A and 7550A.

-2 180 degree rotation on series HP ColorPro(7440A), 7470A, 7475A and 7550A.

In most cases it is best to let the rotation default to option 2, which lets GPL select the optimal plot
rotation based on the plotter being used and the dimension of the plot being drawn.

SUMMARY

GPL has several subprograms to define the size and location of a plot. Default values exist for each of
these specifications, allowing the programmer to either rely on these default values or to set up

specifications of his own. Less complicated plots will require only the use of Gpl defldc and

Gpl physarea. More advanced plots will also make use of the Gpl devorigin, Gpl physrotate and

Gpl physviewp subprograms to define the exact size and layout of the coordinate system.

SEP 86
6-8

All GPL calls to change the position of the pen or to draw a line reference either a point or a distance on
the logical coordinate system. A logical pen position is maintained, but does not always coincide with the
physical position of the pen at any point in time. The pen physically moves only when there is some
drawing to be done, whether text or straight lines.

The following subprograms are introduced in this chapter:

Gpl move Moves the logical pen to a location specified by an (X,Y) coordinate position.

Moves the logical pen an incremental distance in the X and Y directions.

Returns the current position of the logical pen.

GpI_imove

Gpl where

Gpl frame

Gpl draw

Gpl idraw

Gpl linestyle

Draws a frame around the current window rectangle (windows are defined in Chapter
10).

Draws from the current logical pen position to the specified (X,Y) coordinate position.

Draws an incremental distance in the X and Y directions from the current logical pen
position.

Defines the style of line to be used for all drawing until another linestyle is specified.
Various linestyles are available, including solid, dotted, and dashed.

CURRENT POSITION (CP)

All graphics are drawn relative to a "logical pen" called "Current Position", or "CP". The CP is an (X,Y)
position that is used as the starting point of all straight lines and text. The term "CP" was chosen to
conform with terms commonly used in computer graphics.

GPL__MOVE, GPL_JMOVE

CALL Gpl_move(Gpl$,X_wc,Y_wc)

CALL Gpl_imove(Gpl$,Dx_wc,Dy_wc)

To move the CP to some desired location, either Gpl move or Gpl imove may be used. Gpl move

moves the CP to some absolute position (X,Y). Gpl_imove moves the CP incrementally from the previous
CP value.

SEP 86

7-1

Drawing Straight Lines

For example,

CALL Gpl_move(Gpl$, 10,20)
CALL Gpl~imove(Gpl$,2,0)

first moves the CP to (1 0,20) and then moves the CP to (1 2,20).

The plotter pen only moves when some actual drawing is to occur. Thus, the calls to Gpl move and

Gpl imove in the above example do not result in any physical plotter pen movement unless they are

followed by a "draw" or "text" call.

There is no default or initial value for the CP. Therefore, set the value with Gpl move before any

drawing is done.

GPL_WHERE

Sometimes, you need to know where the CP is located after drawing straight lines or text. To find out the
CP, use Gpl_where.

For example,

CALL Gpl_where(Gpl$,X,Y)

results in the CP coordinates being stored in (X,Y).

STRAIGHT LINES

All plotting is done with straight lines or text. To get curves, symbols, and shaded regions, you build the
figure out of a sequence of straight lines.

GPL_FRAME

CALL Gpl_frame(Gpl$)

Gpl frame may be used to draw a box around the current plotting region. Four straight lines are used,

and the CP is restored to its value before the call to Gpl frame.

The meaning of the words "current plotting region" will be sharpened in the more advanced sections
below. For the moment, the current plotting region will be defined to be the LDC (logical device
coordinate) limits specified by Gpl defldc.

SEP 86

7-2

Drawing Straight Lines

GPL._DRAW, GPL_IDRAW

CALL Gpl_draw(Gpl$,X_wc,Y_wc)

Gpl_idraw(Gpl$,Dx_wc,Dy_wc)

Gpl_draw draws a straight line from the CP to the specified (X,Y) location. Gpl_idraw draws from the
CP incrementally by the specified (Dx.Dy) incremental units. In both cases, the CP is updated to the end
point of the line.

For example,

CALL Gpl_move(Gpl$, 10,20)
CALL Gpl_draw(Gpl$,30,40)
CALL Gpl_idraw(Gpl$,0,10)

first draws a straight line from (10,20) to (30,40). Then another straight line is drawn from (30,40) to
(30,50). After these calls, the CP is located at (30,50).

LIMITS OF CP

The CP can be placed anywhere, on or off your plotting area. If a line is drawn partly on and partly off
the plotting area, the software will "clip" away the unplottable portions of the line.

Example:

1000 CALL Gpl_frame(Gpl$)

1010 CALL Gpl_move(Gpl$,0,)

1020 CALL Gpl_draw(Gpl$,100,100)

1030 CALL Gpl_imove(Gpl$,-50,0)

1040 CALL Gpl_idraw(Gpl$,0 -50)

1050 CALL Gpl_move(Gpl$,-20,30)

1060 CALL Gpl_draw(Gpl$, 120,30)

SEP 86

7-3

Drawing Straight Lines

GPL LINESTYLE

CALL Gpl_linestyle(Gpl$,Linestyle)

Up to this point we have been drawing straight lines with solid lines. Actually, there are 9 different
linestyles available for producing visual differences, and these are numbered from 1 to 9. To select a
particular linestyle, use Gpl_linestyle. For example,

CALL Gpl_linestyle(Gpl$,5)

selects linestyle 5.

The next figure shows the various linestyles. The linestyles are also shown on the confidence test plot that
is created by program GPLCFT.

SEP 86

7-4

Drawing Straight Lines

LINE STYLES

(no line)

SUMMARY

In this chapter we have covered the subprograms necessary to draw lines and move the logical pen. All
plotting to be done by GPL is done as a series of straight lines. All points on the plotting area are
referenced by an (X,Y) coordinate position. If a point outside of the current plotting region is specified,
actual drawing outside of the plotting limits will be clipped, although the CP is allowed to move outside of
this area.

SEP 86

7-5

SEP 86

7-6

Plotters compatible with your computer systems have from one to eight pens. Some have variable pen
velocity capability. GPL can detect the model number of each plotter and send appropriate signals to it.
Programmed calls that cannot be understood by a plotter are ignored.

This chapter discusses the following subprogram calls:

Gpl_pen Selects a pen on multiple -pen plotters, and can also return to pen to its stall.

Gpl penspeed Specifies the speed of the plotting in cm/sec.

GPL PEN

CALL Gpl_pen(Gpl$,Pen_number)

The plotter can have from one to eight pens. A particular pen may be selected under program control
with the Gpl_pen function.

Gpl_pen accepts integer values from to 8. (The parameter Pen_number must be a REAL variable.)
puts the pen in the stall on 7220 and 7221 plotters. 1 (default) selects pen 1,2 selects pen 2,etc.

The Gpl pen call is ignored for single-pen plotters.

On the two-pen plotter, even values select the right pen; odd values select the left pen. On the four-pen
plotter, Gpl_pen values 5 through 8 will select pens 1 through 4, respectively. On the six-pen plotter
Gpl_pen values 7 and 8 will select pens 1 and 2 respectively. On the eight -pen plotters, Gpl_pen values
1 through 8 will select pens 1 through 8.

CALL Gpl_pen(Gpl$,7)

selects pen 7 on the eight-pen plotter, selects pen 1 on the six -pen plotter, selects pen 3 on the four-pen
plotter, selects pen 1 on the two-pen plotter, and is ignored for the one-pen plotter. Parameter value
also suppresses text and straight lines even if the pen cannot be put away. GPL behaves as if the pen had
been put away in this case.

GPL_PENSPEED

CALL Gpl_pens peed (Gpl$,Ve loci ty_cps)

Many applications require that the pen velocity be changed, depending on the types of pens and paper
being used in the plotter. For example, when plotting on overhead transparency acetate, it is advisable to
slow down the pen velocity to lOcm/sec or less. This permits easier transfer of the ink to the acetate
plotting surface, which is nonabsorbent.

SEP 86

8-1

Pen Control

The parameter to be supplied is a value which represents the pen velocity in cm/sec. The value should be
in the range from 1 to 36 in order for the call to be valid. Any value outside that range causes the call to
be ignored.

For example:

CALL Gpl_penspeed(Gpl$,10)

sets the penspeed to 10 cm /sec.

If your plotter does not have programmable velocity select, this call will be ignored.

NOTE

Some models of the HP 7225A have velocity select, and some do not. If
your plotter does not have velocity select, use "7225A/3" or "7225A/4" for
the model number. If your plotter does have velocity -select, use
7225A/3V" or "7225A/4V" for the model number in the Gpl_plotteris
and in GPL%CF. If you specify the "V" when no "V" should have been
specified, the plotter will not operate correctly. A similar problem exists for
the HP 7225B series plotters. The four possible model numbers are
"7225B/3", "7225B/3V", "7225B/4" and "7225B/4V".

NOTE

On the 7470A and 7 47 5 A plotters, there is a dead range of pen speed

between 0. 38 and 3. 8 cm/sec. A Gpl penspeed value of 1 yields a speed of

0. 3 8 cm/sec. Values 2 and 3 yield 3. 8 cm/sec. Any value above 3 yields
the accural e speed.

SEP 86

8-2

DRAWING TEXT STRINGS

SECTION

Graphs and charts may be annotated with text strings using the text subprogram calls available in GPL.
Both the height and width of the text cells may be specified, as well as the rotation (horizontal, vertical,
etc.).

The subprogram calls introduced in this chapter are as follows:

Gpl_text

Gpl tsize

Gpl lorg

Gpl textrotate

Gpl cset

Gpl itextwidth

Draws a text string at the current pen position.

Defines the height and width of the text character cell.

Specifies the label origin of the text, or the origin point of the text string
with respect to the current pen position.

Determines the rotation of text horizontal, or rotated in increments of 90
degrees.

Specifies the character set from which text characters will be drawn.
Characters may be drawn from the plotter firmware or from GPL's character
files.

Returns the width of a specified character string in terms of logical device
coordinates, used in computing text formats.

PLOTTER FIRMWARE CHARACTERS AND SOFTWARE-GENERATED
CHARACTERS

PLOTTER FIRMWARE CHARACTERS — the firmware of each plotter contains the code to plot the US ASCII
character set. The plotter -resident character sets can vary between plotters.

SOFTWARE -GENERATED CHARACTERS —GPL includes data files containing alternate character sets which
can be specified to override the plotter firmware characters.

Of the software -generated fonts, some are of standard width, and some are of proportional width.
ROMAN, STICK, and ITALIC are proportional fonts.

example of standard spacing
example of proportional spacing

GPL TEXT

This is a plottir
This is a plotting excn

CALL Gpl_Text(Gpl$,Text$)
To draw text on your graphics plotter, simply pass the information as a string.

SEP 86

9-1

Drawing Text Strings

For example,

CALL Gpl_text(Gpl$, "HELLO!")

draws HELLO! on your plotter.

The entire 96 character US ASCII character set may be displayed. The default character set is the plotter
firmware set. To override the default, or to draw other non-US ASCII characters, see
"SOFTWARE-GENERATED CHARACTERS" in this chapter.

