THE
E D W I N
USER'S GUIDE
(Fourth Edition)
EDWIN is a set of graphics programs developed in the
Edinburgh University Computer Science Department. This
document describes how the procedures provided by EDWIN
may be used to produce two dimensional line drawings.
The subsequent editions of this guide reflect changes
made to EDWIN as a result of user feedback. This edition
of the user's guide refers to version 4 of EDWIN.
J. Gordon Hughes
December 1981
CONTENTS
Section Page
Contents 1
A historical and logical overview of EDWIN. 2
User's guide to the EDWIN procedures.
A) Initialisation and termination routines 5
B) Primitive output routines 6
C) Control routines 8
D) Attribute handling routines 11
E) Miscellaneous procedures 13
The structure of the device drivers. 14
The Calcomp device driver. 15
The Charles driver. 17
The Cursor Addressable Terminal drivers. 19
The H P model 2648 terminal driver. 21
The H P model 7221 plotter driver. 22
The Printronix printer driver. 24
The Tektronix device driver. 25
The VT15 device driver. 27
A set of geometric utility routines. 29
A transformation stack. 31
Acessing EDWIN 33
A) Under VMS on the VAX 11/780
B) Under EMAS on the ICL 2900 range
C) Under MOUSES on the Perkin-Elmer machines
D) Under RSX-11/M on the PDP-11 range
E) Under ISYS on the Interdata series 70
F) Under the IMP 15 system on the PDP-15s
Cross calling of EDWIN from other languages. 35
Use of the VIEWPDF program. 37
Use of the PDFDEC program. 37
Appendices
A) EDWIN error messages 38
B) Listing of the normal EDWIN procedure specs 39
C) The EDWIN character set 40
D) Some example programs 41
E) The structure of the EDWIN PDF 49
F) Acknowledgements 51
G) References 52
A historical and logical overview of EDWIN
'EDWIN' is a graphics package consisting of set of procedures which
provide basic facilities for producing two dimensional line drawings. The
major design aims when writing EDWIN were :
a) The package should be portable;
b) The package should be small;
c) The package should be independent of the graphics terminal being used.
Before EDWIN was written there existed a number of local graphics
packages, mostly based on a Tektronix package called the MacPherson Package
[1]. These packages had been implemented on a wide range of machines, but
in each case by a different person, who added new procedures and
consequently more incompatibilities. The importance of the first design
aim is that a user should have an identical interface on each machine, and
this has been achieved in EDWIN. At the time of the first release of EDWIN
the following machines were required to support it:
a) DEC PDP-15 (18 bit machines) [2]
b) Interdata series 70 (16 bit machines) [3]
c) ICL system 4-75 (32 bit machines) [4,5]
d) ICL 2900 (32 bit machines) [6]
All of these systems were running the operating systems described in the
references mentioned above. During the first year of use EDWIN was also
implemented on a VAX-11/780 running the VMS operating system [7]. It has
since been implemented on Perkin-Elmer models 7/32 and 3220 under MOUSES
[8], and the PDP-11 series of computers under RSX-11/M.
All of the above mentioned systems support the IMP language [9,10], and
for this reason the IMP language was used to write EDWIN. All the IMP
compiler implementations are similar, but there are a number of minor
differences, and consequently EDWIN is written using a subset of the IMP
language. Because of this, EDWIN could be translated into another
Algol-like language fairly easily. Although all the above machines have
different word lengths this does not pose a problem as EDWIN does not
assume that it has a larger word length than 16 bits. Users can however
make use of any 'world space' which the machine will allow, with the
knowledge that if they use one greater than + 32 K, then their programs are
no longer portable.
Another machine-dependent feature is the length of name which is
significant when matching external procedures. Of the original systems,
EMAS on the ICL system 4 processors has the lowest limit (8 characters) and
all the procedure names were chosen to be distinct in eight characters. On
the DECsystem-10 and PDP-11s running RSX-11/M, external names are only
matched to six characters. The IMP77 include statement should be used to
declare the EDWIN procedures with the system provided file of procedure
specs, as the names have been made distinct at 6 characters by the alias
mechanism. Any user requiring to mount EDWIN under RSX-11/M or on the
DECsystem-10 should consult J. Gordon Hughes to get a suitable version
released.
The second design aim was to make EDWIN small. This requirement arises
because on the PDP-15 there is a limit of 8K words on the size of an IMP
program, and on the Interdata 70's and PDP-11's this limit is 64K bytes.
There is no significant limit on the 32 bit machines. One of the things
which had made previous packages non-standard was the addition of 'frills'
on the larger machines. The philosophy taken by EDWIN is to allow the user
to make full use of the graphics capabilities of the devices that are being
driven, but not to provide facilities which users can easily provide
themselves (such as the provision of menus).
The reason for the third design aim is that in the past, local graphics
packages have been written for specific devices, and a new set of
procedures had to be written for each new device which became available,
frequently having the same facilities, but with incompatible procedures. A
superior approach is used in GINO [11] and suggested by the ACM in their
SIGGraph proposals [12], to have device specific code localised, forming a
'device driver', which is interfaced to the machine and device independent
'core' of the graphics package. The following diagram shows how EDWIN may
be thought of in relation to a user's program -
______________
| |
| Charles |
---->| Driver |
| |______________|
| ______________
_______________ ___________________ | | |
| | | |----- | Tektronix |
| U S E R |--------->| | | Driver |
| | procedure| |-------->|______________|
| P R O G R A M | calls | E D W I N | ______________
| |--------->| |-------->| |
| |--------->| | | Plotter |
|_______________| |___________________|----- | Driver |
| |______________|
(User shielded from |
specific device ----> to other
idiosyncrasies) device drivers
On the large virtual machines all the device drivers can be included in
the version of EDWIN with little overhead, but on the smaller machines the
version of EDWIN is normally pruned to include only a small number of
device drivers. Device drivers now exist for
a) Tektronix 4000 series storage tubes [13,14,15,16]
b) A range of Calcomp plotters [1]
c) VT15 vector display processor [17]
d) Perkin-Elmer 550 terminals (Bantams) [18]
e) Hewlett Packard 7221 flat bed plotter [19]
f) 'CHARLES' colour graphics terminal [20]
g) Visual 200 terminals [21]
h) Hewlett Packard 2648 terminal [22]
i) Printronix printers [23]
The facilities provided by EDWIN have been developed from ideas in the
existing MacPherson package, with the use of names and other ideas from the
ACM SIGGRAPH proposals. Because of the requirement to run EDWIN on the
local mini-computers it was not possible to provide the ACM's segmented
data structure, although this would have been desirable. EDWIN has
provided a low level graphics package which is machine and device
independent. If the user wishes to disregard the device independence,
virtual coordinate space, ability to produce software characters, and
checking of parameters, it would be possible to use the EDWIN device
drivers as a 0th level graphics package, or they could be used as drivers
for a more complex graphics system. EDWIN has been used in research
projects (eg. the ESDL suite [24] and a system to plot Integrated Circuit
descriptions [25]), and in undergraduate teaching and projects [26].
The rest of this guide describes:
i) The user facilities -
Drawing pictures with EDWIN is a matter of writing a program which
incorporates the procedure calls which are descibed in this section.
ii) The device drivers -
This section describes the device specific features of the devices which
EDWIN can be used to draw pictures on. It should be noted that users
should very rarely require to call the device drivers directly as the
purpose of EDWIN is to provide a user with a device independant interface.
iii) Some useful utilities -
This section describes a set of geometric drawing routines, and a
transformation stack which users may find useful. Utilities for drawing
and analysing stored picture descriptions are also described.
iv) Appendices which cover -
The EDWIN error messages
The standard procedures provided
The EDWIN character set
A selection of example programs
A definition of the stored picture format
Acknowledgements and references
Users Guide to the EDWIN procedures
A) Initialisation and Termination routines:
routine INITIALISE FOR (integer DEVICE TYPE)
This is normally always the first EDWIN routine to be called. It
initialises EDWIN and selects the device driver to be used. If the device
driver selected is not available or if an unidentified device is specified,
EDWIN signals error 0 (see appendix A).
The following DEVICE TYPES are valid :-
0 : The 'null' device
15 : VT15
120 : Soroc IQ 120 terminal
300 : Printronix printers
550 : Perkin Elmer 550 terminal (Bantam)
200 : Visual 200 terminal (VT52 compatable)
69 ('E'), 101 ('e') : Hazeltine Esprit terminal
564, 565, 663, 963 : E.R.C.C. Calcomp plotters
2648 : Hewlett Packard terminal
7221, 7220 : Hewlett Packard plotters
4002, 4010, 4012, 4014 : Tektronix storage tubes
67 ('C'), 99 ('c') : CHARLES driver
76 ('L'), 108 ('l') : Line printers
Further details of these device drivers may be found in the sections
following the description of the EDWIN procedures.
routine TERMINATE EDWIN
This must always be the last EDWIN routine to be called. It ensures
that any pending output is forced out, and the device is left in its normal
state.
Examples of what is meant by 'normal' are -
a) Tektronix terminals are set to alpha-numeric mode
b) Roll plotters have all the paper used moved past the pen
c) The VT15 processor is stopped
d) The HP plotter pen is put away
B) Primitive output routines :
The following routines may be used to generate line drawings. The
parameters refer to virtual coordinates (ie. any number in the range -32K
to +32K). If storing of the picture is enabled, the procedure calls are
noted and the picture may be redrawn by utilities described later. In all
cases the vectors are clipped to the current WINDOW setting, and projected
to the current VIEWPORT. This is described in more detail in section C.
Lines are drawn at the current line style and colour settings if the device
has them available. Changing these is described in section D.
routine MOVE ABS (integer X,Y)
This routine moves the current position to the point (X,Y).
routine MOVE REL (integer DX,DY)
This changes the current position (say (CX,CY)) to the point (CX+DX,
CY+DY). If the specified point lies outside the current window, then the
current screen position remains unaltered.
routine LINE ABS (integer X,Y)
This routine causes a line to be drawn from the current position to the
point (X,Y), updating the current position to the point (X,Y).
routine LINE REL (integer DX,DY)
This routine draws a line to (CX+DX, CY+DY), where (CX,CY) is the
current position, and updates the current position appropriately.
routine MARKER ABS (integer N,X,Y)
routine MARKER REL (integer N,X,Y)
These routines provide a set of symbols which can be drawn after an
implicit call on MOVE ABS or MOVE REL, depending on which routine is used.
At present eleven are available; N identifies which symbol is to be drawn .
0 Point ( . )
1 Octagon ( O )
2 Square ( [] )
3 Triangle ( A )
4 Transformation point ( X )
5 Flag point ( one with six )
6 Visual Centroid ( + )
7 Right pointing arrow
8 Left pointing arrow
9 Upward pointing arrow
10 Downward pointing arrow
The following routines may be used to output text on graphics terminals.
