TH PREREX.STY 7 2014-04-11 "prerex.sty-6.6" ""
SH NAME
prerex.sty  \- a LaTeX document style for prerequisite charts
SH DESCRIPTION
B prerex.sty
defines macros that
B [pdf]latex
can use
to draw charts consisting of labelled course boxes linked by arrows
that represent pre- and co-requisite requirements.
P
If the source file satisfies the constraints
of the
BR prerex (5)
format, a chart description may be edited using the
BR prerex (1)
interactive editor (as well as any conventional text editor).
SH TERMINOLOGY
A prerequisite chart consists of several
I course boxes,
linked by
I arrows.
Courses are either
I half
or
I full,
and may be
I required
or
I optional
(or neither).
Each course box can contain a course
I code
(upper left corner),
a course
I title
(lower half),
and
I timetable
information
(upper right corner).
An arrow can be either a
I prerequisite
(solid),
a
I corequisite
(dotted),
or
I recommended
(dashed).
When a conventional arrow would be inappropriate, it is possible to use
a
I mini
course "box" (consisting of just a course code) just above a target box.
An arbitrary line of text may be placed anywhere on the chart.
SH COORDINATE SYSTEM
A conventional two-dimensional
Cartesian coordinate system is used to specify the locations of
diagram elements.
The
origin (where
I x = 0
and
IR "y = 0" )
is at the lower-left corner of the diagram.
The diagram height is configurable; the width is determined by
the values of
I \etextwidth
and
an adjustable
I \eunit
length, which defines the absolute value of a coordinate unit.
It is possible to put a coordinate grid with labelled axes
in the background of a chart.
The coordinates of a
I box,
I mini,
or
I text-line
are those of its centre point.
An
I arrow
is described by the
coordinates of the centre points of its source and target boxes/minis/text-lines.
SH USAGE
The command
B \eusepackage{prerex}
should appear in the document preamble.
This will define a LaTeX environment
IP
BI \ebegin{chart} " ... " \eend{chart}
LP
within which the following commands may be used
to produce course boxes, minis, text-lines, and arrows.
The order of commands is not significant except
that the commands for the source and target boxes of an arrow should
I precede
the command for the arrow.
SH COURSE BOXES
The commands producing course boxes have the following forms:
IP
BI \ehalfcourse " x,y" :{ code }{ title }{ timetable }
IP
BI \efullcourse " x,y" :{ code }{ title }{ timetable }
IP
BI \ereqhalfcourse " x,y" :{ code }{ title }{ timetable }
IP
BI \ereqfullcourse " x,y" :{ code }{ title }{ timetable }
IP
BI \eopthalfcourse " x,y" :{ code }{ title }{ timetable }
IP
BI \eoptfullcourse " x,y" :{ code }{ title }{ timetable }
LP
where
I x,y
are the coordinates of the
I centerpoint
of the box, relative to the origin
of the coordinate system at the lower-left corner of the diagram.
The
I code,
I title,
and
I timetable
arguments are arbitrary (well-bracketed) text, possibly with LaTeX markup.

The following are similar but take an additional argument to specify the (non-default)
background color of the course box:
IP
BI \ehalfcoursec " x,y" :{ code }{ title }{ timetable }{ color }
IP
BI \efullcoursec " x,y" :{ code }{ title }{ timetable }{ color }
IP
BI \ereqhalfcoursec " x,y" :{ code }{ title }{ timetable }{ color }
IP
BI \ereqfullcoursec " x,y" :{ code }{ title }{ timetable }{ color }
IP
BI \eopthalfcoursec " x,y" :{ code }{ title }{ timetable }{ color }
IP
BI \eoptfullcoursec " x,y" :{ code }{ title }{ timetable }{ color }
LP
SH MINI COURSE BOXES AND TEXT LINES
A mini course "box" is produced by a command of the form
IP
BI \emini " x,y" :{ code }
LP
The following instruction places a line of text centered at the coordinates:
IP
BI \etext " x,y" :{ text-line }
LP
There are several differences between minis and text-lines.
