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diagram(n) Documentation toolbox diagram(n)

____________________________________________________________________________________________________________

NAME
diagram - Diagram drawing

SYNOPSIS
package require Tcl 8.5

package require Tk 8.5

package require diagram 1

::diagram objectName canvas ?script?

diagramObject new direction name ?key value...?

diagramObject new element name attributes cmdprefix

diagramObject new alias name cmdprefix

diagramObject new command name arguments body

diagramObject new attribute name ?key value...?

diagramObject unknown attribute cmdprefix

diagramObject draw script

arc attr...

arrow attr...

--> attr...

<--> attr...

block script attr...

box attr...

circle attr...

O attr...

diamond attr...

<> attr...

drum attr...

ellipse attr...

line attr...

-- attr...

move attr

spline attr...

text attr...

west

left

south

down

bottom

bot

east

right

north

top

northwest

up-left

upleft

leftup

northeast

up-right

upright

rightup

southwest

down-left

downleft

leftdown

southeast

down-right

downright

rightdown

number cm

number mm

number inch

number pt

number number

by distance direction

point1 + point2

point1 - point2

point by distance direction

point1 | point2

n between poin1 point2

intersect elem1 elem2

element names ?pattern?

element corner

element corner1 corner2...

element ?corner1... ?names ?pattern??]?

nth ?corner?

nth last ?corner?

nth shape ?corner?

nth last shape ?corner?

last ?corner?

last shape ?corner?

1st

2nd

3rd

____________________________________________________________________________________________________________

DESCRIPTION
Welcome to diagram, a package for the easy construction of diagrams (sic), i.e. 2D vector graphics,
sometimes also called pictures. Note that this package is not a replacement for Tk's canvas, but
rather a layer sitting on top of it, to make it easier to use. In other words, using the canvas as
the core graphics engine diagram abstracts away from the minutiae of handling coordinates to position
and size the drawn elements, allowing the user to concentrate on the content of the diagram instead.

This is similar to Brian Kernighan's PIC language for troff, which is the spiritual ancestor of this
package.

This document contains the reference to the API and drawing (language) commands. Its intended audi-ence audience
ence are users of the package wishing to refresh their memory. Newcomers should read the Diagram
Language Tutorial first. Developers wishing to work on the internals of the package and its support-ing supporting
ing packages should look at section Diagram Classes first, and then the comments in the sources of
the packages itself.

In the remainder of the document we first describe the APIs of the diagram class and its instances,
followed by the language reference for the drawing language itself.

API
CLASS API
The package exports the API described here.

::diagram objectName canvas ?script?
The command creates a new instance of a diagram controller and returns the fully qualified
name of the object command as its result. The new instance is connected to the specified can-vas canvas
vas object, which is used as the diagrams graphics engine. This is usually an instance of Tk's
canvas, however any object which is API compatible to Tk's canvas can be used here.

The API of this object command is described in the following section, Object API. It may be
used to invoke various operations on the object.

If the script argument is specified then method draw will be invoked on it.

OBJECT API
Instances of the diagram class support the following methods:

diagramObject new direction name ?key value...?
This method defines a new named direction and its attributes. The latter is given through the
key/value pairs coming after the name.

Users are mostly free to specify arbitrary attributes with whatever meaning they desire. The
exception are the names angle and opposite. They are special to the diagram package and have a
fixed meaning.

angle This attribute specifies the angle of the direction in degrees, where 0 points east (to
the right) and 90 points north (up).

opposite
This attribute specifies the name of the direction which should be considered as com-plementary complementary
plementary to the named one.

diagramObject new element name attributes cmdprefix
This method defines a new graphics element for the drawing language. I.e. name will become a
new command in the language, and the specified command prefix (cmdprefix) will be called to
perform the actual drawing.

attributes specifies the set of attributes for which data has to be available. I.e. the system
will run the See the method new attribute for more information on attribute definitions.

The command prefix is expected to conform to the following signature:

cmdprefix canvas attributes
Where canvas is the handle of the canvas widget to draw to, and attributes is a dictio-nary dictionary
nary holding the attributes for the element, be they user-specified, or defaults.

The results of the command has to be a list containing at least two and at most four
items. These are, in order:

[1] The list of canvas items the drawn element consists of.

[2] The dictionary of named locations in the element, its corners.

[3] An optional mode, either "relative" or "absolute". When not returned "relative"
is assumed. In the case of a relative element position the attributes "with" and
"at" are used to determine the final position of the new element.

[4] An optional name of a direction. If not the empty string this is handed to the
automatic layouter as the new direction to follow.

diagramObject new alias name cmdprefix
This method defines a new command for the drawing language. I.e. name will become a new com-mand command
mand in the language, and the specified command prefix (cmdprefix) will be called on use of
this new command. Any arguments given to the command are simply passed to the prefix. There is
no fixed siganture.

Note that the prefix is run in the context of the drawing language, allowing the direct use of
any existing commands.

diagramObject new command name arguments body
This is like new alias except that the new command is defined as a procedure in the language's
context, with regular argument list and body.

diagramObject new attribute name ?key value...?
This method defines a new named attribute which can be used by graphical elements. The han-dling handling
dling of the attribute by the processor is declared through the key/value pairs coming after
the name.

The accepted keys and their meanings are:

key The value of this key is the name of the key under which the attribute's value shall be
stored in the attribute dictionary given to the drawing command after attribute pro-cessing processing
cessing is complete.

This key is optional. If it is not specified it defaults to the name of the attribute.

get The value of this key is a command prefix which will be invoked to retrieve the
attribute's argument(s) from the command line.

This key is optional. If it is not specified a default is used which takes the single
word after the attribute name as the attribute's value.

The signature of the command prefix is

cmdprefix wordqueue
Where wordqueue is the handle of a queue object conforming to the API of the
queues provided by package struct::queue. This queue contains the not-yet-pro-cessed not-yet-processed
cessed part of the attribute definitions, with one entry per word, with the
first entry the word after name of the attribute. In other words, the
attribute's name has already been removed from the queue.

