add more reference tests

[docutils.git] / docutils / docs / dev / todo.txt

.. include:: ../header.txt

======================
 Docutils_ To Do List
======================

:Author: David Goodger (with input from many); open to all Docutils
         developers
:Contact: docutils-develop@lists.sourceforge.net
:Date: $Date$
:Revision: $Revision$
:Copyright: This document has been placed in the public domain.

.. _Docutils: https://docutils.sourceforge.io/

.. contents::


Priority items are marked with "@" symbols.  The more @s, the higher
the priority.  Items in question form (containing "?") are ideas which
require more thought and debate; they are potential to-do's.

Many of these items are awaiting champions.  If you see something
you'd like to tackle, please do!
Please see also the Bugs_ document for a list of bugs in Docutils.

.. _bugs: ../../BUGS.html


Minimum Requirements for Python Standard Library Candidacy
==========================================================

Below are action items that must be added and issues that must be
addressed before Docutils can be considered suitable to be proposed
for inclusion in the Python standard library.

Many of these are now handled by Sphinx_

* Support for `document splitting`_.  May require some major code
  rework.

* Support for subdocuments (see `large documents`_).

* `Object numbering and object references`_.

* `Nested inline markup`_.

* `Python Source Reader`_.

* The HTML writer needs to be rewritten (or a second HTML writer
  added) to allow for custom classes, and for arbitrary splitting
  (stack-based?).

* Documentation_ of the architecture.  Other docs too.

* Plugin support.

* Suitability for `Python module documentation
  <https://docutils.sourceforge.io/sandbox/README.html#documenting-python>`_.

.. _Sphinx: http://www.sphinx-doc.org/

Repository
==========

Move to a Git repository.

* This is a long standing `feature request`__
  (with pointers to Sphinx issues and discussion).

  __ https://sourceforge.net/p/docutils/feature-requests/58/

* From a `post by David Goodger`__

    An absolute requirement, for me, is that such a change be complete.
    We can't lose any data or have to refer to the old system as an
    "archive". So all the SVN history, all branches, and the full sandbox
    need to be converted at the same time.

  __ https://sourceforge.net/p/docutils/mailman/message/31878077/

Convert with reposurgeon_?

  If you are doing a full import rather than gatewaying, reposurgeon is
  probably what you want. It has been tested against a lot of large, old,
  nasty repositories and is thus known to be robust in the presence of
  repository malformations (a property regularly checked by a test suite
  that is a rogue's gallery of Subversion botches).

  -- `Git Wiki`__

The comprehensive `Reposurgeon documentation`_ comes with
`a guide to repository conversion`__
as well as info about `reading Subversion repositories`__.
Converting from an SVN dump file is faster than from a checkout.

.. _reposurgeon: http://www.catb.org/esr/reposurgeon/
.. _reposurgeon documentation:
    http://www.catb.org/esr/reposurgeon/repository-editing.html
__ https://git.wiki.kernel.org/index.php/
   Interfaces,_frontends,_and_tools#Subversion
__ http://www.catb.org/esr/reposurgeon/repository-editing.html#conversion
__ http://www.catb.org/esr/reposurgeon/repository-editing.html
   #_reading_subversion_repositories


Adam Turner wrote a conversion Makefile and ``.lift`` scripts that
downloads the repo from SF with rsync, converts it to a SVN mirror and
finally to Git, splitting sandbox, prest, and web from docutils.


Sourceforge supports multiple Git repositories per project, so we can
switch the version control system independent of the decision on an
eventual switch of the host.
Cf. https://sourceforge.net/p/forge/documentation/Git/


General
=======

Miscellaneous
-------------

Code cleanup and modernization:
  Use flake8_? See also the configuration in `<../../tox.ini>`__.

  Check and solve issue from  :PEP:`290` - Code Migration and Modernization.
  (Covers issues up to Python 2.4, is there an equivalent for more recent
  modernizations?)

  Ensure `backwards compatibility`_!

  .. _flake8: https://pypi.org/project/flake8/
  .. _backwards compatibility: policies.html#backwards-compatibility-policy

* Improve handling on Windows:

  - Get graphical installer.
  - Make rst2html.py an .exe file using py2exe.
    (Is this still required after we have "console scripts" entry points?
    GM 2023-06-25)

* .. _GUI:

  The user interface is very difficult to use for most Windows users;
  you can't really expect them to use the command line.  We need some
  kind of GUI that can launch ``rst2html``, and save the HTML output to
  a file, and launch a browser.  What's important is that we get
  settings to work with the GUI.  So we need some way to dynamically
  generate a list of settings for the GUI.  The current settings_spec
  for OptionParser doesn't seem to be usable for this for the
  following reasons:

  - It's biased toward the command line -- there are *two* options for
    one boolean setting.

