Creating a clean presentation style in 40 commits

Did you always want to learn ConTeXt, but did not know where to start? I have written a git-based tutorial that should help you get started.

The idea of the tutorial is to start with an empty document, and add features one-by-one. Each git commit corresponds to one small change in the document, and includes pointers to the documentation corresponding to that change. Continue reading

Separation of content and presentation for tables (part 1)

Separation of content and presentation is one of the selling points of TeX over word-processors. Strictly speaking, TeX is not superior compared to word-processors in this regard. It is possible to obtain a clean separation between content and presentation in word-processors (using styles) and it is possible to mix content and presentation in TeX code, as is illustrated by the following example from sample tex file for the IEEE Conference on Decision and Control:

\title{\LARGE \bf
Preparation of Papers for IEEE CSS Sponsored Conferences \& Symposia
}


(Seriously, how can anyone recommend writing TeX code like that!) In spite of the falseness of the argument, the general sentiment is true. It is much easier to write structured code (that separates content and presentation) in TeX than in word-processors. A testament to this is the ease with which one can convert a LaTeX document written in the style of one publisher house to that in the style of another publisher by simply changing the class file.

However, when it comes to tabular data, TeX, or rather LaTeX, is a mess. Simply browse through the questions tagged tables on TeX.SE if you don’t believe me. In this blog post, I want to argue that a clean separation between content and presentation is possible in TeX. The mess that is LaTeX tables is a limitation of LaTeX, and not of TeX. To illustrate this point, I’ll use ConTeXt and LuaTeX.

which was typeset using the following code:

\bTABLE
\bTR
\bTD Course      \eTD
\bTD Description \eTD
\bTD Term Taught \eTD
\bTD Enrollment  \eTD
\eTR

\bTR
\bTD NAME 101 \eTD
\bTD A description of the course that is typically one paragraph long.
A description of the course that is typically one paragraph long.
A description of the course that is typically one paragraph long. \eTD
\bTD Fall 2010 \eTD
\bTD 45 \eTD
\eTR
\bTR
\bTD NAME 215 \eTD
\bTD A description of the course that is typically one paragraph long.
A description of the course that is typically one paragraph long.
A description of the course that is typically one paragraph long. \eTD
\bTD Winter 2011 \eTD
\bTD 120 \eTD
\eTR
\bTR
\bTD NAME 555 \eTD
\bTD A description of the course that is typically one paragraph long.
A description of the course that is typically one paragraph long.
A description of the course that is typically one paragraph long. \eTD
\bTD Fall 2012 \eTD
\bTD 15 \eTD
\eTR
\eTABLE


The ConTeXt interface is relatively clean. Rows are indicated by \bTR...\eTR and columns by \bTD...\eTD. The names of the command and the user interface is inspired from HTML tables.

So far, there is a clear separation between content and presentation, simply because we haven’t tweaked the presentation at all. Now suppose, I want to typeset the header as white on blue.

The clean way to add this achieve this is to define a new setup

 \startsetups table:header
\setupTABLE[row][first][background=color, backgroundcolor=darkblue, color=white, style=bold]
\stopsetups


and simply change the first line of the table to

\bTABLE[setups={table:header}]


Note that the presentation element (how to style the first row) is defined in the document preamble, and the setup can be shared in all the tables that need that particular style. Now, suppose that in addition to the header, we want to remove the vertical lines in the middle of the table.

Again, to achieve this, define a new setups as follows:

\startsetups table:frame
\setupTABLE[frame=off]
\setupTABLE[topframe=on,bottomframe=on]
\setupTABLE[column][first][leftframe=on]
\setupTABLE[column][last][rightframe=on]
\stopsetups


and add the setups table:frame to the first line of the table

\bTABLE[setups={table:header, table:frame}]


Continuing this way, suppose we want to change the alignment of cells, say vertically middle align the first column, horizontally middle align the third column, add hyphenation to the second column; and add some offset between the cells.

(I am not arguing that this is a good visual style; just using this as an example without making the use case too complicated). As before, we define a new setups

\startsetups table:style
\setupTABLE[column][1][align={middle,lohi}]
\setupTABLE[column][2][align={normal,hyphenated,verytolerant}]
\setupTABLE[column][3][align=middle]
\setupTABLE[loffset=1mm,roffset=1mm]
\stopsetups


and add the setups table:style to the first line of the table.