The result of the command is the value of the attribute, which may have been
taken from the queue, or not.

transform
The value of this key is a command prefix which will be invoked to transform the
retrieved value (See get) into their final form.

This key is optional. If it is not specified no transformation is done. The signature
of the command prefix is

cmdprefix value
Where value is the value to transform.

The result of the command is the final value of the attribute.

type The value of this key is a command prefix which will be invoked to validate the
attribute's argument(s).

This key is optional. If it is not specified no validation is done.

The signature of the command prefix is that of snit validation types. See the documen-tation documentation
tation of the snit package.

merge The value of this key is a command prefix which will be invoked to insert the trans-formed transformed
formed and validated attribute value into the dictionary of collected attributes.

This key is optional. If it is not specified a default merge is chosen, based on the
data for key aggregate, see below. The signature of the command prefix is

cmdprefix value dict
Where value is the value to insert, and dict the dictionary of attributes and
values collected so far.

The result of the command is the new dictionary of attributes.

aggregate
The value of this key is a boolean flag. It has an effect if and only if the key merge
was not specified. This key is optional. If it is not specified it defaults to False.

If the key is effective, the value of False means that the attribute's value is set
into the dictionary using the value of key key (see above) as index, overwriting any
previously specified value.

If the key is effective, the value of True means that the attribute's value is added to
the dictionary using the value of key key (see above) as index, extending any previ-ously previously
ously specified value. This means that the final value of the attribute as seen after
processing will be a list of the collected values.

default
The value of this key is a command prefix which will be invoked after collection of
attributes has been completed and this attribute is in the list of required attributes
for the drawing element (See argument attributes of method new element).

Note that the connection is made through the value of key key, not through the
attribute name per se.

Further note that this command prefix is invoked even if a user specified attribute
value is present. This allows the command to go beyond simply setting defaults, it can
calculate and store derived values as well.

This key is optional. If an element requires this attribute, but default is not speci-fied specified
fied then nothing will be done.

The signature of the command prefix is

cmdprefix init
This method is run when the attribute is defined, its responsibility is to ini-tialize initialize
tialize anything in the language namespace for the attribute and default pro-cessing. processing.
cessing.

The result of this method is ignored.

cmdprefix fill varname
This method is run to put defaults, or derived values into the attribute dictio-nary dictionary
nary named by varname. This variable will be found in the calling context.

The result of this method is ignored.

cmdprefix set name value
This method is run to push current a attribute value into the language names-pace, namespace,
pace, to make it the new default.

The result of this method is ignored.

linked This key is effective if and only if key default is not specified. In that case is sup-plies supplies
plies a default handling for default, linking the attribute to a variable in the lan-guage language
guage context.

The value for this key is a 2-element list containing the name of the variable to link
to, and its initial value, in this order.

diagramObject unknown attribute cmdprefix
This method registers the command prefix with the subsystem processing the attributes for ele-ment element
ment commands, telling it to call it when it encounters an attribute it is unable to handle on
its on.

It is allowed to register more than callback, these will be called in order of registration
(i.e. first to last), until one of the callbacks accepts the current input. The command pre-fix prefix
fix is expected to conform to the following signature:

cmdprefix wordqueue
Where wordqueue is the handle of a queue object conforming to the API of the queues
provided by package struct::queue. This queue contains the not-yet-processed part of
the attribute definitions, with one entry per word, with the first entry the name of
the attribute which could not be processed.

The results of the command has to be a boolean value where True signals that this call-back callback
back has accepted the attribute, processed it, and the new state of the wordqueue is
where the general processing shall continue.

Given the signature the command has basically two ways of handling (rewriting) the
attributes it recognizes:

[1] Replace the attribute (and arguments) with a different attribute and arguments.

[2] Push additional words in front to get the general processing unstuck.

diagramObject draw script
This method runs the given script in the context of the drawing language definitions. See
section Language Reference for details on the available commands.

Note that script is trusted. It is executed in the current interpreter with access to its
full abilities. For the execution of untrusted diagram scripts this interpreter should be a
safe one.

LANGUAGE REFERENCE
ELEMENTS
This section lists the commands for the predefined drawing elements, aka shapes. These commands are
all defined in the language's context. All commands of this section return the handle of the newly
created element as their result. This handle also exists as a command which can be used to query the
element for its corners (names, values). See section Miscellaneous Commands. IMAGE: fig-ure-02-basic-shapes figure-02-basic-shapes
ure-02-basic-shapes

arc attr...
IMAGE: figure-02-arc An open element with the corresponding corners, i.e. "start", "end", and
"center". Note however that it also has the compass rose of closed elements as its corners,
with the center of the arc's circle as the center of the compass and the other points on the
circle the arc is part of. It handles the attributes

anchor name

ljust

rjust

above

below IMAGE: figure-22-text-anchoring-3 Specifies the anchor of the text which is to be
placed at the element's center, by name. I.e. this attribute defines the text's posi-tion position
tion relative to the element's center. The value is ignored if no text was specified
for the element. If not specified the system falls back to the value taken from the
language variable anchor, which itself defaults to center. The legal values are all
those accepted by Tk_GetAnchor [http://www.tcl.tk/man/tcl8.5/TkLib/GetAnchor.htm]. The
commands without arguments are all shorthands with the anchor implied. Note that they
do not combine, only the last is used. For comined directions the main attribute com-mand, command,
mand, anchor has to be used.