The character drawing instructions are recorded if the picture is being
stored. Although on some terminals (eg. Tektronix, Cursor Addressable
terminals and the HP 2648 terminal) users can mix output produced by the
standard I/O routines with output from EDWIN, this practice is not
encouraged as problems can arise in the synchronisation of the two outputs.
If this must be done the routine UPDATE can be used to ensure that any
pending graphics output is forced out.
By default the characters are drawn in a 12 (X) by 20 (Y) box in virtual
coordinates. EDWIN supports two types of character. The first of these
are 'hardware' characters, which are generated by the device, and are
usually of fixed size and orientation. The second type, 'software'
characters, may be scaled and rotated by routines described later.
Software characters are generated as sequences of lines and moves by EDWIN.
The routine SET CHAR QUALITY (page 12) selects the font in which text is to
be drawn.
routine CHARACTER (integer CH)
This causes the character CH to be drawn at the current position and the
current position is advanced by the character width. The routine call is
ignored if CH is a character of quality one and is outside of the range of
ISO characters whose codes lie in the range 32 to 127.
routine TEXT (string (255) ST)
This routine causes sequence of characters making up ST to be output.
Users should note that most systems provide procedures for converting
integers and reals to strings and vice versa. Because the names vary
between systems, users are referred to the appropriate system library
manuals.
PDP-15 users should refer to the section describing the PDP-15
implementation of EDWIN for details of restrictions placed on the character
handling routines on the PDP-15.
C) Control Routines :
The following routines may be used to control the drawing of the
picture.
routine NEWFRAME
This causes a blank surface to be found for the graphics output to be
displayed on. In the case of Tektronix, VT15 and Video terminals this
results in the screen being cleared, and in the case of roll plotters the
paper is fed to the start of a new plot. The fact that a new frame has
been taken is recorded if the picture is being stored.
routine UPDATE
This routine causes any output buffers to be flushed, so that after a
call of UPDATE the picture is guaranteed to be up to date. The routine
needs to be used if graphics output is to be mixed with other output to the
same device. In the case of a Tektronix, UPDATE results in the terminal
being left in alpha-numeric mode.
routine STORE ON (integer STREAM)
This causes calls of drawing routines to be recorded on output stream
STREAM. This representation of the picture, often called the Pseudo
Display File or PDF, can then be re-read, or used as input to other EDWIN
utility programs described later. The storing of the picture does not
alter the currently selected output stream.
routine STORE OFF
This disables the recording of graphics instructions, and is the
default.
routine VIEW ON (integer STREAM)
This causes the graphics output to go to the stream specified. By
default this is stream number one if the device is not a terminal, and
stream zero for terminals. For terminals the graphics output usually
reaches the terminal through a different mechanism than the standard I/O
routines and trying to view on another stream will have no effect. The
default is for viewing to be enabled.
routine VIEW OFF
This disables viewing. Calling any of the routines described in section
B will have no visible effect, but the routine calls will be stored if
storing is enabled.
routine WINDOW (integer XL, XR, YB, YT)
The picture is built up in a coordinate system which is known as the
VIRTUAL SPACE (sometimes called the "WORLD SPACE"). Within this space
there is an area known as a WINDOW, and this area is mapped to the
user-selected area of the graphics device called the VIEWPORT (see below).
The routine WINDOW defines the size of the window in the virtual space.
The parameters are the lower and upper X value, and the lower and upper Y
values respectively, the default values being (0, 1023, 0, 1023). If a
lower window bound exceeds an upper window bound the two parameters are
swapped by EDWIN; thus it is not possible to invert the picture by swapping
the window limits. The limits of the virtual space are dependent on the
machine, but the virtual space must not exceed + 32K square if the user
program and PDF are to be portable. In any particular implementation the
maximum size of the virtual space is equal to the largest integer which the
machine can hold. The following diagram shows the arrangement for
windowing -
routine VIEWPORT (integer XL, XR, YB, YT)
The picture is drawn within an area in the output device's coordinate
space which is known as the VIEWPORT. This routine may be used to alter
the size of the viewport (the parameters have the same significance as for
the routine WINDOW) and they have default values which are device dependent
but have been chosen so that if the viewport is unaltered an 'average' size
of picture results. For graphics terminals this is the complete screen,
and for plotters the default viewport is typically 15 cm square. The
descriptions of the individual device drivers give details of the possible
and default settings of the viewport.
The package automatically maps the currently specified window onto the
current viewport and clips the drawing appropriately.
If the coordinates of the viewport are set greater than the maximum
viewport possible on the device, then the largest viewport settings
possible are used. If the upper X or Y bound is greater than the
corresponding lower bound then the bounds are reversed, and the effect is
the same as calling VIEWPORT with the parameters in the opposite order.
With the Tektronix 4014, the users can either have 1024 unit resolution
or enhanced 4096 unit resolution. If a viewport with a maximum X value of
greater than 1023 is given then the 4014 will be driven in enhanced
graphics mode, until it is re-initialised by a call of INITIALISE FOR.
routine ASPECT RATIOING (integer STATE)
If the parameter is 0 then the automatic adjustment of window bounds to
keep the picture with the correct aspect ratio is suppressed. A value of 1
(the default) for the parameter causes the window bounds to be enlarged to
maintain the correct aspect ratio for the picture. When the routine ASPECT
RATIOING or VIEWPORT is called the current window is altered to reflect the
current aspect ratio.
When aspect ratioing is enabled; if a square is drawn in the virtual
co-ordinate space then a square will be seen on the screen. If aspect
ratioing is disabled and if the terminal does not have a aspect ratio of
unity then the square which has been drawn in the virtual co-ordinate space
will appear as a rectangle on the screen. When aspect ratioing is enabled,
EDWIN checks the aspect ratio that a picture will have on the screen, and
extends the window in either the X or Y direction to give correct aspect
ratio on the screen.
D) Routines for changing Attribute settings :
The following routines are used to set values of attributes, which
remain set until they are changed again. Any parameter given outside the
specified parameter range causes the default to be used. The information
about the attribute change is recorded if the picture is being stored. If
the device being used cannot support the attribute change then it is
ignored, but the attribute change is still recorded if storing was enabled.
routine SET COLOUR (integer COLOUR)
This allows the colour being used for drawing to be changed. For most
devices colour changes are carried out automatically, but on some plotters
(eg. the Calcomp 564) this must be done manually by stopping plotting,
removing the current pen, and inserting in the new one. It is consequently
good practice to draw all the output required in one colour before changing
the pen. The following parameters are valid -
1 = Black (default)
2 = Blue
3 = Green
4 = Red
The driver for the ERCC Calcomp plotter and the CHARLES terminal allow a
wider range of parameters. Details of these codes can be found in the
sections describing the device drivers.
routine SET LINE STYLE (integer STYLE)
This routine allows the user to make use of the different line styles
which are available on the Tektronix 4014, plotters, and VT15. The driver
for Cursor Addressable Terminals uses this routine to choose the symbol
which is used to generate lines on the terminal, (see the section on the
Cursor Addressable Terminal driver).
The following parameters are significant -
0 = Normal Lines (default)
1 = Dotted lines
2 = Chain Lines (on 4014 and HP plotter; otherwise normal lines)
3 = Short Dashed lines
4 = Long dashed lines
routine SET INTENSITY (integer BRIGHTNESS)
The only device currently driven by EDWIN which has variable intensity
is the VT15. BRIGHTNESS should be a number in the range zero to seven,
with seven being the brightest. An intensity of 5 is the default, 0 and 1
are effectively invisible, and 7 is brightest.
routine SET CHAR SIZE (integer SIZE)
This routine may be used to change the size of the characters to be
drawn by CHARACTER and TEXT. The size should be a positive integer,
representing the size of the character in the X direction. The default
size is 12 units wide (which corresponds to 20 units high). If hardware
characters are being used then the nearest size of character available is
used, but in most cases only size 12 is available. In general nothing
about low quality text should be relied on when moving programs to run on
other devices. Details of hardware characters available on devices can be
found by referring to the sections describing the device drivers. If
software characters are used then any size is possible, but choosing
factors or multiples of 12 avoids rounding errors in text strings which may
otherwise arise.
routine SET CHAR ROT (integer DEGREES)
If software characters are being used, DEGREES gives a clockwise
rotation of the appropriate amount. DEGREES is currently rounded to a
multiple of 90 degrees. The default value for DEGREES is 0.
routine SET CHAR QUALITY (integer QUALITY)
If QUALITY=0 (the default) then hardware characters (that is characters
which are generated by the device hardware, or by local device driving
software) are used, otherwise the EDWIN software characters set is used.
Hardware characters are frequently provided in only a small number of
sizes, and with limited or no rotation possible.
routine SET CHAR FONT (integer FONT)
If the device being used has alternative character fonts, then this sets
the character font which is used for subsequent hardware characters. (There
is only one software character font available at present).
routine SET CHAR SLANT (integer DEGREES)
If the character set which is currently being used can have a slant
specifed, this routine can be used to set it. Currently the only two
devices which this applies to is the Calcomp and Hewlett Packard plotters.
In the case of the HP plotters, DEGREES may be any number in the range -90
to 90, but the Calcomp plotters have only one alternate slant angle which
is 15 degrees forward.
F) Miscellaneous procedures:
routine INQUIRE POSITION (integer name X, Y)
This routine sets X and Y equal to the X and Y coordinates of the
current virtual position.
routine INQUIRE WINDOW (integer name XL, XR, YB, YT)
This routine sets the parameters to the current window bounds. The
parameters are lower X, upper X, lower Y, upper Y, respectivly.
routine INQUIRE VIEWPORT (integer name XL, XR, YB, YT)
This routine sets the parameters to the current viewport bounds. The
order of the parameters is the same as for INQUIRE WINDOW.
routine MAP TO DEVICE COORDS (integer name X, Y)
This routine can be used to ask EDWIN to transform the point specified
from the world space to the device space, using the appropriate
transformation for the current window and viewport settings. The
coordinates have no clipping performed on them.
routine MAP TO VIRTUAL COORDS (integer name X, Y)
This routine performs the inverse operation to the routine above. If
converts the coordinates X and Y to the equivalent coordinates in the world
space. The coordinates have no clipping performed on them.
routine CURSOR (integer name STATUS, X, Y)
Many devices have a means of allowing the user to point at the screen,
for example the cursor on a Tektronix tube or the BIT PAD on the CHARLES
terminal. This routine can be used to allow a limited form of interaction
with EDWIN. The contents of STATUS vary between devices; for example it
contains the character hit to leave cursor mode on a Tektronix, the value
of the buttons on the VT15, or the pen status on the HP plotter. The
parameters X and Y are set to the pointer's X and Y coordinates. If the
device has no cursor then EDWIN error 8 is signalled when the routine is
called. Users are referred to the sections describing the device drivers
for further details of this routine.
routine D CURSOR (integer name STATUS, X, Y)
This routine is similar to the routine CURSOR, except that the
coordinates are returned in device units, and are not scaled. The value of
STATUS is the same as for CURSOR.
