New devbook-mode for editing the Gentoo Devmanual.

* devbook-mode.el: New file. Major mode for editing the
Gentoo Devmanual, derived mode of nxml-mode.
* ebuild-mode.texi (devbook-mode): Document it.
* Makefile (DISTFILES): Add devbook-mode.el.

Signed-off-by: Ulrich Müller <ulm@gentoo.org>

4 files changed, 105 insertions, 4 deletions

diff --git a/ChangeLog b/ChangeLog
index 35ca3aa..f6cc1f6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2020-02-08  Ulrich Müller  <ulm@gentoo.org>
+
+	* devbook-mode.el: New file. Major mode for editing the
+	Gentoo Devmanual, derived mode of nxml-mode.
+	* ebuild-mode.texi (devbook-mode): Document it.
+	* Makefile (DISTFILES): Add devbook-mode.el.
+
 2019-12-21  Ulrich Müller  <ulm@gentoo.org>
 
 	* Version 1.49 released.
diff --git a/Makefile b/Makefile
index a42987e..b193723 100644
--- a/Makefile
+++ b/Makefile
@@ -6,8 +6,9 @@ PV = $(shell sed '/^;.*[Vv]ersion/!d;s/[^0-9.]*\([^ \t]*\).*/\1/;q' \
 	ebuild-mode.el)
 P = $(PN)-$(PV)
 
-DISTFILES = ebuild-mode.el ebuild-mode-keywords.el gentoo-newsitem-mode.el \
-	glep-mode.el ebuild-mode.texi keyword-generation.sh ChangeLog
+DISTFILES = ebuild-mode.el ebuild-mode-keywords.el \
+	devbook-mode.el gentoo-newsitem-mode.el glep-mode.el \
+	ebuild-mode.texi keyword-generation.sh ChangeLog
 
 
 .PHONY: all dist clean
diff --git a/devbook-mode.el b/devbook-mode.el
new file mode 100644
index 0000000..5978258
--- /dev/null
+++ b/devbook-mode.el
@@ -0,0 +1,78 @@
+;;; devbook-mode.el --- edit the Gentoo Devmanual
+
+;; Copyright 2020 Gentoo Authors
+
+;; Author: Ulrich Müller <ulm@gentoo.org>
+;; Maintainer: <emacs@gentoo.org>
+;; Keywords: languages
+
+;; This file is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 2 of the License, or
+;; (at your option) any later version.
+
+;; This file is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'nxml-mode)
+(require 'easymenu)
+(require 'skeleton)
+
+;;;###autoload
+(define-derived-mode devbook-mode nxml-mode "DevBook"
+  "Major mode for editing the Gentoo Devmanual."
+  ;; The style guide says 80 characters. Set to 79 to keep diff output
+  ;; within the limit (and arguably, 80 includes the newline).
+  (setq fill-column 79)
+  (setq indent-tabs-mode nil)
+  ;; *** FIXME *** The style guide says no indentation, except inside
+  ;; <tr>, <ul>, <ol> and <dl>, where it must be 2 spaces. There is no
+  ;; easy way to achieve this, so set to 0 which is right more often.
+  (setq nxml-child-indent 0))
+
+(define-skeleton devbook-insert-skeleton
+  "Insert a skeleton for a DevBook XML document."
+  nil
+  "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
+  "<guide "
+  (let* ((dirname (file-name-directory buffer-file-name))
+	 (path (if (string-match ".*/devmanual[^/]*/\\(.*\\)" dirname)
+		   (match-string 1 dirname)
+		 (skeleton-read "Path: "))))
+    (if (string= path "")
+	"root=\"true\""
+      (concat "self=\"" (file-name-as-directory path) "\"")))
+  ">\n"
+  "<chapter>\n"
+  "<title>" (skeleton-read "Title: ") "</title>\n"
+  - "\n"
+  "</chapter>\n"
+  "</guide>\n")
+
+(define-key devbook-mode-map
+  "\C-c\C-n" 'devbook-insert-skeleton)
+
+(easy-menu-define devbook-mode-menu devbook-mode-map
+  "Menu for devbook-mode."
+  `("DevBook"
+    ["Insert skeleton" devbook-insert-skeleton]))
+
+;;;###autoload
+(add-to-list 'auto-mode-alist '("/devmanual.*\\.xml\\'" . devbook-mode))
+
+(provide 'devbook-mode)
+
+;; Local Variables:
+;; coding: utf-8
+;; End:
+
+;;; devbook-mode.el ends here
diff --git a/ebuild-mode.texi b/ebuild-mode.texi
index c524a83..418050a 100644
--- a/ebuild-mode.texi
+++ b/ebuild-mode.texi
@@ -61,6 +61,7 @@ by skeleton support.
 * Commands:: What ebuild-mode provides.
 * ebuild-mode:: Editing ebuilds.
 * eclass-mode:: Editing eclasses.
+* devbook-mode:: Editing the Gentoo Devmanual.
 * gentoo-newsitem-mode:: Editing GLEP 42 news items.
 * glep-mode:: Editing Gentoo Linux Enhancement Proposals.
 @end menu
@@ -174,12 +175,26 @@ Run Portage's ebuild command, you are prompted for the phase you want.
 Create a ChangeLog entry.
 @end table
 
-@node eclass-mode, gentoo-newsitem-mode, ebuild-mode, Top
+@node eclass-mode, devbook-mode, ebuild-mode, Top
 @chapter eclass-mode
 There is no special eclass-mode but ebuild-mode is used without the
 commands that make no sense in eclasses.
 
-@node gentoo-newsitem-mode, glep-mode, eclass-mode, Top
+@node devbook-mode, gentoo-newsitem-mode, eclass-mode, Top
+@chapter devbook-mode for the Gentoo Devmanual
+This is a very simple derived major mode for editing the Devmanual.
+Because the Devmanual is written in DevBook XML, this mode is derived
+from @code{nxml-mode} and inherits its syntax highlighting and editing
+functions.  A skeleton for a new Devmanual file can be inserted via
+the @code{devbook-insert-skeleton} function bound to @kbd{C-c C-n}.
+
+It is recommended to install the @code{app-emacs/nxml-gentoo-schemas}
+package in addition, which will enable on-the-fly syntax validation.
+
+Currently @code{devbook-mode} works with GNU Emacs only, because the
+underlying @code{nxml-mode} does not support XEmacs.
+
+@node gentoo-newsitem-mode, glep-mode, devbook-mode, Top
 @chapter gentoo-newsitem-mode for GLEP 42 news items
 This mode supports the highlighting of relevant keywords for GLEP 42
 news items.  These news items get displayed if special criteria for