There's been a lot of work on contrib syntax highlighting plugins. One should be
picked and added to ikiwiki core.

We want to support both converting whole source files into wiki
pages, as well as doing syntax highlighting as a preprocessor directive 
(which is either passed the text, or reads it from a file). But,
the [[ikiwiki/directive/format]] directive makes this easy enough to 
do if the plugin only supports whole source files. So, syntax plugins
do no really need their own preprocessor directive, unless it makes
things easier for the user.

## The big list of possibilities

* [[plugins/contrib/highlightcode]] uses [[!cpan Syntax::Highlight::Engine::Kate]],
  operates on whole source files only, has a few bugs (see
  [here](http://u32.net/Highlight_Code_Plugin/), and needs to be updated to
  support [[bugs/multiple_pages_with_same_name]].
* [[!cpan IkiWiki-Plugin-syntax]] only operates as a directive.
  Interestingly, it supports multiple highlighting backends, including Kate
  and Vim.
* [[plugins/contrib/syntax]] only operates as a directive
  ([[not_on_source_code_files|automatic_use_of_syntax_plugin_on_source_code_files]]),
  and uses [[!cpan Text::VimColor]].
* [[plugins/contrib/sourcehighlight]] uses src-highlight, and operates on
  whole source files only. Needs to be updated to
  support [[bugs/multiple_pages_with_same_name]].
* [[sourcecode|todo/automatic_use_of_syntax_plugin_on_source_code_files/discussion]]
  also uses src-highlight, and operates on whole source files.
  Updated to work with the fix for [[bugs/multiple_pages_with_same_name]].  Untested with files with no extension, e.g. `Makefile`.
* [[users/jasonblevins]]'s code plugin uses src-highlight, and supports both
  while file and directive use.

* [hlsimple](http://pivot.cs.unb.ca/git/?p=ikiplugins.git;a=blob_plain;f=IkiWiki/Plugin/hlsimple.pm;hb=HEAD) is a wrapper for the the perl module Syntax::Highlight::Engine::Simple.  This is pure perl, pretty simple, uses css. It ought to be pretty fast (according to the author, and just because it is not external).
On the other hand, there are not many predefined languages yet.  Defining language syntaxes is about as much 
work as source-highlight, but in perl.  I plan to package the base module for debian. Perhaps after the author 
releases the 5 or 6 language definitions he has running on his web site, it might be suitable for inclusion in ikiwiki. [[DavidBremner]]

## General problems

* Using non-perl syntax highlighting backends is slow. I'd prefer either
  using a perl module, or a multiple-backend solution that can use a perl
  module as one option. (Or, if there's a great highlighter python module,
  we could use an external plugin..)
* Nothing seems to support 
  [[wiki-formatted_comments|wiki-formatted_comments_with_syntax_plugin]]
  inside source files. Doing this probably means post-processing the 
  results of the highlighting engine, to find places where it's highlighted
  comments, and then running them through the ikiwiki rendering pipeline.
  This seems fairly doable with [[!cpan Syntax::Highlight::Engine::Kate]],
  at least.
* The whole-file plugins tend to have a problem that things that look like
  wikilinks in the source code get munged into links by ikiwiki, which can
  have confusing results. Similar problem with preprocessor directives.
  One approach that's also been requested for eg,
  [[plugins/contrib/mediawiki]] is to allow controlling which linkification
  types a page type can have on it.

  > The previous two points seem to be related.  One thought: instead of
  > getting the source from the `content` parameter, the plugin could
  > re-load the page source.  That would stop directives/links from
  > being processed in the source.  As noted above, comments
  > could then be parsed for directives/links later.
  >
  > Would it be worth adding a `nodirectives` option when registering
  > an htmlize hook that switches off directive and link processing before
  > generating the html for a page?

* The whole-file plugins all get confused if there is a `foo.c` and a `foo.h`.
  This is trivially fixable now by passing the keepextension option when
  registering the htmlize hooks, though. That also should handle the
  case of source files with names that do not contain an extension (ie,
  "Makefile") -- in this case you just register the while filename
  in the htmlize hook.
* Whole-file plugins register a bunch of htmlize hooks. The wacky thing
  about it is that, when creating a new page, you can then pick "c" or
  "h" or "pl" etc from the dropdown that normally has "Markdown" etc in it.
  Is this a bug, or a feature? Even if a feature, plugins with many
  extensions make the dropdown unusable.. 

  Perhaps the thing to do here is to use the new `longname` parameter to
  the format hook, to give them all names that will group together at or
  near the end of the list. Ie: "Syntax: perl", "Syntax: C", etc.

## format directive and comments

Hmm, the [[ikiwiki/directive/format]] directive would also allow comments
inside source files to have mdwn embedded in them, without making the use
of mdwn a special case, or needing to postprocess the syntax highlighter
output to find comments.

	/* \[[!format mdwn """

	This is a comment in my C file. You can use mdwn in here.

	"""]] */

Note that this assumes that directives are expanded in source files,
which has its own set of problems.