The structure of the EDWIN device drivers.
All the graphics output from EDWIN goes into a module called the "device
driver". This can take two forms, either it is a specific device driver,
in the case of machines which have a limited version of EDWIN, or it is
just a switch which selects the true device driver, after the switch has
been initialised. All the device drivers have the following format -
routine DRIVE DEV (integer COM, X, Y)
This rigid format makes it easy to produce new device drivers, and it is
also easy to configure versions of EDWIN which reflect the devices
available. The above named routine may be assumed to be present in any
version of EDWIN which supports multiple devices, otherwise the device
driver is one of the routines which are described in the following
sections.
COM is the command code which instructs the device driver which
operation is to be performed, and the parameters X and Y give further
information for some of the codes. Codes 1 to 9 are defined for all device
drivers, but other codes are accepted by specific device drivers to allow
users to make use of device dependent features. These additional codes are
described in the descriptions of the device drivers.
The following is the significance of the general codes -
Code X Y Description
0 TYPE - Initialise the driver for TYPE.
1 - - Terminate
2 - - Update
3 - - Newframe
4 X Y Move Abs to (X,Y)
5 X Y Line Abs to (X,Y)
6 CHAR - Output character CHAR
7 WHICH VAL Change attribute WHICH to VAL
8 XL YB Set lower device window bounds
9 XR YT Set upper device window bounds
Note that calls to a device driver are ignored if another device has
been selected, or if viewing is disabled. This means that calls such as
SET COLOUR MAP to the CHARLES device driver are ignored if the current
device is not CHARLES.
In the versions of EDWIN on the multi-user systems VAX, MOUSES, and
EMAS, the following routines are present to perform graphics input and
output.
routine TTPUT (integer SYM)
routine FLUSH OUTPUT
integer fn TTREAD
integer fn TTGET
The routine TTPUT places its parameter into an internal buffer, which is
flushed when it gets full, or explicitly by the use of the routine FLUSH
OUTPUT. The output is automatically forced out when the routines UPDATE or
TERMINATE EDWIN are called. The function TTREAD returns the next character
on the console stream. TTGET is the same as TTREAD except the character is
not echoed.
The Calcomp device driver
The Calcomp device driver produces pictures on a range of Calcomp drum
plotters. These plotters are now all driven by means of calls to the
Graphpack plotter routines provided by the E. R. C. C., but a version which
directly drives a model 563 plotter also exists. The use of Graphpack
allows all the plotters to have a range of line styles and characters, even
though the plotters themselves cannot support these.
Graphpack, and consequently EDWIN, can be used to drive the models 564,
565, 663, and 963 plotters, but the use of the model 963 (device .GP23 on
EMAS) is recommended. The Calcomp device driver currently exists on the
VAX and EMAS implementations of EDWIN. In the case of EMAS, the process
username and current delivery information appear at the start of the plot,
and the plotter output goes to the plotter automatically. In the case of
VAX the process username and a delivery message is appended to the start of
the plot. If the VAX user has the logical name "NETFS$DELIVER" defined,
then this is used as the delivery information, otherwise it is set to
"E.R.C.C. Front Door". The logical name NETFS$DELIVER may be set by the
command -
$ DEFINE NETFS$DELIVER "Level 3 of the J.C.M.B.
On VAX the plotter driver produces the output for the plotter in the file
"T.GP", which must be explicitly sent to a plotter by the NETFS command, as
shown in the following example -
$ NETFS
>> device 2972
>> fire t.gp
>> stop
Users are referred to chapter 3 of the ERCC Graphics Manual [1] for
specific details of the plotters mentioned above, and also how the specific
models are addressed on the ERCC network. The plotters all have a default
viewport of 0 to 1500 in both the X and Y directions. Y is the distance
across the paper, and X is the distance along the paper, so that the
maximum Y coordinate of the viewport is dictated by the width of the
plotter being used, and the maximum X coordinate of the viewport is almost
infinite. The default viewport is set to be 15 cm, so if a plot of size 30
cm is required, the viewport bounds should be set to (0,3000,0,3000).
If the user wishes to send the plotter output to explicit files, then
the routine call VIEW ON (n) should be given before the call to
INITIALISE FOR where 'n' is the stream which is to be used for the plotter
file. In the case of VAX and EMAS, the stream should be set up by the
routine call
OPEN OUTPUT (21, "MYPLOTFILE")
The routine OPEN OUTPUT (integer STREAM, string (255) FILE) requires to be
explicitly declared on EMAS.
The device driver is present as
routine C963 (integer COM, X, Y)
which has the same parameters as the general device driver described on
page 14.
The plotters have multiple colour facilities. In the case of student
users only black may be used (any attempt to draw other colours will still
result in black). Other users can make use of the four colours mentioned
in the description of the SET COLOUR routine. There are also facilities
for doing liquid ink drawing, for which permission from the ERCC is
required. Users are referred to the ERCC graphics manual for details of
how to get in touch with the appropriate ERCC personnel, and also for the
range of valid pen numbers for SET COLOUR.
The plotters provide 4 line styles: these are the ones mentioned in the
routine SET LINE STYLE, with the exception of the 'chain lines'.
If 'hardware' characters are used, these are the characters from the
ERCC Graphpack, while 'software' characters are the standard EDWIN software
character set. This means that hardware characters on the plotter may be
set to any size.
The CHARLES driver
This device driver controls the 'CHARLES' terminals, based on a design
by Charles Minter at Caltech. The terminals consist of a small PDP-11 (eg.
PDP-11/03), which controls a colour display, and also talks to a console.
Once the Charles station has been switched on, the PDP-11 runs a small
program in ROM which allows the terminal to talk to the selected host
computer. The PDP-11 must then be loaded with the software to interpret
the protocol sent by the device driver. The information about switching on
the terminal, and loading the PDP-11 software from VAX, EMAS and the
DEC-system 10, is contained in a black folder beside the terminal.
The display is a 512 x 512 x 4 bit raster scan display, where the 4 bits
assigned to each point determine which of 16 user programmable colour
registers are to be used. This gives a range of 16 colours, which can be
selected by the SET COLOUR routine. Colours 1 to 4 are defined to be the
standard EDWIN colours, and colour 0 is defined as black (the background).
The default colour is 1, which is white. The remaining colours are
undefined. Users can set their own colour map registers by the routine
SET COLOUR MAP described below. The Charles station includes a 'Bit pad',
an analogue device which can be used by the PDP-11 to control a tracking
cross. The position of the cross can be accessed by the EDWIN routine
CURSOR. The status returned by the cursor contains the value of the
buttons on the bit pad.
The Charles terminal can either be in console mode, where it acts like a
normal terminal, or in drawing mode. EDWIN automatically sets the terminal
to the correct mode; if users wish to enter console mode to interact with a
graphics program which is running, the routine UPDATE must be called.
When the Charles terminal is in drawing mode, the PDP-11 may be in one
of five states. The first of these is 'text mode', which is automatically
selected by the routines CHARACTER and TEXT and terminated by an attempt to
enter another mode. The second mode is 'line mode', where the terminal
performs like a standard line drawing terminal, and this is the default
mode for any graphics output done by EDWIN. The other modes are 'dot
mode', 'polygon mode', and 'box mode', the first of which causes lines to
be converted into a 'point' primitive. Thus points may be drawn over the
screen by just a sequence of calls to LINE ABS or LINE REL. The next mode
is polygon mode. Once in polygon mode, ie. the first call to LINE after
either polygon mode has just been set, or the last polygon terminated, this
is used to start a polygon. Then any sequence of moves or lines are
treated as defining the vertices of a polygon. The polygon is
automatically shaded by Charles when a call to END MODE is given. The
other mode is used to draw boxes on Charles. Each two calls to LINE are
taken to describe the upper and lower corners of a box, which the Charles
terminal will draw, and shade. Although these low level features are
present, users are recommended to use the routines to generate polygons and
boxes which are described in the section following the device driver
descriptions. These save the user knowing about the Charles driving modes,
and also clip the shapes to the current screen window.
Routines specific to the Charles driver
routine CHAS (integer COM, X, Y)
This is the Charles device driver. It accepts all the standard device
driver commands, and also commands 10 and 11.
Command 10 is 'mode change', and is used to select the appropriate mode.
The parameter X chooses the mode to be used until the mode is next changed.
Mode 0 is text mode, mode 1 is line drawing mode (the default), mode 2 is
point mode, mode 3 is polygon mode, and mode 4 is box mode. Users are
encouraged to use the routines S BOX and POLYGON described above rather
than altering modes themselves.
Command 11 is used to set the colour replacement mode. When part of the
picture is drawn on the Charles terminal the user can choose 3 modes of
colour replacement by the use of this command. The required mode of
replacement is specified by the X parameter. Mode 0 is 'replace' mode,
where the colour currently selected is used regardless of which colour is
currently at the point. Mode 0 is the default. Mode 1 causes the
currently selected colour number, to be ANDed with the colour number which
is currently at the point, and the resulting colour number is used as the
colour which the point is to be. Mode 2 is similar to mode 1, but the
colour numbers are ORed together.
routine END MODE
This routine is used to end the currently selected mode. This routine
is not required by users unless they wish to change the Charles driving
modes themselves.
routine SET COLOUR MAP (integer REG, RED, BLUE, GREEN)
This sets one of the 16 colour registers, given by the value of REG, (0
to 15), to be the colour given by the appropriate proportions of the three
primary colours. Each colour should be specified with a value in the range
of 0 to 15.
routine C BIT PAD POS (integer name X, Y)
This routine returns the current position of the BIT PAD cursor in X and
Y. These are in device units, ie. in the range 0 to 511, which can be
mapped to the current virtual coordinates by the routine
MAP TO VIRTUAL COORDS
routine C CURSOR (integer name STATE, X, Y)
This routine waits for the next button change to occur on the BIT PAD,
and the parameter STATE is set to the current value of the buttons, and the
parameters X and Y are set to the current device position.
The Cursor Addressable Terminal drivers
The main driver for Cursor Addressable Terminals was written for
terminals made by Visual Technology Inc. called Visual 200s. These
terminals are DEC VT52 compatible. In addition the driver has been
extended to drive a number of other Cursor Addressable Terminals such as
the Perkin-Elmer 550 terminal and the Soroc IQ120 terminal. All these
terminals have the drawback of having very poor resolution for general
purpose graphics. However, this has to be traded off with the very high
availability of these terminals. The default and maximum settings of
viewport are 0 to 79 in the X direction, and 0 to 23 in the Y direction.