  - You cannot have both a one-line description and a longer
    description for tooltips/help-texts.

  - It doesn't provide hints for the input type.  You cannot easily
    infer the type of a setting from its validator, because any
    component can add new validators.  In fact, it may be necessary to
    have both a hint about the input type (e.g. string) and a
    validator (valid ID), or it may be necessary to have a different
    set of choices for the CLI (1, INFO, 2, ...) and for the GUI
    (INFO, WARNING, ...).

  - It's coupled to the OptionParser.  We want to be able to change
    the underlying system without breaking everything.

  - It's a bunch of primitive structures.  We want an extensible (thus
    object-oriented) interface.

  So we probably need to create a class for storing all the settings,
  and auto-generate the OptionParser data from that.

  I talked to Stephan Deibel about getting Docutils integrated into
  Wing IDE.  He said it's possible, and he'd be willing to help.
  There's a scripting interface to Wing, which we'd use.  We can
  dynamically generate a list of preferences and not worry too much
  about the rendering (from what I understood); Wing's whole GUI is
  dynamic anyway.  The interface could be made usable for other GUIs.
  For example, we could try to get option support for DocFactory.  //
  FW

* Allow different report levels for STDERR and system_messages inside
  the document?

* Change the docutils-update script (in sandbox/infrastructure), to
  support arbitrary branch snapshots.

* Move some general-interest sandboxes out of individuals'
  directories, into subprojects?

* Add option for file (and URL) access restriction to make Docutils
  usable in Wikis and similar applications.

  2005-03-21: added ``file_insertion_enabled`` & ``raw_enabled``
  settings.  These partially solve the problem, allowing or disabling
  **all** file accesses, but not limited access.

* Configuration_ file handling needs discussion:

  - There should be some error checking on the contents of config
    files.  How much checking should be done?  How loudly should
    Docutils complain if it encounters an error/problem?

  - Docutils doesn't complain when it doesn't find a configuration
    file supplied with the ``--config`` option.  Should it?  (If yes,
    error or warning?)

* Internationalization:

  - I18n needs refactoring, the language dictionaries are difficult to
    maintain.  Maybe have a look at gettext or similar tools.

    (This would make a nice Google Summer of Code project)

  - Language modules: in accented languages it may be useful to have
    both accented and unaccented entries in the
    ``bibliographic_fields`` mapping for versatility.

  - Add a "--strict-language" option & setting: no English fallback
    for language-dependent features.

    Make this the default for output (as opposed to input)?
    Throw an error with a helpful message, e.g.

      Default "contents" title for language %s missing, please specify
      an explicit title.

    or

     "attention" title for language %s missing, please use a generic
     admonition with explicit title.

  - Add internationalization to _`footer boilerplate text` (resulting
    from "--generator", "--source-link", and "--date" etc.), allowing
    translations.


* Add validation?  See http://pytrex.sourceforge.net, RELAX NG, pyRXP.

* In ``docutils.readers.get_reader_class`` (& ``parsers`` &
  ``writers`` too), should we be importing "standalone" or
  "docutils.readers.standalone"?  (This would avoid importing
  top-level modules if the module name is not in docutils/readers.
  Potential nastiness.)

* Perhaps store a _`name-to-id mapping file`?  This could be stored
  permanently, read by subsequent processing runs, and updated with
  new entries.  ("Persistent ID mapping"?)

* Perhaps the ``Component.supports`` method should deal with
  individual features ("meta" etc.) instead of formats ("html" etc.)?
  Currently, it is not used at all.

  Do we need it at all?  Or rather let the writers just ignore some
  nodes (like we already do for "class" values)?

  The current implementation of the framework also leads to bug
  `bug #241`__ "doctree-based publishing != publish_string".
  The "components.Filter" transform is run by publish_doctree(). When
  filtering based on the output format, it should be run by
  publish_from_doctree() instead because only then the writer is
  known.

  So we need to either remove or fix the framework.

  __ https://sourceforge.net/p/docutils/bugs/241/


* Think about _`large documents` made up of multiple subdocument
  files.  Issues: continuity (`persistent sequences`_ above),
  cross-references (`name-to-id mapping file`_ above and `targets in
  other documents`_ below), splitting (`document splitting`_ below).

  When writing a book, the author probably wants to split it up into
  files, perhaps one per chapter (but perhaps even more detailed).
  However, we'd like to be able to have references from one chapter to
  another, and have continuous numbering (pages and chapters, as
  applicable).  Of course, none of this is implemented yet.  There has
  been some thought put into some aspects; see `the "include"
  directive`__ and the `Reference Merging`_ transform below.

