 |
LArSoft
v06_85_00
Liquid Argon Software toolkit - http://larsoft.org/
|
|
LArSoft
v06_85_00
Liquid Argon Software toolkit - http://larsoft.org/
|
| Document name: | UsingDoxygen |
|---|---|
| Type: | Policy and recommendations |
| Author: | Gianluca Petrillo (petrillo@fnal.gov) |
| Created on: | December 28, 2017 |
| Version: | 1.0 |
This document describes aspects of the documentation of LArSoft code from sources.
The sections of this document can be read independently.
Note that the document was written with doxygen 1.8.13 as reference.
The format is Markdown format, that you can convert it to something else with:
pandoc -s -S --toc -o README.html README.md pandoc -s -S --toc -o README.pdf README.md
et cetera. Note that this file is about doxygen, and it is also processed by doxygen. This means that typing in the document complete doxygen commands (either with @ or with \) will trigger a doxygen action. For that reason, the commands names here are printed with a prefix \@ (e.g. \@defgroup).
The goal of structuring documentation is to have the main page and subpages of LArSoft doxygen page grouping the documentation in a sensible and usable way.
There are two levels of documentation:
For example, proxy::Tracks is a proxy object which has its own usage, while the proxy concept and patterns are a vaster topic which includes, among others, that proxy::Tracks object.
The intention is to provide the object documentation in the same source file as the code itself (typically in the header files where the interfaces are declared), and provide the overview documentation in separate documents.
Structuring these two levels in a consistent whole can be achieved with some careful use of doxygen. The document files are written in Markdown format, which Doxygen can more or less parse and render. Doxygen itself has three different levels of documentation [Doxygen grouping][grouping]:
\@defgroup family of commands, creating a module\@page family of commands, creating a pageThe \@defgroup way defines a topic group into a "module". All modules are listed in the main page under the "Modules" tab. Groups can be nested, and their content can be contributed from different parts of the code.
The \@page way defines a documentation "page". All documentation pages are listed in the main page under the "Related Pages" tab. Pages can contain subpages.
The approach we use is to use pages to have the documentation be driven by the modules, which describe the higher level topics and which contain the documentation of the specific code objects. The pages are used only for extensive high level documentation that has the flavour of a self-sufficient document, like the complete documentation of an example. These pages are provided in a more strict Markdown format, so that they can be moved outside doxygen. This is a fairly vague guideline, which should not be enforced over readability.
Pages and modules are pretty distinct elements in doxygen. With an example (larexamples!), we illustrate how they can be merged. The idea is that each example is described in its own page, and this page is connected to the documentation of all the code objects in the example, which live in their module. The outer element will be the module. The examples are structured as follows:
larexamples |-- Services | |-- AtomicNumber | `-- ShowerCalibrationGalore |-- Algorithms | |-- RemoveIsolatedSpacePoints | `-- TotallyCheatTracks `-- AnalysisExample
We will pursue a similar structure in terms of Doxygen modules.
First, we focus on a single example: TotallyCheatTracks.
We already have a README.md file describing the example in detail. With no special care, that file will show among the "Related pages" as "README". First, we make sure the title of the document is in the very first line, and we also add a label to identify it in doxygen:
# An algorithm producing a new data product: `TotallyCheatTrackingAlg` {#TotallyCheatTracks_README}
The table (which used to be above the title) is moved just after the title. With this change, a page now appears at the top level of the related pages, as An algorithm producing a new data product: TotallyCheatTrackingAlg. It is rendered in doxygen, but we don't guarantee on the correct rendering since doxygen has its own interpretation of Markdown, and also of its own special commands. Defining a label for it also makes this a doxygen documentation block, feature that will come handy in a moment.
Next, we create a new documentation file, TotallyCheatTracks.dox. The dox suffix is recognised and parsed by doxygen by default. This file will contain doxygen commands within a C-style comment block. We use this file as the head of documentation, which provides connections but almost no content. For starts, we define a doxygen group for the example itself:
\@defgroup TotallyCheatTracks TotallyCheatTracks
(remember that the \ in \@defgroup is spurious and it's in this document only for rendering needs). The first element is a doxygen identifier (with the same name as the example, following its capitalisation despite doxygen recommendations), and the second is a "title" associated with the group. We also add a brief description of the group:
\@brief Defines a new data product and produces it and its associations.