If low quality text is used with the Cursor Addressable Terminal driver,
then the normal terminal text is used. Software characters are available,
but rapidly fill the screen. Users must use the routine UPDATE if they
wish to mix program interaction with drawing. The only other attribute
which is available is line style. Style 0 is the 'best' graphics
approximation to lines that the terminal can provide, for example the
Visual 200 graphics primitives allow line segments from the centre to the
four boundaries of each character position, and the Perkin-Elmer terminals
have a 'splodge' character. If the other line styles are selected then the
lines are drawn by the characters '-', '#', '+', '*' (for styles 1 to 4)
respectively. Any other style selected causes an asterix to be used, which
is also the default character used if the device has no graphics character
set. In the case of the Visual 200 the routine SET CHAR FONT may be used
to select the alternate character set, but this has no effect on other
terminals. (The alternative character set is used if a non-zero setting of
the character font is specified). All other attribute setting commands are
ignored.
Since the driver is concerned with manipulating points on a character
grid it can be used for any hard copy terminal or line printer. In this
case the characters are stored in the character map of the screen and sent
to the terminal when the EDWIN routine UPDATE is called. The default
viewport for line printers is 0 to 131 in X and 0 to 63 in Y.
The following table summarises the devices which can be driven by this
driver and the number which should be given to select them at
initialisation.
Device No. for INIT Default/Max Viewport Cursor?
Visual 200 200 0 - 79 x 0 - 23 Yes
VT52 52 0 - 79 x 0 - 23 Yes
Perkin-Elmer 550 550 0 - 79 x 0 - 23 Yes
Soroc IQ 120 120 0 - 79 x 0 - 23 Yes
Hazeltine Esprit 'E' (69) 0 - 79 x 0 - 23 Yes
General video/h.copy 'V' (86) 0 - 79 x 0 - 23 No
Line printer 'L' (76) 0 - 131 x 0 - 63 No
Routines specific to the Cursor Addressable Terminal Drivers
routine CATS (integer COM, X, Y)
This is the two terminal driver that is described above. The commands
are the same as for the standard device driver described previously.
routine V CURSOR (integer name STATUS, X, Y)
If the terminal is a true cursor addressable terminal then the
programmer can call the routine CURSOR which then allows the user to move
the current position marker about the screen. This is usually done by
means of cursor control keys with the exception of the Perkin-Elmer
terminal and Hazeltine Esrit where the following keys have to be used -
BACK SPACE = cursor left TAB = cursor right
LINE FEED = cursor down DEL = cursor up
Cursor mode is terminated by pressing any non-control character. The ISO
value of this character is returned in the variable STATUS, and the current
screen point is returned in the parameters X any Y.
The CURSOR routines are NOT available on the EMAS implementation of
EDWIN.
The H P terminal driver
The Hewlett-Packard terminal driver drives the HP model 2648A
raster-scan graphics terminal. This terminal can be used as a standard
terminal connected to a computer in a similar manner to Tektronix
terminals, but it also has an array of points which can allow diagrams to
be drawn. The array of screen points is 720 in X by 360 in Y, which gives
the default, and maximum, setting of Viewport to be 0 to 719 in X, and 0 to
359 in Y.
The terminal has two character sets. The first of these is used when
the terminal is in normal text conversation with the host machine, and the
other set, which has a range of 8 sizes between 4 and 53 screen units, is
generated by the routine CHARACTER. The terminal has a hardware zoom
facility which can be used on the picture and the second of the character
sets described above. The routine UPDATE should be used to force the
terminal to use the lower quality character set. The terminal character
set may be changed to italics by the use of the EDWIN routine SET CHAR FONT
with a non-zero parameter.
The range of line styles which are described in the documentation of the
routine SET LINE STYLE are all supported. Line styles, character size and
font are the only attributes described in section D which are supported by
the terminal.
The terminal has a tracking cross which may be invoked by the EDWIN
routine CURSOR. This may be moved about the screen by means of four cursor
control keys. Any keyboard character may be used to terminate cursor mode,
and the ascii value of the character which is typed is returned as the
'status' when cursor mode is terminated.
Routines specific to the HP 2648A terminal driver -
routine HP 2648A (integer COM, X, Y)
This is the device driver, which only accepts the standard device driver
commands which have been described previously.
routine H CURSOR (integer name STATUS, X, Y)
This evokes the terminals tracking cross, and returns the key which was
used to terminate cursor mode in STATUS, and the current device coordinates
of the tracking cross in X and Y.
The H P plotter driver
The Hewlett-Packard plotter driver drives the HP model 7221 flat bed
plotter. This takes sheets of paper up to size A3. The plotter has a
terminal connected to it, and the plotter sits between the computer being
used and the terminal in 'transparent mode', ie. the plotter has no
noticeable effect on the use of the terminal. Under program control the
plotter may be placed in 'plotting mode', and all output sent to the
plotter is interpreted as graphics protocol.
The following is the procedure for using the plotter: Switch on the
plotter at the switch on the front of the plotter, and switch on the
terminal. The plotter will be in transparent mode, which allows the user
to log on to the system which they wish to use. Before drawing any
pictures it is recommended that users disable messages from being sent by
other users or operators, as these give rise to random lines over plots!
Users are referred to the system documentation of the system that they are
using for details of how this is done. Paper is loaded by pressing the
'CHART LOAD' button, then laying the paper flat on the bed of the plotter,
and pressing the 'CHART HOLD' button. The paper is held down
electrostatically. No other buttons on the front need to be used when
using EDWIN to drive the plotter. If the EDWIN routine NEWFRAME is called,
the string "Enter new sheet of paper, type YES to continue", appears
followed by the prompt "ready?". The user must type YES or Y to continue,
after adding a new sheet of paper. If a user wishes to escape from a
program which is plotting, they must press the BREAK key on the terminal,
followed by the appropriate key to attract the computer's attention.
The HP plotter has 4 pens which are chosen by the EDWIN routine SET
COLOUR, and are picked up by the plotter automatically. The plotter has 6
built-in character sets. The primary character set (set 0) is used by
default, but the others may be nominated the routine SET CHAR FONT, with
the values 0 to 5 selecting the set required. Users are referred to the
plotter manual for a full description of all the character sets. The EDWIN
driver also produces 5 line styles on the plotter, as described for the
routine SET LINE STYLE.
The default values for the viewport are 0 to 11200 in the X direction
and 0 to 8000 in the Y direction, which is the size of A4 paper. The
maximum viewport is 0 to 16000 in the X direction, and 0 to 14000 in the Y
direction. One device unit is 0.0025 cm. The following calls to viewport
set the paper size to be A4 and A3 respectivly -
VIEWPORT (0, 28 * 400, 0, 20 * 400); ! For A4 (28 cm x 20 cm)
VIEWPORT (0, 40 * 400, 0, 28 * 400); ! For A3 (40 cm x 28 cm)
The EDWIN routine CURSOR is available on the HP plotter, and its use is
described in the documentation for the routine P CURSOR on the next page.
If users require to use the terminal attached to the plotter for any
input or output during the drawing of a picture, the routine UPDATE must be
called to ensure that the plotter is set to transparent mode.
Routines specific to the HP Plotter driver
routine P7221 (integer COM, X, Y)
This routine is the plotter driver. The commands accepted are the same
as the general device driver discussed previously.
routine HP AC ARC (integer RAD, IA, FA)
This routine draws an anti-clockwise arc of radius RAD, from an initial
angle of IA to a final angle FA (both angles specified in degrees) centered
on the current point.
routine HP C ARC (integer RAD, IA, FA)
This routine is the same as the routine HP AC ARC, except that a
clockwise arc is used.
routine HP CIRCLE (integer RAD)
A circle of radius RAD is drawn centred on the current position. Note
that RAD should be specified in device co-ordinates.
routine HP SPEED (integer SPEED)
This routine sets the speed at which the plotter draws lines. The
default is that it draws lines at 36 cm/s, the fastest speed: but this may
be reduced if the pens are old. A speed of 10 cm/s is recommended for the
plotting of overhead projection slides.
routine P CURSOR (integer name STATE, X, Y)
Once this routine is called, the pen assembly can be moved about by the
buttons on the front of the plotter surrounding the ENTER button. When the
pen has been positioned in the desired place, the ENTER button is pressed,
and the plotter sends the current state, which consists of whether the pen
is up or down, followed by which pen is selected: (UPDOWN*16!PEN). UPDOWN
is 0 if the pen is up, and 1 if the pen is down. PEN refers to the current
slot which is empty, which is 5 minus the current EDWIN colour number. The
X and Y coordinates are returned in device coordinates.
The Printronix printer driver
The Printronix printer driver is designed to produce pictures on matrix
line printers which are made by Printronix. Such printers can be accessed
from the VAX, Mouses, and EMAS systems. In normal mode the printer prints
a page of 64 rows by 132 characters on a page, but when placed in matrix
mode the printer treats the page as an array of 780 x 780 points. If the
printer is being used by EDWIN, the picture is entered into a bit map of
the page as it is drawn, and this is sent to the printer when NEW FRAME or
TERMINATE EDWIN is called when the dot matrix is not all empty.
When the Printronix driver is initialised the output is sent to stream
one if the user has not previously called VIEW ON with the stream that he
wishes to use. After the graphics program has completed, the user should
send the file produced to the printer in the following way -
a) Mouses
COPY <file> / LP:
b) EMAS
LIST <file> , .LP?? where ?? can currently be 15, 41 or 78
c) VAX
i) PRINT <file>
ii) Send the file to an ERCC printer with the command NETFS.
Users should note that the routine VIEWPORT must be used if the printer
that they are using is fitted with paper of width 132, which is the default
assumed by the EDWIN driver.
The driver is present as
routine P300 (integer COM, X, Y)
which only accepts the standard device driver commands. The picture is
only drawn in black, and there are no alternate line styles available. If
characters are used these are all drawn as characters of quality 1 owing to
difficulties in mixing the printer's character set with arbitrary pictures.
The Tektronix device driver
The Tektronix device driver is designed to drive the Tektronix 4000
series storage tubes, and also drives ADM3A terminals when they are fitted
with the Tektronix graphics option card. The Tektronix terminals are
'storage tubes', which means that once a picture has been drawn, any
changes to the picture can only be shown by completely erasing the screen,
and drawing the altered picture.
The terminals operate in two distinct modes. The first of these is
'Graph mode', where the screen is addresed as an array of 1023 x 1023
points (of which only the points whose Y coordinates are in the range 0 to
779 are visible). The Tektronix hardware allows the beam to be positioned
at a specific point, and then allows vectors to be drawn to other points.
The other mode is 'alpha-numeric mode', in which the Tektronix simulates a
normal terminal. In this mode the user must explicitly clear the screen
periodically by the use of the ERASE and HOME keys for 4002s, SHIFT and
CLEAR keys for the ADM3A, and PAGE or PAGE RESET for the other models. It
is also necessary to clear the screen when a Tektronix is first switched
on. EDWIN automatically ensures that the terminal is in the correct mode
for the function that it is to perform, but the routine UPDATE may be used
to force the terminal into alpha-numeric mode.