\bTABLE[setups={table:header, table:frame, table:style}]


See, separation of presentation and content need not be difficult in TeX. Let’s see if this approach is flexible to change. Suppose, I don’t like the vertical middle alignment of the first column. I can simply change the \setupTABLE[column][2][align=...] to my liking, and the change will be applied to all tables using the table:style setups. (Contrast this with what you need to do in LaTeX to achieve the same, and you’ll understand why LaTeX tables are considered hard.)

The above examples illustrate a simple example. In a future blog post, I’ll show how one can use Lua to simplify typesetting of complicated tables, while still maintaining a separation of content and presentation.

Announcing the visualcounter module

It has been almost two years since I posted about the main idea of the visualcounter module. I am happy to announce the official release of the module. I have been using this module in my presentations for almost two years without any problems, so I believe that it is stable enough to be released.

At present, the module is available on github and it should be available through ConTeXt garden soon. Look at the documentation to see some of the features of the module (in particular, the "star rating" example based on Jim Hefferon’s article in the Practex Journal).

The module provides six counters. Two of these were created for proof of concept and are not well tested; the remaining four—scratchcounter, mayanumbers, markers, and countdown—are well tested and, hopefully, their interface will not change.

This was my first module that uses the ConTeXt namespace macros. If you peek into the module, you’ll notice that I only define one macro; everything else is handled by the ConTeXt namespace macro \definenamespace.

The other interesting feature of this module is that I use a separate metapost instance for displaying the counters. This avoids conflict with user definitions. For example, if a user decides to change the metapost definition of fill for whatever reason,

\startMPdefinitions
let fill = draw;
\stopMPdefnition


such a change will not affect the visual counter module!

Any feedback is appreciated.

Removing multiple blank lines when typesetting code listings

The listings package in LaTeX has an option to collapse multiple empty lines into a single empty line when typesetting code lists. Today, there was a question on TeX.se how to do something similar when using the minted package. Since the vim module uses the same principle as the minted package, I wondered how one could collapse multiple empty lines into a single line?

One of the fetures of the vim module is that you can source an arbitrary vimrc file before processing the code through the vim editor to generate syntax highlighted code. This feature makes it possible to delegate the task to collapsing multiple blanks lines into a single blank line to vim, the editor. Since the vim module first writes the source code in a file with extension .tmp, the following vimrc snippet will collapse all multiple blank lines into a single blank line whenever a .tmp file is loaded:

au BufEnter *.tmp %s/$$^\s*\n$$\{2,\}/\r/ge | w


Use this inside the vim module as follows (example also available on github):

\usemodule[vim]

\startvimrc[name=collapse]
au BufEnter *.tmp %s/$$^\s*\n$$\{2,\}/\r/ge | w
\stopvimrc

\definevimtyping[CPPtyping][syntax=cpp, vimrc=collapse]

\starttext
\startCPPtyping
i++;

i++;

i--;
\stopCPPtyping
\stoptext


Agreed, this is not as simple as the extralines=1 option in the listings package. But, it is not too complicated when you consider the fact that I had not thought about this feature at all when I wrote the vim module.

How I stopped worrying and started using Markdown like TeX

These days I type most of simple documents (short articles, blog entries, course notes) in markdown. Markdown provides only the basic structured elements (sections, emphasis, urls, lists, footnotes, syntax highlighting, simple tables and figures) which makes it easy to transform the input into multiple output formats. Most of the time, I still want PDF output and for that, I use pandoc to convert markdown to ConTeXt. At the same time, I have the peace of mind that if I need HTML or DOC output, I’ll be able to get that easily.

For most of the last decade, I have almost exclusively used LaTeX/ConTeXt for writing all my documents. After moving to Markdown, I miss three features of TeX: separation of content and presentation; conditional inclusion of content; and including external documents. In this post, I’ll explain how to get these with Markdown.