In addition, Roman Extension characters appearing on European keyboards may also be displayed (See
"Drawing European Characters", below. )

The placement of the text depends on the position of the CP before the call to Gpl_text. Normally (lower
left justification case), the CP is at the lower left corner of the string before the call. After the call, the
CP is at the lower right corner of the string. This allows multiple calls to Gpl_text to be used to produce
a long concatenated string.

These justification rules are modified by use of the Gpl__lorg subprogram described in a later section.

A call to Gpl text is usually preceded by a call to Gpl move to ensure proper text placement.

Use of CR and LF Control Characters with Gpl__text

ASCII control characters (0-31) are normally ignored in the Gpl__text call. The exceptions are Carriage
Return (CR -ASCII 1 3) and Line Feed (LF -ASCII 10).

The CR and LF functions produce the same results as normally encountered in printing: CR returns the
CP to the beginning of the string of text, and LF moves the CP down one line.

The CR and LF characters are not automatically inserted at the end of a string of text; you have to put
them there. If omitted, the CP will be left at the end of the text, ready to concatenate additional text.
These control characters should only be used at the end of a string.

Text Clipping

In the HP 7221 series plotter firmware, text is not properly clipped if the beginning of the text string is
outside the current window. If your application requires clipped text, software-generated character sets
(described later) will give proper text clipping.

Drawing European Characters with Gpl_text

The HP Computer System is capable of using a full 8 bit ASCII code (0-255). Within the system, ASCII
codes from 128 to 159 are used for 32 additional control characters. The ASCII codes from 160 to 255
are used for additional 96 character printable character sets, including Roman Extensions for European
applications.

The GPL software produces the Roman Extension characters when the appropriate code from 160 to 255
is included in the string. Katakana, Math symbols, and HP 250/260 special characters cannot be drawn.

SEP 86
9-2

Drawing Text Strings

NOTE

You should remove unused control characters before passing; a string to
Gpl_text.

GPL TSIZE

CALL Gpl_tsize(Gpl$,Cell_height_ldc,Cell_width_dev_ptc)

The text character height and width is controlled by Gpl tsize.

A character cell is the region around a character that determines the amount of white space between lines
of text and between characters. In other words, the character cell height is the distance between the bases
of two consecutive printed lines of text. The cell width is the distance between the left edges of the cells
of two characters. See the next figure.

pilB3MbBiZj3Hli...kkbfe

biahbkkJ3.yjr.|ikL|yikb

piqhktukkk.^k].{i..j.ri...

Indicates cell
boundaries

Some software -generated
fonts have varying cell
widths. (See "SOFTWARE-
GENERATED CHARACTERS"
in this chapter. )

In a call to Gpl tsize, the cell height is specified in LDC units. The cell width is specified as a percentage

deviation from default, which is 0. 5 times the cell height.

Thus,

CALL Gpl_tsize(Gpl$,10,0)
results in a cell height of 10 LDC units and a cell width of 0. 5x10-5 LDC units.
To change the character cell width:

CALL Gpl_tsize(Gpl$,10,-20)
results again in a cell height of 1 units but a 20% narrower cell width of 4 LDC units.

SEP 86

9-3

Drawing Text Strings

The default height is nine units and the default width deviation is 0. With the default LDC coordinate
system and mapping to the device, these defaults result in character cells that are 9 mm high.

Specifying Character Size and Placement with Gpl_tsize

The Gpl tsize call refers to character cells, not the characters themselves. On HP Graphics Plotters, the

characters are placed against the lower left edge of the cells. The height of a capital letter in the plotter
firmware is 1/2 the cell height. The height of a software proportional letter is 21/32 the cell height.
Most capital letter widths are 2/3 the cell width. Lower case firmware letters have heights which depend
on the particular plotter model number.

GPL LORG

CALL Gpl_lorg(Gpl$,Label_origin)

Gpl lorg (standing for Label Origin) determines the positioning of the output in relation to a reference

point. Values 1 to 9 indicate different orientations in reference to the current pen (CP) position.

d>-

•d>

LJ.<2>

Remember that the parameter refers to a point on the string of CELLS, not the string of characters.

NOTE

When the font in use is a SOFTWARE -GENERATED PROPORTIONAL
font, like Serif or Decorative, Gpl lorg must be 1.

Slight adjustments may have to be made in the CP when you wish to justify on the characters.

CALL Gpl_lorg(Gpl$,l)

is the default. The CP before the call to Gpl text is at the lower left corner of a line of text. The

justification is "LEFT" horizontally and "BOTTOM" vertically.

CALL Gpl_lorg(Gpl$,4)

is commonly used to center text horizontally. The CP before a call to Gpl text is in the center of a line

of text horizontally and on the base line of the characters. The justification is "CENTER" horizontally
and "BOTTOM" vertically.

CALL Gpl lorg(Gpl$,7)

SEP 86
9-4

Drawing Text Strings

means to "RIGHT" justify horizontally and "BOTTOM" justify vertically.

CALL Gpl_lorg(Gpl$,2)

means to "LEFT" justify horizontally and "CENTER" justify vertically.

The meanings of the Gpl_lorg parameter are summarized in the next figure, which shows the CP before
calling Gpl_text (Gpl$ , "HELLO" ) . In all cases, the CP after the call is at position 7.

#ELL0

HEI*L0

7 HELLO*

ftELLO

he£lo

8 HELLO*

HELLO

9 *
HELLO

* CP before call

SEP 86

9-5

Drawing Text Strings

GPL_TEXTROTATE

CALL Gpl_text rotate (Gpl$, Rotation)

For most business applications, it is recommended by many graphics designers that all text be printed in
the normal horizontal manner. For example, the labels for the Y axis (title and tic mark labels) should be
printed horizontally. A good place to put the Y axis title is just above the Y axis, as was done in Chapter 3
example, GPLEOl.

However, if your application requires text rotation, you may use the Gpl textrotate function. The

parameter supplied is an integer with the following 4 values:

- (default) normal horizontal text

1 - Rotate text 90 degree counter clockwise (CCW) from horizontal

2 - Rotate text 1 80 degrees CCW from horizontal

3 - Rotate text 270 degrees CCW from horizontal

The text rotation chosen will be in effect until another call to Gpl textrotate is made. See next figure.

iyJSp T MTATE -

x
-i

GPL__ITEXTWIDTH

CALL Gpl_itextwidth(Gpl$,Text$, Width)

Function Gpl itextwidth stands for Inquire Text Width. It determines the width of a proportional or

non -proportional string for your use in computing formats.

CALL Gpl_itextwidth(Gpl$, "ABC", Width)

The width of Text$ is returned by Width, and is given in LDC units. This example will center a string
horizontally about the point 50,70.

CALL Gpl_lorg(Gpl$,1)

CALL Gpl itextwidth(Gpl$, "ABC", Width)

SEP 86

9-6

Drawing Text Strings

CALL Gpl_move(Gpl$,50-Width/2,70)
CALL Gpl_text(Gpl$,"ABC")

Gpl_itextwidth calls Gpl_transmit which is not present in Gpl_251 or Gpl_252; therefore, always
load one of the files Gpl_253 through Gpl_257 with file Gpl_258. Remember that the width of a
particular string depends on the last value specified in the Gpl_tsize statement (which specifies the
character heights and widths).

SEP 86

9-7

Drawing Text Strings

SOFTWARE-GENERATED CHARACTERS

Gpl_cset

CALL Gpl_cset(Gpl$,Char_set,Character_file$)

The Roman Extension characters used with European keyboards (and all software fonts described in this
manual) are produced from software "digitizations." The standard "plotter fonts" (used by default) are
produced from firmware in the plotter. Plotter firmware fonts have also been digitized and stored in GPL
files, but files GPL 271 through GPL276 are not normally used because GPL produces these characters by
default.

Roman

US ASCII

Extensions

Font Name

File name
GPLRLO

File Name

Serif Roman Light

GPLRL1

Serif Roman Medium

GPLCRO

GPLCR1

Serif Roman Bold

GPLTRO

GPLTR1

Serif Italic Light

GPLLIO

GPLLI 1

Serif Italic Medium

GPLCIO

GPLCI1

Serif Italic Bold

GPLTIO

GPLTI 1

Stick Light

GPLSRO

GPLSR1

Stick Medium

GPLDRO

GPLDR1

Sans Serif Italic Light

GPLLJO

GPLLJ 1

Sans Serif Italic Medium

GPLMJO

GPLMJ1

Gothic English

GPLGEO

GPLGE1

7220A/S, 7221A/B/S, 7225A/B

GPL271

GPL 27 2

7220C/T, 7221C/T Plotters

GPL273

GPL274

7470A/, HP ColorPro(7440A) plotters

GPL275

GPL276

7475A/, 7550A Plotters

GPL275

GPL276

Depending on the plotter in use, one of GPL272, 274, or 276 is used if Gpl cset is not called.

Use Gpl cset to specify a software character set or to return to the hardware default.

CALL Gpl_cset(Gpl$,Char_set,Character_file$)

Char set - Specifies whether to use the lower 96 characters (US ASCII) or the upper 96 characters

(Roman Extensions) with this file.

0- Lower (ASCII 32-127)
1 -Upper (ASCII 160-255)

Character file$ - String containing the name of a character file, including volume specifier if necessary.
See the tables above for software character file names.

A null string may be supplied if Char set=0. This means to use the default hardware character set for

the plotter.

SEP 86
9-8

Drawing Text Strings

A typical usage is to use the "best" plotter characters (as produced by default on the HP 7220C, 7220T,
722 1C, and 722 IT) on all plotters. These best characters look better than the characters produced on
other plotters. To do this, make calls of the form:

IF Model$[5;l]o"C" AND Model$[5;1 ]<>"T" THEN
CALL Gpl_cset(Gpl$,0,"GPL273")
CALL Gpl_cset(Gpl$,1,"GPL274")
END IF

The first line calls the software characters only if the plotter has the old character sets. This allows usage
of the hardware generated characters, which are drawn much faster, whenever possible.

Software character sets typically take 2 or 3 times longer to plot than firmware generated characters.

SUMMARY

The firmware of each plotter contains code to create the default character font. The default plotter
firmware fonts can be overridden by a software-generated font in a GPL file. Default values exist for all
text definition subprograms. Once these definitions are changed, however, the new values stay in effect
until another call to the subprogram is made. This means that once a text size and rotation are specified,
that size and rotation will be in effect until a new text size and rotation are specified.

SEP 86
9-9

SEP 86

9-10

This chapter supplements Chapter 9, and should be read by the programmer who plans to use
software-generated characters with HP plotters.

WIDTH OF PLOTTER FIRMWARE FONTS

Plotter firmware characters are of fixed width — two-thirds the width of the cell and left -justified
within the cell.

WIDTH OF SOFTWARE-GENERATED FONTS

Some software characters are of fixed width like plotter firmware fonts, and some are proportional. The
proportional software characters are centered within their cells. When underlining or drawing boxes
around characters, plot the lines with respect to cell edges.