If the display is not altered for a while, the Tektronix reduces the
intensity of the display to avoid damage to the screen. The normal
intensity is restored by pressing the VIEW key on the 4002 or any key (eg.
the SHIFT key) on the later models.
Some models in the range of Tektronix terminals support a cross-hair
cursor which users can use to interact with their program. The cursor
appears when the EDWIN routine CURSOR is called, and the user can then move
the cursor around the screen by means of a joystick or thumb wheels
(depending on the type of Tektronix being used). When the user hits a key
on the terminal the cursor disappears and the routine CURSOR returns the
ISO value of the key struck in STATUS and the virtual coordinates of the
cursor in the parameters X and Y. A control character should not be used
to terminate cursor mode, as this can cause problems with some operating
systems.
Routines specific to the Tektronix driver
routine T4000 (integer COM, X, Y)
This routine is the Tektronix device driver. The parameters are the
same as those of the general device driver described on page 14.
routine T CURSOR (integer name CHAR, X, Y)
This routine has the same effect as the general EDWIN CURSOR routine,
but the coordinates of X and Y are returned in device coordinates, rather
than virtual coordinates. The parameter CHAR is set to the ISO value of
the key struck to terminate cursor mode.
The maximum size of VIEWPORT is 0 to 1023 in both the X and Y
directions, and this is also the default. Note that only Y coordinates in
the range 0 to 779 are visible. In the case of the model 4014 the default
viewport is also 0 to 1023 in both the X and Y directions which maps onto
the whole screen, but if the terminal is being driven in enhanced mode, the
maximum size of viewport becomes 0 to 4095 in X and Y, of which Y
coordinates in the range 0 to 3209 are visible. Enhanced mode is
automaticaly entered if a Tektronix 4014 has an upper viewport bound of
more than 1023 set.
The details of each model are: -
4002
These have upper and lower case, and two hardware character sizes of 12
and 24 units respectively. The cursor is controlled by an external joy
stick if one is provided.
4006
These terminals are upper case only, with no adjustable attributes, and
have no cursor.
4010
These terminals are identical to the model 4006 except that they have a
cursor, which is controlled by means of thumb wheels.
4012
These terminals are identical to the 4010, with the addition of a lower
case character set.
4014
These terminals have upper and lower case, 5 line styles, 4 character
sizes of 14, 12.75, 8.5, 7.5 screen units. The largest of these is
selected when the terminal is switched on, and the character size desired
can be selected by entering local mode, and typing ESCAPE followed by '8',
'9', ':', or ';' to set the respective sizes mentioned above. When EDWIN
initialises for a 4014 the 12.75 character size is selected, which means
that drawings will have a similar size of character to that which they
would have if they were running on other models in the range, and TERMINATE
EDWIN resets to the smallest size, as this is what most users prefer. The
enhanced resolution available on the model 4014 has been mentioned
previously.
ADM 3A (made by Lear Siegler inc.)
This terminal is similar to a 4006, 4010 or 4012 depending on whether it
has been fitted with a lower case option. They have no cursor. Any of the
model numbers mentioned may be used to initialise this terminal.
The VT15 device driver
This device driver controls the VT15 graphics processor which is a
PDP-15 option. This processor controls VT04 displays, which are line
drawing refresh displays. The picture is continually being redrawn by the
VT15 processor, while the PDP-15 runs a program which interacts with the
VT15.
The VT15 driver can be used in two ways. The first of these is to write
a program for the PDP-15 which uses EDWIN. This approach is not
recommended, as the user is likely to run into problems with the amount of
store available for his program, and has also to work with a subset of the
IMP language. The other approach is to give the command .VTSAT on the
PDP-15, and then the PDP-15 can be used as a satellite from VAX. The
device type 15 should be given to initialise for the VT15 device driver.
The VT04 terminals have 0 to 1023 points in both the X and Y directions,
and this is the default and maximum view of the viewport. They have a set
of seven intensities, of which 5 is the default. There are four line
styles, the standard EDWIN set with the exception of 'chain lines'.
Although there is a limited hardware character set EDWIN does not make use
of it, as it has no lower case, and the characters are of very low quality.
All characters are thus drawn as EDWIN software characters. The VT15
driver provides a simulated cursor on the VT04 by displaying a tracking
cross, and the user can use the light pen to indicate points on the screen.
The routine CURSOR returns control to the user program with the current X
and Y coordinates in the parameters X and Y, after 30 seconds with no
initial light pen hit, or 5 seconds since the last light pen hit. The
STATUS value which the cursor returns is the binary value of the six
buttons on the VT04 terminal.
Routines specific to the VT15 driver
routine VT15 (integer COM, X, Y)
This is the VT15 device driver, which accepts the instructions which
were mentioned for the general device driver, and also a set of
instructions having command code 12, which allow the full use of the VT15
hardware facilities. The X coordinate defines which function is desired,
and the Y parameter is ignored.
STOP VT - VT15 (12, 1, 0)
START VT - VT15 (12, 2, 0)
These routines can be used to explicitly stop, and start the VT15
processor. An example of their use is when the user wants to draw all of a
picture, and then have it appear on the VT04 terminal suddenly, without a
slow buildup. In this case they would call STOP VT after initialising,
then draw the picture and finaly call START VT.
ENABLE PEN - VT15 (12, 3, 0)
DISABLE PEN - VT15 (12, 4, 0)
These routines determine whether any lines drawn are sensitive to the
light pen. The default is that lines will not be noticed by the light pen.
ENABLE BLINK - VT15 (12, 5, 0)
DISABLE BLINK - VT15 (12, 6, 0)
The VT15 has a hardware blink feature, which may be enabled, and
disabled by the above calls to VT15. The default is for the blinking to be
disabled. If blinking is enabled, all lines drawn afterwards will blink.
If the blinking is to be stopped, the picture will have to be cleared and
redrawn by the use of NEWFRAME.
routine V CURSOR (integer name STATE, X, Y)
This routine is similar to the EDWIN CURSOR routine for the VT15, except
that the X and Y values are returned in device coordinates. The integer
STATE contains the logical OR of the sets of six buttons on each VT04
console. If the parameters to this routine are assigned, then the tracking
cross appears at this point on the screen.
routine TRACK (integer name X , Y)
This routine may be used to display the tracking cross, but to return
after the first light pen hit, or a 30 second time out. It can
consequently be used to interact with programs in a more immediate way than
the routine CURSOR. The coordinates X and Y are returned in device
coordinates. An example of the use of TRACK would be in a program which
was only interested in a light pen hit which was within a certain area.
TRACK (X, Y) until X<20 and 10<=Y<=100
integer fn VT BUTTONS
This function returns the value of the six buttons on the front of the
VT04 display. Note that it is the logical OR of buttons on all displays.
Bits are set to 1 if the button light is on, and the most significant bit
(32) is the left hand button.
Users of the VT15 who wish to have 'moving' pictures are referred to the
device specific package, 'SOGGY' [27].
A set of geometric utility routines
The routines described in this section provide the user with a standard
set of routines for drawing geometric shapes on any of the EDWIN devices.
It must be emphasised that there is nothing 'magic' about these routines,
and that any user could write them. Also although this set of routines is
described in the EDWIN users guide, it is not strictly part of EDWIN, and
cannot be assumed to be present in every EDWIN library. In particular, it
is not possible to provide the routines in this section on machines which
cannot perform floating point arithmetic. All the routines in this section
are designed to generate closed shapes, and on devices such as CHARLES,
these closed shapes are automaticaly shaded. On devices which have no
automatic shading only the outline of the resulting shape is drawn. All
the routines clip the resulting polygon, if clipping is enabled. The
routines make as much use of device specific features as possible, (eg.
using hardware circles on the HP plotter) while retaining the device
independence of the picture.
All the routines assume the following record format has been declared -
record format POINTF (integer X, Y)
Owing to that fact that the routines in this section are not strictly
part of the EDWIN package, the following routines must be explicitly
declared.
routine POLYGON (integer NUM ELE, record (POINTF) array name PTS)
This routine draws an arbitary polygon, on the current device. The
polgon is assumed to be defined by the set of points PTS(1) to
PTS(NUM ELE). The polygon need not be closed. VAX Pascal users should see
the section on cross-calling for details of how to access this routine.
The polygon is clipped to the current window by default. Clipping entails
a significant expenditure of CPU time, so that if all the polygons to be
drawn are known to be inside the current window, and there are a large
number to draw, then the routine CLIP OFF may be called to suppress
clipping. Clipping is enabled again by calling the routine CLIP ON.
routine S BOX (record (POINTF) name L, U)
This routine draws a Simple BOX, ie. one which is orthogonal to the
axes. This can often be done faster and more simply than for the general
box drawing routine which is described below. L and U are assumed to
represent the lower left and upper right corners of the box, but they are
swapped if they have been specified in the wrong order.
routine BOX (integer L, W, record (POINTF) name C, D)
This routine draws an arbitary box, with length L, width W and centre C,
with D representing a direction vector. The box is rotated so that side L
lies in the direction given by the direction vector. A direction vector of
(1,3) would result in the box having an anti-clockwise rotation of 60
degrees applied about its centre before it is drawn. The box is converted
to a polygon for clipping and drawing.
routine FLASH (record (POINTF) name C, integer D)
This routine draws a round circle with diameter D centered at the point
C. If the device does not have a hardware circle primitive, then the
number of sides used can be set by the following routine. The default
number of sides is 8.
routine SET FLASH POINTS (integer SIDES)
This routine decides how many sides a flash should be drawn with if the
flash has to be converted to a polygon. The default number of sides is 8,
and this is the minimum number of sides which may be set. The maximum
number of sides is 100, and any attempt to try to use more sides results in
100 being used. The user must choose SIDES to give as round a circle as
possible, but a large choice of SIDES results in longer plot times. This
routine is also used to enable an alternative drawing mode of the routine
WIRE, which is described below.
routine WIRE (integer W, N, record (POINTF) array name PTS)
The array PTS is assumed to define a 'wire' from PTS(1) to PTS(N). The
strict definition of a wire is the area which is covered by moving a circle
of width W along the set of points defined by the array PTS. This results
in the wire having a rounded ends, and rounded corners. As this would be
time consuming to plot, the default mode of drawing wires is to extend the
wire at the ends and convert the wire to a polygon, and draw it. If a user
wishes to use the strict definition of WIRE he can set the number of flash
points by the routine SET FLASH POINTS, and then wires are drawn as a
series of boxes, with round flashes superimposed at the junctions. VAX
Pascal users should see the section on cross calling of Pascal and IMP for
details of how to access this routine.