  When I was working with SGML in Japan, we had a system where there
  was a top-level coordinating file, book.sgml, which contained the
  top-level structure of a book: the <book> element, containing the
  book <title> and empty component elements (<preface>, <chapter>,
  <appendix>, etc.), each with filename attributes pointing to the
  actual source for the component.  Something like this::

      <book id="bk01">
      <title>Title of the Book</title>
      <preface inrefid="pr01"></preface>
      <chapter inrefid="ch01"></chapter>
      <chapter inrefid="ch02"></chapter>
      <chapter inrefid="ch03"></chapter>
      <appendix inrefid="ap01"></appendix>
      </book>

  (The "inrefid" attribute stood for "insertion reference ID".)

  The processing system would process each component separately, but
  it would recognize and use the book file to coordinate chapter and
  page numbering, and keep a persistent ID to (title, page number)
  mapping database for cross-references.  Docutils could use a similar
  system for large-scale, multipart documents.

  __ ../ref/rst/directives.html#including-an-external-document-fragment

  Aahz's idea:

      First the ToC::

          .. ToC-list::
              Introduction.txt
              Objects.txt
              Data.txt
              Control.txt

      Then a sample use::

          .. include:: ToC.txt

          As I said earlier in chapter :chapter:`Objects.txt`, the
          reference count gets increased every time a binding is made.

      Which produces::

          As I said earlier in chapter 2, the
          reference count gets increased every time a binding is made.

      The ToC in this form doesn't even need to be references to actual
      reST documents; I'm simply doing it that way for a minimum of
      future-proofing, in case I do want to add the ability to pick up
      references within external chapters.

  Perhaps, instead of ToC (which would overload the "contents"
  directive concept already in use), we could use "manifest".  A
  "manifest" directive might associate local reference names with
  files::

      .. manifest::
         intro: Introduction.txt
         objects: Objects.txt
         data: Data.txt
         control: Control.txt

  Then the sample becomes::

      .. include:: manifest.txt

      As I said earlier in chapter :chapter:`objects`, the
      reference count gets increased every time a binding is made.

* Add support for _`multiple output files` and _`generic data
  handling`:

  It should be possible for a component to **emit or reference** data
  to be either **included or referenced** in the output document.
  Examples of such data are stylesheets or images.

  For this, we need a "data" object which stores the data either
  inline or by referring to a file.  The Docutils framework is
  responsible for either:

  * storing the data in the appropriate location (e.g. in the
    directory of the output file, or in a user-specified directory)
    and providing the paths of the stored files to the writer, *or*

  * providing the data itself to the writer so that it can be embedded
    in the output document.

  This approach decouples data handling from the data source (which
  can either be embedded or referenced) and the destination (which can
  either be embedded or referenced as well).

  See <http://article.gmane.org/gmane.text.docutils.devel/3631>.

* Add testing for Docutils' front end tools?

* Publisher: "Ordinary setup" shouldn't require specific ordering; at
  the very least, there ought to be error checking higher up in the
  call chain.  [Aahz]

  ``Publisher.get_settings`` requires that all components be set up
  before it's called.  Perhaps the I/O *objects* shouldn't be set, but
  I/O *classes*.  Then options are set up (``.set_options``), and
  ``Publisher.set_io`` (or equivalent code) is called with source &
  destination paths, creating the I/O objects.

  Perhaps I/O objects shouldn't be instantiated until required.  For
  split output, the Writer may be called multiple times, once for each
  doctree, and each doctree should have a separate Output object (with
  a different path).  Is the "Builder" pattern applicable here?

* Perhaps I/O objects should become full-fledged components (i.e.
  subclasses of ``docutils.Component``, as are Readers, Parsers, and
  Writers now), and thus have associated option/setting specs and
  transforms.

* Multiple file I/O suggestion from Michael Hudson: use a file-like
  object or something you can iterate over to get file-like objects.

* Add an "--input-language" option & setting?  Specify a different
  language module for input (bibliographic fields, directives) than
  for output.  The "--language" option would set both input & output
  languages.

* Auto-generate reference tables for language-dependent features?
  Could be generated from the source modules.  A special command-line
  option could be added to Docutils front ends to do this.  (Idea from
  Engelbert Gruber.)

* Enable feedback of some kind from internal decisions, such as
  reporting the successful input encoding.  Modify runtime settings?
  System message?  Simple stderr output?

* Rationalize Writer settings (HTML/LaTeX/PEP) -- share settings.