UNDERLINING PLOTTER FIRMWARE CHARACTERS

To underline the string "ABCDE", use this algorithm:

CALL Gpl_cset(Gpl$,0,"GPL273")
CALL Gpl_cset(Gpl$,1,"GPL274")

•
Text_height=7

CALL Gpl_tsize(Gpl$,Text_height,0)
CALL Gpl_move(Gpl$,X,Y)
CALL Gpl text (Gpl$, "ABCDE")
CALL Gpl~move(Gpl$,X,Y-Text_height*3/32)
CALL Gpl_idraw(Gpl$, (5-1/3)*Text_height/2,0)

The factor in Gpl idraw is designed to prevent underline overhang at the end of the string. Each

character occupies the left two thirds of its cell. The last one-third of the last cell in the string is vacant,
and should not be underlined.

The next algorithm performs the same function, but is generalized to allow variable values, including a
variable width deviation of the characters in the string. This next algorithm calls for all characters to be
1 7 percent narrower (Width_dev_ptc - - 1 7) than normal.

CALL Gpl_cset(Gpl$,0,"GPL273")
CALL Gpl_cset(Gpl$,1,"GPL274")

SEP 86
10-1

Using Software Characters

Text_height=7

Width_dev_ptc=-17

CALL Gpl_tsize(Gpl$,Text_height, Width dev_ptc)

CALL Gpl_move(Gpl$,X,Y)

Text$="ABCDE"

L=LEN(Text$)

CALL Gpl_text(Gpl$,Text$,)

CALL Gpl_itextwidth(Gpl$,Text$, Width)

CALL Gpl_move(Gpl$,X,Y-Text_height*3/32)

CALL Gpl_idraw(Gpl$, (L-1/3)*Width/L,0)

UNDERLINING PROPORTIONAL SOFTWARE CHARACTERS

Proportional characters are centered within their cells, so underlining is simple.

CALL Gpl_cset(Gpl$,0,"GPLTRO")
CALL Gpl cset(Gpl$,1,GPLTR1")

CALL Gpl_tsize(Gpl$,T_height,Width_dev_pct)

CALL Gpl_lorg(Gpl$,1)

CALL Gpl_move(Gpl$,X,Y)

CALL Gpl_text(Gpl$,Text$)

CALL Gpl_itextwidth(Gpl$,Text$, Width)

CALL Gpl_move(Gpl$,X,Y-T_height*7/32)

CALL Gpl_idraw(Gpl$, Width, 0)

CALL Gpl_idraw(Gpl$,0,-T_height/32)

CALL Gpl_idraw(Gpl$,-Width,0)

CALL Gpl_idraw(Gpl$,0,T_height/32)

Similar algorithms can be developed to draw boxes around one or more lines of text.

CREATING A CHARACTER SET FILE

Example program GPLE06, included with the GPL library and loaded whenever GPLLOD is used to load
GPL, gives the algorithm and instructions for packing the data into strings. The PACK DROM must be
configured to create character set files.

CHARACTER FILE FORMAT

Each character set file contains exactly 97 records. When called, Gpl cset checks that the file contains

97 records.

The first record contains two integers packed into a four -character string. Both integers are in the range
1 to 998. The first specifies cell height normalization, which is the height of the symbol cells in this file,
and corresponds to the Cell height ldc parameter of Gpl tsize. The second is cell width normalization,

SEP 86

10-2

Using Software Characters

which is usually one half the height normalization. When called, Gpl_cset checks that the first record
contains these two integers packed into a string.

Records 2 through 97 each contain the digitization data for one of the 96 different characters. The
digitization of a character, contained in one record, consists of coordinate pairs packed into a string. Each
pair occupies four bytes (four characters). The record is organized as follows:

Cell width (in LDC units)

Number (N) of coordinates pairs which follow

First X coordinate

First Y coordinate

Second X coordinate

Second Y coordinate

Nth X coordinate
Nth Y coordinate

<0.25)

(0,-7)

< 11.25)

(20,25)

(11.-7)

\ x character cells
the coordinate plane

(20,-7)

Q] = 2 bytes

pair = 4 bytes

record 1

record 2

pair

...

record 73

(4*39) +4 byt63

record 79

record 97

The number of bytes in each string (or record) is (4*N)+4. Determine which string has the greatest

number of bytes, and let Max bytes equal that length. When creating the file in which to keep this data,

let it be 97 records of Max bytes+4 bytes per record.

CREATE "SYMFIL", 97, Max_bytes+4

Your computer's file system uses the additional four bytes. The X and Y values of the pairs are in the
range -998 to +998. The special pair (999,999) means to lift the pen and move it to the point specified by
the next pair. GPL is in use, the pen moves to the point specified by the first X,Y coordinate, draws to the
second coordinate, then to the next, and continues drawing until the (999,999) pair. The pen raises, moves

SEP 86
10-3

Using Software Characters

to the next point, lowers, and draws until the next (999,999) point. The last pair in the record does not
have to be (999,999); the pen raises automatically.

SEP 86
10-4

In this chapter, we embark on one of the hardest, and most useful, concepts in GPL: viewing
transformations.

The following subprograms are discussed in this chapter:

Gpl_window Defines the 'World Coordinates' which will apply to the viewport area.

Gpl_viewport Specifies that subset of the LDC area which will serve as a viewport. The world
coordinates apply to this area.

Gpl_useldc Defines the current plotting region to be the LDC area and the current units to be

LDC units.

Gpl__usewc Defines the current plotting region to be the viewport and the current units to be WC

units.

The viewing transformation allows you to map any set of rectangular coordinates onto your logical
plotter. This is useful when plotting units such as "dollars per month" or percentages on a chart or graph.

You will find it worth your time to be patient and learn the concepts of WINDOW and VIEWPORT,
which collectively make up the viewing transformation.

DEFINITIONS

Some useful concepts will be defined in this section. The terminology chosen is not very mnemonic, but it
coincides with state-of-the-art terminology as used by computer graphics experts. In particular, "world
coordinates", "window", and "viewport" are used frequently in computer graphics standardization efforts.

World Coordinates

"World Coordinates" are the particular coordinates that are natural for your data, such as MILLIONS OF
DOLLARS vs YEAR or UNIT SALES plotted as a function of WEEKS.

Logical Device Coordinates

To refresh your memory, "Logical Device Coordinates" are the coordinates to represent your (device
independent) plotter. This coordinate system remains fixed throughout your problem, and allows you to
place text annotation along with plotted curves in one convenient coordinate system.

"Logical Device Coordinates" are a generalization of "normalized device coordinates" or "graphical display
units" that are used in typical graphics subroutine liberals. They allow you to use any convenient
coordinate system that you desire as the model for the plotting surface.

SEP 86

11-1

Viewing Transformations

Viewing Transformation

A "Viewing Transformation" is a mapping between your problem coordinates (world coordinates) and the
plotter (logical device coordinates). It is specified by a "window" rectangle in world coordinates that is
mapped onto a "viewport" rectangle in logical device coordinates.

100000

CALL Gpljrtndow (Gpl$, 1970. 1980. 0. 100000)

1970

\
\

\ . on ^LLGpl jJef ldc (6pl$. 0. 250. 0. 1B0)
\ lour —

250

Window

All graphic lines and text within the window rectangle will be mapped onto the viewport rectangle in

plotter coordinates. When a window is specified, using Gpl window, all MOVE and DRAW functions will

be in the world coordinates defined by the window.

SEP 86
11-2

Viewing Transformations

Viewport

The "viewport" rectangle may be viewed as a subset of the logical device coordinate area and is defined in
LDC units. All graphic; lines and text within the window rectangle will be mapped onto the viewport
rectangle. The lower left corner of the window maps to the lower left corner of the viewport, the lower
right corner of the window maps to the right corner of the viewport, and so on.

The window and viewport may each be independently specified. The default window and viewport are the
logical device coordinate system, and the defaults are used whenever Gpl defldc is called.

Clipping (or Scissoring)

All graphic lines and text with world coordinates outside the window are "clipped" or "scissored". That is,
plotting only occurs within the window, just as if a pair of scissors were used to cut out a picture defined
by the window.

GPL WINDOW

CALL Gpl_window(Gpl$,Xmin_ldc,Xmax_ldc,Ymin_ldc,Ymax_ldc)

The subprogram Gpl window is used to define the window rectangle. Like all rectangles in GPL, it is

defined by the following four parameters in sequence:

Xmin wc - Minimum X coordinate

Xmax_wc - Maximum X coordinate

Ymin wc - Minimum Y coordinate

Ymax wc - Maximum Y coordinate

The default is the logical device coordinate space, and the default is reset each time Gpl defldc is called.

Thus, Gpl window should be called after calling Gpl defldc

Suppose, for example, that you want the X units range to be from the years IS 1 70 to 1980 and the Y units
range to be from 10,000 to 1000,000 dollars. Then use

CALL Gpl_window(Gpl$ , 1970 , 1 980 , 1 0000 , 1 00000)

GPL VIEWPORT

CALL Gpl_viewport(Gpl$,Xmin_ldc,Xmax_ldc,,Ymin_ldc,Ymax_ldc)

The subprogram Gpl viewport is used to define the viewport rectangle. Again, four rectangle

parameters are specified in the following sequence:

Xmin ldc - Minimum logical device coordinate

Xmax ldc - Maximum logical device coordinate

Ymin ldc - Minimum logical device coordinate

Ymax ldc - Maximum logical device coordinate

SEP 86
11-3

Viewing Transformations

For example,

CALL Gpl_viewport(Gpl$,30,40,50,60)

will place the graphical data in a rectangle with

Xmin_ldc«30
Xmax_ldc«40
Ymin_ldc-50
Ymax_ldc«60

on the logical plotter.

The default is the logical device coordinate space, and the default is reset each time Gpl defldc is called.

Thus, Gpl viewport should be called after calling Gpl defldc.

Normally, Gpl window and Gpl_viewport are called paired together to completely define a viewing

transformation. You can, if you choose, call them individually and in any order.

100000

CALL Epl_windOH (Gpll 1970. I960. 10000. 100000)

/ .'

^JC

100

CALi EpljJef ldc (Gpll 0. 100. 0, ldd)

1^80

/ '

\ \cALL GpWewport (Gpll 30. 40, 50. BO)

\ BOY— ' '

SC&

30 40

100

SEP 86
11-4

Viewing Transformations

GPL__USELDC

CALL Gpl_useldc(Gpl$)

This call allows the current viewing transformation to be temporarily suspended and to make the window
and viewport temporarily equal to the logical device coordinates. The normal viewing transformation is
restored when Gpl usewc, described in the next section, is called.

The CP is not converted to a meaningful value. Thus Gpl move should be used before drawing a line

(Gpl draw, etc. ) or text (Gpl text). The call syntax is simply

CALL Gpl useldc(Gpl$)

GPL__USEWC

CALL Gpl_usewc(Gpl$)

This call restores the viewing transformation to the value before a call to Gpl useldc. This mode is also

restored by a call to Gpl window, Gpl viewport, or Gpl defldc.

The pair of calls, Gpl_useldc and Gpl usewc, are useful when plotting several sets of data on a graph,

and you wish to annotate outside the graph between plots. They are also useful when you wish to do
rectangle shading or to create plotting symbols, as shown in later chapters.