A transformation stack
The following routines may be used to provide a graphics program with a
transformation stack for a two dimensional coordinate system. The routines
come under two headings,
a) Routines for creating transformation matrices
b) Routines for manipulating the transformation stack
The transformation stack routines are only available on versions of EDWIN
which are running on machines with floating point arithmetic, and any
routines which are used from this section require explicit declarations.
The routines in this section may not be cross called from most other
langages, but users are referred to the system library manuals of the
machine which they are using if they wish to check. The transformation
matrices which these routines work on are described in more detail in
Newman and Sproull [28]. All the arrays for the following routines are
addressed from 0 to 8, and these are assumed to represent matrices of the
following format -
( 0 1 2 )
( 3 4 5 )
( 6 7 8 )
a) Routines to create transformation matrices -
routine M TRANSLATE (integer X, Y, real array name TX)
This routine sets the array TX to be the transformation which will
translate a point (a, b) to a point (a', b') such that -
a' = a + x
b' = b + y
routine M MX (real array name TX)
This routine sets the array TX to be the transformation which mirrors a
point in the X axis. eg.
a' = - a
b' = b
routine M MY (real array name TX)
This routine sets the array TX to be the transformation which mirrors a
point in the Y axis. eg.
a' = a
b' = - b
routine M ROTATE (integer X, Y, real array name TX)
This routine sets the array TX to be the transformation which is a
rotation, the value of which is specified by the direction vector (X, Y),
and Z = SQRT( X * X + Y * Y).
a' = (X/Z) * a + (-Y/Z) * b
b' = (Y/Z) * a + (X/Z) * b
b) Routines to manipulate the transformation stack
routine INIT TRANS
This initialises the transformation stack module. It is automatically
called if there is an attempt to add a transformation to the stack when it
has not been initialised. The base element of the stack is set to be a
null transformation, (ie. the unit matrix).
routine PUSH TRANS (real array name TX)
This routine pushes the transformation TX onto the stack, by multiplying
the transformation with the transformation which was previously top of the
stack. EDWIN error 10 is signalled if the stack overflows. The stack
limit is currently set to be 25 matrices.
routine POP TRANS (real array name TX)
The transformation at the top of the stack is discarded, and the one
which is now at the top of the stack becomes the current transformation.
EDWIN error 9 is signalled if an attempt is made to pop a transformation
before the stack is initialised, and EDWIN error 11 is signalled if the
user attempts to pop more transformations than have been pushed.
routine INQUIRE TRANSFORM (real array name TX)
This routine sets TX to be the transformation at the top of the stack.
In this way a compound transformation can be stored and later restored by
pushing it onto the stack, (when the current transformation is unity) to be
used as the current transformation.
routine TRANSFORM POINT (record (POINTF) name P, NP)
This routine transforms the point P to the point NP under the current
transformation. Addressing the current transformation as array A, the
effect of this routine is
NP_X = A(0) * X + A(3) * Y + A(6)
NP_Y = A(1) * X + A(4) * Y + A(7)
routine TRANSFORM VECTOR (record (POINTF) name V, NV)
This routine transforms the direction vector V to the vector NV under
the current transformation. The effect is the same as for the routine
TRANSFORM POINT, except that the displacement in A(6) and A(7) is not added
in.
Accessing EDWIN
a) Under VMS on the VAX-11/780
Users should add the command GRAPHSETUP in their LOGIN.COM files
to set up the aliasses described in this guide.
The file $EDWIN:.INC contains the routine specs (see appendix B).
Graphics programs should be linked by the commands -
LINK PROG,$EDWIN/OPT
or SLINK PROG,$EDWIN/OPT for IMP with streams
The VAX version of EDWIN contains device drivers -
C963 CATS CHAS HP2648 P300 P7221 T4000
b) Under EMAS on the ICL 2900 range
The file CONLIB.EDWIN_INC contains the routine specs.
The EDWIN library is made available by executing the command
OPTION SEARCHDIR=CONLIB.EDWINDIR
The EMAS version of EDWIN contains device drivers -
C963 CATS CHAS HP2648 P300 P7221 T4000
While initialising, EDWIN automatically sets graphics mode if
a terminal is being used.
c) Under MOUSES on the Perkin-Elmer machines.
The file EDWIN:EDWIN.INC contains the routine specs.
EDWIN is made available by the command -
LIB EDWIN:EDWIN
The MOUSES version of EDWIN contains device drivers -
CATS P300 T4000
d) Under RSX-11/M on PDP-11s
The file LB:[1,1]EDWIN.INC contains the routine specs.
The library is automatically searched by the task builder, so no
special action is necessary for linking.
The RSX-11/M version of EDWIN contains device drivers -
HP2648 CATS T4000
e) Under ISYS on the Interdata series 70
The file EDWIN.EDWIN:INC contains the routine specs.
Graphics programs should be linked by the command -
LINK program,EDWIN.EDWINLIB
This version currently only supports a CATs driver.
f) Under the IMP15 system on PDP-15s
Graphics programs should be compiled with the command -
C .EDWIN+prog/obj,map
where .EDWIN contains the initial begin, and EDWIN is added to
the program in source form. The limited PDP-15 library mechanism
prevents the use of external routines. This version of EDWIN
only contains a driver for the VT15s.
The command .VTSAT is used to run the satellite software,
allowing the VT15s to be used from VAX.
There are space problems in fitting EDWIN into the PDP-15 as
there is a limit of 8K on the program size. If the array
describing software characters is declared as own then this would
count as 2000 words of code, but if it is just a normal array it
does not count as code. For this reason on the PDP-15 the
routine SET CHAR PDF must be used, and this reads the software
character definitions into an internal array from the current
input stream. For example if stream 3 was selected before SET
CHAR PDF was called then the program would be run on the PDP-15
by the command
R <stream1>,<stream2>,.CHAR PDF/any outputs
Cross calling EDWIN from other languages
On machines such as VAX, MOUSES, and EMAS where there are a number of
compilers for different languages which conform to a standard format of
object file, any of the compilers may be used to write graphics programs
using the EDWIN library. Users are referred to the system library
manuals of the system which they are using for the information which is
applicable to their machine, but some details of the use of EDWIN from
Fortran and Pascal are given below.
a) Fortran
In Fortran all subroutines are defined to have reference-type
parameters, (ie. in IMP terms only integer name parameters can be used).
To allow Fortran programs to access EDWIN a number of interface routines
have been provided, with the same function as described elsewhere in
this guide, but with different names, and parameter passing modes.
Subroutines with no parameters, or only name type parameters, may be
called directly. The following routines are provided -
Fortran name IMP name
INIT FOR INITIALISE FOR
MOVE A MOVE ABS
MOVE R MOVE REL
LINE A LINE ABS
LINE R LINE REL
MARK A MARKER ABS
MARK R MARKER REL
CHAR CHARACTER
STR ON STORE ON
V ON VIEW ON
ASPECT RAT ASPECT RATIOING
F WINDOW WINDOW
F VIEW PORT VIEW PORT
All the attribute routines described in section D have the word SET
replaced by the letter S. (eg. SET COLOUR becomes S COLOUR).
All other device specific routines which are not directly callable
from Fortran have the routine name prefixed by the letter 'F'.
Note that the versions of Fortran on VAX, MOUSES and EMAS do not
impose a limit of 6 characters in names.
b) Pascal
In general the IMP routine specification is converted to the Pascal
procedure spec as shown by the following example.
external routine spec INITIALISE FOR (integer DEV)
becomes
procedure INITIALISEFOR (DEV : integer ); extern;
The files '$EDWIN:.PAS', 'CONLIB.EDWINPAS' and 'EDWIN:EDWIN.PAS' on
VAX, EMAS and MOUSES respectivly contain a full set of the EDWIN
procedure declarations in the required Pascal format for the machine
which they are using. Users can edit these files into their own Pascal
programs.
In the case of VAX, external Pascal procedures have different
parameter passing formats from external IMP routines, but this is
catered for in the file $EDWIN:.PAS. On VAX the Pascal compiler allows
the statement
%include '$EDWIN:.PAS'
and this should be used (with no ';') rather than users declaring their
own external procedures. It should be placed after any declarations and
before the initial begin. Programs should be linked with $EDWIN/OPT as
described in the previous section.
VAX users are referred to the format of the file $EDWIN:.PAS if they
need to declare any of the machine/device specific routines. If the VAX
user wishes to use the routines WIRE or POLYGON, owing to the way that
arrays are passed between IMP and Pascal they should use the routines
PASWIRE and PASPOLYGON which convert the parameters to the appropriate
IMP call. The following example shows the calling of the procedure
PASPOLYGON -
program skeleton (input, output)
type pointf = record
x, y : integer;
end;
pointa = array [0..10] of pointf;
{ note the user must choose the max size at compile time}
var p : pointa;
i : integer;
%include '$edwin:.pas'
procedure paspolygon (%immed numpts : integer; var parray : pot); extern;
begin
initialisefor (ord('C')); { Charles}
newframe;
{ fill in points 1 to 10 of P, set I to be the number used}
paspolygon (i, p);
terminateedwin
end.
Use of the VIEWPDF program
This utility can be used to view pictures which have been dumped by
the storing feature of EDWIN. The form of the command is -
VIEWPDF picture/outfile
where 'picture' is a picture produced by the use of the EDWIN routine
"STORE ON", and 'outfile' is an optional file which is used for
printronix output.
The program starts by prompting "Device type: ", (with the exception
of the PDP-15 version, which only draws on the VT15), and the number of
a valid EDWIN device should be given. If the device is a plotter, the
user is also prompted for the size of plot. This should be a number of
centimeters. If one number is given on the line then a square viewport
is set, otherwise the two numbers specify the X and Y sizes of the plot
respectivly.
The program then interprets the instructions describing the picture,
until either an end of picture instruction (produced by TERMINATE EDWIN)
or a NEWFRAME instruction is encountered. The program then prompts
"Another?", and if the response "N" or "NO" is received, the program
stops, otherwise the program continues hoping to find another picture
description on stream one. The program automatically stops if the
picture description runs out.
Notes -
a) Each picture is self defined, and any number of pictures can be
joined together in one file.
b) This provides a useful method of plotting pictures, without wasting
plotter paper and time on unwanted plots.
Accessing the VIEWPDF program on the different implementations -
VIEWPDF pic/file under VMS
VIEWPDF pic/.LP15 under EMAS
EDWIN:VIEWPDF pic/file under MOUSES
EDWIN.VIEWPDF pic under ISYS
.VIEW pic on the PDP-15/40
Use of the PDFDEC program
This utility can be used to decode a PDF into a HEX dump and an IMP
program. The form of the command is
PDFDEC pdf/decode
where the program is called in the same manner as the VIEWPDF program
described above. Although the program is mainly designed for the
inspection of PDFs, a number of users have found it useful for
recreating programs to draw pictures. The program terminates when the
file ends, or if the PDF is found to be corrupt.
