Using MMM Mode for Mason: An Overview
Since many users of MMM Mode use it for Mason <www.masonhq.com>, and
since the Mason submode class is the most complex one supplied, a
few comments regarding its usage are in order. Even if you don't
use Mason, this file may be of interest to you as an example of MMM
usage and possible problems.
INSTALLATION AND LOADING
For general installation and information, see the README file and
the texinfo documentation. The submode class for Mason components
is called `mason' and is automatically loaded from `mmm-mason.el'
the first time it is used.
MODES AND EXTENSIONS
If you want to have mason submodes automatically in all Mason files,
you can use `mmm-mode-ext-classes-alist'; the details depend on what
you call your Mason components and what major mode you use. Some
example elements of `mmm-mode-ext-classes-alist' follow, with
comments on the corresponding naming scheme.
(html-mode "\\.html\\'" mason) ;; Any .html file in html-mode
(hm--html-mode nil mason) ;; Any buffer in hm--html-mode
(sgml-mode nil mason) ;; Any buffer in sgml-mode
(nil "\\.\\(mason\\|html\\)\\'" mason) ;; All .mason and .html files
(nil "\\.m[dc]\\'" mason) ;; All .md and .mc files
(nil "\\`/var/www/mason/" mason) ;; Any file in the directory
(nil nil mason) ;; All buffers.
In order for any of these to work, you must set `mmm-global-mode' to
a non-nil value, such as `t' or `maybe' (the two of which mean
different things; see the documentation). This can be done with a
line in .emacs such as the following:
(setq mmm-global-mode 'maybe)
If you use an extension for your Mason files that emacs does not
automatically place in your preferred HTML Mode (be it html-mode,
sgml-html-mode, hm--html-mode, or whatever), you will probably want
to associate that extension with your HTML Mode (this is a feature
of emacs, not MMM Mode). An example is shown below.
(add-to-list 'auto-mode-alist '("\\.mason\\'" . html-mode))
This also goes for "special" Mason files such as autohandlers and
dhandlers. The code below tells emacs to use html-mode for files
named `autohandler' and `dhandler'.
(add-to-list 'auto-mode-alist '("\\(auto\\|d\\)handler\\'" . html-mode))
An alternate solution is to change the names of your autohandlers
and dhandlers so that emacs recognizes them as HTML automatically.
Similar code can be used to recognize all files in a given directory
as HTML and/or Mason.
There are certain problems with CPerl mode in submode regions. (Not
to say that the original perl-mode would do any better--it hasn't
been much tried.) First of all, the first line of a Perl section
is usually indented as if it were a continuation line. A fix for
this is to start with a semicolon on the first line. The insertion
key commands do this whenever the Mason syntax allows it.
In addition, some users have reported that the CPerl indentation
sometimes does not work. This problem has not yet been tracked
down, however, and more data about when it happens would be helpful.
Some people have reported problems using PSGML with Mason. Adding
the following line to a .emacs file should suffice to turn PSGML off
and cause emacs to use a simpler HTML mode:
(autoload 'html-mode "sgml-mode" "HTML Mode" t)
Earlier versions of PSGML may require instead the following fix:
(delete '("\\.html$" . sgml-html-mode) auto-mode-alist)
(delete '("\\.shtml$" . sgml-html-mode) auto-mode-alist)
Other users report using PSGML with Mason and MMM Mode without
difficulty. If you don't have problems and want to use PSGML, you
may need to replace `html-mode' in the suggested code with
`sgml-html-mode'. (Depending on your version of PSGML, this may not
be necessary.) Similarly, if you are using XEmacs and want to use
the alternate HTML mode `hm--html-mode', replace `html-mode' with
One problem that crops up when using PSGML with Mason is that even
ignoring the special tags and Perl code (which, as I've said,
haven't caused me any problems), Mason components often are not a
complete SGML document. For instance, my autohandlers often say
<% $m->call_next %>
in which case the actual components contain no doctype declaration,
<html>, <head>, or <body>, confusing PSGML. One solution I've found
is to use the variable `sgml-parent-document' in such incomplete
components; try, for example, these lines at the end of a component.
%# Local Variables:
%# sgml-parent-document: ("autohandler" "body" nil ("body"))
%# sgml-doctype: "/top/level/autohandler"
This tells PSGML that the current file is a sub-document of the file
`autohandler' and is included inside a <body> tag, thus alleviating
its confusion, and also instructs it where to find the doctype
declaration (assuming your top-level autohandler has one). This
alleviates most problems for me. I admit to not understanding PSGML
internals very well, so YMMV.