Again, the CP is not transformed to a meaningful value. The call syntax is

CALL Gpl_usewc(Gpl$)

SUMMARY

In this chapter, you learned how to use viewing transformations. These allow you to map your problem
coordinates (world coordinates) onto your logical plotter coordinates. If no viewport or world coordinates
are defined, the viewport will be equal to the logical device coordinate space; and the world coordinates
will be equal to the logical device coordinates.

It is recommended that you use the viewing transformation whenever you change the coordinate system
within an application.

It is also recommended that you not change the following parameters within a single plot (after defining
them at the start):

Gpl defldc parameters

Gpl physarea parameters

Gpl devorigin parameters

Gpl physrotate parameters

This preserves device independence of the plots, and the code is easier to maintain.

SEP 86
11-5

SEP 86
11-6

GPL allows device dependent picture files to be created for future use. These files are useful when a
plotter is unavailable or when multiple copies of the same plot are to be generated, or when plotters need
to be used with maximum efficiency.

The following subprograms and utilities are introduced in this chapter:

Gpl__fileis Sets up a data file into which plotter protocol and messages will be written.

Gpl_message Writes a message into the data file defined using Gpl_fileis. Optionally, allows a

GPLFIL program pause after displaying the message.

GPLFIL Utility program used to recreate a plot from a GPL data file which was created using

Gpl_fileis. The device used to recreate such a plot must be identical to the device
originally used to draw the plot.

GPL picture files contain device protocol for a particular plotter. The first record contains the model
number of the plotter to protect GPLFIL from sending the picture to the wrong device.

GPL_.FILEIS

Subprogram Gpl_fileis is used to create a picture file. Either a new picture file may be created or a
previously created file may be replaced with a new picture.

The call syntax is

CALL Gpl_fileis(Gpl$,Pic_file$,Protect$, Opt ion, Error)
with the following parameter meanings:

Pic_file$ - Name of picture file to be created or replaced. The GPL software CREATE's the file and any
scratch files that it needs. A file of 500 records times 80 data bytes is first created. This is extended by
500 records whenever the end of the file is encountered when writing into it. When Gpl_terminate is
called, the file is reduced to the actual number of records used. Gpl_abortplot causes the file to have
incorrect or incomplete data, and the file should be purged by the application programmer.

Protects - Protect code for this file. Optional. If no protect is used, just supply a null string.

Option - Used to decide whether to purge a previously existing file with the same name and protect code.

- 1 - PURGE any previously existing file with the same name and protect code. Then CREATE the new
picture file. Essentially a replace option.

- CREATE a picture file only if a previous does not exist with the same name. This prevents
accidental destruction of a previously created file.

SEP 86
12-1

Picture Files

Error - Error return parameter. If no errors are encountered, then is returned. To display an error
message for non-zero parameter values, use DISP FNGpl errm$(Error).

Subprogram Gpl_fileis is contained in LOAD SUB file "GPL 2 5 2", which also contains Gpl_plotteris. If

the initialization call to Gpl plotteris is successful (Error-0), then the next GPL call should be

Gpl fileis. This prevents plotter initialization data from being lost; it is still stored in internal buffers

after the call to Gpl plotteris.

GPL MESSAGE

Operator messages, such as "CHANGE PENS" or "CHANGE PAPER", may be embedded in picture files
through the use of a call to Gpl message. The syntax is

CALL Gpl_message(Gpl$,Message$,Wait)

The parameters are:

MessageS - Message to be stored in file.

Wait - Parameter used to specify a pause after the message is displayed.

- No pause

1 - Pause and prompt for a continue.

When your application program is run , the operator message will appear with an LDISP command if you

specified a Message address of 8 when calling Gpl plotteris. In addition, a pause prompt will be

displayed of the form "PRESS ENTER TO CONTINUE".

If the Message address in Gpl plotteris is 9, then neither the message nor a pause prompt will appear

when your application program is run. When GPLFIL is used to display the picture, however, the message
and/or pause prompt will appear.

GPLFIL UTILITY PROGRAM

RUN "GPLFIL [device-spec]"

Utility program GPLFIL may be used to display pictures stored in files on a plotter. Just run the program,
and it will prompt you for the name of the file.

SEP 86
12-2

To produce multi -color overhead transparencies, order the appropriate HP Overhead Transparency Kit for
your plotter. Note that all plotters with 'Grit Wheel Drive' require a special paper-backed acetate sheet
that is different from the acetate used by other plotters.

When plotting on acetate, the programmer must design certain precautions into the software.

OVERHEAD TRANSPARENCY KIT

The HP Overhead Transparency Kits, which are different according to the plotter you own, contain
plotter pens and sheets of acetate. When the kit supplies are used up, individual items can be ordered
separately.

SPECIAL CONSIDERATIONS

Ink Transfer and Drying

The plotting occurs directly on acetate, which is non -porous and does not absorb ink. This characteristic is
different from paper, which readily absorbs ink. Special pens, containing a fast drying ink, must be used to
plot on this acetate.

The paper pen normally in a plotter must be replaced with the special acetate pens whenever plotting on
acetate. The pens should remain capped whenever not being used for a long time to prevent the tip from
drying up. If a tip does become dry, it may often be restored by using the special solvent supplied with the
Overhead Transparency Kit.

The acetate must be carefully handled to avoid transferring oils from your hand to the acetate prior to
plotting. After plotting, care must be used to avoid touching the surface for about 1 minutes while the
ink dries. In addition to these handling precautions, the programmer should perform some other
operations described in the programming section below.

Viewing Area

Many overhead acetate slide projectors have a useful viewing area that is limited to a square about 8 to 9
inches (200 to 225 mm) to a side. Thus the physical plotting area must have to be reduced to fit into this
area. In addition the origin of the plot may have to be adjusted to center on the acetate. Use
Gpl physarea and Gpl devorigin to perform these adjustments.

The film and paper provided with the Transparency Plotter Film Kits and Paper and Pen Kits is supplied
in both English/US 'A'size (8. 5" X 11") and Metric 'A4'size (210 X 297 mm).

SEP 86
13-1

Plotting an Acetate

PROGRAMMING GUIDELINES
Viewing Area

You can use Gpl_physarea to cut down the size of your plot to fit the limits of the overhead
transparency projector. For example, for a plot that is normally 250 mm wide by 180 mm high, you
would use:

CALL Gpl_physarea(Gpl$,250,180)

To cut this down to say 200 mm wide (80% or original size), just use:

CALL Gpl_physarea(Gpl$,200,144)

Centering

After getting the proper viewing area, adjust the Gpl devorigin parameters to give a centered plot on the

acetate.

Pen Velocity

The pen velocity needs to be slowed down for maximum ink transfer. A velocity of 1 cm/sec seems to
work well for most situations:

CALL Gpl_penspeed(Gpl$,10)

Multiple Passes

After drawing the entire plot, you may want to repeat it again at least once. The lines will have much
better definition.

Avoiding Ink Run

You should be careful when lines of different color cross or when shaded regions of different color touch.
Ink run can occur because of the slow drying time.

Suggestions:

1. For shaded regions, separate them slightly so that the regions do not touch.

2. For lines that cross, adjust the order of plotting so that one line has a chance to dry somewhat
before a crossing line of a different color intersects. One way to do this is to plot all pen 1 lines
and text. Then plot all pen 2 lines and text, etc.

SEP 86
13-2

The GPL library imposes a natural structure on an application program.

SIMPLE APPLICATIONS

The graphics portions of simple applications should proceed in the following sequence:
DIM Gpl$[l200]

REQUEST device

LOAD "GPL252" library

DEL 5001,9999

LOAD SUB "GPL252", 5001,1

Initialize plotter
Gpl plotteris

LOAD "GPL253" library

DEL 5001,9999

LOAD SUB "GPL253", 5001,1

Define LDC space

Gpl_defldc

Define physical area and origin

Gpl physarea

Gpl devorigin

LOAD "GPL254" library

DEL 5001,9999

LOAD SUB "GPL254", 5001,1

Define the window and viewport

Gpl window

Gpl viewport

Gpl useldc

Gpl usewc

Draw text and straight lines

SEP 86
14-1

Program Design Tips

Gpl move Gpl imove

Gpl draw Gpl idraw

Gpl_text

Gpl_pen Gpl linestyle Gpl_penspeed

Gpl__tsize Gpl textrotate Gpl_lorg

Repeat the previous two steps as often as needed

Abort plot, if needed

Gpl abortplot

Clear the plot (should always be called)

Gpl clear

Go back to any step after plotter initialization if additional plots are desired

LOAD "GPL257" library

DEL 5001 ,9999

LOAD SUB "GPL257", 5001,1

Terminate plotting

Gpl terminate

DELETE GPL library

DEL 5001,9999

RELEASE device

COMPLEX APPLICATIONS

The graphics portions of more complex or larger applications should proceed in the following sequence:

DIM Gpl$[1200]

LOAD "GPL251" library

DEL 5001,9999

LOAD SUB "GPL251", 5001,1

Read configuration

file

Gpl config

Select device

REQUEST

device

SEP 86

14-2

Program Design Tips

Check device

Gpl devident

LOAD "GPL252" library

DEL 5001 ,9999

LOAD SUB "GPL252", 5001,1

Initialize plotter

Gpl_plotteris

Initialize picture file (if used)

Gpl fileis

LOAD "GPL253", library

DEL 5001,999

LOAD SUB "GPL253", 5001,1

Define LDC space

Gpl_defldc

Define physical area and origin

Gpl physarea

Gpl devorigin

Gpl physrotate

Gpl physviewp

Pick character set options

Gpl cset

LOAD "GPL254" library

DEL 5001,9999

LOAD SUB "GPL254", 5001,1

Define the window and viewport

Gpl window

Gpl viewport

Gpl useldc

Gpl usewc

Draw text and straight lines

Gpl move Gpl imove

Gpl draw Gpl idraw

Gpl_text

SEP 86
14-3

Program Design Tips

Gpl_pen Gpl linestyle Gpl penspeed

Gp] tsize Gpl textrotate Gpl_lorg

Repeat the previous two steps as often as needed

Abort plot, if needed

Gpl abortplot

Clear the plot (should always be called)
Gpl clear

Go back to any step after plotter initialization if additional plots are desired

LOAD "GPL267' library

DEL 5001,999

LOAD SUB "GPL257", 5001,1

Terminate plotting

Gpl terminate

DELETE GPL library

DEL 5001 ,9999

RELEASE device

MEMORY USAGE

The GPL library was implemented in BASIC and takes a lot of user memory space. It was broken into the
files "GPL251" through "GPL 2 5 8" in order to conserve memory space as much as possible. The largest file,
"GPL254", uses approximately 34K bytes of memory.

SEP 86
14-4

Charts offer a convenient way to summarize and analyze data. Visual aids allow fast interpretation of
data, and allow trends to be spotted. Modern businesses are realizing the value of business charts, and are
producing them with computer graphics products like GPL.

This appendix contains helpful hints on developing graphics programs. The four types of charts most
commonly developed by programmers, and discussed here, are line charts, column charts, bar charts, and
pie charts.