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

clockwise

cw Specifies the direction of the arc element, here going clockwise. The complementary
attribute is counterclockwise. If not specified the system falls back to the value
taken from the language variable clockwise, which itself defaults to false, for
counter-clockwise direction.

color spec
IMAGE: figure-21-style-colors Specifies the color used to draw the lines of the ele-ment. element.
ment. If not specified the system falls back to the value taken from the language
variable linecolor, which itself defaults to black.

counterclockwise

ccw Specifies the direction of the arc element, here counter-clockwise. The complementary
attribute is clockwise. If not specified the system falls back to the value taken from
the language variable clockwise, which itself defaults to false, for counter-clockwise
direction.

fillcolor spec
IMAGE: figure-21-style-colors Specifies the color used to draw the inside of the ele-ment. element.
ment. If not specified the system falls back to the value taken from the language
variable fillcolor, which itself defaults to the empty string, signaling "no filling".

from location
Specifies the location where the arc element begins. Defaults to the current location
as maintained by the layouting system.

justify left|center|right
Specifies how multi-line text associated with the element is positioned within its box.
The value is ignored if no text was specified for the element. If not specified the
system falls back to the value taken from the language variable justify, which itself
defaults to left. The legal values are left, right, and center.

radius length
Specifies the radius of the arc element, or rather, the radius of the circle the shown
arc is a part of. If not specified the system falls back to the value taken from the
language variable arcradius, which itself defaults to the pixel equivalent of 1 cm.

stroke width
IMAGE: figure-20-style-stroke Specifies the width of the lines drawn for the the ele-ment, element,
ment, in pixels. If not specified the system falls back to the value taken from the
language variable linewidth, which itself defaults to 1.

style spec
IMAGE: figure-18-style-dash Specifies the style used to draw the lines of the element.
If not specified the system falls back to the value taken from the language variable
linestyle, which itself defaults to solid lines. The legal values are all those
accepted by Tk_GetDash [http://www.tcl.tk/man/tcl8.5/TkLib/GetDash.htm], and addition-ally additionally
ally all which are listed below:

solid, empty string
Draw solid line.

dash, dashed, -Draw dashed,Draw
Draw a dashed line.

dot, dotted, .
Draw a dotted line.

dash-dot, -.
Draw a dash-dotted line

dash-dot-dot, -..
Draw a dash-dot-dotted line.
Note that the values "solid", "dot(ted)", "dash(ed)", "dash-dot", and "dash-dot-dot" are all
accepted as shorthands for the style command using them as argument.

text string
Specifies the text to associate with the element. Defaults to nothing. When specified
multiple times the actually shown text is the concatenation of the individual strings,
vertically stacked, with the first string specified being the topmost element.

textcolor spec
Specifies the color used to draw the text of an element with. Ignored if there is no
text. If not specified the system falls back to the value taken from the language
variable textcolor, which itself defaults to black.

textfont spec
Specifies the font used to draw the text of an element with. Ignored if there is no
text. If not specified the system falls back to the value taken from the language
variable textfont, which itself defaults to Helvetica 12pt.

to location
Specifies the location where the arc element ends. Defaults to a location such that a
90-degree arc is drawn in the chosen direction, starting at from.

arrow attr...

--> attr...

<--> attr...

<--> attr...
IMAGE: figure-02-arrow An alias for the line element (see below), with the attribute arrowhead
preset to ->, <->, or <-. The arrow is equivalent to -->.

block script attr...
A closed element with the corresponding corners, i.e. the eight directions of the compass
rose, and "center". The main effect is the aggregration of all elements created by the script
into one element. This also means that while the elements created by the script are visible
in the element history while the script is executing, afterward the history contains only the
block itself, and not the elements it is composed of.

The script has access to the current state of all variables in the language context. Any
changes to the variables will be reverted after execution of the block. However, also, any
variables set in the script will be exported as corners of the element, allowing users to
define their own named locations in the block.

Regarding the layout mechanism any changes made by the script are reverted after the element
is done. In other words, a block is an implicit group.

Blocks handle all attributes, propgating their settings into the script as the default values
active during script execution.

box attr...
IMAGE: figure-02-box A closed element with the corresponding corners, i.e. the eight direc-tions directions
tions of the compass rose, and "center". It handles the attributes

anchor name

ljust

rjust

above

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

at location
Specifies the location of the element's corner named by the attribute with. Defaults
to the current location as maintained by the layouting system.

height length

ht length
Specifies the height of the element. If not specified the system falls back to the
value taken from the language variable boxheight, which itself defaults to the pixel
equivalent of 2 cm.

slant angle
Specifies the angle by which the box element is slanted, in degrees. If not specified
the system falls back to the value taken from the language variable slant, which itself
defaults to 90, i.e. vertical, no slant. 0 degrees is slanting straight east, pointing
to the right. 90 degrees is slanting to the north, pointing straight up.

solid, empty string
Draw solid line.

dash, dashed, -Draw dashed,Draw
Draw a dashed line.

dot, dotted, .
Draw a dotted line.

dash-dot, -.
Draw a dash-dotted line

width length

wid length
Specifies the width of the element. If not specified the system falls back to the
value taken from the language variable boxwidth, which itself defaults to the pixel
equivalent of 2 cm.

with corner
Specifies the corner of the element to place at the location given by the attribute at.
Defaults to the current corner as maintained by the layouting system, except if the
value for at was specified by the user. In that case it defaults to center.

circle attr...

O attr...
IMAGE: figure-02-circle A closed element with the corresponding corners, i.e. the eight direc-tions directions
tions of the compass rose, and "center". It handles the attributes

anchor name

ljust

rjust

above

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

at location
Specifies the location of the element's corner named by the attribute with. Defaults
to the current location as maintained by the layouting system.

diameter length

diam length
Specifies the diameter of the circle element, as an alternative way to specify its
radius. Effective if and only if the radius was not specified. I.e. if both diameter
and radius are specified then the radius infomration has precendence. This attribute
has no default, because the defaults are taken from the radius.

radius length

rad length
Specifies the radius of the circle element. If not specified the system falls back to
the value taken from the language variable circleradius, which itself defaults to the
pixel equivalent of 1 cm.

solid, empty string
Draw solid line.

dash, dashed, -Draw dashed,Draw
Draw a dashed line.

dot, dotted, .
Draw a dotted line.

dash-dot, -.
Draw a dash-dotted line

diamond attr...

