From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.bugs Subject: bug#20613: Font locking is poorly documented Date: Tue, 19 May 2015 15:42:05 -0700 Organization: UCLA Computer Science Department Message-ID: <555BBC3D.4060503@cs.ucla.edu> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1432075403 25703 80.91.229.3 (19 May 2015 22:43:23 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 19 May 2015 22:43:23 +0000 (UTC) To: 20613@debbugs.gnu.org Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Wed May 20 00:43:11 2015 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YuqEA-0002pN-L7 for geb-bug-gnu-emacs@m.gmane.org; Wed, 20 May 2015 00:43:10 +0200 Original-Received: from localhost ([::1]:49231 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YuqE9-0007LN-Uh for geb-bug-gnu-emacs@m.gmane.org; Tue, 19 May 2015 18:43:09 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:50074) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YuqE6-0007L5-70 for bug-gnu-emacs@gnu.org; Tue, 19 May 2015 18:43:07 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YuqE3-00072e-3J for bug-gnu-emacs@gnu.org; Tue, 19 May 2015 18:43:06 -0400 Original-Received: from debbugs.gnu.org ([140.186.70.43]:40452) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YuqE2-00072a-Vo for bug-gnu-emacs@gnu.org; Tue, 19 May 2015 18:43:03 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.80) (envelope-from ) id 1YuqE2-0006l8-GA for bug-gnu-emacs@gnu.org; Tue, 19 May 2015 18:43:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Paul Eggert Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Tue, 19 May 2015 22:43:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: report 20613 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: X-Debbugs-Original-To: Emacs bug reports Original-Received: via spool by submit@debbugs.gnu.org id=B.143207534425922 (code B ref -1); Tue, 19 May 2015 22:43:01 +0000 Original-Received: (at submit) by debbugs.gnu.org; 19 May 2015 22:42:24 +0000 Original-Received: from localhost ([127.0.0.1]:50427 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from ) id 1YuqDP-0006k2-3u for submit@debbugs.gnu.org; Tue, 19 May 2015 18:42:23 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:36500) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from ) id 1YuqDM-0006jm-K7 for submit@debbugs.gnu.org; Tue, 19 May 2015 18:42:21 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YuqDG-0006vj-DR for submit@debbugs.gnu.org; Tue, 19 May 2015 18:42:15 -0400 Original-Received: from lists.gnu.org ([2001:4830:134:3::11]:35078) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YuqDG-0006vQ-9y for submit@debbugs.gnu.org; Tue, 19 May 2015 18:42:14 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:50007) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YuqDF-0007JP-7E for bug-gnu-emacs@gnu.org; Tue, 19 May 2015 18:42:14 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YuqDC-0006mj-2Q for bug-gnu-emacs@gnu.org; Tue, 19 May 2015 18:42:13 -0400 Original-Received: from smtp.cs.ucla.edu ([131.179.128.62]:54938) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YuqDB-0006lI-Tc for bug-gnu-emacs@gnu.org; Tue, 19 May 2015 18:42:10 -0400 Original-Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp.cs.ucla.edu (Postfix) with ESMTP id 1EDE6A6000C for ; Tue, 19 May 2015 15:42:07 -0700 (PDT) X-Virus-Scanned: amavisd-new at smtp.cs.ucla.edu Original-Received: from smtp.cs.ucla.edu ([127.0.0.1]) by localhost (smtp.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hvpqpZfRFWsZ for ; Tue, 19 May 2015 15:42:05 -0700 (PDT) Original-Received: from Penguin.CS.UCLA.EDU (Penguin.CS.UCLA.EDU [131.179.64.200]) by smtp.cs.ucla.edu (Postfix) with ESMTPSA id 9DF6FA60008 for ; Tue, 19 May 2015 15:42:05 -0700 (PDT) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6.x X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 140.186.70.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Original-Sender: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.bugs:102966 Archived-At: I was recently urged to use font locking to support a feature in Emacs,=20 and I must say that I am still confused about how it works even after=20 reading the Elisp manual several times. The manual has a lot of=20 low-level discussion of mechanism, but it doesn't explain policy and=20 since crucial features seem to be undocumented, I'm at a loss as to how=20 to use it, or how to debug it when it's not working. I finally gave up=20 and used Google and found cookbook stuff, but I have no idea how or why=20 it works as well as it does, or why it fails when it does. For example: http://www.emacswiki.org/emacs/PrettyLambda gives this example: (defun pretty-lambdas () (font-lock-add-keywords nil `(("(\\(lambda\\>\\)" (0 (progn (compose-region (match-beginning 1) (match-end 1) ,(make-char 'greek-iso8859-7 107)) nil)))))) but I can't find documentation explaining why a progn is needed, or why=20 it must return niil, or why one must use compose-region, or why one must=20 use it with a single =CE=BB rather than just having a =CE=BB character th= ere. One small suggestion: add a section explaining how the above example work= s.