Separation of content and presentation

TeX gives you a lot of control for creating new structural elements. Let’s take a simple example. Suppose I want to write a file name in a document. Normally, I want the filename to appear in typewriter font. In LaTeX, I could type it as

\texttt{src/hello.c}

but it is better to define a custom macro \filename and use

\filename{src/hello.c}

The advantage is two-fold. Firstly, while writing the file, I am thinking in term of content (filename) rather than presentation (typewriter font). Secondly, in the future, if I want to change how a filename is displayed (perhaps as a hyper-link to the file), all I need to do is change the definition of the macro. Markdown, with its simplistic structure, lacks the ability to define custom macros.

Conditional compilation

TeX also makes it trivial to generate multiple versions of the document from the same source. Again, lets take an example. Suppose I am writing notes for a class. Normally, I like to include a short bullet list on my lecture slides, but include a detailed description in the lecture handout. In ConTeXt I can use modes as follows (LaTeX has a similar feature using the comments package):

Feature of the solution
\startitemize[n]
\item Feature 1

\startmode[handout]
Explanation of the feature ...
\stopmode

\item Feature 2

\startmode[handout]
Explanation of the feature ...
\stopmode
\stopitemize

To generate the slides version of my lecture notes, I compile them using

context --mode=slides --result=slides <filename>

This version just contains the bullet list. Since the handout mode is not set, the content between \startmode[handout] ... \stopmode is omitted.

To generate the handout version of my lecture notes, I compile them using

context --mode=handout --result=slides <filename>

Since the handout mode is set, the content between \startmode[handout] ... \stopmode is included

Such a conditional compilation is extremely useful to keep the slides and handouts in sync. Again, markdown with its simplistic feature set, lacks the ability of conditional compilation. Neither does Pandoc add this feature.

Including external documents

TeX makes it easy to include external documents. This is really important when you want to include source code in your documents. I teach an introductory programming class, and want to make sure that the example code included in my notes is correct. I write the code in a separate file, write the corresponding test files to ensure that the code works correctly, and then include it in my notes using

\typeJAVAfile[src/FactoryExample.java]

which gives me syntax highlighted source code. Pandoc does generate syntax highlighted source code, but does not provide any means to include external source code. So, I have to copy paste the code from the actual source file to the markdown document, but that is an error-prone process.

If I only cared about PDF output (via LaTeX/ConTeXt backend), I could simply use the same TeX macros in the markdown document. Pandoc passes the TeX macros unchanged to the LaTeX/ConTeXt backend, so I would get a TeX document with all the bells and whistles. But, if I tried to generate HTML or DOC output, these TeX macros will be omitted, and I’d get a broken document. One of my reasons to switching to Markdown was the peace of mind that I can generate HTML or DOC output if needed. Using TeX macros in the source takes away that advantage.

So, I started looking for possible solutions and found gpp—the generic pre-processor. It is similar to the C-preprocessor (that handles the #include, #define, stuff in C/C++) but provides many configuration options. I use it with the -H option, which requires macros to be specified in an HTML-like mode:

<#include "file">
<#define MACRO|value>
Use <#MACRO>

Normally the <#...> does not appear in a document, so using gpp is safe.
See the gpp documentation for complete details. I’ll show how to get the three features that I miss from TeX:

1. Separation of content and presentationWith gppI can define new macros that denote new structural elements, e.g.,
<#define filename|#1>
The source is included in <#filename src/hello.c>

When I compile the document using gpp -H, I get

The source is included in src/hello.c

Sure, this requires more typing that simply using ..., but that is the price that one has to pay for getting more structure. More importantly, I can define the #filename macro based on the output format:

<#define filename|#1>
<#ifdef HTML>
<#define filename|<code class="filename">#1</code>>
<#endif>
<#ifdef TEX>
<#define filename|\\filename{#1}>
<#endif>
The source is included in <#filename src/hello.c>

Now, if I compile the document using gpp -H -DHTML=1, I get

The source is included in <code class="filename">src/hello.c</code

and if I compile using gpp -H -DTEX=1, I get

The source is included in \filename{src/hello.c}

This ensures that the document structure is passed to the output as well.

