diagrams-haddock
is a preprocessor which allows embedding images
generated using the diagrams
framework within Haddock
documentation. The code to generate images is embedded directly
within the source file itself (and the code can be included in the
Haddock output or not, as you wish). diagrams-haddock
takes care of
generating SVG images and linking them into the Haddock output.
Just cabal install diagrams-haddock
. If you have any trouble, ask
in the #diagrams
freenode IRC channel, or file a ticket on the
bug tracker.
diagrams-haddock
Before getting into the details of using diagrams-haddock
, it should
be noted that diagrams-haddock
has been carefully designed so that
you only have to maintain a single copy of your source files. In
particular, you do not have to maintain one copy of your source
files with embedded diagrams code and another copy where the diagrams
code has been replaced by images. If you find yourself scratching
your head over the quirky ways that diagrams-haddock
works, now you
will know why.
diagrams-haddock
modifies files in place! While we have worked
hard to ensure that it cannot make catastrophic changes to your files,
you would be wise to only run diagrams-haddock
on files under
version control so you can easily examine and (if necessary) undo
the changes it makes. (Of course, being a conscientious developer,
you would never work with source files not under version control,
right?)
Haddock supports inline links to images with the syntax <<URL>>
. To
indicate an image which should be automatically generated from some
diagrams code, use the special syntax
<<URL#diagram=name&key1=val1&key2=val2&...>>
. The URL will be
automatically filled in by diagrams-haddock
, so when you first
create an inline image placeholder you can simply omit it (or put any
arbitrary text in its place). For example, you might write
<<#diagram=mySquare&width=200&height=300>>
indicating an image which should be generated using the definition of
mySquare
, with a maximum width of 200 and maximum height of 300.
(Incidentally, this syntax is used because everything following the
#
symbol will be ignored by browsers.)
Continuing with the above example, you must also provide a definition
of mySquare
. You must provide it in a code block, which must be set
off by bird tracks (that is, greater-than symbols followed by at least
one space). For example,
-- > mySquare = square 1 # fc blue # myTransf
-- > myTransf = rotateBy (1/27)
In this case, mySquare
has type Diagram SVG R2
. Additionally, you
may give identifiers of type IO (Diagram SVG R2)
; in that case the
IO
action will be run to determine the diagram to render. This can
be useful, for example, when producing a diagram built from some
external data or using randomness.
You can choose to have the code block included in the Haddock output
or not, simply by putting it in a Haddock comment or not. Note that
the code block defining mySquare
can be anywhere in the same file;
it does not have to be right before or right after the diagram URL
referencing it.
diagrams-haddock
does a simple dependency analysis to determine
which code blocks should be in scope while compiling each diagram.
First, it locates a code block containing a binding for the requested
diagram name. Then, it pulls in any code blocks containing bindings
for identifiers referenced by this code block, and so on transitively.
(Note that this analysis is overly simplistic and does not take things
like shadowing into account; this may sometimes cause additional code
blocks to be included which would not be included with a more careful
analysis.)
This has a few implications. First, code blocks containing irrelevant bindings will not be considered. It is common to have code blocks which are intended simply to show some example code---they may not even be valid Haskell. However, as long as such code blocks do not contain any bindings of names used by a diagram, they will be ignored. For example:
-- The algorithm works by doing the equivalent of
--
-- > rep = uncurry replicate
-- >
-- > algo = map rep . zip [1..]
--
-- as illustrated below:
--
-- <<#diagram=algoIllustration&width=400>>
--
-- > algoIllustration = ...
The first code block shown above (beginning rep = ...
) contains some
bindings, but none of those bindings are referenced by any diagram
URLs, so the code block is ignored.
Another convenient implication is that supporting code can be put in separate code blocks and even shared between diagrams. For example:
-- > makeitblue d = d # fc blue # lc blue
--
-- Here is a blue circle:
--
-- <<#diagram=blueC&width=200>>
--
-- > blueC = circle 1 # makeitblue
--
-- And here is a blue square:
--
-- <<#diagram=blueS&width=200>>
--
-- > blueS = square 1 # makeitblue
This also means that diagrams are recompiled only when necessary. For
example, if the definition of blueC
is changed, only blueC
will be
recompiled. If the definition of makeitblue
is changed, both
blueC
and blueS
will be recompiled.
Invoking the diagrams-haddock
tool is simple: just give it a
list of targets, like so:
diagrams-haddock foo.hs baz/bar.lhs ~/src/some-cabal-directory
For file targets, diagrams-haddock
simply processes the given file.
Directory targets are assumed to contain Cabal packages, which
themselves contain a library. diagrams-haddock
then finds and
processes the source files corresponding to all modules exported by
the library. (Note that diagrams-haddock
does not currently run on
unexported modules or on the source code for executables, but if you
have a use case for either, just file a feature
request; they
shouldn't be too hard to add.)