The maximum length allowed for a course-code may be less than that
for a text-line. A sans-serif font and a reduced font size is used for a course-code.  A course-code
may be hyperlinked but a text-line is not (except when the coordinate grid is on).
A
B \eparbox
command
may be used in the
I text-line
argument if more than one line is desired.
SH ARROWS
Arrows between course boxes (or from a mini or text-line to a course box) are produced
by commands of the form
IP
BI \eprereq " x0,y0,x1,y1" :
IP
BI \ecoreq " x0,y0,x1,y1" :
IP
BI \erecomm " x0,y0,x1,y1" :
LP
These produce, respectively, solid, dotted, and dashed arrows from
the course box (or mini or text-line) centered at coordinates
I x0,y0
to the course box centered at coordinates
I x1,y1.
PP
Arrows by default have a
non-zero curvature (unless they are very short).  It is possible to override the default curvature
for a particular arrow by using
the instructions
IP
BI \eprereqc " x0,y0,x1,y1;c" :
IP
BI \ecoreqc " x0,y0,x1,y1;c" :
IP
BI \erecommc " x0,y0,x1,y1;c" :
LP
where
I c
is an integer in the range 0-100 specifying the desired curvature; for example,
IR c= 0
will produce a
I straight
arrow. Negative curvatures are also allowed. To change the default curvature, the user program may redefine the
B \eDefaultCurvature
command.
SH WEB LINKS
Course boxes (including minis) may be hyperlinked.
The default URL for course boxes is
IR ./course-code .html
where
I course-code
is
the
I code
argument
of the course box. The URL scheme may be changed by the user
by re-defining the
B   \eCourseURL
command.
SH COORDINATE GRID
The following command produces a coordinate grid, which is
useful for editing a diagram:
IP
B \egrid
LP
The grid lines will be covered by course boxes and arrows.
The
B \egrid
command
also redefines the
B \eCourseURL
command
so that,
if the mouse cursor is placed over a box or mini in (some) PDF viewers,
the
I coordinates
of the box, mini, or text-line will be displayed
as follows:
in the status bar in
BR xpdf
and
BR gpdf ,
and in a "tooltip" in recent versions of
BR kpdf " (now re-named"
BR okular ),
BR evince ,
and
the Adobe Reader.
Similarly, the coordinates of the source and target boxes of arrows
are displayed if the mouse hovers over the mid-point of an arrow,
Such coordinate displays make it easier to edit chart descriptions.
When the grid is on, the mid-point of every arrow is highlighted by a
"bullet".
PP
There is a GUI frontend
BR vprerex (1)
to the
BR prerex (1)
editor which incorporates a minimalistic prerex-enabled PDF viewer.
SH STAND-ALONE COMMANDS
The following commands may be used outside a
B chart
environment, such as in the explanatory notes for a chart:
IP
B \esolidarrow
IP
B \edottedarrow
IP
B \edashedarrow
IP
B \elightbox
IP
B \eboldbox
IP
B \edashedbox
LP
SH CONFIGURATION
The following are defined by the style file but may be re-defined by the
user:
IP
BI   \enewcommand{\eDefaultCurvature}{ 20 }
LP
where the argument should be in the range 0-100; 0 means no curvature.
IP
BI   \enewcommand{\eCourseURL}[3]{ #3.html }
LP
where the arguments supplied at the call are the
I x
and
I y
coordinates of the box or mini and the course code.
IP
BI   \enewcommand{\ebackground}{ LightYellow }
LP
where
I LightYellow
is defined by
IP
BI       \edefinecolor{LightYellow}{ rgb }{ "1.0, 1.0, 0.878431" }
IP
BI   \esetlength{\eunit}{ 5.7816pt }
LP
which defines the absolute size of a coordinate unit; this yields 10 pixels per
coordinate unit if the chart is converted to an image at 125 dpi.
