Wiki

Clone wiki

SCons / DeveloperGuide / Documentation / Discussion

[[!toc 1]]

Sphinx as a documentation tool

techtonik: Historically, we use Docbook format to maintain documentation. Docbook is XML based format that should allow to convert source files into various formats, such as HTML, PDF, man pages and allow easy skinning and customizing. This was in theory. In practice it appeared that Docbook transformations in either XSLT or DSSSL languages are beautiful at micro level, but clumsy, hard to comprehend and maintain when you need to make a bigger thing done. The complexity in Docbook templates (and in customizations) grows significantly faster than with traditional template engines, and there are almost no free tools to debug XSLT templates. Docbook was good at the beginning, because there were no alternative, but today there is at least Sphinx.

We still maintain docs in Docbook, but we don't use XSLT for transformation. Transformation is made using even more "prehistoric" DSSSL templates and tool-chain that only runs on *nix like systems.

Greg: There are two issues with using Sphinx.

One issue is that Sphinx is a reStructuredText editor. Now, reStructuredText is a fine language for documentation, but we have many dozens of pages in XML that would have to be converted, and converted losslessly. I don't see an automated tool that would provide any assistance, and without such a tool, I can't see any way we could proceed.

  • techtonik: There is one that can be tweaked - http://code.google.com/p/db2rst/ Greg: The other, and far more important, issue is that I don't see how a workflow can be constructed to extract the examples, run them, <ins>verify that any changes are correct</ins>, and then proceed with the example output inserted in the documentation. Without such a workflow in hand, Sphinx is a non-starter.

  • techtonik: issue no.1 for research DB: I have never worked with Sphinx (took a short look at the reST primer right now), but know Docbook a little. I don't think that reST is a good language for technical documentation at all, because it does not restrict the user to "structured authoring". You can freely assign attributes like italic or bold to text passages, which automatically leads to trouble when you try to get the output for, let's say, a guibutton consistent across all input files (and users!). This is where I feel that Docbook is still superior, you can also immediately check an input document against the DTD...and if it is valid, you are able to process it. There is (or: should be) a clear separation between the user that edits documents and one (or a few people) that actually process the XML to a HTML or PDF documentation. I don't like any support for fancy WYSIWYG to get in the way of this.

  • techtonik: I do not know if it is possible to restrict Sphinx to process only a subset or markup leaving only "structured markup" elements thus restricting user to "structured authoring". This probably an issue no.2 worth investigation. But poor appearance (and usability) of SCons manual as it now is mostly due to Docbook "structured authoring". There is no CHM, no Eclipse Help, no searchable indexes for help systems, no appealing design, no DHTML beautifiers - nothing except plain text in paragraphs. Current SCons docs are boring. Just because rigid Docbook markup doesn't have all necessary elements and XSLT is a very bad language for analyzing/calculating anything. They are hard to customize. Time waste in introducing a change into Docbook process is enormous in comparison with Sphinx, mostly because Python people are more familiar with reST than with XML, DTD, XSLT and corresponding toolchain. I also do not agree with your separation between doc authors and doc builders. As an author - I always want to see the final result of my efforts as soon as possible. * DB: Sorry, but you are mixing things up a little too much here, for my taste. It is not Docbook's fault that the current output looks boring and dull (to you). The problem is that actually nobody really cares...and this may be due to the fact that the current docs use some tags, special to SCons, for the support of automatically created examples and such. Like this, you cannot easily edit doc sources in a Docbook-Editor...it does not know these tags and your document is not valid, regarding the official DTD. If you start to introduce "SConsic" tags to reST (tweaking it, if you like) you will have the same effect there, I guess. People might get put off by having to learn all that extra stuff. I, as an author, am mostly concerned with the contents of my texts...not how they look in the final output. In a first step we should work on getting the current docs up-to-date and consistently marked up, in what format ever. Then we can start the catfights about whether the SCons logo should appear in the page header or in the footer ;). DB: It may be true that Docbook toolchains are difficult to set up and I would also vote for the step DSSSL->XSL asap, but with Sphinx you also need LaTeX for the conversion to PDF as a prerequisite. This could be another source for trouble because LaTeX distributions can differ a lot, when looking at which packages are installed and which not, for example. So, you don't necessarily get it all for free with Sphinx...

  • techtonik: XSL toolchain for Docbook is not much lighter. Not every XSLT processor can handle the complexity of Docbook stylesheets, so you are pretty limited. Even processors that come bundled with Eclipse Java Enterprise Edition can not do this. And Sphinx doesn't need LaTeX for conversion to PDF - http://code.google.com/p/rst2pdf/ - very responsive and active project, and integrates well with Sphinx. * DB: ...and is based on the ReportLab library (replacing one dependency with another), which is available in a OpenSource and Commercial version. The OpenSource branch does not support vector graphics and you cannot use stylesheets...hmmmm, I wonder whether this could stop anything? I don't want to keep you from any of your investigations, but when trying to reach high-quality output, there is no way around a central place for managing fonts. And it needs to be configured for your local installation, such that it knows which font families, types, ..., are available. So, creating good-looking documents is complex stuff, that's why it is a good idea to keep the authors/editors far away from fiddling with the actual page layouts.
    DB: Yes, Docbook stylesheets are pretty complex and need some care if you try to do special things. But if you stick to the default set of XSL for HTML and PDF (=FO), some basic customization like "displaying the SCons logo in page headers" is quite easy to accomplish.

