Documenting Lentic

With a previous release of lentic [1], I got a couple of suggestions. One of which was a complaint that it was hard to get going, because lentic lacks documentation. This is a bit unfortunate. Lentic actually did have documentation but it is hidden away as comments in source code; although, it’s not specific to it, I wanted lentic to enable literate programming and it uses itself to document itself.

Now, this makes perfect sense, but there is a problem. The end-user form of the documentation needs generating from the source code. This is true in general in Emacs land, although the standard form is texinfo. The usual solution to this problem is to generate the documentation up during the packaging process.

This should work, but it doesn’t. Or, rather, it does not work in all cases. For an archive such as Marmalade, it is entirely possible. But for MELPA it fails. The problem is that MELPA works directly from a git checkout. My documentation, of course, is not source but generated. Now MELPA has support for the generation of info from texinfo. But my source is Emacs Lisp and I need to use Lentic to generate a readable form.

One solution would, of course, be not to use MELPA. Nic Ferrier recently argued on the emacs-devel mailing list that the idea was fundamentally broken — a package is something that the developers should generate and publish as with Java or Clojure . He makes a good point, and one that is correct. Moving to Marmalade would solve this problems; after Nic’s work it is largely stable, so this was definately an option.

However, I like MELPA (although I have only used it since stable came out). It is nice that it uses what I am doing anyway (tagging, pushing, so forth). And I like the download stats. So I talked with the MELPA folks but, entirely reasonably, they did not want to add specific support to MELPA for this. Nor support for, for example, downloading the source from somewhere else.

Other possibilities did raise themselves; I could just check in my documentation. But my documentation depends on my source, so pretty much every commit would require also require a documentation commit. Not nice. I thought about adding the documentation as an independent package. Then my documentation commits would be in a repo with nothing else; but this hassles the user, even if it auto-installs. And I’d need different packages for MELPA and Marmalade. So, I was left with no good solution.

At the same time, as all of this, I was working on the documentation, generating Org files from my lisp documentation, then converting that to info. This sort of worked, but not nicely. A significant problem was that something in the toolchain did not like having multiple sections with the same names and I have a lot of these (“Commentary, Header, Code”). I have not tracked down yet whether this is a problem with Org’s texinfo export, texinfo itself or info, nor am I sure it would be worth the effort.

Instead, I decided to try HTML output. This worked quite nicely; I use a single Org driver file (called and imported all the generated org files from here. I also found org-info which I had not seen before — this is Javascript which gives an Info like experience — next, previous, occur, search and so on. It’s imperfect, but pretty usable, and gives a quite nice documentation experience. It’s also possible to view in EWW although there is no Info like paging here.

Dropping info has one other big advantage — my tool chain for generating the documentation is now entirely in Emacs. So, my source code is now enough, because lentic can generate it’s own documentation on-demand after installation. The first time the user requests the documentation either in EWW or a browser, lentic generates org files from it’s own source and then the HTML [2]. The only limitation is that this forces the requirement for a recent Emacs version, since the org mode exporter framework has just been updated; unfortunate but acceptable for a 0.x release.

Not all problems disappear. Because my documentation fits into the Emacs-Lisp commenting standards, it is not structured-ideally for info. For instance, the headers of all the lentic Emacs-Lisp files are included. I also would like to extend org-info so I can switch the “Code” sections on and off (embedded literate sources are useful, but not for everyone). It will need some work on Lentic, and probably also the org-mode HTML exporter.

But, then, neither is it that far off. It is good enough and a bit advance on the previous situation. Perhaps, too, it demonstrates a future for Emacs documentation in general as well, with Info replaced with HTML.

The new release [3] of Lentic is now available on Marmalade and MELPA, complete with documentation avaialble from the menu. Please feel free to try both lentic and its documentation system out now.


  1. P. Lord, "Lenticular Text: Looking at code from different angles", An Exercise in Irrelevance, 2015.
  2. P. Lord, "Lenticular Text For Emacs", 2015.
  3. P. Lord, "Lentic 0.7", An Exercise in Irrelevance, 2015.