# 7 Editing SGML Documents

The PSGML package for emacs provides a very nice editing environment for SGML documents. You might put the following in your `~/.emacs` file:

> `(setq load-path (cons "`PSGML_DIR`" load-path))
> (autoload 'sgml-mode "psgml" "Major mode to edit SGML files." t)`

where PSGML_DIR is the directory in which PSGML is installed. At our lab, this directory is: `/project/ps/emacs/lisp/psgml`

To turn on fontification of SGML document, also add the following:

> `(setq sgml-set-face 't)`

You may also specify what font faces to use for highlighting. Here is what I (Denys) am using today:

> `(setq sgml-markup-faces
> '((start-tag . font-lock-reference-face)
> (end-tag . font-lock-reference-face)
> (comment . font-lock-comment-face )
> (pi . font-lock-keyword-face )
> (sgml . font-lock-type-face )
> (doctype . font-lock-type-face )
> (entity . font-lock-keyword-face )
> (shortref . font-lock-reference-face)))`

Strangely enough, when you open an SGML file for editing, the fontification process always waits for 6 seconds of idleness before it actually gets going. This is annoying, but hard coded.

For each document, `psgml-mode` parses the DTD and uses this information to help editing (it knows what is legal, where). Normally it uses the `<!DOCTYPE ...>` declaration at the top of the document to find theDTD. There are 2 common cases where that doesn't work well: when the DTD is in a location that PSGML cannot find and when editing part of a document in a separate file that doesn't have the `DOCTYPE` declaration.

In such cases it is easier to load a ``parsed DTD''; it is also much faster. The easiest way to save a parsed DTD is to create, in the directory where the DTD is located, a file containing the following line:

> `<!DOCTYPE` ELEM`SYSTEM "`DTD`">`

and to invoke ``Parse DTD'' and then ``Save Parsed DTD'' from the DTD menu. Then, when editing a partial document, you can manually invoke ``Load Parsed DTD'' from that same menu.

`fill-mode` is also nice to get automatic line breaking, but, in my experience, it is better to turn `adaptive-fill-mode` off, otherwise, due to the indentation of nested element, you'll soon be writing in a very narrow column at the right of the page. For example, you might add the following code at the end of and SGML document:

> `<!--
> Local Variables:
> mode: sgml
> mode: auto-fill
> adaptive-fill-mode: nil
> End:
> -->`

as far as SGML is concerned, this is a comment, but is meaningful to emacs.