GRAPHICS CONSIDERATIONS

An often neglected part of computer generated charts is the graphic design. In this section, we have
adapted commonly accepted principles that graphic designers and artists use to the capabilities of the HP
plotters and the GPL software.

Simplicity

The first commandment in the art of charts is KEEP IT SIMPLE. A chart simplifies the analysis of data,
as long as there is not too much data. If the chart starts to become very cluttered, or too many different
trends are displayed, then break the chart down into several charts.

Too much or unnecessary text distracts the viewer from the data. Thus, the chart should contain only text
that is necessary for the viewer to understand which specific data he is viewing. Conclusions from that
data, strategy, recommendations, etc. should be printed elsewhere if the data is to have any impact.

You should keep your charts as simple as possible.

Select the Right Chart Type

This appendix discusses four common chart types. Select a chart type according to how you wish to
analyze your data. For example, you may wish to compare several different sets of data. Or you may
wish to see the trend of a single set of data as a function of some parameter. Or you may wish to see how
the components of data compare.

Line charts offer a convenient means of comparing several sets of data or of looking at the trend for a
single set of data. They are most often used when:

( 1 ) there are many points in each data set

(2) points in a data set are spaced irregularly

(3) there are four or less sets of data

Column charts allow one to see more easily the trend of totals while breaking up data into components.
They are not good for comparing several sets of absolute data.

SEP 86
A-l

Chart Design

Bar charts are used in much the same way as column charts, and the decision as to which to use depends
on the number of sets of data and the magnitudes of the data.

Pie charts are used when the component breakdown is of interest. They should not be used for showing
absolute magnitudes.

In choosing which chart to use, be sure to ask

(1) What am I trying to see? The trend of a single set of data, comparing the trends of several sets, or just
showing the component breakdown.

(2) Is the data irregularly or regularly spaced?

(3) How many points in each data set? How many data sets?

(4) What is the range of data? If the range is very wide, perhaps logarithmic axes are required.

Plot Sizes

It is assumed that the plotting is to be done on ISO A4 size (210 mm by 297 mm) or English A size (8. 5 in
by 1 1 in) paper. For other sizes of paper, scaling may be done but one must be careful in handling the
text.

A convenient aspect ratio for plots is for the Width/Height ratio to be the square root of 2 or the inverse.
In this appendix, we will always consider the case where the plot is wider than its height. The square root
of 2 is convenient when putting 2,4, or even 8 plots into the same plotting region as for a single plot. A
convenient size is 254. 6 mm ( 1 0. 02 inches) wide by 1 80 mm high (7. 09 inches), which has an aspect ratio
very close (within . 02%) of the square root of 2. The default LDC space was chosen to have an aspect ratio
close to the square root of 2 while rounding to the easily remembered 250 by 180 region. When you know
that you need to scale the plot to fit several on a page, you should use more exact values.

Text

Most text will be generated with the narrow line pens on a pen plotter (0. 3 mm line width is typical for a
new pen). The ideal aspect ratio for the height of a capital letter to the width of a line is in the range of 6
to 1 0. By picking capital letter heights of 3 mm, the aspect ratio begins at 1 for a new pen and goes
down in value as the pen wears down. The text sizes in these recommended guidelines have been chosen to
range from 2. 5 to 4 mm, within the ideal range.

When fitting two or more plots on a single page, the application programmer should adjust the size and
placement of the characters so that the characters stay at least 2. 5 mm high, for purposes of readability as
pens wear down.

Most text on a chart is used to generate a (1) title, (2) subtitle, (3) axis titles, (4) axis data point labels, (5)
legends (data set labels), (6) footnotes, and (7) annotation.

Titles should be lettered with 4mm high characters, and a title should be limited to about 45 characters of
width (1 80 mm max width). Subtitles should use 3. 5 mm high characters, and should be limited to about
50 characters of width.

Three mm high characters are used for most other data: axis titles, axis data point labels, legend names,
footnotes, and most annotation. Some annotation that is not part of the data, such as initials and date,
may be drawn with 2. 5 mm high characters.

SEP 86

A-2

Chart Design

When making the charts smaller than a full page, such as when fitting two or more on a single page, most
of the text should still be in 3 mm high characters, and the width of lines and the number of text entries
will have to be cut down to fit the smaller region.

SEP 86

A-3

SEP 86

A-4

Coordinate Systems: Four different coordinate systems control GPL plotting. The WC and LDC systems
are used for device -independent plotting. The PLMM and PAMM systems are used for placing the plot on
a specific physical plotter.

CP: Abbreviation for "Current Position".

Current Position: (X,Y) location in the world coordinate system that is used as a reference for drawing
straight lines and graphics text. For straight lines, it represents the starting point for the line. Graphics
text will be justified against the Current Position (abbreviated CP) depending on the current Label origin
(Gpl lorg) attribute value.

LDC: Abbreviation for "Logical Device Coordinates".

Logical Device Coordinates. Coordinate system for specifying placement on the (device independent)

logical plotter. This logical plotter is defined in the application program (Gpl defldc) before actually

doing any plotting with straight lines and text.

PAMM: Abbreviation for "Physical Area Millimeters".

Physical Area Millimeters: Coordinates which are used to specify the actual plotting area on a physical

device. The plotting area boundaries are specified by Gpl physarea, and the placement of the LDC

(Logical Device Coordinate) Limits is specified by a call to Gpl physviewp.

PLMM: Abbreviation for "Plotter Millimeters".

Plotter Millimeters: Coordinates used to specify the actual placement of a plot on a plotting surface. The
coordinates are in millimeters and are positive or 0. The point (0,0) refers to the minimum possible X and
Y plotting coordinates; not the lower left corner of the paper. On most plotters, it is not possible to plot to
the lower and left edges of the paper. The placement of a plot is specified by a call to Gpl devorigin.

Viewing Transformation: Mapping between world coordinates and the logical device coordinates. It is
specified by a window rectangle (in world coordinates) that is mapped onto a viewport rectangle ( in
logical device coordinates). All lines and text drawn within the window will be mapped to the viewport.
Lines and text outside the window will be "clipped" (not plotted).

Viewport: The viewport is a rectangle that specifies the placement of graphical data on the logical plotter

(logical device coordinates). It is specified by a call to Gpl viewport. The viewport and window

(Gpl window) are usually specified together and are collectively called the "viewing transformation".

WC: abbreviation for "World Coordinates"

Window: The window is a rectangle in world coordinates that is to be mapped onto the logical plotter

(logical device coordinates). It is specified by a call to Gpl window. The window and viewport

(Gpl viewport) are usually specified together and are collectively called the "viewing transformation".

All graphical data outside the window will not be plotted.

World Coordinates: Also called problem coordinates, user coordinates, or application coordinates. These
may be defined for your application by specifying a viewing transformation.

SEP 86
B-l

GPL SUBPROGRAM FILES
AND FONTS

APPENDIX

SUBPROGRAM FILES

GPL uses these files during execution.

GPL251 - Device Selection

GPL252 - Plotter initialization and Plot Setup

GPL253 - Plot Setup and Specifications

GPL254 - Text and Straight Lines

GPL255 - Straight Lines

GPL256 - Text

GPL257 - Plot Termination

GPL258 - Text Width Inquiry function

FONT FILES

Font Name

Serif Roman Light

Serif Roman Medium

Serif Roman Bold

Serif Italic Light

Serif Italic Medium

Serif Italic Bold

Stick Light

Stick Medium

Sans Serif Italic Light

Sans Serif Italic Medium

Gothic English

7220A/S, 7221A/B/S, 7225A/B

7220C/T, 7221C/T Plotters

7470A/HP ColorPro(7440A) plotters

747 5A/ 7 5 50A plotters

Roman

Lower 96

Extensions

File name

GPLRLO

GPLRL1

GPLCRO

GPLCR1

GPLTRO

GPLTR1

GPLLIO

GPLLI1

GPLCIO

GPLCI1

GPLTIO

GPLTI1

GPLSRO

GPLSR1

GPLDRO

GPLDR1

GPLLJO

GPLLJ1

GPLMJO

GPLMJ1

GPLGEO

GPLGE1

GPL271

GPL272

GPL273

GPL274

GPL275

GPL276

GPL275

GPL276

OTHER GPL FILES

GPL242 UsedbyGPLCFT
GPL243 UsedbyGPLCFT
GPL261 - Used by GPLFIL
GPLEnn - A series of example and reference programs

SEP 86
C-l

GPL Subprogram Files and Fonts

Summary of HP 250 Sans Serif Fonts

S ans Serif Light

GPLSRO, GPLSR1

a§6Qa66uadduae6u

A?0/E:ai0aeAi6U&' / S

Sans Serif Medium

GPLDRO, GPLDR1

a§6Qd66ua6duaeou
AT0/Eaf0aeAt6UET/S

Sans Serif Light Italic Sans Serif Medium Italic

GPLLJO, GPLLJ1
!"#$%&'()*+,-./
0123456789:;<=>?

"\NfiiiU£ § ..
aeoila&6ixc£diiae6u
AW/t'al08eAidOti/3

GPLMJO, GPLMJ1
!"#$%&'()*+-./
0123456789:;<=>?
@ABCDEFGHIJKLMNO
PQRSTUVWXYZ[\]~_
^abcdefgfiijktmno
pqrstuvwxyz}jf~
£

aeo€.ae'6'Q.a£d'CLae6u
A°W/Eaies9eA\dQti/$

SEP 86

C-2

GPL Subprogram Files and Fonts

Summary of HP 250 Plotter Fonts

7220A/L. 7221A/B/S. 7225A/J. 7220C/T. 722-IH/T 747C1A

GPL271. GPL272

! "#$%&' ()*+. -. /
0123456789: ; <=>?
8ABCDEFGHIJKLMN0
PQRSTUVWXYZC\] "_
'abcdefghijklmno
pcjr-stuvwxyz {! } ~
£
*" 9 fsiff iioiYS

GPL273, GPL274

! "#$%&' () *+,-./
0123456789: ; <=>?
SABCDEFGHUKLMNO
PQRSTUVWXYZ[\] "_
v abcdef ghi jklmno
pqrstuvwxyz {I } ~
£
" "QNn iiaiTS
aeouaeouaeduaeou
Ai0£ai0aeAiOUEiB

GPL275. GPL276

! "#$%&' ()*+. -. /
0123456789s ; <=>?
8ABCDEFGHIJKLMN0
PQRSTUVWXYZ [\] "_
1 abcdef gh i Jk 1 mno
pqrstuvwxyz <! > ~h
£
"\R?S i<La£YS
a660666udd6ua8KU
Al0f6i0»XiDUEYPI-

§>ummanj of 18$ 250 Herorattur ifonts

(Sotfrtr iEnqltgfr
Ol2345e7fi0:;< = >?

$<$*&aKina«xigz[\]~_

s abr6pfglftjklmno
pqratuuvuxijz|||~
I

AtW^aiaaeAiOia^t/l?

