diagram - Diagram drawing

Api

CLASSAPI
The package exports the API described here.

::diagramobjectNamecanvas ?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 canvas 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, ObjectAPI. 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.

OBJECTAPI
Instances of the diagram class support the following methods:

diagramObjectnewdirectionname ?keyvalue...?
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
complementary to the named one.

diagramObjectnewelementnameattributescmdprefix
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 ...-callbacks for these attributes. See the method newattribute for more
information on attribute definitions.

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

cmdprefixcanvasattributes
Where canvas is the handle of the canvas widget to draw to, and attributes is a dictionary
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.

diagramObjectnewaliasnamecmdprefix
This method defines a new command for the drawing language. I.e. name will become a new command 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.

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

diagramObjectnewattributename ?keyvalue...?
This method defines a new named attribute which can be used by graphical elements. The handling 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 processing
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

cmdprefixwordqueue
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 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

cmdprefixvalue
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 documentation
of the snit package.

merge The value of this key is a command prefix which will be invoked to insert the transformed
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

cmdprefixvaluedict
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 previously
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 newelement).

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 specified
then nothing will be done.

The signature of the command prefix is

cmdprefixinit
This method is run when the attribute is defined, its responsibility is to
initialize anything in the language namespace for the attribute and default
processing.

The result of this method is ignored.

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

The result of this method is ignored.

cmdprefixsetnamevalue
This method is run to push current a attribute value into the language namespace, 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 supplies
a default handling for default, linking the attribute to a variable in the language
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.

diagramObjectunknownattributecmdprefix
This method registers the command prefix with the subsystem processing the attributes for element
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 prefix is
expected to conform to the following signature:

cmdprefixwordqueue
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 callback
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.

diagramObjectdrawscript
This method runs the given script in the context of the drawing language definitions. See section
LanguageReference 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.

Bugs, Ideas, Feedback

       This  document,  and  the package it describes, will undoubtedly contain bugs and other problems.  Please
       report such in the category diagram of the TklibTrackers [http://core.tcl.tk/tklib/reportlist].   Please
       also report any ideas for enhancements you may have for either package and/or documentation.

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 audience
       are users of the package wishing to refresh their memory.  Newcomers should  read  the  DiagramLanguageTutorial  first.   Developers wishing to work on the internals of the package and its supporting packages
       should look at section DiagramClasses 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.

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 features
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 operations
on it.

diagram::point
General support class handling various vector operations.

Keywords

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

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 MiscellaneousCommands. IMAGE: figure-02-basic-shapes

arcattr...
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

anchornameljustrjustabovebelow 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"

clockwisecw 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.

colorspec
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.

counterclockwiseccw 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.

fillcolorspec
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".

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

justifyleft|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.

radiuslength
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 1cm.

strokewidth
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.

stylespec
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 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.

textstring
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.

textcolorspec
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.

textfontspec
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 Helvetica12pt.

tolocation
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.

arrowattr...

-->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 -->.

blockscriptattr...
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.

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

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

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

heightlengthhtlength
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 2cm.

slantangle
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 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.

widthlengthwidlength
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
2cm.

withcorner
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.

circleattr...

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

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

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

diameterlengthdiamlength
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.

radiuslengthradlength
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 1cm.

solid, empty string
Draw solid line.

dash, dashed, -
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.

diamondattr...

<>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

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

aspectnumber
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
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 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 2cm. For the aspect it uses either the user-specified value or
the default taken as described in the previous paragraph.

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

heightlength
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 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.

solid, empty string
Draw solid line.

dash, dashed, -
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.

widthlength
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 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.

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

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

aspectnumber
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.

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

solid, empty string
Draw solid line.

dash, dashed, -
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.

ellipseattr...
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

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

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

solid, empty string
Draw solid line.

dash, dashed, -
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.

lineattr...

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

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

arrowheadspec
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 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.

atlocationLine 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 1cmcolorspec
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.

fromlocation
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 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.

thenlocationthen (<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 2cm. 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

tolocation
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.

withcornerLine 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.

moveattr
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.