<> attr...
IMAGE: figure-02-diamond A closed element with the corresponding corners, i.e. the eight
directions of the compass rose, and "center". It handles the attributes

anchor name

ljust

rjust

above

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

aspect number
Specifies the aspect ratio, i.e ratio of width to height, of the diamond element. The
manner in which a default is calculated when not specified also depends on the specifi-cations specifications
cations of the attributes width and height, if any.

If both width, and height are specified then any specification of aspect is ignored, as
it is implicitly defined in the width and height as well, and this takes precedence. A
missing specification is ignored in that case well, i.e. no defaults are required.

If the aspect is specified, and one of the attributes width or height, then the missing
attribute is calculated from the two which are specified. No defaults are required for
these cases either.

If only one of the attributes width or height is specified then the system uses a fall-back fallback
back for the aspect, the value taken from the language variable diamondaspect, which
itselfs defaults to 2.

If none of of the attributes width or height is specified then the system uses a fall-back fallback
back for the width, the value taken from the language variable boxwidth, which itselfs
defaults to the pixel equivalent of 2 cm. For the aspect it uses either the user-speci-fied user-specified
fied value or the default taken as described in the previous paragraph.

at location
Specifies the location of the element's corner named by the attribute with. Defaults
to the current location as maintained by the layouting system.

height length
Specifies the height of the diamond element. The manner in which a default is calcu-lated calculated
lated when not specified also depends on the specifications of the attributes aspect
and width, if any.

If the aspect is specified, and one of the attributes width or height, then the missing
attribute is calculated from the two which are specified. No defaults are required for
these cases either.

solid, empty string
Draw solid line.

dash, dashed, -Draw dashed,Draw
Draw a dashed line.

dot, dotted, .
Draw a dotted line.

dash-dot, -.
Draw a dash-dotted line

width length
Specifies the width of the diamond element. The manner in which a default is calcu-lated calculated
lated when not specified also depends on the specifications of the attributes aspect
and height, if any.

If the aspect is specified, and one of the attributes width or height, then the missing
attribute is calculated from the two which are specified. No defaults are required for
these cases either.

drum attr...
IMAGE: figure-02-drum A closed element with the corresponding corners, i.e. the eight direc-tions directions
tions of the compass rose, and "center". It handles the attributes

anchor name

ljust

rjust

above

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

aspect number
Specifies the aspect ratio, i.e ratio of width to height, of the ellipses which are
used to draw the top and bottom of the drum element. If not specified the system falls
back to the value taken from the language variable drumaspect, which itself defaults to
0.35.

at location
Specifies the location of the element's corner named by the attribute with. Defaults
to the current location as maintained by the layouting system.

height length

ht length
Specifies the height of the element. If not specified the system falls back to the
value taken from the language variable boxheight, which itself defaults to the pixel
equivalent of 2 cm.

solid, empty string
Draw solid line.

dash, dashed, -Draw dashed,Draw
Draw a dashed line.

dot, dotted, .
Draw a dotted line.

dash-dot, -.
Draw a dash-dotted line

width length

wid length
Specifies the width of the element. If not specified the system falls back to the
value taken from the language variable boxwidth, which itself defaults to the pixel
equivalent of 2 cm.

ellipse attr...
IMAGE: figure-02-ellipse A closed element with the corresponding corners, i.e. the eight
directions of the compass rose, and "center". It handles the attributes

anchor name

ljust

rjust

above

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

at location
Specifies the location of the element's corner named by the attribute with. Defaults
to the current location as maintained by the layouting system.

height length

ht length
Specifies the height of the element. If not specified the system falls back to the
value taken from the language variable boxheight, which itself defaults to the pixel
equivalent of 2 cm.

solid, empty string
Draw solid line.

dash, dashed, -Draw dashed,Draw
Draw a dashed line.

dot, dotted, .
Draw a dotted line.

dash-dot, -.
Draw a dash-dotted line

width length

wid length
Specifies the width of the element. If not specified the system falls back to the
value taken from the language variable boxwidth, which itself defaults to the pixel
equivalent of 2 cm.

line attr...

-- attr...
IMAGE: figure-02-line An open element with the corresponding corners, i.e. "start", "end", and
"center". It handles the attributes

anchor name

ljust

rjust

above

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

arrowhead spec
IMAGE: figure-19-style-arrowheads Specifies where to draw arrowheads on the line ele-ment, element,
ment, at the beginning or end, at both ends, or none. If not specified the system
falls back to the value taken from the language variable arrowhead, which itself
defaults to none. The legal values are

none, -Draw none,Draw
Draw no arrowheads, at neither end of the line.

start, first, <-
Draw an arrowhead at the beginning of the line, but not at its end.

end, last, ->
Draw an arrowhead at the end of the line, but not at its beginning.

both, <->
Draw arrowheads at both ends of the line.
Note that the values "start", "end", "-", "->", "<-", and "<->" are all accepted as shorthands
for the arrowhead command using them as argument.

at location
Line elements are normally positioned absolutely, using the locations specified through
the attributes from, then, and to. If at is specified however then these positions are
translated a last time, moving the line's corner named by the attribute with to the
location given by this attribute.

chop ?length?
Specifies the length of the line element to remove from the beginning and/or end.
Defaults to nothing. If specified once the chopping applies to both beginning and end
of the line. If specified twice or more the last two specifications are used, and
applied to beginning and end of the line, in this order. Whenever the attribute is
specified without an explicit length, the system falls back to the value taken from the
language variable circleradius, which itself defaults to the pixel equivalent of 1 cm

from location
Specifies the location where the line element begins. Defaults to the current location
as maintained by the layouting system.

noturn Specifies that the direction of line element at its end is not propagated to the layout
management. If not specified the direction of the line becomes the new direction the
layout.

smooth Specifies the use of bezier splines for the line element. If not specified lines are
drawn exactly through the specified waypoints, without any smooth curves.

solid, empty string
Draw solid line.

dash, dashed, -Draw dashed,Draw
Draw a dashed line.

dot, dotted, .
Draw a dotted line.

dash-dot, -.
Draw a dash-dotted line

then location

then (<direction> ?length?)...