SEP 86
C-3

GPL Subprogram Files and Fonts

Summary of HP 250 Serif Fonts

Serif Light

GPLRLO, GPLRL1

m "Q$tL\<,m §

a§6ilae6uae6tiae6u
At0iE&i08eAi6ufii'jS

Serif Light Italic

CPLLIO, GPLLI1

!"#$%&'()*+,-■/
0123456789:;<=>?
@ABCDEFGHIJKLMNO
PQRSTUVWXYZ[\]~_
s abcdefghijklmno
pqrstuvwxyz{\}~
£
' " cRn i(L U£ §
ae6'Clae'6u&dd'il&e6u
AWMMeaeAidUfrifl

Serif Medium

GPLCRO, GPLCR1
!"#$%&'()* + ,-./
0123456789:;< = >?
©ABCDEFGHIJKLMNO
PQRSTUVWXYZ[\]~_
v abcdefghijklmno
pqrstuvwxyzf||~
£

'"qM-^UI §
ag6uae6iiaeduaeou
At0/Eai0a3Ai6UEij(?

Serif Bold

GPLTRO, GPLTR1

!••#$%&'()•+.-•/
0123456789:;< = >?

PQRSTUVWXYZ[\]~_

s abcdefghijklmno

pqrstuvwxyzf||~

S66uae6tiaeduae6u
Ai0/Eai0aeAiOUEi^

Serif Medium Italic Serif Bold Italic

GPLCIO, GPLCI1

'" c^nm §

at 611 ae~ 6uae dude bu
AWJEal06eAlOUEi0

GPLTIO, GPLTI1
!"#$%&'()*+,-./
0123456789:;<=>?
©ABCDEFGHIJKLMNO
PQRSTUVWXYZ[\]~_
^ab c defg hijk Imno
pqrs tuvwxy z \\\ ~
£

"cNfXnXX£ §
&§6Ha66uaeduae6u
AWJEaiemAlb UEifi

SEP 86
C-4

GENERAL PHILOSOPHY

Four types of errors commonly appear, categorized as follows:

• Soft errors - Caused typically by invalid parameter values in GPL, subprogram calls that are
non-catastrophic in nature.

• Hard errors - Caused typically by invalid parameter values in GPL subprogram calls that are
catastrophic in nature.

• Parameter Reference Errors - Occur during program development. Caused typically by:

a) Incorrectly typing a variable name

b) Using an invalid variable type (such as INTEGER when REAL should have been used)

c) Using an incorrect dimension (such as forgetting to dimension the GPL$ string)

• Miscellaneous - Usually occur during program development. Caused by:

a) Memory overflow

b) Improper subprogram loading

Each of these error categories is handled differently by GPL and is covered in more detail in the following
sections.

SOFT ERRORS

The most common errors are caused by parameters out of range, which result in a GPL subprogram call
being ignored. These errors are called "Soft Errors". Soft errors tend to cause part of a picture to be
incorrect, such as a missing line, or an incorrect linestyle. A code specifying the routine in which the
LAST soft error occurred is returned with GPL terminate (unless a hard error occurred).

1101 -Gpl__clear

1102 -Gpl_defldc

1103 -Gpl_draw

1 1 04 - Gpl_f rame

1105 -Gpl_idraw

1 1 06 - Gpl_imove

1 1 07 - Gpl_linestyle

SEP 86
D-l

GPL Errors

1108

-Gpl

_lorg

1109

-Gpl

message

1110

-Gpl

move

1111

-Gpl

penspeed

1112

-Gpl

physarea

1113

-Gpl

devorigin

1114

-Gpl

pen

1115

-Gpl

physrotate

1116

-Gpl

physviewp

1117

-Gpl

terminate

1118

-Gpl

text

1119

-Gpl

transmit

1120

-Gpl

textrotate

1121

-Gpl

tsize

1122

-Gpl

useldc

1123

-Gpl

usewc

1124

-Gpl

viewport

1125

-Gpl

where

1126

-Gpl

window

1127

-Gpl

cset

HARD ERRORS

Certain errors, called "Hard Errors", can cause disastrous run time results. These can occur in two areas:

1. Invalid parameters during initialization of a device or file. This occurs when using Gpl plotteris

of Gpl fileis. An error return parameter is included with each of these calls. A non-zero error

return should always cause the application program to take corrective action before proceeding
with a plot.

- No hard error encountered
1-1099 - ERRN for system errors not explicitly handled by Gpl plotteris.

1 1 51 - Invalid Gpl$ (probably insufficient length)

1 1 52 - Invalid Model $ (not one of the supported devices)

1 1 53 - Invalid Device address (Must be 8-9 or 1 1-20)

1 1 54 - Invalid Message address (must be in range 8-20)

1 1 5 5 - Invalid file name syntax

1 1 56 - Invalid protect code syntax

1 1 57 - Invalid Option in Gpl fileis

1 1 6 1 - Plotter ownership error - must do REQUEST before calling

Gpl plotteris.

1 162 - No response from plotter (when the devices address ranges

from 1 1 to 20)

1 1 6 3 - Device is not the specified model (for device address ranging

from 1 1 to 20)
1 164 - Plotter could not be initialized (for a variety of reasons)
1 1 6 5 - Unsupported plotter at Device address

1 166 - Invalid plotter response during identify sequence

1 167 - Incorrectable device error

1 1 70 - File already exists (Gpl fileis Option*0)

1 1 76 - Old file could not be purged (Option 3 - 1)

SEP 86
D-2

GPL Errors

1 1 8 1 - Plotter responded initially but later did not.

All sending of further data to plotter stopped.
1 1 8 2 - Invalid plotter response during plotting

1 1 8 3 - Picture file unavailable during plotting

1 1 9 1 - Configuration file not found

1 192 - Configuration file protected

1 193 - Wrong file type for configuration file

1 194 - Configuration file access error

1 195 - Configuration file could not be opened

1 196 - Invalid configuration file data format
1 196 - Invalid model in configuration file

1 1 9 8 - Invalid device address in configuration file

1 199 - Invalid message address in configuration file

2. Lost data during output. This can occur due to a device being removed from on line status or due
to system/device problems during data transfer. Some of these errors; are detected and some are
not. If such an error is detected, it will be signalled in the Gpl terminate error parameter.

1181 - Plotter responded initially but later stopped.

Further plotting to device terminated.

1182 - Invalid plotter response.

Further plotting to device terminated.
118 3 - Picture file could not be opened during plotting.
Sending plot data to file terminated.

PARAMETER REFERENCE ERRORS

The "Parameter Reference Error" causes the program to halt. It is usually caused by passing incorrect
variable names, types, or dimensions to the subprogram parameter lists. For example, it is common for the
programmer to supply an incorrect name for Gpl$. Such an error will cause error 202 to occur in most
cases with a program halt. GPL does not detect or warn the programmer of such errors. The application
programmer must thoroughly debug the program to prevent parameter reference errors.

Common errors:

8 - Improper parameter matching

9 - Incorrect # of parameters

in subprogram call

1 8 - Subscript out of range. Most common
cause: Improperly dimensioned Gpl$.
Be sure to use

DIM Gpl$[1200]

131, 132, 133 - Plotter is not available, of wrong type, or plotter
is down

202 - Insufficient dimension length in PACK statement. Probable cause:
Improperly passed Gpl$ array name in subprogram call.

SEP 86
D-3

GPL Errors

MISCELLANEOUS ERRORS

2 - Memory overflow.

7 - Undefined function or subprogram

56 - File name is undefined.

3 1 4 - Device must be requested before using Gpl_plotteris or
Gpl devident.

SEP 86
D-4

List of GPL Subprograms
and the files in which they are found

A file containing the subprogram you need must be loaded at the time you call the subprogram.

GPL GPL GPL GPL GPL GPL GPL GPL

251 252 253 254 255 256 257 258

Gpl abortplot

Gpl clear

Gpl config x

Gpl cset

Gpl_defldc

Gpl devident x

Gpl devorigin

Gpl draw

FNGpl errm$ x

Gpl fileis

Gpl frame

Gpl idraw

Gpl itextwidth

Gpl imove

Gpl linestyle

Gpl lorg

Gpl message

Gpl move

Gpl pen

Gpl penspeed

Gpl physarea

Gpl physrotate

Gpl physviewp

Gpl_plotteris

Gpl terminate

Gpl_text

Gpl textrotate

Gpl transmit

Gpl_tsize

Gpl useldc

Gpl usewc

Gpl viewport

Gpl where

Gpl window

X
X

SEP 86

E-l

Summary of GPL Subprograms

NOTE

If Gpl_cset is called from GPL252 an error 7 might occur; therefore,
always call Gpl cset from files Gpl 253 or Gpl 256.

GPL__ABORTPLOT

Gpl_abortplot(Gpl$)

Used to abort a plot. Typically, this is used when there is a problem with paper or pens. Clears internal
Gpl$ buffer. Clears device buffer.

GPL_CLEAR

Gpl_c lea r(Gpl$, Crt, Hardcopy)

Clears the plotter display, if possible. Sets up the device for paper change if the change is not
programmable. Stores a special code in picture file to indicate the separation between plots. Moves pen
stable out of way and/or puts pen away as a convenience when changing paper.

When doing any plotting this command should always be called at the end of a plot. It is especially useful
when doing multiple plots.

Crt - Unused parameter reserved for future use. Intended to be used in clearing graphics Crt displays if
and when such devices are supported by GPL. As Hewlett-Packard will make no guarantee about future
device support, you should always set this parameter to 0.

Hardcopy - Used to clear a plotter. Currently allowed values include 0, 1, 3 and 4. No other values should
be used at this time, as other values are reserved for other possible devices that might be supported in the
future.

NOP (no operation)

1 Put pen away and/or move pen put of way

3* Advance paper a half page on chart advance plotters. Put pen away

and/or move pen out of way for non -chart advance.
4* Advance paper a full page (ISO A3 or English 11x17) and cut the left

edge for chart advance plotter. Put pen away and/or move pen

out of way for non -chart advance plotters.

♦When used with the new HP 7550A plotter, this parameter can also be used to feed a full page of paper
from the plotter's paper magazine; setting the hardcopy parameter to either "3" or "4" causes a full page of
paper to be fed to the HP 7550 plotter from the plotter's paper magazine.

Note: Chart advance commands are sent to chart advance plotters only when roll paper is loaded.

SEP 86

E-2

Summary of GPL Subprograms

GPL__CONFIG

Gpl_config(Config$,Protect$,No_devices,Model$(*),Dev_add(*),
Mess_add(*) .Error)

Interrogates the graphics device configuration file (GPL%CF or a user supplied file name) and returns the
device addresses and model numbers for graphics devices connected to the system.

ConfigS - Name of the configuration file. If left blank, GPL%CF in the current MSI disc is assumed.

Protect$ - Protect code for the configuration file name.

No devices - Number of model numbers returned.

Model $(*) - String array containing the models connected to the system.

Dev add(*) - Array of device addresses

Mess add(*) - Array of message addresses

GPL__CSET

Gpl_cset(Gpl$,Char_set,Character_file$)

Used to select a software character set or to specify that the default hardware set be used.

Char_set - Specifies whether Character_file$ applies to ASCII codes 32-127 or to 160-255.

