// -*- mode:doc; -*-
// vim: syntax=asciidoc

=== Infrastructure for asciidoc documents

[[asciidoc-documents-tutorial]]

The Buildroot manual, which you are currently reading, is entirely written
using the http://asciidoc.org/[AsciiDoc] mark-up syntax. The manual is then
rendered to many formats:

* html
* split-html
* pdf
* epub
* text

Although Buildroot only contains one document written in AsciiDoc, there
is, as for packages, an infrastructure for rendering documents using the
AsciiDoc syntax.

Also as for packages, the AsciiDoc infrastructure is available from a
xref:outside-br-custom[br2-external tree]. This allows documentation for
a br2-external tree to match the Buildroot documentation, as it will be
rendered to the same formats and use the same layout and theme.

==== +asciidoc-document+ tutorial

Whereas package infrastructures are suffixed with +-package+, the document
infrastructures are suffixed with +-document+. So, the AsciiDoc infrastructure
is named +asciidoc-document+.

Here is an example to render a simple AsciiDoc document.

----
01: ################################################################################
02: #
03: # foo-document
04: #
05: ################################################################################
06:
07: FOO_SOURCES = $(sort $(wildcard $(FOO_DOCDIR)/*))
08: $(eval $(call asciidoc-document))
----

On line 7, the Makefile declares what the sources of the document are.
Currently, it is expected that the document's sources are only local;
Buildroot will not attempt to download anything to render a document.
Thus, you must indicate where the sources are. Usually, the string
above is sufficient for a document with no sub-directory structure.

On line 8, we call the +asciidoc-document+ function, which generates all
the Makefile code necessary to render the document.

==== +asciidoc-document+ reference

The list of variables that can be set in a +.mk+ file to give metadata
information is (assuming the document name is +foo+) :

* +FOO_SOURCES+, mandatory, defines the source files for the document.

* +FOO_RESOURCES+, optional, may contain a space-separated list of paths
  to one or more directories containing so-called resources (like CSS or
  images). By default, empty.

* +FOO_DEPENDENCIES+, optional, the list of packages (most probably,
  host-packages) that must be built before building this document.

* +FOO_TOC_DEPTH+, +FOO_TOC_DEPTH_<FMT>+, optionals, the depth of the
  table of content for this document, which can be overridden for the
  specified format +<FMT>+  (see the list of rendered formats, above,
  but in uppercase, and with dash replaced by underscore; see example,
  below). By default: +1+.

There are also additional hooks (see xref:hooks[] for general information
on hooks), that a document may set to define extra actions to be done at
various steps:

* +FOO_POST_RSYNC_HOOKS+ to run additional commands after the sources
  have been copied by Buildroot. This can for example be used to
  generate part of the manual with information extracted from the
  tree. As an example, Buildroot uses this hook to generate the tables
  in the appendices.

* +FOO_CHECK_DEPENDENCIES_HOOKS+ to run additional tests on required
  components to generate the document. In AsciiDoc, it is possible to
  call filters, that is, programs that will parse an AsciiDoc block and
  render it appropriately (e.g. http://ditaa.sourceforge.net/[ditaa] or
  https://pythonhosted.org/aafigure/[aafigure]).

* +FOO_CHECK_DEPENDENCIES_<FMT>_HOOKS+, to run additional tests for
  the specified format +<FMT>+ (see the list of rendered formats, above).

Buildroot sets the following variable that can be used in the definitions
above:

* +$(FOO_DOCDIR)+, similar to +$(FOO_PKGDIR)+, contains the path to the
  directory containing +foo.mk+. It can be used to refer to the document
  sources, and can be used in the hooks, especially the post-rsync hook
  if parts of the documentation needs to be generated.

* +$(@D)+, as for traditional packages, contains the path to the directory
  where the document will be copied and built.

Here is a complete example that uses all variables and all hooks:

----
01: ################################################################################
02: #
03: # foo-document
04: #
05: ################################################################################
06:
07: FOO_SOURCES = $(sort $(wildcard $(FOO_DOCDIR)/*))
08: FOO_RESOURCES = $(sort $(wildcard $(FOO_DOCDIR)/resources))
09:
10: FOO_TOC_DEPTH = 2
11: FOO_TOC_DEPTH_HTML = 1
12: FOO_TOC_DEPTH_SPLIT_HTML = 3
13:
14: define FOO_GEN_EXTRA_DOC
15:     /path/to/generate-script --outdir=$(@D)
16: endef
17: FOO_POST_RSYNC_HOOKS += FOO_GEN_EXTRA_DOC
18:
19: define FOO_CHECK_MY_PROG
20:     if ! which my-prog >/dev/null 2>&1; then \
21:         echo "You need my-prog to generate the foo document"; \
22:         exit 1; \
23:     fi
24: endef
25: FOO_CHECK_DEPENDENCIES_HOOKS += FOO_CHECK_MY_PROG
26:
27: define FOO_CHECK_MY_OTHER_PROG
28:     if ! which my-other-prog >/dev/null 2>&1; then \
29:         echo "You need my-other-prog to generate the foo document as PDF"; \
30:         exit 1; \
31:     fi
32: endef
33: FOO_CHECK_DEPENDENCIES_PDF_HOOKS += FOO_CHECK_MY_OTHER_PROG
34:
35: $(eval $(call asciidoc-document))
----