(<direction> ?length?)...
This attribute specifies an intermediate location the line element has to go through.
It can be specified multiple times, with each use adding one additional location to the
series which the line will go through. These location will be traversed in the order
they were specified.

The location can be given explicitly, or as a series of directions with distances. In
the latter case the names of all known directions are accepted for the direction part.
If no distance is specified for a direction the system falls back to the value taken
from the language variable movelength, which itself defaults to the pixel equivalent of
2 cm. The whole set of direction,distance pairs is treated as a series of translations
which are added up to provide the final translation specifying the intermediate point
(relative to the preceding point).

The last named direction is propagated to the layout system as the direction to follow.
The use of noturn is not able to overide this behaviour.

At last, the names of the registered directions also serve as attribute commands, with
an implicit attribute then in front of them.

If no intermediate or last location is specified for the line the system falls back to
a point movelength pixels away from the starting location, in the current direction as
maintained by the layouting system

to location
Specifies the location where the line element ends. This attribute has no default. The
default is handled by the attribute then, which makes it appear as if to has a default
when not specified.

with corner
Line elements are normally positioned absolutely, using the locations specified through
the attributes from, then, and to. If at is specified however then these positions are
translated a last time, moving the line's corner named by the attribute with to the
location given by this attribute. This means that with is effective if and only if the
attribute at was specified as well for the line.

move attr
An open element with the corresponding corners, i.e. "start", "end", and "center". A move
element is in essence an invisible line. While the main effect we are interested in is the
change it makes to the layout system, it is an actual element, i.e. it has the same corners as
an ordinary line, and shows up in the history as well, allowing future references to all the
places it touched. It handles the same attibutes as line elements.

spline attr...
IMAGE: figure-02-spline An alias for the line element (see above), with the attribute smooth
preset.

text attr...
IMAGE: figure-02-text A closed element with the corresponding corners, i.e. the eight direc-tions directions
tions of the compass rose, and "center". It handles the attributes

anchor name

ljust

rjust

above

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

at location
Specifies the location of the element's corner named by the attribute with. Defaults
to the current location as maintained by the layouting system.

height length
Specifies the height of the text element. Defaults to the natural height of its text.

width length
Specifies the width of the text element. Defaults to the natural width of its text.

ATTRIBUTES
The set of all attributes supported by all the element commands is shown below. While we speak of
them as commands, and provide a syntax, they are not truly available as actual commands, but only as
part of the arguments for an element command.

Note that some of the attribute names are overloaded, i.e. have multiple, different, definitions.
During processing of attributes for an element the actual definition used is chosen based on the type
of the element the processing is for.

Further, as a catch-all clause, any attribute which could not be processed according to the defini-tions definitions
tions below will be treated as the argument of an implicit text attribute.

anchor name

ljust

rjust

above

below IMAGE: figure-22-text-anchoring-3 Specifies the anchor of the text which is to be placed at
the element's center, by name. I.e. this attribute defines the text's position relative to the
element's center. The value is ignored if no text was specified for the element. If not
specified the system falls back to the value taken from the language variable anchor, which
itself defaults to center. The legal values are all those accepted by Tk_GetAnchor
[http://www.tcl.tk/man/tcl8.5/TkLib/GetAnchor.htm]. The commands without arguments are all
shorthands with the anchor implied. Note that they do not combine, only the last is used. For
comined directions the main attribute command, anchor has to be used.

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

arrowhead spec
IMAGE: figure-19-style-arrowheads Specifies where to draw arrowheads on the line element, at
the beginning or end, at both ends, or none. If not specified the system falls back to the
value taken from the language variable arrowhead, which itself defaults to none. The legal
values are

none, -Draw none,Draw
Draw no arrowheads, at neither end of the line.

start, first, <-
Draw an arrowhead at the beginning of the line, but not at its end.

end, last, ->
Draw an arrowhead at the end of the line, but not at its beginning.

both, <->
Draw arrowheads at both ends of the line.
Note that the values "start", "end", "-", "->", "<-", and "<->" are all accepted as shorthands for
the arrowhead command using them as argument.

aspect number
Specifies the aspect ratio, i.e ratio of width to height, of the diamond element. The manner
in which a default is calculated when not specified also depends on the specifications of the
attributes width and height, if any.

If both width, and height are specified then any specification of aspect is ignored, as it is
implicitly defined in the width and height as well, and this takes precedence. A missing spec-ification specification
ification is ignored in that case well, i.e. no defaults are required.

If the aspect is specified, and one of the attributes width or height, then the missing
attribute is calculated from the two which are specified. No defaults are required for these
cases either.

If only one of the attributes width or height is specified then the system uses a fallback for
the aspect, the value taken from the language variable diamondaspect, which itselfs defaults
to 2.