Finally, I would like to point at a paragraph in the reST primer about sections. It talks about the adornments for section headers and requires the user (!) to "Be consistent, since all sections marked with the same adornment style are deemed to be at the same level".

Sorry, but this is not the right path to follow, or is it?

All together, our main concern should not be to make documentation (and its processing) easier for the core developer, but for the average user. If we can agree on this, then Docbook is still my choice. I will come up with an example workflow for Docbook, using XIncludes and PIs (processing instructions) in the next days and post it to this page.

  • techtonik: It would be a very welcome addition for a comparison. While Sphinx all new and shiny, it may have some deficiencies that I overlooked in my vision, so I look forward to add my variant of workflow once your example is ready.

Improving the Docbook workflow

Overall goals are:

  • simplifying the toolchains, especially reducing the number of required tools/packages
  • getting the output of documents cross-platform again (Windows and *nix), including the special processing for SCons examples in the User's guide
  • stronger decoupling of the mere "Editing" from the actual creation of the HTML/PDF output
  • for the editing: better support for validation (a user, as editor of a text, should be able to ensure that his changes do not break validity of the whole XML document...before he decides to commit...and without having to create all docs first)

Validation/Editing

For a start, I created a first draft of a special "SCons Docbook DTD".

dtd.tgz

It can be used to check the User's guide for validity, after changing the doctype in main.xml accordingly. I also prepared configuration packages for two visual XML editors, namely the Xmlmind editor

xxe4.tgz

and Syntext's Serna

scons.tgz

. They should enable you to edit the User's guide WYSIWYG style. For more infos about how to install these archives, please have a look at the "SCons Docbook DTD Reference manual"

docbook_dtd.pdf

Some issues to attack

I had another close look at the top-level SConstruct and the SConscript in the doc folder. The following points are worth further investigation, in my opinion:

  • The PDF/HTML output files from the Jade toolchain have to be moved/renamed each time. With xsltproc/libxml2 this will not be needed anymore...
  • The SConscript checks for fig2dev, although it is not really used at the moment. It was required for the conversion FIG -> JPEG in the design docs...but they don't include any reference to images?
  • The builder SConscript_revision (top-level SConstruct) is run for all XML files in the doc folder. This is not really needed, these are intermediate files...so what's the use in replacing the COPYRIGHT notice? There is one exception: doc/user/build_install.xml uses VERSION, but this can be replaced with the entries from version.xml...or not?
  • tidy is run on the HTML files, for a cleanup to XHTML. Again, this would get superfluous with a modern Docbook toolchain, using recent XSL stylesheets.
  • Finally, the man pages are still edited in groff format (shudder). Switching this to Docbook would remove the dependencies on groff and man2html, and make editing much easier. I gave this a first try and converted the current man pages of SCons, SConsign and SCons-time to Docbook with doclifter 2.3 (by Eric S. Raymond). The archive doclifter_examples.tgz

  • contains the new source XML files and output in the form of Man pages, HTML and PDF files. Here is the HTML version of SCons-time for taking a short peek: scons-time.html

All together, I see good chances to trade a new dependency on xsltproc (or the libxml2/libxslt Python modules) for removing groff, man2html, tidy, fig2dev and (at least for HTML) jw. When another FOP renderer is installed on the user's system (fop,XEP,...), it could replace the whole jade/openjade/jadetex/pdfjadetex stuff for PDF output.

SCons titlepages

I started to work on a design for the SCons documentation titlepages. Here is a first version of the User Guide 2.0.0,

scons_manual.pdf

illustrating what the current customizations look like.

What we have, so far

  • Customized SCons Docbook DTD.
  • Configuration sets for XmlMind and Serna XML editors.
  • Designs for a new titlepage and chapter pages (SCons PDF documents).
  • SCons Docbook Tool.
  • Simple script for validating single XML files, against the internal DTD or an external URL.

Soon to come

I am currently working on restructuring the User Guide source to use XIncludes instead of entity references. My thoughts revolve around a processing chain that looks something like this:

  1. User edits some input file(s) for documentation.
  2. Ensure that all required include files are present, e.g. for the example outputs of the User Guide. If not, create dummy files where needed.
  3. Validate all single input files.
  4. (optional) Rerun all SCons examples in the User Guide. Compare new vs. old output and report differences. Also check for errors during the SCons processing, in order to detect flaws in the examples (like missing files).
  5. Preprocess the User Guide by resolving all XIncludes and replacing special SCons DTD elements, e.g. scons_example, with valid Docbook counterparts.
  6. Finally, create the different output formats with the SCons Docbook Tool. A normal user or technical writer would usually stop with step 3 and then commit his changes. The points 4-6 should be reserved for members of the Release Team, when a new version is about to be published.

Updated