6. Miscellany

6.1 Ignoring some files		Don't to complete on certain file names
6.2 Buffer completion		An application of lightning completion
6.3 HTML mode completion		Another example

6.1 Ignoring some files

If you are using this package to complete on file names, then you should be aware of the lisp variable completion-ignored-extensions. (Lightning completion on file names is based on a completion mode already present in Emacs, and this variable comes from that mode.)

Here is its documentation: "Completion ignores filenames ending in any string in this list. This variable does not affect lists of possible completions, but does affect the commands that actually do completions."

Lightning completion mode uses a similar variable, called lc-ignored-file-extensions, whose default value is equal to completion-ignored-extensions.

I use LaTeX, and when I start with a file `bozo.tex', then LaTeX produces a number of auxiliary files: `bozo.aux', `bozo.dvi', `bozo.log', and possibly `bozo.bbl', `bozo.blg', `bozo.toc', `bozo.lof', etc. When I am editing such a file, I edit the file `bozo.tex' frequently, and I almost never touch the others. So I make sure that lc-ignored-file-extensions contains the strings ".toc" ".log" ".aux" ".lof" ".blg" ".bbl" ".dvi". The easiest way to do this is to customize this variable.

In case you haven't been paying attention: suppose I have added ".aux" to lc-ignored-file-extensions, and I want to find the file `bozo.aux', with lightning completion enabled. One way to do this is to type `bozo.aux' quickly enough that emacs is never idle for half a second. Another option is to hit C-c right at the start, to turn off lightning completion; then just type in `bozo.aux' at one's leisure. Another way to do this is to use lightning completion to get `bozo.tex' and ending completion there (if this is the only file that starts `bozo' that doesn't end in an ignored extension, completion will end automatically at this point; otherwise, hit SPC). Then delete `tex' and type in `aux'. There are other ways of doing this, no doubt, but I'll let you figure them out.

6.2 Buffer completion

Buffer completion is an example of a use of lightning completion: it lets you complete on reasonably balanced substrings of a buffer. The main function is

(completing-insert-buffer-contents BUF)

where BUF is interactively the current buffer or, with a prefix argument, a buffer specified by the user.

In other words, if I want to repeat something I said somewhere else in this buffer, I call the function completing-insert-buffer-contents. At that point, I enter lightning completion mode on the contents of this buffer. If I want to repeat something I said in a different buffer, I hit C-u and then call completing-insert-buffer-contents. Emacs prompts me for a buffer name, and then does lightning completion on the contents of that other buffer. This is useful if you're too lazy to switch buffers, find the material you want to copy, mark it, kill it, and yank it.

The `dabbrev' package (included as part of the standard GNU Emacs distribution) does some similar things, so you might want to look at that, too. I won't advocate the use of one package over the other--I think each has its uses.

6.3 HTML mode completion

Here is another example of how to use lightning completion: you can automatically complete on HTML tags when in html mode. I have the following lines in my `.emacs' file. The first line binds the < key to the function html-lightning-tag (you could use a different key, if you wanted, but since HTML tags all start with this character, it seems to make sense). The next lines define this function--it does lightning completion on HTML tags. And the remaining lines (starting with `(defvar html-light-alist') define the list of HTML tags on which to complete. A typical line is `("<h3></h3>" -5)'; the first entry is the tag, and the second entry is the number of characters from the end by which the point should be offset (i.e., Emacs inserts the string `"<h3></h3>"' and then moves forward -5 characters). (This whole business is intended to be used with the version of html-mode that is contained in the file `sgml-mode.el', part of (for example) the standard GNU Emacs distribution.

(define-key html-mode-map "<" 'html-lightning-tag) (defun html-lightning-tag nil "Lightning complete control sequence." (interactive) (insert "<") (completing-insert html-light-alist nil 1 'point-adjust-hook "html tags")) (defvar html-light-alist '( ("<a href=\"\"></a>" -6) ("<h1></h1>" -5) ("<h2></h2>" -5) ("<h3></h3>" -5) ("<h4></h4>" -5) ("<h-5></h-5>" -5) ("<h6></h6>" -5) ("<hr> " 0) ("<!-- -->" -5) ("<img src=\"\" alt=\"\">" -9) ("<ol> <li> </ol>" -6) ("<ul> <li> </ul>" -6) ("<li> " 0) ("<dl> <dt> <dd> </dl>" -12) ("<dt> <dd> " -6) ("<p> " 0) ("<table> <tr> <th> </th> </tr> </table>" -20) ("<th> </th>" -5) ("<tr> <td> </td> </tr>" -11) ("<td> </td>" -5) ("<html> <head> <title> </title> </head> <body lang=\"EN\"> </body> </html>" -32) ("<address>John H. Palmieri, Department of Mathematics, University of Washington, palmieri@math.washington.edu</address> " 0) ("<address></address> " -11) ("<cite></cite>" -7) ("<kbd></kbd>" -6) ("<dfn></dfn>" -6) ("<em></em>" -5) ("<samp></samp>" -7) ("<small></small>" -8) ("<strong></strong>" -9) ("<sub></sub>" -6) ("<sup></sup>" -6) ("<tt></tt>" -5) ("<var></var>" -6) ("<code></code>" -7) ("<blockquote> </blockquote> " -15) ("<math> </math> " -9) ("<pre> </pre> " -8) ("<br> " 0)) "Alist of html tags for use with lightning completion")