Appendix A : EDWIN error messages
Errors with EDWIN are reported by the IMP77 signal mechanism. Event
14 is signalled, with the sub event giving which of the following errors
occurred. These events may be trapped and then analysed by the IMP
event trapping mechanism.
Error number Description:
0 Device driver initialisation fails.
1 No room left in VT15 display file.
2 Internal error in the device driver.
5 Attempting to review a corrupt PDF.
6 Trying to change an undefined attribute.
7 Internal error in the geometric routines.
8 There is no CURSOR on currently selected device.
9 Transformation stack not intialised.
10 Transformation stack underflow, ie. too many POPs.
11 Transformation stack overflow.
In general EDWIN tries to avoid giving up. Examples of this are if a
viewport outside the coordinate range is given, the largest one that the
device supports is used, and any attempt to draw software control
characters is ignored.
If a program wishes to find out what error is meant by a given number
then the following function returns a text description of what is meant
for each error.
string (63) function EDWIN ERROR (integer NUM)
Appendix B : Listing of the normal EDWIN procedure specs
! EDWIN routine specs added.
end of list
!
! Routines for initialisation and termination
external routine spec INITIALISE FOR (integer DEVICE TYPE)
external routine spec TERMINATE EDWIN
!
! Output primitives
external routine spec MOVE ABS (integer X,Y)
external routine spec MOVE REL (integer DX,DY)
external routine spec LINE ABS (integer X,Y)
external routine spec LINE REL (integer DX,DY)
external routine spec MARKER ABS (integer N,X,Y)
external routine spec MARKER REL (integer N,DX,DY)
external routine spec CHARACTER (integer SYM)
external routine spec TEXT (string (255) ST)
!
! Control
external routine spec NEW FRAME
external routine spec UPDATE
external routine spec CLIP ON
external routine spec CLIP OFF
external routine spec STORE ON (integer STREAM)
external routine spec STORE OFF
external routine spec VIEW ON (integer STREAM)
external routine spec VIEW OFF
external routine spec ASPECT RATIOING (integer MODE)
external routine spec WINDOW (integer XL, XR, YB, YT)
external routine spec VIEWPORT (integer XL, XR, YB, YT)
!
! Attributes
external routine spec SET COLOUR (integer COLOUR)
external routine spec SET LINE STYLE (integer STYLE)
external routine spec SET INTENSITY (integer BRIGHTNESS)
external routine spec SET CHAR SIZE (integer SIZE)
external routine spec SET CHAR ROT (integer ROT)
external routine spec SET CHAR QUALITY (integer WHICH)
external routine spec SET CHAR FONT (integer WHICH)
external routine spec SET CHAR SLANT (integer ANGLE)
!
! Miscellaneous routines
external routine spec REVIEW
external routine spec INQUIRE POSITION (integer name X,Y)
external routine spec INQUIRE WINDOW (integer name XL,XR,YB,YT)
external routine spec INQUIRE VIEWPORT (integer name XL,XR,YB,YT)
external routine spec MAP TO DEVICE COORDS (integer name X,Y)
external routine spec MAP TO VIRTUAL COORDS (integer name X,Y)
external routine spec CURSOR (integer name STATE,X,Y)
external string (31) fn spec DEVICE NAME
external string (63) fn spec EDWIN ERROR (integer N)
external integer fn spec DEFAULT DEVICE
external routine spec DRIVE DEV (integer COM, X, Y)
!
list
end of file
Appendix C : The EDWIN software character set
Appendix D : Some Example programs
Note that the IMP %include statement causes 3 lines to appear in the
listing which are NOT part of the source file.
ERCC. Imp80 Compiler Release 1 Version 27 May 81
255 765
1 include "CONLIB.EDWIN_INC"
2 ! EDWIN routine specs added.
3 end of list
56 end of file
57 external routine spec PROMPT (string (15) S)
58 begin
59
60 ! EDWIN test program 1
61 ! This program tests the ability to draw lines and to read the cursor.
62 ! The program reads four cursor locations, and then joins these by
63 ! a mesh of lines.
64 ! This is repeated until 'S' is the key hit in response to the cursor.
65
66 const integer NUM = 10
67 integer I,CVAL,TYPE
68 integer array X,Y (1:4)
69
70 PROMPT ("Device Type:")
71 READ (TYPE)
72 INITIALISE FOR (TYPE)
73
74 NEW FRAME; ! This clears the screen
75
76 cycle
77 for I=1,1,4 cycle
78 ! This cycle reads the 4 points defining the two primary lines.
79 CURSOR (CVAL, X(I) , Y(I))
80 exit if CVAL = 'S' or CVAL = 's' ;! This stops the program.
81 if I&1=1 then MOVE ABS(X(I),Y(I)) else LINE ABS (X(I),Y(I))
82 repeat
83
84 exit if CVAL = 'S' or CVAL = 's'
85
86 ! Now the points on these lines are joined up.
87
88 for I=0,1,NUM cycle
89 MOVEABS (X(1) + I*(X(2)-X(1))//NUM, Y(1) + I*(Y(2)-Y(1))//NUM)
90 LINEABS (X(3) + I*(X(4)-X(3))//NUM, Y(3) + I*(Y(4)-Y(3))//NUM)
91 repeat
92 repeat
93
94 TERMINATE EDWIN
95
96 end of program
96 LINES ANALYSED IN 458 MSECS - SIZE= 2288
CODE 1096 BYTES GLAP 376+ 0 BYTES DIAG TABLES 104 BYTES
TOTAL 1576 BYTES
80 STATEMENTS COMPILED IN 1047 MSECS
Computer Science IMP-77 Compiler. Version 4.17
1 include "EDWIN.EDWIN:INC"
& ! EDWIN routine specs added.
& end of list
& end of file
2 begin
3
4 ! EDWIN test program 2
5 ! This tests some of the attribute commands, for altering colour,
6 ! line style, and character size.
7 ! The picture is designed to show how windowing in EDWIN operates.
8 ! It is best run on a 4014 or VT15 to get the correct attributes set,
9 ! because the other devices can't support the attributes.
10
11 const integer BLACK = 1, BLUE = 2, RED = 4
12 const integer NORMAL = 0, DOTTED = 1, SDASH = 3, LDASH = 4
13 integer TYPE
14
15 routine PRINT TEXT (string (255) S, integer X, Y)
16 MOVE ABS (X,Y)
17 TEXT (S)
18 end
19
20 routine JOIN (integer X1, Y1, X2, Y2)
21 MOVE ABS (X1,Y1)
22 LINE ABS (X2,Y2)
23 end
24
25 routine RECT (integer X, Y, H, V)
26 MOVE ABS (X,Y)
27 LINE REL (H,0); LINE REL (0,-V)
28 LINE REL (-H,0); LINE REL (0,V)
29 end
30
31 PROMPT ("Device Type:")
32 READ (TYPE)
33 INITIALISE FOR (TYPE)
34
35 NEW FRAME
36
37 STORE ON (2)
38 ! A copy of the picture will be made on stream 2.
39
40 ! Now that everything is set up the picture can be drawn.
41
42
43 RECT (0,1023,1023,1023)
44
45 SET CHAR SIZE (14)
46 SET LINE STYLE (LDASH)
47 RECT (300,900,600,400)
48 PRINT TEXT ("VIEW PLANE", 700, 920)
49
50 SET CHAR SIZE (12)
51 RECT (200,400,500,300)
52 PRINT TEXT ("VIEW SURFACE", 720, 250)
53
54 SET COLOUR (BLUE)
55 SET LINE STYLE (SDASH)
56 RECT (500,800,300,200)
57 PRINT TEXT ("WINDOW", 620,810)
58
59 RECT (300,350,200,200)
60 SET CHAR SIZE (9)
61 PRINT TEXT ("VIEW PORT", 350,170)
62
63 SET LINE STYLE (DOTTED)
64 SET COLOUR (RED)
65 JOIN (500, 800, 300, 350)
66 JOIN (800, 800, 500, 350)
67 JOIN (500, 600, 300, 150)
68 JOIN (800, 600, 500, 150)
69
70 SET CHAR SIZE (7)
71 PRINT TEXT ("VIEWING TRANSFORMATION", 720,450)
72
73 TERMINATE EDWIN
74
75 end of program
? NORMAL unused
? BLACK unused
90 Statements compiled
Computer Science IMP77 Compiler. Version 6.02
Compiled on 10-JUN-1981 at 16:24:19
Source file: _DRA0:[GRAFIX.EDWIN]TEST3.IMP;1
1 include "$EDWIN:.INC"
& ! EDWIN routine specs added.
& end of list
& end of file
2 begin
3
4 ! EDWIN test program 3
5 ! Program to check software characters,
6 ! It checks both the size and rotation of the characters.
7
8 const integer GOOD = 1
9 const integer PDF STREAM = 1
10 integer I
11
12 PROMPT ("Device: ")
13 READ (I)
14 INITIALISE FOR (I)
15 NEW FRAME
16
17 OPEN OUTPUT (PDF STREAM, "TEST3.PDF")
18 STORE ON (PDF STREAM)
19
20 SET CHAR QUALITY (GOOD)
21
22 for I = 0,1,3 cycle
23 MOVE ABS (511, 500)
24 SET CHAR ROT (I*90)
25 SET CHAR SIZE (12)
26 TEXT ("CHAR at 12 OK")
27 SET CHAR SIZE (24)
28 TEXT ("CHAR at 24 OK")
29 repeat
30
31 TERMINATE EDWIN
32
33 end of program
Code 292 bytes Glap 88 bytes Diags 138 bytes Total size 518 bytes
62 statements compiled in 3.10 seconds. (1200 statements/minute)
Computer Science VAX-11 IMP77 Compiler. Version 8.01
Compiled on 10-JUN-1981 at 16:24:26
Source file: _DRA0:[GRAFIX.EDWIN]TEST4.IMP;1
1 include "$EDWIN:.INC"
& 1 ! EDWIN routine specs added.
& 2 end of list
& 55 end of file
2 begin
3 ! EDWIN test program 4
4 ! Program to draw the EDWIN character set on a plotter to check for
5 ! consistancy of letters, and also demonstrate the character set.
6
7 const integer PDF STREAM = 2, GOOD = 1
8 integer I, X, Y
9
10 PROMPT ("Device:") ; READ (I) ; INITIALISE FOR (I)
11
12 NEW FRAME
13 STORE ON (PDF STREAM)
14
15 MOVE ABS (400, 20) ; ! Bottom right corner
16
17 ! The boxes are now drawn to minimise moves.