To make it easy to manage macros, create three files, macros.gpp containing all macros, html.gpp overwriting some of the macros with HTML equivalents, and tex.gpp overwriting some of the macros with TeX equivalents. End macros.cpp file with

....
<#ifdef HTML>
<#include "html.gpp">
<#endif>
<#ifdef TEX>
<#include "tex.gpp">
<#endif>

and then preprocess the document using gpp -DTEX=1 --include macors.gpp <filename> (or -DHTML=1 for HTML output).

2. Conditional compilationActually, the previous example already shows how to get conditional compilation: use the -D command line switch and check the variable definition using #ifdef. Thus, the above example translates to:
Feature of the solution

1. Feature 1

<#ifdef HANDOUT>
Explanation of the feature ...
<#endif>

2. Feature 2

<#ifdef HANDOUT>
Explanation of the feature ...
<#endif>

When I compile without -DHANDOUT=1, I get the slides version; when I compile with -DHANDOUT-1, I get the handout version.

3. Including external documentsExternal documents can be included with #includedirective. So, I can include an external file using
~~~ {.java}
<#include "src/Factory.java">
~~~

Putting it all together

All that is needed is to run the gpp preprocessor and then pass the output to pandoc.

gpp -H <options> <filename> | pandoc -f markdown -t <format> -o <outfile>

Hide this in a wrapper script or a shell function or a Makefile, and you have a markdown processor with the important features of TeX!

A ConTeXt style file for formatting RSS feeds for Kindle

As I said in the last post, I bought an Amazon Kindle Touch sometime back, and I find it very useful for reading on the bus/train while commuting to work.I use it read novels and books, a few newspapers and magazines that I subscribe to, and RSS feeds of different blogs that I follow. Until now, I had been using ifttt to send RSS feeds to Instapaper; Instapaper then emails a daily digest as an ebook to kindle account at midnight; in the morning, I switch on my Kindle for a minute; the Kindle syncs new content over Wifi; and off I go.

However, Kindle typesets ebooks very poorly,  so I decided to write a ConTeXt style file to typeset RSS feed (check it out on github).  To use this style:

\usemodule[rssfeed]

\starttext
\setvariables
[title={Title of the feed},
description={Description of the feed},
]

\starttitle[title={First feed entry}]
....
\stopttitle

\starttitle[title={Second feed entry}]
...
\stoptitle

\stoptext

It uses the eink module to set the page layout and fonts, and use a light and clean style for formatting feed entries. Since the proof is in the pudding, look at following PDFs to see the style for different types of blogs.

I use a simple ruby script to parse RSS feeds and uses Pandoc to convert the contents of each entry to ConTeXt. The script is without bells and whistles, and there is no site specific formatting of feeds. All feeds are handles the same way, and as a result, there are a few glitches: For example, IEEE uses some non-standard tags to denote math) which Pandoc doesn’t handle and the images generated by WordPress blogs that use $latex=...$ to typeset math are not handled correctly by ConTeXt, etc.

The script also uses Mutt to email the generated PDF to my Kindle account. This way, I can simply add a cron job that runs the script at appropriate frequency (daily for usual blogs, weekly for low traffic blogs, and once a month for table of contents of different journals).

A style file for eink readers

Recently I bought an Amazon Kindle touch. It is more convenient than the IREX DR1000 for reading morning news and blogs (thanks to instapaper’s automated delivery of “Read Later” articles, and ifttt for sending RSS feeds to Instapaper).