Also, if you simply invoke diagrams-haddock
with no targets, it will
process the Cabal package in the current directory.
diagrams-haddock
also takes a few command-line options which can be
used to customize its behavior:
-c
, --cachedir
: When diagrams are compiled, their source code is
hashed and the output image stored in a file like 068fe.......342.svg
,
with the value of the hash as the name of the file. This way, if
the source code for a diagram has not changed in between invocations
of diagrams-haddock
, it does not need to be recompiled. This
option lets you specify the directory where such cached SVG files
should be stored; the default is .diagrams-cache
.
-o
, --outputdir
: This is the directory into which the final
output images will be produced. The default is diagrams
.
-d
, --distdir
: When building diagrams for a cabal package, this
is the directory in which diagrams-haddock
should look for the
setup-config
file (i.e. the output of cabal configure
). An
explicit value for this flag takes precedence; next,
diagrams-haddock
checks whether there is an active
hsenv environment, and
if so uses dist_<hsenv name>
; otherwise, it defaults to using
dist
.
-i
, --includedirs
: diagrams-haddock
does its best to process
files with CPP directives, even extracting information about where
to find #include
s from the .cabal
file, but sometimes it might
need a little help. This option lets you specify additional
directories in which diagrams-haddock
should look when searching
for #include
d files.
--cppdefines
: likewise, this option allows you to specify
additional names that should be #define
d when CPP is run.
--dataURIs
: embed the generated SVG images directly in the source
code with data URIs
(the default is to generate external SVG files and link to them).
See the section below for a discussion of the tradeoffs involved.
-q
, --quiet
: diagrams-haddock
normally prints some logging
information to indicate what it is doing; this option silences the
output.
There are two ways one may include generated SVG images with your
documentation: as data URIs, or as external images. The two options
are discussed below, along with pros and cons of each. Note that in
either case, consumers of your library (including Hackage itself) do
not need to have diagrams-haddock
installed in order to build your
documentation.
If you pass the --dataURIs
option to diagrams-haddock
, any
generated images will be embedded directly in your source file (and
hence also in the HTML ultimately produced by haddock
) as
data URIs. To use
this method,
diagrams-haddock --dataURIs
.The benefit of this scheme is that there are no extra files to deal
with, and no need to alter your .cabal
file in any way. The
downside is that it significantly bloats your source code, and may
make it extremely inconvenient to edit without some sort of tool
support (e.g. an editor that can "collapse" certain sections of the
source file).
By default, diagrams-haddock
generates external SVG image files.
This makes for much less invasive changes to your source files, but
requires some work to manage the extra files. To use this method,
diagrams-haddock
.The generated SVG files need to be copied in alongside the generated Haddock documentation. There are two ways to accomplish this:
As of Cabal-1.18
, the .cabal
file format has acquired
an extra-doc-files
field, specifying files which should be
copied in alongside generated Haddock documentation. So the
preferred method is to add something like
extra-source-files: README.md, CHANGES.md, diagrams/*.svg
extra-doc-files: diagrams/*.svg
to your .cabal
file. Note that you must list the generated
images in both the extra-source-files
field (so they will be
included in your package tarball) and the extra-doc-files
field
(so they will be copied alongside generated Haddock
documentation). Hackage is now built on Cabal-1.18
, so
uploading a package using the extra-doc-files
field in this way
works just fine.
If you need to make your documentation buildable with a pre-1.18
version of cabal-install
, it is possible to take advantage of
cabal
's system of user hooks to manually copy the images right
after the Haddock documentation is generated. Add something like
build-type: Custom
extra-source-files: diagrams/*.svg
to your .cabal
file, and then put something like the following in your
Setup.hs
:
import Data.List (isSuffixOf)
import Distribution.Simple
import Distribution.Simple.Setup (Flag (..), HaddockFlags,
haddockDistPref)
import Distribution.Simple.Utils (copyFiles)
import Distribution.Text (display)
import Distribution.Verbosity (normal)
import System.Directory (getDirectoryContents)
import System.FilePath ((</>))
-- Ugly hack, logic copied from Distribution.Simple.Haddock
haddockOutputDir :: Package pkg => HaddockFlags -> pkg -> FilePath
haddockOutputDir flags pkg = destDir
where
baseDir = case haddockDistPref flags of
NoFlag -> "."
Flag x -> x
destDir = baseDir </> "doc" </> "html" </> display (packageName pkg)
diagramsDir = "diagrams"
main :: IO ()
main = defaultMainWithHooks simpleUserHooks
{ postHaddock = \args flags pkg lbi -> do
dias <- filter ("svg" `isSuffixOf`) `fmap` getDirectoryContents diagramsDir
copyFiles normal (haddockOutputDir flags pkg)
(map (\d -> ("", diagramsDir </> d)) dias)
postHaddock simpleUserHooks args flags pkg lbi
}
It may not be pretty, but it works!
For now, diagrams-haddock
assumes that all .hs
and .lhs
files
are encoded using UTF-8. If you would like to use it with source
files stored using some other encoding, feel free to file a feature
request.
For most use cases, simply using the diagrams-haddock
executable
should get you what you want. Note, however, that the internals are
also exposed as a library, making it possible to do all sorts of crazy
stuff you might dream up. Let us know what you do with it!
Please report any bugs, feature requests, etc., on the github issue tracker.