18 MOVE REL (-36, 0) and LINE REL (-36, 0) for I = 1, 1, 4
19 LINE REL (0, 720)
20 MOVE REL (36, 0) and LINE REL (36, 0) for I = 1, 1, 4
21 for I = 1, 1, 4 cycle
22 LINE REL (0, -720 ) ; LINE REL (-36, 0)
23 LINE REL (0, 720) ; LINE REL (-36, 0)
24 repeat
25 for I = 1, 1, 6 cycle
26 MOVE REL (0, -60) ; LINE REL (288, 0)
27 MOVE REL (0, -60) ; LINE REL (-288, 0)
28 repeat
29
30 X = 112 ; Y = 697 ; MOVE ABS (X, Y) ; I = 32
31
32 SET CHAR SIZE (36)
33 SET CHAR QUALITY (GOOD)
34
35 cycle; ! To draw the characters
36 MARKER REL (4, 0, 0)
37 CHARACTER (I)
38 I = I + 1 ; exit if I=127
39 if X = 364 start; ! The end of a row
40 MARKER REL (4, 0, 0)
41 Y = Y - 60
42 X = 112
43 finish else X = X + 36
44 MOVE ABS (X, Y)
45 repeat
46
47 TERMINATE EDWIN
48 end of program
Code 732 bytes Glap 48 bytes Diags 232 bytes Total size 1012 bytes
85 statements compiled in 2.96 seconds. (1722 statements/minute)
Source file: test5 compiled on 10-JUN-81 at 19.04.00
Object file: TEST5.EXE
Edinburgh IMP77 Compiler - Version 8.1
1 include "edwin:edwin.inc"
& 1 ! EDWIN routine specs added.
& 2 end of list
& 55 end of file
2 begin
3 ! EDWIN test program 5
4 ! A demonstration program for the EDWIN CATs driver.
5
6 const integer GOOD=1, LOW=0
7 integer SYM,TYPE
8
9 routine BOX (integer XL,YL,XR,YR)
10 MOVE ABS (XL,YL)
11 LINE REL (0,YR-YL)
12 LINE REL (XR-XL,0)
13 LINE REL (0,-(YR-YL))
14 LINE REL (-(XR-XL),0)
15 end
16
17 routine PAGE 1
18 NEWFRAME
19 MOVE ABS (12,21)
20 TEXT ("This introduces a new version of")
21 MOVE ABS (10,6)
22 SET CHAR QUALITY (GOOD)
23 TEXT ("EDWIN")
24 MOVE ABS (41,4)
25 SET CHAR QUALITY (LOW)
26 TEXT ("for the ")
27 TEXT ("Visual 200") if TYPE=200
28 TEXT ("Bantam 550") if TYPE=550
29 TEXT (" terminals")
30 BOX (5,3,74,22)
31 MOVE ABS (0,1)
32 UPDATE
33 end
34
35 routine PAGE2
36 routine CROSS
37 LINE REL (20,20)
38 MOVE REL (-20,0)
39 LINE REL (20,-20)
40 end
41
42 NEW FRAME
43 MOVE ABS (0,2)
44 CROSS
45 MOVE ABS (55,2)
46 CROSS
47 MOVE ABS (31,12)
48 TEXT ("When things go wrong")
49 MOVE ABS (32,10)
50 TEXT ("Don't get cross!!")
51 UPDATE
53
54 Prompt ("Terminal type: ")
55 Read (TYPE)
56 Initialise for (TYPE)
57 Aspect ratioing (0); ! Off
58 Window (0, 79, 0, 23)
59
60 Print string ("Enter line style required as a number between 0 and 4")
61 Newline
62 Prompt ("Number: ")
63 Read (SYM) until 0<=SYM<=7
64 Set line style (SYM)
65 Read symbol (SYM) until SYM=NL
66
67 Prompt ("Hit RETURN key")
68
69 Page1
70 Read symbol (SYM) until SYM = NL
71 Page2
72
73 Terminate edwin
74 end of program
IMP77 Compiler for PDP-11
File: _DRA0:[GRAFIX.EDWIN]TEST6.IMP;1 16:24:54 10-JUN-1981
Edinburgh IMP77 Compiler - Version 8.1a
1 include "$edwin:.inc"
& 1 ! EDWIN routine specs added.
& 2 end of list
& 55 end of file
2 begin
3 ! EDWIN test program 6
4 ! Acknowledgements to PSR and ADC for this program.
5 ! Something to do with a fast video
6
7 own string (40) array pic(1:8) =
8+ " ~\",
9+ " \ /~~~~~~~~~\",
10+ " / / ~\ /~\",
11+ " / / ~\ | |",
12+ " ( / ___ ~\_\ /_",
13+ " ( | \ \",
14+ " \_| \___ | o \",
15+ " \___________\_______\_______\"
16 byte integer name eye == charno(pic(7),31)
17 const integer open = 'o', closed = '*'
18 integer j, left
19
20 prompt ("Terminal: ")
21 read (j)
22 initialise for (j)
23 aspect ratioing (0)
24 viewport(2,66,1,8)
25 window(2,66,1,8)
26 newframe
27
28 left = 2
29 cycle
30 moveabs(left,9-j) and text(pic(j)) for j = 1,1,8
31 left = left + 2
32 eye = open + closed - eye
33 repeat until left = 74
34
35 terminate edwin
36
37 end of program
Appendix E : The Structure of the EDWIN PDF
The EDWIN Pseudo Display File (PDF) consists of a number of coded
graphics instructions, one per line, which can be dumped into a file.
These instructions contain all the information to re-generate the
picture. The file can be redrawn by the use of -
routine REVIEW
which reads the current input and uses it to redraw the picture which it
represents. This appendix describes the instruction formats of in the
PDF.
Drawing Instruction Formats
These are of two types :
1) Normal Form-
This consists of one integer for the code giving the instruction
type, this is stored in the first half byte, and the other three half
bytes are zero. The next integer contains the X co-ordinate which the
instruction uses, and the final integer contains the Y co-ordinate.
eg. | 0 0 0 code | | X value | | Y value |
2) Short Form -
This consists of the code integer, with the instruction code having
had 16 added to it, the X and Y co-ordinates are packed into two eight
bit fields inside the second integer. This means that for any drawing
instruction where both co-ordinates are in the range -128 to 127, the
shorter form may be used. This is frequently the case.
eg. | 0 0 1 code | | X value , Y value|
The codes for the drawing instructions are -
0 - Line Abs
1 - Move Abs
2 - Marker Abs
3 - Line Rel
4 - Move Rel
5 - Marker Rel
The top byte of the first number is used to specify marker selection
for codes 2 and 5.
Other Instruction Formats
Window
If the EDWIN routine WINDOW is called, the parameters are stored in
the PDF in the following form. The window is automatically altered if
the PDF is being reviewed.
eg. | 0 0 0 8 | | XL | | XR | | 0 0 0 8 | | YB | | YT |
Characters
This requires one integer. The code dumped is -
| 0 , char val , 9 |
CHAR VAL is a byte, containing the ASCII value of the character to be
drawn, and this is drawn at the current settings of character size,
rotation, and quality as set by change attribute value commands.
Change of attribute value.
This has code 10. The centre two half bytes contain the value of the
attribute, and the top half byte is one of the following codes :-
| 0 value A | => Colour Change
| 1 value A | => Line Type Change
| 2 value A | => Char Size Change
| 3 value A | => Char Orientation Change
| 4 value A | => Char Quality Change
| 5 value A | => Char Font Change
| 6 value A | => Intensity Change
| F value A | => Aspect ratioing
Newframe and End
These require one integer of value eleven or twelve respectively. If
either are encountered when interpreting a PDF it causes control to
return to the point where the interpreting routine was called from.
Appendix F : Acknowledgements
If everyone who had contributed to EDWIN was mentioned the list would
go on for pages. The people who contributed most to the design were
Irene Buchanan
Alan Gray
Lee Smith
Jeff Tansley
Rainer Thonnes
Ian Young
Most users of EDWIN have reported their criticisms, and suggestions
for enhancements, a number of which have appeared in the latest version.
Thanks go to them, and to the users who have helped to get rid of bugs.
The systems programmers of all the systems which EDWIN runs on have also
provided valuable help in providing machine specific driving routines.
Special thanks to Nick Rothwell, whose interactive design program
(which uses EDWIN) was used to design the cover picture.
Appendix G : References
[1] Edinburgh Regional Computing Centre
E. R. C. C. Graphics Manual July 1979
[2] H. Dewar
PDP-15 Users Guide
E. U. C. S. D. 1974
[3] P. McLellan
LEGOS Users Guide
E. U. C. S. D. report CSR-49-79 Dec 1979
[4] H. Whitfield & A. S. Wight
EMAS : The Edinburgh Multi-Acess System
E. U. C. S. D. EMAS report 1 1977
[5] Edinburgh Regional Computer Centre
EMAS Users Guide Dec 1976
[6] Edinburgh Regional Computer Centre
EMAS 2900 Users Guide Jan 1980
[7] VAX-11 Software Handbook
Digital Equipment Co. 1977
[8] P. S. Robertson & C. Whitfield
MOUSES
Moray House, Edinburgh Mar 1980
[9] P. Stephens
The IMP programming language
E. U. C. S. D. EMAS report 6 1977
[10] P. S. Robertson
The IMP-77 language
E. U. C. S. D. report CSR-19-77 May 1979
[11] C. A. D Centre
GINO-F User Manual Dec 1978
[12] A. C. M. SIGGRAPH proposals
A. C. M. Computer Graphics Fall 1977
[13] Tektronix 4002 Programming manual
Tektronix co. 1969
[14] Tektronix 4010 Users Manual
Tektronix co. 1971
[15] Tektronix 4012 Users Manual
Tektronix co. 1971
[16] Tektronix 4014 Computer Display Terminal Users Manual
Tektronix co. 1974
[17] VT15 Graphics Processor
Digital Equipment Co. DEC-15-H2J2-D 1970
[18] Model-550 Users Guide
Perkin-Elmer Sep 1978
[19] Hewlett Packard 7221A plotter operating and programming manual
Hewlett Packard Nov 1977
[20] Charles R. Minter
Two Prototypes of the Colour Graphics Display
California Institute of Technology, internal report. 1978
[21] Visual 200 Video Display terminal reference manual
Visual Technonlgy Inc. 1980
[22] Graphics Terminal reference manual 2648A
Hewlett Packard Mar 1978
[23] Printronix 300 Applications Manual
Printronix Nov 1977
[24] L. D. Smith
The Elementry Structural Description Language
E. U. C. S. D. report CSR-53-80 Jan 1980
[25] W. Laing (ed.)
V L S I Design Tools
E. U. C. S. D. report 1980
[26] E. E. Barton & I. Buchanan
The Polygon Package
E. U. C. S. D. report CSR-44-79 Oct 1979
[27] I. A. Young
The 'SOGGY' users manual
E. U. C. S. D. Internal file Jul 1980
[28] W. M. Newman & R. F. Sproull
Principles of Interactive Computer Graphics
McGraw Hill 1980