If none of of the attributes width or height is specified then the system uses a fallback for
the width, the value taken from the language variable boxwidth, which itselfs defaults to the
pixel equivalent of 2 cm. For the aspect it uses either the user-specified value or the
default taken as described in the previous paragraph.

aspect number
Specifies the aspect ratio, i.e ratio of width to height, of the ellipses which are used to
draw the top and bottom of the drum element. If not specified the system falls back to the
value taken from the language variable drumaspect, which itself defaults to 0.35.

at location
Specifies the location of the element's corner named by the attribute with. Defaults to the
current location as maintained by the layouting system.

at location
Line elements are normally positioned absolutely, using the locations specified through the
attributes from, then, and to. If at is specified however then these positions are translated
a last time, moving the line's corner named by the attribute with to the location given by
this attribute.

chop ?length?
Specifies the length of the line element to remove from the beginning and/or end. Defaults to
nothing. If specified once the chopping applies to both beginning and end of the line. If
specified twice or more the last two specifications are used, and applied to beginning and end
of the line, in this order. Whenever the attribute is specified without an explicit length,
the system falls back to the value taken from the language variable circleradius, which itself
defaults to the pixel equivalent of 1 cm

clockwise

cw Specifies the direction of the arc element, here going clockwise. The complementary attribute
is counterclockwise. If not specified the system falls back to the value taken from the lan-guage language
guage variable clockwise, which itself defaults to false, for counter-clockwise direction.

color spec
IMAGE: figure-21-style-colors Specifies the color used to draw the lines of the element. If
not specified the system falls back to the value taken from the language variable linecolor,
which itself defaults to black.

counterclockwise

ccw Specifies the direction of the arc element, here counter-clockwise. The complementary
attribute is clockwise. If not specified the system falls back to the value taken from the
language variable clockwise, which itself defaults to false, for counter-clockwise direction.

diameter length

diam length
Specifies the diameter of the circle element, as an alternative way to specify its radius.
Effective if and only if the radius was not specified. I.e. if both diameter and radius are
specified then the radius infomration has precendence. This attribute has no default, because
the defaults are taken from the radius.

fillcolor spec
IMAGE: figure-21-style-colors Specifies the color used to draw the inside of the element. If
not specified the system falls back to the value taken from the language variable fillcolor,
which itself defaults to the empty string, signaling "no filling".

from location
Specifies the location where the line element begins. Defaults to the current location as
maintained by the layouting system.

from location
Specifies the location where the arc element begins. Defaults to the current location as
maintained by the layouting system.

height length

ht length
Specifies the height of the element. If not specified the system falls back to the value
taken from the language variable boxheight, which itself defaults to the pixel equivalent of 2
cm.

height length
Specifies the height of the diamond element. The manner in which a default is calculated when
not specified also depends on the specifications of the attributes aspect and width, if any.

If both width, and height are specified then any specification of aspect is ignored, as it is
implicitly defined in the width and height as well, and this takes precedence. A missing spec-ification specification
ification is ignored in that case well, i.e. no defaults are required.

If the aspect is specified, and one of the attributes width or height, then the missing
attribute is calculated from the two which are specified. No defaults are required for these
cases either.

If only one of the attributes width or height is specified then the system uses a fallback for
the aspect, the value taken from the language variable diamondaspect, which itselfs defaults
to 2.

height length
Specifies the height of the text element. Defaults to the natural height of its text.

justify left|center|right
Specifies how multi-line text associated with the element is positioned within its box. The
value is ignored if no text was specified for the element. If not specified the system falls
back to the value taken from the language variable justify, which itself defaults to left.
The legal values are left, right, and center.

noturn Specifies that the direction of line element at its end is not propagated to the layout man-agement. management.
agement. If not specified the direction of the line becomes the new direction the layout.

radius length

rad length
Specifies the radius of the circle element. If not specified the system falls back to the
value taken from the language variable circleradius, which itself defaults to the pixel equiv-alent equivalent
alent of 1 cm.

radius length
Specifies the radius of the arc element, or rather, the radius of the circle the shown arc is
a part of. If not specified the system falls back to the value taken from the language vari-able variable
able arcradius, which itself defaults to the pixel equivalent of 1 cm.

slant angle
Specifies the angle by which the box element is slanted, in degrees. If not specified the
system falls back to the value taken from the language variable slant, which itself defaults
to 90, i.e. vertical, no slant. 0 degrees is slanting straight east, pointing to the right.
90 degrees is slanting to the north, pointing straight up.

smooth Specifies the use of bezier splines for the line element. If not specified lines are drawn
exactly through the specified waypoints, without any smooth curves.

stroke width
IMAGE: figure-20-style-stroke Specifies the width of the lines drawn for the the element, in
pixels. If not specified the system falls back to the value taken from the language variable
linewidth, which itself defaults to 1.

style spec
IMAGE: figure-18-style-dash Specifies the style used to draw the lines of the element. If not
specified the system falls back to the value taken from the language variable linestyle, which
itself defaults to solid lines. The legal values are all those accepted by Tk_GetDash
[http://www.tcl.tk/man/tcl8.5/TkLib/GetDash.htm], and additionally all which are listed below:

solid, empty string
Draw solid line.

dash, dashed, -Draw dashed,Draw
Draw a dashed line.

dot, dotted, .
Draw a dotted line.

dash-dot, -.
Draw a dash-dotted line

dash-dot-dot, -..
Draw a dash-dot-dotted line.
Note that the values "solid", "dot(ted)", "dash(ed)", "dash-dot", and "dash-dot-dot" are all accepted
as shorthands for the style command using them as argument.

text string
Specifies the text to associate with the element. Defaults to nothing. When specified multi-ple multiple
ple times the actually shown text is the concatenation of the individual strings, vertically
stacked, with the first string specified being the topmost element.

textcolor spec
Specifies the color used to draw the text of an element with. Ignored if there is no text.
If not specified the system falls back to the value taken from the language variable text-color, textcolor,
color, which itself defaults to black.

textfont spec
Specifies the font used to draw the text of an element with. Ignored if there is no text. If
not specified the system falls back to the value taken from the language variable textfont,
which itself defaults to Helvetica 12pt.

then location

then (<direction> ?length?)...

(<direction> ?length?)...
This attribute specifies an intermediate location the line element has to go through. It can
be specified multiple times, with each use adding one additional location to the series which
the line will go through. These location will be traversed in the order they were specified.

