Книга: Learning GNU Emacs, 3rd Edition

Chapter 8. Markup Language Support

It's true that many of the people who use Emacs are developers, writing code, tweaking it, recompiling it, and just generally enjoying the services of an amazingly extensible work environment. A variety of people, including developers, need to produce text for publication, whether internally, online, or in book format. This chapter describes the markup language support that Emacs offers, a topic relevant to both information publishers and developers, as more and more development work uses variants of the Extensible Markup Language, XML.

Choosing a format for producing documents isn't all that straightforward these days, especially if you eschew Microsoft Word. Some people write HTML, and Emacs offers a few options for this. HTML gives you some control over formatting but displays differently on various browsers. Of course, it is important as the lingua franca of the Web.

Other text publishing options include the TEX family. TEX (pronounced "tek") is a formatter that was developed by Donald Knuth for generating books. LATEX (pronounced "lay-tek") is a set of TEX commands created by Leslie Lamport. With TEX and LATEX , you can produce very precisely formatted text with equations, interesting fonts, graphics, headers and footers, and the like. Whether using filters or features of the program itself, you can publish TEX documents in a variety of formats.

Another option for publishing text—as well as programming—is XML. XML, when combined with a Document Type Definition (DTD) or schema, enables you to write text once and publish it in a variety of formats. Extensible Style Language (XSL) is also important in this regard. Because the standards are still being defined, organizations involved in document production may choose an established XML dialect, such as DocBook, as their publication format. XML at this point provides less precise control over format, but maximizes flexibility.

XML bridges the programming and publishing worlds, and what you do with XML will in part determine what tools you use and what support you need. We discuss a few options for writing XML in Emacs, including psgml mode and Jim Clark's nxml mode, which uses Relax NG schemas rather than DTDs for validation.

Some word processors and other tools integrate formatting and editing. These tools are often called WYSIWYG (what you see is what you get) tools. What's the advantage of using Emacs versus a WYSIWYG tool? Well, whether you're writing LATEX, XML, or HTML, you can be crystal clear about what's in the file and how it's structured if you use Emacs. Save a Microsoft Word file as HTML and then open the resulting file in Emacs. Word bloats the file with additional tags and formatting that is not strictly required. In terms of output, the streamlined and straightforward code you picture in your mind's eye when viewing a page is definitely not what you get, an ironic consequence of using a WYSIWYG tool like Word to create markup files. Chances are, if you've read this far, you're planning to use Emacs anyway, so we won't belabor the point.

In this chapter, we talk about these markup modes:

• For writing HTML, Emacs HTML mode (a subset of SGML mode) and the add-on HTML helper mode are discussed.

• For writing XML, Emacs SGML mode and the add-on modes psgml mode and nxml mode are described in brief.

• For writing LATEX documents, Emacs LaTeX mode is discussed.

These major modes help you insert formatting commands, or markup, into your text. While the amount of help that Emacs offers varies, using the mode designed for your text formatter will streamline your work.

At this point we must insert a caveat. We provide a barebones introduction to the markup modes described in this chapter. What we say here will get you started, but not much more than that. Entire books could be and have been written about using each of the markup tools described here. Now that that's out of the way, let's talk about a few features that are important in all the modes: comment handling and font-lock mode.

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