The title and brief description will appear in the table of doxygen modules. Rendering this will show, in fact, the module "TotallyCheatTracks". We then tell doxygen to include the content of the documentation element associated to the README.md file directly into this module. The file TotallyCheatTracks.dox now looks like:
/** \@defgroup TotallyCheatTracks TotallyCheatTracks \@brief Defines a new data product and produces it and its associations. \@copydoc TotallyCheatTracks_README */
And blam! opening the doxygen module TotallyCheatTracks now renders the brief description above and then the whole content of the README.md file (again, with all the limits of doxygen markdown).
The doxygen module is still empty: no code is associated with it. To fix that, a detailed tagging action has to be performed. We add the line
\@ingroup TotallyCheatTracks
to each of the file documentation blocks, and then we wrap the relevant objects in a documentation group like:
namespace lar {
namespace example {
// BEGIN group TotallyCheatTracks --------------------------------------
/// \@ingroup TotallyCheatTracks
/// \@{
// ...
/// \@}
// END group TotallyCheatTracks ----------------------------------------
} // namespace example
} // namespace lar
In this way everything that is defined in the block of code starting at namespace example will be included in the doxygen group TotallyCheatTracks, while the namespace examples itself will not be (in fact, it shouldn't be since it contains also examples other than TotallyCheatTracks). The comment lines with BEGIN and END are for readability only and have no special meaning neither in doxygen nor in C++ (but some editors may use them to mark a editing block).
It may be helpful to add a link to the example overview in some key classes that may be "access points". For example, we can add:
\@see \@ref TotallyCheatTracks "TotallyCheatTracks example overview"
to the documentation of lar::example::TotallyCheatTracker module and lar::example::TotallyCheatTrackingAlg algorithm class.
After all of this, the module TotallyCheatTracks is rendered in doxygen with
README.md file.While it is a good idea to instrument tests with doxygen documentation, we currently skip the test directories from the rendering of the standard LArSoft documentation. The "ingrouping" is still recommended in tests as well.
We have learned how to document a single example, with the result that the example documentation appears at the top level of both the Related pages and Modules tabs. This section describes the creation of the final structure.
We want the TotallyCheatTracks group to be a subgroup of the algorithm example documentation. Therefore, we create a head file in the Algorithms directory, called Algorithms.dox (following the self-imposed convention of using the directory name for the group name and the documentation head file name). In it, we create, in a doxygen documentation block, a new group larexamples_Algorithms with a brief description:
\@defgroup larexamples_Algorithms Algorithms \@brief Examples of LArSoft algorithms and _art_ modules.
We follow with some high level documentation of algorithm guidelines and whatever we want to put here. Since this is high-level information, there are probably better places for it to live than with the source code, so links to web pages are recommended. Then we can add a line:
\@ingroup larexamples_Algorithms
in each of the group definitions of the relevant algorithm example groups (e.g. TotallyCheatTracks). Rendering the documentation will show that the algorithms have become submodules of the larexamples_Algorithms module, while their pages are still in the wild, at top level. To pick them, we create a new placeholder page, and add to it the subpages related to the subgroups:
\@page larexamples_Algorithms_mainpage Algorithms Please refer to the full documentation in \@ref larexamples_Algorithms "algorithm example module". Contents --------- \@subpage TotallyCheatTracks_README
The page is called larexamples_Algorithms_mainpage and will appear as Algorithms in the listing. Rendering it it will show that Algorithms now contains subpages. For convenience, a reference to the doxygen module is spelled out, too. Note that the inclusion of the pages is top-down, with each page picking all its subpages, while the module composition is bottom-up, with each group picking its parent group(s).
In the same way, larexamples.dox can be created to enclose the algorithm example module and page, as well as the others at the same level.
in the \@file documentation line, spell the whole path of the file, up to the repository name (excluded). For example:
\@file larcorealg/Geometry/GeometryCore.h
instead of just \@file GeometryCore.h. The advantages are:
include lines will link to the header documentationconsider the most likely access point objects (e.g. art module or algorithm class) and add a reference to the doxygen overview module (group):
@see @ref OverviewGroupName
For discussions and proposals, please contact the LArSoft management at larsoft-team@fnal.gov.
Version 1.0: December 28, 2017 (petrillo@fnal.gov) original, unvetted version
1.8.11