The location can be given explicitly, or as a series of directions with distances. In the lat-ter latter
ter case the names of all known directions are accepted for the direction part. If no dis-tance distance
tance is specified for a direction the system falls back to the value taken from the language
variable movelength, which itself defaults to the pixel equivalent of 2 cm. The whole set of
direction,distance pairs is treated as a series of translations which are added up to provide
the final translation specifying the intermediate point (relative to the preceding point).

The last named direction is propagated to the layout system as the direction to follow. The
use of noturn is not able to overide this behaviour.

At last, the names of the registered directions also serve as attribute commands, with an
implicit attribute then in front of them.

If no intermediate or last location is specified for the line the system falls back to a point
movelength pixels away from the starting location, in the current direction as maintained by
the layouting system

to location
Specifies the location where the arc element ends. Defaults to a location such that a
90-degree arc is drawn in the chosen direction, starting at from.

width length

wid length
Specifies the width of the element. If not specified the system falls back to the value taken
from the language variable boxwidth, which itself defaults to the pixel equivalent of 2 cm.

width length
Specifies the width of the diamond element. The manner in which a default is calculated when
not specified also depends on the specifications of the attributes aspect and height, if any.

If both width, and height are specified then any specification of aspect is ignored, as it is
implicitly defined in the width and height as well, and this takes precedence. A missing spec-ification specification
ification is ignored in that case well, i.e. no defaults are required.

If the aspect is specified, and one of the attributes width or height, then the missing
attribute is calculated from the two which are specified. No defaults are required for these
cases either.

If only one of the attributes width or height is specified then the system uses a fallback for
the aspect, the value taken from the language variable diamondaspect, which itselfs defaults
to 2.

width length
Specifies the width of the text element. Defaults to the natural width of its text.

with corner
Specifies the corner of the element to place at the location given by the attribute at.
Defaults to the current corner as maintained by the layouting system, except if the value for
at was specified by the user. In that case it defaults to center.

with corner
Line elements are normally positioned absolutely, using the locations specified through the
attributes from, then, and to. If at is specified however then these positions are translated
a last time, moving the line's corner named by the attribute with to the location given by
this attribute. This means that with is effective if and only if the attribute at was speci-fied specified
fied as well for the line.

CORNERS
Corners are named values for in elements, usually locations.

• The closed elements define corners for the compass rose, including the "center", and their
"width" and "height".

IMAGE: figure-27-corners-closed

• block elements additionally export all variables which were set during their definition as
corners.

• The open elements on the other hand define "start", "end", and "center". The first two map to
the locations originally provided through the attributes from and to of the element.

IMAGE: figure-28-corners-open

• The center of line and move elements is the location halfway between "start" and "end" cor-ners, corners,
ners, this is regardless of any intermediate locations the element may have.

• The line and move elements additionally name all their locations as corners using numbers as
names, starting from 1 (equivalent to "start"), in order of traversal.

IMAGE: figure-15-spline-1

• The center of arc elements is the center of the circle the arc is part off.

• The arc elements additionally define the compass rose of closed elements as well.

NAMED DIRECTIONS
The named directions are commands which tell the layout system in which direction to go when placing
the next element without an explicit position specification. They can also be used as arguments to
the attribute then, and the command by for relative points, see there for the relevant syntax.

The diagram core defines the directions of the compass rose, plus a number of aliases. See below for
the full list.

IMAGE: figure-27-corners-closed

This overlaps with the pre-defined corners for closed elements. This is used by the layout system,
when are going in direction X the name of the opposite direction is the name of the corner at which
the new element will be attached to the current position, and if this corner does not exist the near-est nearest
est actual corner by angle is used.

west

left

south

down

bottom

bot

east

right

north

top

northwest

up-left

upleft

leftup

northeast

up-right

upright

rightup

southwest

down-left

downleft

leftdown

southeast

down-right

downright

rightdown

MISCELLANEOUS COMMANDS
number cm

number mm

number inch

number pt
These commands allow the specification of distances and coordinates in metric and imperial
units, returning the equivalent distance or coordinate in pixels, which is the unit used
internally for all calculations.

The conversion factors are based on the result of tk scaling and are computed once, at the
time the package is sourced, future changes of the tk scaling factor have no effect.

number number

IMAGE: figure-50-point-cons-absolute

This command takes the x and y coordinates of a location and returns the absolute point for
it.

by distance direction

IMAGE: figure-51-point-cons-relative

This command takes a distance and direction (angle in degress, or registered direction name)
and returns the relative point for it, i.e. the delta or translation it represents.

Note also the (dis)similarities to the directional specifications for the attribute then of
line and move elements. Where we say here
by 50 east
for the attribute we say
or just

point1 + point2

IMAGE: figure-48-point-vectoradd

This command interprets two points as vectors and adds them together. If at least one of the
points is absolute the result is absolute as well. The result is a relative point if and only
if both points are relative.

point1 - point2

IMAGE: figure-49-point-vectorsub

This command interprets two points as vectors and subtracts the second from the first. If at
least one of the points is absolute the result is absolute as well. The result is a relative
point if and only if both points are relative.

point by distance direction
This command is a more convenient, or at least shorter, form of

[$point + [by $distance $direction]]

point1 | point2

IMAGE: figure-31-point-projection

This command calculates the projection of two points, i.e. the result is the point having the
x-coordinate of point1 and the y-coordinate of point2.

n between poin1 point2

IMAGE: figure-29-point-interpolation-1

This command computes the point which is n*100 percent of the way between point1 and point2,
and returns it as its result. This means that for

n == 0 The result is point1.

n == 1 The result is point2.

n == 0.5
The result is half way between the two points.
etc. Note that it is allowed to use values < 0 and > 1 for n

intersect elem1 elem2

IMAGE: figure-32-point-intersection

This command takes two open elements, computes the lines going through their "start"- and
"end"-corners, and returns the point where these two lines intersect. The command throws an
error if the lines do not intersect, or are coincident.

element names ?pattern?
This command returns a list containing the names of all corners for the element. If a pattern
is specified then only the names matching it (via string match are returned. Otherwise all
names are returned (equivalent to a default pattern of *).

element corner
This command returns the value for the corner of the element. This can be anything, including
points and elements.

element corner1 corner2...
This is a convenience shorthand for

[[[$elem $corner1] $corner2] ...]

assuming that the value for
[$elem $corner1]
again an element.

element ?corner1... ?names ?pattern??]?