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

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

ljust "anchor west"

rjust "anchor east"

above "anchor south"

below "anchor north"

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

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

widthlength
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 definitions
below will be treated as the argument of an implicit text attribute.

anchornameljustrjustabovebelow 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"

arrowheadspec
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 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.

aspectnumber
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
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 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 2cm. For the aspect it uses either the user-specified value or the default taken as
described in the previous paragraph.

aspectnumber
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.

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

atlocationLine 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 1cmclockwisecw 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.

colorspec
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.

counterclockwiseccw 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.

fillcolorspec
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".

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

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

heightlengthhtlength
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 2cm.

heightlength
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
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 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 2cm. For the aspect it uses either the user-specified value or the default taken as
described in the previous paragraph.

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

justifyleft|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
management. If not specified the direction of the line becomes the new direction the layout.

radiuslengthradlength
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 1cm.

radiuslength
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 1cm.

slantangle
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.

strokewidth
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.

stylespec
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 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.

textstring
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.

textcolorspec
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.

textfontspec
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 Helvetica12pt.

thenlocationthen (<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 2cm. 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

tolocation
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.

tolocation
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.

widthlengthwidlength
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 2cm.

widthlength
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
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 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 2cm. For the aspect it uses either the user-specified value or the default taken as
described in the previous paragraph.

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

withcorner
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.

withcornerLine 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.

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" corners,
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.

NAMEDDIRECTIONS
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 nearest actual
corner by angle is used.

westwleftlsouthsdownbottombotbeasterightrnorthnuptoptnorthwestnwup-leftupleftleftupnortheastneup-rightuprightrightupsouthwestswdown-leftdownleftleftdownsoutheastsedown-rightdownrightrightdownMISCELLANEOUSCOMMANDSnumbercmnumbermmnumberinchnumberpt
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 tkscaling and are computed once, at the time
the package is sourced, future changes of the tkscaling factor have no effect.

numbernumber

IMAGE: figure-50-point-cons-absolute

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

bydistancedirection

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

... then east 50 ...

or just

... then east ...

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.

pointbydistancedirection
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.

nbetweenpoin1point2

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 nintersectelem1elem2

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.

elementnames ?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 stringmatch are returned. Otherwise all names are
returned (equivalent to a default pattern of *).

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

elementcorner1corner2...
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 lastshape ?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?

lastshape ?corner?
Convenience commands mapping to "1stlast" and "1stlastshape".

1st2nd3rd 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 various
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 1cm.

arrowhead
The default value for the attribute arrowhead. Initialized to none. The legal values are

none, -
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 2cm.

boxwidth
The default value for the attribute width of box, diamond and ellipse elements. Initialized to
the pixel equivalent of 2cm.

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
1cm.

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/GetDash.htm], and additionally all which are listed below:

solid, empty string
Draw solid line.

dash, dashed, -
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 2cm.

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 Helvetica12pt.

Name

       diagram - Diagram drawing

References

Synopsis

       package require Tcl8.5

       package require Tk8.5

       package require diagram1::diagramobjectNamecanvas ?script?

       diagramObjectnewdirectionname ?keyvalue...?

       diagramObjectnewelementnameattributescmdprefixdiagramObjectnewaliasnamecmdprefixdiagramObjectnewcommandnameargumentsbodydiagramObjectnewattributename ?keyvalue...?

       diagramObjectunknownattributecmdprefixdiagramObjectdrawscriptarcattr...

       arrowattr...

       -->attr...

       <-->attr...

       <-->attr...

       blockscriptattr...

       boxattr...

       circleattr...

       Oattr...

       diamondattr...

       <>attr...

       drumattr...

       ellipseattr...

       lineattr...

       --attr...

       moveattrsplineattr...

       textattr...

       westwleftlsouthsdownbottombotbeasterightrnorthnuptoptnorthwestnwup-leftupleftleftupnortheastneup-rightuprightrightupsouthwestswdown-leftdownleftleftdownsoutheastsedown-rightdownrightrightdownnumbercmnumbermmnumberinchnumberptnumbernumberbydistancedirectionpoint1+point2point1-point2pointbydistancedirectionpoint1|point2nbetweenpoin1point2intersectelem1elem2elementnames ?pattern?

       elementcornerelementcorner1corner2...

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

       nth ?corner?

       nth last ?corner?

       nth shape ?corner?

       nth lastshape ?corner?

       last ?corner?

       lastshape ?corner?

       1st2nd3rd

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