0-32-127 (usually used for US ASCII codes)
1 - 160-255 (usually used for Roman Extensions)

Character file$ - Name of character set file. See Appendix A for a list of available character file names.

When Char set*0, use "" to specify default plotter set.

GPL__DEFLDC

Gpl_defldc(Gpl$,Xmin_ldc,Xmax_ldc,Ymin_ldc,Ymax_ldc)

Defines the logical device coordinate system. When called, the window and viewport are set equal to the
specified LDC coordinate limits. The physical viewport is reset to the default of centered, isotopic,
maximum size mapping onto the physical area. The units mode is reset to WC mode (Gpl usewc).

Xmin ldc - Minimum LDC x coordinate. Default is 0.

Xmax ldc - Maximum LDC x coordinate. Default is 250. Should be greater than Xmin ldc.

Ymin ldc - Minimum LDC y coordinate. Default is 0.

Ymax_ldc - Maximum LDC y coordinate. Default is 180. Should be greater than Ymin ldc.

SEP 86
E-3

Summary of GPL Subprograms

The defaults are (0,250,0, 1 80).

A soft error occurs if either Xmin ldc >- Xmax ldc or Ymin ldc >=Ymax ldc.

GPL_DEVIDENT

Gpl_dev ident(Dev_add, Mode 1$, Advance, Buffer, Pens, Error)

Used to interrogate the plotter and important parameters at the specified plotter address.

Dev add - Specified device address. Only input to subprogram. Note that Gpl$ is NOT a parameter for

this call.

Model$ - Model number at this address. Important: Because of ambiguities in the identification process,
the exact model number may not be returned. In that case, the model number returned will be sufficient

for an input to Gpl plotteris (because Gpl plotteris also uses Gpl devident). For example, if the device

is a 7220T and the chart advance is not operational, the model number that is returned is "7220C".

NOTE

For the plotters 7470A, HP ColorPro(7440A), 7475A and 7550A a call to

Gpl devident returns the paper size for which the plotter is set. Model $

contains information of the form: model number/paper size. The source

of the paper size information varies with the plotting device. With the
7470A, HP ColorPro(7440A) and 747 5A plotters the maximum
plot -surface (paper size) depends on the position of the plotter's paper size
switch. With the HP 7550A the paper size is determined automatically by
the plotter. Thus, a user program can automatically adjust plotting
parameters, such as the actual size of the plot.

Advance - Parameter specifying whether automatic chart advance is present.

- No auto advance is present

1 - Auto advance is present

Buffer - Number of bytes in the device buffer.

Pens - Number of pens on the plotter.

Error - Error return parameter. Zero if no error. Use FNGpl_errm$ to display the error message.

GPL_DEVORIGIN

Gpl_devorigin(Gpl$,X_lower_left_plmm,Y_lower_left_plmm)

SEP 86
E-4

Summary of GPL Subprograms

Places the physical plotting area (as specified by Gpl_physarea) on the plotter. The origin gives the
minimum x and y coordinates for plotting in the PLOTTER'S coordinate system, regardless of whether the
physical area is rotated.

X_lower__lef t_plmm - Minimum plotter x coordinate for any plotting to occur.

Y lower left plmm - Minimum plotter y coordinate for any plotting to occur.

The defaults and minimum and maximum values depend on the plotter.

Defaults

Minimum

Maximum

ModelS

7220A/C

400

285

7221A/B/C

7220S/T

400

285

7221S/T

7225A/B

285.5

203.5

7470A(US)

10.2

259.1

190.2

7470A(A4)

9.5

274.2

190.2

7440A(US)

7.0

8.0

191.5

257.3

7440A(A4)

9.2

5.6

191.5

272.3

7475AOJS-A)

14.5

198.2

257.9

7475A(US-B)

3.5

4.9

257.9

414.2

7475A(A4)

13.5

11.5

192.2

274.7

7475A(A3)

0.6

13.1

274.7

402.2

7550A(US-A)

2.2

15.3

196

254.2

7550A(US-B)

0.8

1.9

254.2

411.2

7550A(A4)

10.7

9.8

190

271.7

7550A(A3)

10.2

271.7

399.2

US, US-A, US-B, A4, and A3 refer to rocker switch settings on the back panel of each plotter.

SEP 86
E-5

Summary of GPL Subprograms

GPL__DRAW

Gpl_draw(Gpl$,X_wc,Y_wc)

Draws a straight line from the CP to (X_wc,Y_wc). After the draw, the CP is updated to
(X_wc,Y_wc).

X wc - X world coordinate

Y wc - Y world coordinate

Either X wc or Y wc may take on any real value.

FNGPL_ERRM$

DISP FNGpl_errm$(Error)

Used to display error messages corresponding to an error returned in call to one of the following:

Gpl plotteris

Gpl fileis

Gpl terminate

Gpl devident

Gpl config

The error parameter is the one returned by the subprogram with the error.

SEP 86

E-6

Summary of GPL Subprograms

GPL__FILEIS

Gpl_fileis(Gpl$,Picture_file$,Protect$, Opt ion, Error)

Used to create and open a picture file in which plotter data will be stored. The data is specific to the

model number declared by Model $ in Gpl plotteris. After terminating the application (after

Gpl_terminate is encountered and zero Error is returned), the picture may be sent to the device with
program GPLFIL.

Picture file$ - file spec for the file. It must satisfy the naming conventions for files. It must not have

been created if Option* and must have been created if Option 8 "- 1.

Protects - Protect code for Picture file$. If a file is to be appended, this is necessary for access. If a new

file is created, then this code will be assigned to the file.

Option - Specifies whether a new picture file is to be created (Option=0) or replaced (Option=-l).
Option"- 1 creates a file after purging any previously existing file with the same name.

Error - Error return parameter for all errors that may be caused. Returned values include:

- No error encountered
1151 -Invalid Gpl $

1 1 55 - Invalid picture file name syntax

1 1 56 - Invalid protect code for picture file

1 1 57 - Invalid value for Option

1 1 70 - File already exists (Option" 0)

1 1 76 - Old file could not be purged (Option=- 1)

GPL__FRAME

Gpl_frame(Gpl$)

Draws a frame around the current window rectangle (or equivalently, around the current viewport

rectangle). Uses current physical pen (Gpl pen) and linestyle (Gpl linestyle). The CP is unchanged from

the value prior to the call.

SEP 86

E-7

Summary of GPL Subprograms

GPL_JDRAW

Gpl_idraw(Gpl$ , Dx_wc , Dy_wc )

Draws a straight line incrementally from the CP to CP+(Dx_wc,Dy_wc). The CP is updated to the end
point after the draw.

Dx wc - X incremental world coordinate

Dy wc - Y incremental world coordinate

Either Dx wc or Dy wc may take on any real value.

GPL_JMOVE

Gpl_imove(Gpl$,Dx_wc,Dy_wc)

Moves the CP incrementally by (Dx wc,Dy wc).

Dx wc - X incremental world coordinate

Dy wc - Y incremental world coordinate

Either Dx wc or Dy wc may take on any real value.

GPL_JTEXTWIDTH

CALL Gpl_itextwidth (Gpl$ , "ABC" , Width )

Function GPL itextwidth stands for Inquire Text Width. It determines the width of a proportional or

non -proportional string for your use in computing formats.

GPL__LINESTYLE

Gpl_linestyle(Gpl$,Linestyle)
Linestyle - Integer from to 9 specifying the current linestyle.

- No lines. Suppresses straight lines from plot.

1 - Solid line (default)

2 - Dotted line

3 - Medium dashes

4 - Long dashes

5 - Very -long dash plus two short dashes

6 - Short dashes

SEP 86

E-8

Summary of GPL Subprograms

7 - Medium long dashes

8 - Very -long dashes

9 - Very -long dash plus one short dash

See the following figure:

LINE STYLES

(no line)

GPL LORG

Gpl_lorg(Gpl$,Label_origin)

Selects the current text formatting option. Text lines will be justified both horizontally and vertically
relative to the CP according to the current Label origin attribute value.

Label origin

Horizontal

Vertical

1 (default)
2

Left
Left
Left

Bottom
Center
Top

4
5
6

Center
Center
Center

Bottom
Center
Top

7
8
9

Right
Right
Right

Bottom
Center
Top

The above table shows where the CP is located relative to the string of text just prior to a call to

Gpl text. See the following figure. Note that the formatting is performed on character CELLS, not the

characters themselves.

SEP 86
E-9

Summary of GPL Subprograms

#ELL0

HEI*L0

7 HELLO*

ftELLO

HEft_0

8 HELLO*

*
HELLO

#
HELLO

9 tt
HELLO

* CP before call
GPL_MESSAGE

Gpl_message(Gpl$,Message$,Wait)
Sends an appropriate operator message to the message address. Optionally waits for an operator response.
Messages - String containing the operator message.
Wait - Specifies whether to wait for an operator response.

- No wait

1 - Wait until operator responds on message device

SEP 86

E-10

Summary of GPL Subprograms

GPL__MOVE

Gpl_move(Gpl$,X_wc,Y_wc)

Moves the CP to (X wc,Y wc). The CP pen is lifted, interrupting the accumulated line patterns on

dashes or dotted lines.

X wc - X world coordinate

Y wc - Y world coordinate

Either X wc or Y__wc may take on any real value.

There is no guaranteed default CP, especially after changing the viewing transformation or outputting a
line of text. Thus each output primitive should be preceeded by a call to Gpl move.

GPL__PFN

Gpl_pen(Gpl$,Pen_number)
Raises physical pen. Selects new pen or puts it away if possible with selected plotter hardware.
Pen number - New pen to be selected. Range: Integer values from to 8.

- Put pen away. Suppresses text and lines.

1 - Select pen 1, if possible, or left pen on 7470A

2 - Select pen 2, if possible, or right pen on 7470A

3 - Select pen 3, if possible.

4 - Select pen 4, if possible.

5 - Select pen 5, if possible.

Select pen 1 on four pen plotters.

6 - Select pen 6, if possible.

Select pen 2 on four pen plotters.

7 - Select pen 7, if possible.

Select pen 3 on four pen plotters.
Select pen 1 on six pen plotters

8 - Select pen 8, if possible.

Select pen 4 on four pen plotters.
Select pen 2 on six pen plotters

SEP 86
E-ll

Summary of GPL Subprograms

GPL_PENSPEED

Gpl_penspeed(Gpl$,Velocity_cps)

Selects the pen velocity in centimeters per second. For devices without velocity select, this command is
ignored.

Velocity cps - Selected velocity in centimeters/sec. Range: 1-40. The default is device dependent and

the results depend on the device capabilities.

The device capabilities include:

Velocity

actual Velocity

Plotter

(char/sec)

(cm/sec)

7220 series

1-36

7221 series

1-36

7225A/3,722SA/4

any

7225B/3.7225B/4

any

7225A/3V.7225A/4V

1-25

7225B/3V,7225B/4V

1-25

7470A/7475A

.38

2-3

3.8

4-36

7550A

1-40

7440A (ColorPro)

1-40

GPL_PHYSAREA

Gpl_physarea(Gpl$,Width_pamm,Height_pamm)

Selects the area for actual plotting. The logical plotter coordinates will be mapped within this physical

plotting area depending on the current physical viewport (Gpl physviewp). The physical area may be

translated by a call to Gpl devorigin and rotated by a call to Gpl physrotate.