I have also started reading novels on the Kindle as opposed to the DR1000. Being small, the Kindle is easier to carry; and its hardware just works better than the DR1000: instant startup, huge battery life, and wifi; all areas where DR1000 was lacking. Still DR1000 is the best device when it comes to reading and annotating academic papers, which is surprising given that DR1000 came out 3.5 years ago; perhaps the “eink devices for reading and annotating academic papers” is too niche a niche market to have a successful product. DR1000 was $800 and IREX is now bankrupt. Anyways, since I am reading novels on Kindle, I have updated my old ConTeXt style file for DR1000 to also handle Kindle and am releasing that as a ConTeXt module. Actually, as two ConTeXt modules: t-eink-devices that stores the dimensions and desired font sizes for eink devices (currently, it has data only for DR1000 and Kindle as those are the only devices that I have) and t-eink that sets an easy to read style that includes: • Paper size that matches the screen dimensions • Tiny margins, no headers and footers • Bookmarks for titles and chapters (both DR1000 and Kindle can use PDF bookmarks as table of contents) • A reasonable default style for chapter and title headings • A \startinterlude\stopinterlude environment for title pages, dedication, etc. I have only tested this with simple novels (mostly texts and pictures). That is why the module does not set any style for sections, subsections, etc, as I did not need them so far. This is mostly for personal use, but I am announcing this module in case someone wants to give it a shot. To use the module, simply add \usemodule[irex] [ % alternative=kinde, % or DR1000 % mainfont={Tex Gyre Schola}, % sansfont={Tex Gyre Heros}, % monofont={Latin Modern Mono}, % mathfont={Xits}, % size=, % By default, kindle uses 10pt and DR1000 uses 12pt font. % Use this setting if you want to set a font size. ] This module passes the font loading to the simplefonts module. So, use any name for mainfont etc. that simplefonts will understand. If you don’t set any option, then the default values, indicated above, are used. So, to test out the module, you can just use (for kindle): \usemodule[eink] or (for DR1000) \usemodule[eink][alternative=DR1000] Below are the samples from Le Petit Prince. The text and images were taken from this website and converted to ConTeXt using Pandoc. The text is also available from Project Gutenburg, Australia. If you have a Kindle or a DR1000, you can compare the quality of these PDFs (hyphenation, line-breaking, widows and orphans) from what you get from the eBook version. If I am to spend 5-10 hours reading a novel, I don’t mind spending 15 minutes extra (to create a PDF version of the book) to make that reading experience pleasant. The output is not perfect, especially in terms for float placement in the Kindle version (Page 5 has an underfull page because the figure was too big to fit in the page, the right float image on page 10 would have been better as a here figure, the right float figures on page 13-14 are much lower compared to where they are referred, etc.). But, I find these more tolerable than a chapter title appearing at the bottom of the page and occasionally loosing pagination when I highlight text (both of which happen with epub documents). Reading remote files Won’t it be nice if TeX could pretty-print files hosted on github, e.g., \typeRUBYfile{https://raw.github.com/adityam/filter/master/Rakefile}  or include a remotely hosted markdown file in your document \processmarkdownfile{https://raw.github.com/adityam/filter/master/README.md}  I wanted to add this feature to the filter and vim modules. Although I knew that ConTeXt could read remote files directly, I thought that it would be hard to plug into this mechanism. Boy, was I wrong. Look at the commit history of the change needed to add this feature. All I needed to do, was add \locfilename to get the local file name for a file. If the requested file is a remote file (i.e., starts with http:// or ftp://), ConTeXt downloads the file and stores it in the cache directory, and return the name of the cached file. Pretty neat, eh? With this change, \process<filter>file macro of the filter module can read remote files. Since, the vim module is built on top of the filter module, the \type<vim>file can also read remote files. The above feature is currently only available in the dev branch. I’ll make a new release once I add hooks to force re-download of remote files. Meanwhile, if you have a ConTeXt macro that reads files, just add a \locfilename at appropriate place, and your macro will be able to read remote files Update for the filter module: faster caching Over the last year, the code base of the filter module has matured considerably. Now, the module has all the features that I wanted when I started with it about a year and a half back. The last remaining limitation (in my eyes, at least) was that caching of results required a call to external programs (mtxrun) to calculate md5 hashes; as such, caching was slow. That is no longer the case. Now (since early December), md5 sums are calculated at the lua end, so there is no time penalty for caching. As a result, in MkIV, recompiling is much faster for documents having lots of external filter environments with caching enabled(i.e., environments defined with continue=yes option). Some thoughts on lowering the learning curve for using TeX (part I) TeX has a steep learning curve. Often times, steeper than it needs to be. Take, for example, the special characters in TeX. Almost every introduction to plain TeX, eplain, LaTeX, or ConTeXt has a section on these special characters \ { }$ & # ^ _ & ~


A good introduction then goes on to explain why these special characters are important; sometimes dropping a hint about category codes. I feel that these details are useless and, at the user level, we should get rid of them.