This is a convenience shorthand for

[[[$elem $corner1] ...] names ?pattern?]

assuming that the value for
[$elem $corner1]
again an element.

nth ?corner?

This command asks the diagram history for the nth element
created, searching from the beginning of the history (counting from 1)
and returns it as its result.

If the corner is specified then the value for this corner is
returned instead.

nth last ?corner?

This command asks the diagram history for the nth element
created, searching from the end of the history and returns it as its
result.

If the corner is specified then the value for this corner is
returned instead.

nth shape ?corner?

This command asks the diagram history for the nth element
created, of the given shape, searching from the beginning of the
history (counting from 1) and returns it as its result.

If the corner is specified then the value for this corner is
returned instead.

nth last shape ?corner?

This command asks the diagram history for the nth element
created, of the given shape, searching from the end of the
history and returns it as its result.

If the corner is specified then the value for this corner is
returned instead.

last ?corner?

last shape ?corner?

Convenience commands mapping to "1st last"
and "1st last shape".

1st

2nd

3rd

Aliases for 1th, 2th, and 3th, for readability,
usable whereever nth can ocur.

VARIABLES
The language context contains a number of predefined variables which hold the default values for var-ious various
ious attributes. These variables, their uses, and values are:

anchor

The default value for the attribute anchor.

Initialized to center.

The legal values are all those accepted by Tk_GetAnchor
[http://www.tcl.tk/man/tcl8.5/TkLib/GetAnchor.htm].

arcradius

The default value for the attribute radius of arc elements.

Initialized to the pixel equivalent of 1 cm.

arrowhead

The default value for the attribute arrowhead.

Initialized to none.

The legal values are

none, -Draw none,Draw

Draw no arrowheads, at neither end of the line.

start, first, <-

Draw an arrowhead at the beginning of the line, but not at its end.

end, last, ->

Draw an arrowhead at the end of the line, but not at its beginning.

both, <->

Draw arrowheads at both ends of the line.

boxheight

The default value for the attribute height of box, diamond and ellipse elements.

Initialized to the pixel equivalent of 2 cm.

boxwidth

The default value for the attribute width of box, diamond and ellipse elements.

Initialized to the pixel equivalent of 2 cm.

clockwise

The default value for the attributes clockwise and counterclockwise of arc elements.

Initialized to False, for counter-clockwise direction.

circleradius

The default value for the attribute radius of circle elements, and also the default for the
attribute chop, when specified without an explicit length.

Initialized to the pixel equivalent of 1 cm.

drumaspect

The default value for the attribute aspect of drum elements.

Initialized to 0.35.

fillcolor

The default value for the attribute fillcolor of all elements which can be filled.

Initialized to the empty string, signaling that the element is not filled.

justify

The default value for the attribute justify.

Initialized to left.

The legal values are left, right, and center.

linecolor

The default value for the attribute color of all elements having to draw lines (all but text).

Initialized to black.

linestyle

The default value for the attribute style of all elements having to draw some line.

Initialized to solid.

The legal values are all those accepted by Tk_GetDash [http://www.tcl.tk/man/tcl8.5/TkLib/Get-
Dash.htm],

and additionally all which are listed below:

solid, empty string
Draw solid line.

dash, dashed, -Draw dashed,Draw
Draw a dashed line.

dot, dotted, .
Draw a dotted line.

dash-dot, -.
Draw a dash-dotted line

dash-dot-dot, -..
Draw a dash-dot-dotted line.

linewidth

The default value for the attribute stroke of all elements having to draw some line.

Initialized to 1 (pixels).

movelength

The default value for the directional specification of intermediate locations by the attribute
then of line and move elements.

Initialized to the pixel equivalent of 2 cm.

slant

The default value for the attribute slant of box elements.

Initialized to 90 degrees, i.e. slant straight up.

textcolor

The default value for the attribute textcolor of all elements having to draw some text.

Initialized to black.

textfont

The default value for the attribute textfont of all elements having to draw some text.

Initialized to Helvetica 12pt.

DIAGRAM CLASSES The intended audience of this section are developers wishing to work
on the internals of the diagram package.

Regular users of diagram can skip this section without missing anything.

The main information seen here is the figure below, showing the hierarchy of the classes implementing
diagram.

IMAGE: figure-00-dependencies

At the bottom, all at the same level are the supporting packages like snit, etc. These can all be
found in Tcllib.

Above them is the set of diagram classes implementing the various aspects of the system, i.e.:

diagram

The main class, that which is seen by the user.

diagram::core

The core engine, itself distributed over four helper classes.

diagram::basic

The implementation of the standard shapes, like box, circle, etc., based on the extension fea-tures features
tures of the core.

diagram::element

Core support class, the database of created elements. It also keeps the history, i.e. the
order in which elements were created.

diagram::attribute

Core support class, the generic handling of definition and processing of attributes.

diagram::direction

Core support class, the database of named directions.

diagram::navigation

Core support class, the state of layout engine, i.e. current position and directin, and opera-tions operations
tions on it.

diagram::point

General support class handling various vector operations.

REFERENCES
KEYWORDS
2D geometry, arc, arrow, box, canvas, circle, diagram, diamond, drawing, drum, ellipse, image, inter-polation, interpolation,
polation, intersection, line, move, picture, plane geometry, plotting, point, raster image, spline,
text, vector

CATEGORY
Documentation tools

diagrams 0.3 diagram(n)

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