IP
BI   \enewcommand{\edpi}{ 125 }
IP
BI   \enewcommand{\ePixelsPerUnit}{ 10 }
LP
IP
BI   \esetcounter{diagheight}{ 75 }
LP
which is the
IR y -coordinate
of the top of the diagram (reduced to 65 in landscape mode);
the nominal diagram width is
IR \etextwidth " / " \eunit " + " 10.
P
The following define the thicknesses of the three kinds of arrows,
and the thickness of bold boxes:
IP
BI   \enewcommand{\esolidwidth}{ 0.5pt }
IP
BI   \enewcommand{\edottedwidth}{ 0.8pt }
IP
BI   \enewcommand{\edashedwidth}{ 0.5pt }
IP
BI   \enewcommand{\eboldwidth}{ 1.0pt }
LP
P
The following command is used to change to a smaller size for course codes,
timetable information, and mini-course codes:
IP
BI   \enewcommand{\esmallersize}{\erelsize{-3}}
LP
P
The following command defines the baseline adjustment for the stand-alone arrows and boxes;
this parameter is font-dependent.
IP
BI   \enewcommand{\ebaselineAdj}{ -0.5ex }
LP
SH DEPEDENCIES
This implementation of
B prerex.sty
uses
B pgf
(version 3.0 or later)
with add-on package
B tikz.
The following additional packages are used:
B relsize,
B calc,
B multido,
B textcomp,
B xcolor,
and
B hyperref.
I Either
BR pdflatex (1)
I or
BR latex (1)
followed by
BR dvips (1)
(and possibly
BR ps2pdf (1))
I or
BR latex (1)
followed by
BR dvipdfmx (1)
may be used.
P
To convert a PDF chart to SVG (Scaleable Vector Graphic) format, it is recommended to
use
BR pdf2svg (1),
obtainable from
http://www.cityinthesky.co.uk/opensource/pdf2svg/.

SH  IMPLEMENTATION DETAILS
P
To improve the appearance, boxes are drawn with slightly rounded corners.  The half-course
boxes are assigned a minimum height to give a more uniform appearance to horizontal
rows of such boxes.
The mini and text boxes have white frames and their
fill colour is white, which is assumed to be the background colour of the chart.
A text box is not normally hyperlinked; however, if the coordinate grid is
on, it is hyperlinked and its chart coordinates are encoded in the URI.
P
Arrows with a small height and arrows whose
source and target points have equal x or y coordinates are always draw straight
(using a specialized and simpler macro)  unless an explicit
non-zero curvature argument is provided.
If the coordinate grid is on, a hyperlink with the source and target coordinates is placed
at the mid-point of the arrow.
A wider background white edge is drawn below an arrow to
improve the appearance
of crossing arrows; the background also
ensures visibility of the
arrow when the coordinate grid is on.
A thin white arrow (with a visible
arrowhead) is drawn beneath the visible arrow to obtain a thin arrowhead.
P
When the coordinate grid is drawn, the
B CourseURL
command
is re-defined to pass node coordinates in URIs. Also,
two "anchor" hyperlinks are inserted at the southwest and northeast corners
of the diagram to allow prerex-enabled
PDF viewers to compute chart coordinates.
SH LICENSE
B prerex.sty
and this document may be distributed and/or modified under the
conditions of the LaTeX Project Public License.
SH AUTHOR
R. D. Tennent ([email protected])
SH SEE ALSO
BR dvipdfmx (1),
BR dvips (1),
BR evince (1),
BR gpdf (1),
BR kpdf (1),
BR latex (1),
BR okular (1),
BR pdf2svg (1),
BR pdflatex (1),
BR prerex (1),
BR prerex (5),
BR ps2pdf (1),
BR tikz (1),
BR pgf (1),
BR vprerex (1),
and
BR xpdf (1).

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