Width_pamm - Width of plot in millimeters. This is the width as the plot (on paper) would be viewed. It
is not the width in the plotter coordinate system. Default is 250 mm.

Height_pamm - Height of plot in millimeters. This is the height as the plot (on paper) is viewed. Default
is 180 mm.

SEP 86
E-12

Summary of GPL Subprograms

GPL PHYSROTATE

Gpl_phys rotate (Gpl$ , Rotat ion )

Controls the rotation of the physical plotting area ( as specified by a call to Gpl_physarea). See Chapter 9
for details.

Rotation - Rotation code. Takes on the following values:

No rotation on 7220, 7221, 7475A and 7550A series plotters. 90 degree clockwise rotation (CW)
rotation on 7225, 7470A and HP ColorPro (7440A) plotters. Used most often for ISO A4 (English A) size
plots that are oriented vertically.

1 Rotate 90 degrees CCW (counter-clockwise) on 7220,7221, HP ColorPro (7440A), 7470A and 7550A
plotters. No rotation on the 7225 plotter. Used most often for ISO A 4 (English A) size plots that are
oriented horizontally.

2 (default) Software looks at Gpl_physarea parameters and attempts to fit on ISO A4 (English A) size
sheet.

-1 90 degree clock-wise rotation (CW) on HP ColorPro (7440A), 7470A, 7475A and 7550A.
-2 180 degree rotation on HP ColorPro (7440A), 7470A, 7475A and 7550A.

GPL_PHYSVIEWP

Gpl_physviewp(Gpl$,Xmin_pamm,Xmax_pamm,Ymin_pamm,Ymax__pamm)

Specifies the placement of the LDC limits in the physical area (Gpl_physarea) coordinate system. The
default is a value which centers the LDC space in the physical area coordinate system with maximum
area. The default is set whenever Gpl_physarea or Gpl_defldc is called. Therefore, Gpl_physviewp
should be called only after any calls to Gpl_defldc and Gpl_physarea.

This function is used whenever you wish to do one or more of the following:

(1) Stretch the plot in one direction, usually when you want to cover the entire physical area. Care must
be used, because circles on the logical plotter will be deformed into ellipses.

(2) Move the plot from the center of the physical area.

(3) Change the size of the plot to something other than determined by the LDC and physarea coordinate
limits.

X min pamm - Minimum x on physical area in millimeters

X max pamm - Maximum x on physical area in millimeters

Y min pamm - Minimum y on physical area in millimeters

Y_max pamm - Maximum y on physical area in millimeters

SEP 86
E-13

Summary of GPL Subprograms

GPL_PLOTTERIS

Gpl_plotter is (Gpl$, Mode l$,Device_address,Message_address, Error)

Initializes the plotter and the Gpl$ parameters for other GPL subprogram calls. Before doing this, it
verifies that the specified model is the one at the specified address.

ModelS - String containing the model number of the plotter (e.g. "7220A" or "7225B/4V").

ModelS can also contain the paper size appended to the model name (as is returned by a call to

the Gpl devident subprogram). For example, the parameter ModelS might now contain a string

similar to "7550A/A3" when calling Gpl plotteris. If a paper code is explicitly specified it must

match the actual plotter setting. If only the model name is given, the Gpl$ string is initialized
with the actual plotter setting.

Device address - system address to which the plotter is connected. Allowed range: 8-9,1 1-20.

Message address - system address to which the operator messages are to be sent. Allowed range: 8-9.

Error - Error return parameter for the hard errors which may occur. Values to be returned include:

- No hard error encountered
1-1099 - ERRN for system errors not explicitly handled by Gpl plotteris

1 1 51 - Invalid GplS (probably insufficient length)

1 1 52 - Invalid ModelS (not one of the supported devices)

1 1 53 - Invalid Device address (Must be 8-9 or 1 1-20)

1 1 54 - Invalid Message address (must be in range 8-20)

1 1 6 1 - Plotter ownership error - must do REQUEST calling Gpl plotteris

1 1 6 2 - No response from plotter (when the devices address range from

1 1 to 20)
1 1 6 3 - Device is not the specified model (for device address

ranging from 1 1 to 20)

1 164 - Plotter could not be initialized

1165 - Unsupported plotter at Device address

1 166 - Invalid plotter response during identify sequence
1 1 8 1 - Plotter responded initially but later did not.

All further sending of data to plotter stopped.

The application program should always check the error parameter for hard errors.

GPL_TERMINATE

Gpl_terminate(Gpl$, Error)

Ends the GPL application. This is the last GPL call in an application.

Error - Error return parameter for soft errors that may have occurred. May be (no errors) or positive
(code specifying the last subprogram call in which an error was encountered).

The codes and the associated subprograms are listed below:

SEP 86

E-14

Summary of GPL Subprograms

101

-Gpl

clear

102

-Gpl

_defldc

103

-Gpl

draw

104

-Gpl

_frame

105

-Gpl

_idraw

106

-Gpl

_imove

107

-Gpl

linestyle

108

-Gpl

_lorg

109

-Gpl

_message

110

-Gpl

_move

111

-Gpl

_penspeed

112

-Gpl

physarea

113

-Gpl

_devorigin

114

-Gpl

pen

115

-Gpl

_physrotate

116

-Gpl

_physviewp

117

-Gpl

_terminate

118

-Gpl

text

119

-Gpl

transmit

120

-Gpl

_textrotate

121

-Gpl

tsize

122

-Gpl

useldc

123 -

-Gpl

_usewc

124 •

-Gpl

viewport

125 -

-Gpl

where

126 •

-Gpl

window

127 ■

-Gpl_

_cset

181 ■

- Plotter respondec

Further plotting to device terminated.

182- Invalid plotter response.

Further plotting to device terminated.

183- Picture file could not be opened during plotting.
Sending plot data to file terminated.

GPL TEXT

Gpl_text(Gpl$,Text$)

Draws a line of text on the graphics display. The placement of the text relative to the Current Position
(CP) is controlled by the Text rotation (Gpl_textrotate) and Label origin (Gpl__lorg) attribute values. The
size of the characters is controlled by the Text size (Gpl_tsize) attribute values. The text supplied must be
in the 96 character printable set or the Roman Extensions. The only control characters that will be
recognized are CR (carriage return ASCII 1 3) and LF (line feed - ASCII 1 0), at the end of the string. If no
CR and LF are present, the CP will be at the end of the string of text, ready for more text to be appended
as if the Label origin attribute were one. A CR moves the CP back to the starting position, and a LF
moves the CP and starting position down one line.

Text$ - String to be plotted.
the string.

The only control characters that may be added are CR and LF, at the end of

SEP 86
E-15

Summary of GPL Subprograms

GPL_TEXTROTATE

Gpl_text rotate (Gpl$ , Rotat ion )

Rotates text in 90 degree increments. Rotation is the number of 90 degree increments to rotate. Allowed
values include:

- No rotation

1 - Rotate 90 degrees CCW (counterclockwise)

2 - Rotate 180 degrees CCW

3 - Rotate 270 degrees CCW

GPL__TRANSMIT

Gpl_transmit(Gpl$,Option)

Clears GPL graphics buffer (stored on Gpl$) of graphic data and sends the data to the device. Used for
optimizing performance and for synchronizing the application program with the plot. Called
automatically when the following are called:

Gpl_clear
Gpl_terminate

Option - Reserved for future use with different classes of graphics devices. It should always be set to 0.

GPL__TSIZE

Gpl_tsize(Gpl$,Cell_height_ldc,Cell_width_dev_pct)

Selects the current text size. The height of the character cell is the base line to base line distance between
lines of text. The width is the distance between the left edges of characters in a line. On the supported
plotters, capital letters are 1/2 the cell height and 2/3 the cell width. The characters are justified against
the left and lower edges of the cells.

Cell_height_ldc - Height of character cell in logical device coordinate units. Range: Any real>0.
Default: 9

Cell_width_dev_pct - Percentage deviation from default. Range: From -99.99 to +200. 00. Default: 0.

GPL_USELDC

Gpl_useldc(Gpl$)

Sets the current units to the LDC space. The window and viewport are temporarily reset to be equal to
the LDC space. The previously specified window and viewport rectangles may be restored with a call to
Gpl_usewc. The value of the CP is lost.

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Summary of GPL Subprograms

GPL__USEWC

Gpl_usewc(Gpl$)

Restores the current units to the last specified windows and viewport. This is used after a call to
Gpl__useldc was used to plot temporarily in the LDC space. The value of the CP is lost.

GPL__VIEWPORT

Gpl_viewport(Gpl$,Xmin_ldc,Xmax_ldc,Ymin_ldc,Yrnax_ldc)

Sets the viewport rectangle to the specified value. The viewport rectangle specifies the placement of
window data on the logical plotter. The viewport is reset to the default of LDC limits whenever

Gpl defldc is called. In addition, Gpl viewport restores the units mode to world coordinates

(Gpl usewc).

Xmin ldc - Minimum x LDC coordinate

Xmax ldc - Maximum x LDC coordinate

Ymin ldc - Minimum y LDC coordinate

Ymax ldc - Maximum y LDC coordinate

A soft error occurs when either Xmin ldc >= Xmax ldc or Ymin ldc >= Ymax ldc

When Gpl plotteris is called, the window, viewport, and LDC space are set to the default of

(0,250,0,1 80). In addition, the units mode is World Coordinates (Gpl usewc).

GPL__WHERE

Gpl_where(Gpl$,X_wc,Y_wc)

Inquires and returns the Current Position (CP). The CP is moved whenever a straight line or text is drawn
on the plotter. In addition, the CP may be set by a call to Gpl move.

X wc - X world coordinate

Y wc - Y world coordinate

GPL__WINDOW

Gpl_window(Gpl$,Xmin_wc,Xmax_wc,Ymin_wc,Ymax_wc)

Sets the window rectangle, which defines the world coordinates to be mapped onto the plotter. The
placement on the logical plotter is specified by the viewport rectangle. All data outside the window
rectangle is "clipped" (suppressed from being plotted). All graphical data (straight lines and text) within
the rectangle is mapped to the viewport. The default window is the logical device coordinates, and it is
reset to the default whenever Gpl_defldc is called. Gpl_window also resets the units mode to World
Coordinates (Gpl usewc)

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Summary of GPL Subprograms

Xmin wc - Minimum X world coordinate

Xmax wc - Maximum X world coordinate

Ymin_wc - Minimum Y world coordinate
Ymax wc - Maximum Y world coordinate

A soft error occurs when either Xmin wc >= Xmax wc or Ymin wc >■ Ymax wc. When

Gpl_plotteris is called, the window, viewport, and LDC space are set to the default of (0,250,0,180). In
addition, the units mode is; World Coordinates (Gpl usewc).

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HEWLETT
PACKARD

Part No. 45261-90064 E0986

Printed in Federal Republic of Germany HERRENBERGER STRASSE 1 30

September 1 9 8 6 D - 7 3 BOEBLINGEN