* Add an "--include file" command-line option (config setting too?),
  equivalent to ".. include:: file" as the first line of the doc text?
  Especially useful for character entity sets, text transform specs,
  boilerplate, etc.

* Support "include" as embedded inline-compatible directive in substitution
  definitions, e.g. ::

    .. |version| include:: version.txt

    This document describes version |version| of ...

  (cf. Grzegorz Adam Hankiewicz's post from 2014-10-01 in docutils-devel)

* Add an ``:optional: <replacement text>`` option to the "include"
  directive? This would not throw an error for a missing file, instead a
  warning is given and ``<replacement text>`` is used instead. It would be
  the responsibility of the author to ensure the missing file does not lead
  to problems later in the document.

  Use cases:

  + Standard rST syntax to replace Sphinx's "literalinclude"::

      .. include:: blah.cpp
         :literal:
         :optional: file ``blah.cpp`` not found

  + Variable content taken from a file, e.g.

    version.txt::

       .. |version| replace:: 3.1

    optionally used as::

       .. include:: version.txt
          :optional: .. |version| replace:: unknown

       This document describes version |version| of ...

    (cf. Grzegorz Adam Hankiewicz's post from 2014-10-01 in docutils-devel)

* Parameterize the Reporter object or class?  See the `2004-02-18
  "rest checking and source path"`_ thread.

  .. _2004-02-18 "rest checking and source path":
     http://thread.gmane.org/gmane.text.docutils.user/1112

* Add a "disable_transforms" setting? Would allow for easy syntax
  checking. Where ("null" writer, generic, parser(s))?
  Cf. the `2004-02-18 "rest checking and source path"`_ thread.

* Add a generic meta-stylesheet mechanism?  An external file could
  associate style names ("class" attributes) with specific elements.
  Could be generalized to arbitrary output attributes; useful for HTML
  & XMLs.  Aahz implemented something like this in
  sandbox/aahz/Effective/EffMap.py.

* .. _classes for table cells:

  William Dode suggested that table cells be assigned "class"
  attributes by columns, so that stylesheets can affect text
  alignment.  Unfortunately, there doesn't seem to be a way (in HTML
  at least) to leverage the "colspec" elements (HTML "col" tags) by
  adding classes to them.  The resulting HTML is very verbose::

      <td class="col1">111</td>
      <td class="col2">222</td>
      ...

  At the very least, it should be an option.  People who don't use it
  shouldn't be penalized by increases in their HTML file sizes.

  Table rows could also be assigned classes (like odd/even).  That
  would be easier to implement.

  How should it be implemented?

  * There could be writer options (column classes & row classes) with
    standard values.

  * The table directive could grow some options.  Something like
    ":cell-classes: col1 col2 col3" (either must match the number of
    columns, or repeat to fill?)  and ":row-classes: odd even" (repeat
    to fill; body rows only, or header rows too?).

  Probably per-table directive options are best.  The "class" values
  could be used by any writer, and applying such classes to all tables
  in a document with writer options is too broad.

  See also the `table_styling Sphinx extension`_ which defines

  :widths: also in Docutils core (but different implementation)
  :column-alignment: Sets per-column text alignment
  :column-wrapping:  Sets per-column text wrapping
  :column-dividers:  Add dividers between columns
  :column-classes:   Add per-column css classes.
  :header-columns:   Specify number of “stub” columns

  .. _table_styling Sphinx extension: https://pythonhosted.org/cloud_sptheme/
                                      lib/cloud_sptheme.ext.table_styling.html

* Add file-specific settings support to config files, like::

      [file index.txt]
      compact-lists: no

  Is this even possible?  Should the criterion be the name of the
  input file or the output file?  Alternative (more explicit) syntax::

      [source_file index.txt]
      ...

      [dest_file index.html]
      ...

  Or rather allow settings configuration from the rst source file
  (see misc.settings_ directive)?

* The "validator" support added to OptionParser is very similar to
  "traits_" in SciPy_.  Perhaps something could be done with them?
  (Had I known about traits when I was implementing docutils.frontend,
  I may have used them instead of rolling my own.)

  .. _traits: http://code.enthought.com/traits/
  .. _SciPy: http://www.scipy.org/

* tools/buildhtml.py: Extend the --prune option ("prune" config
  setting) to accept file names (generic path) in addition to
  directories (e.g. --prune=docs/user/rst/cheatsheet.txt, which should
  *not* be converted to HTML).

* Add support for _`plugins`.

* _`Config directories`: Currently, ~/.docutils, ./docutils.conf/, &
  /etc/docutils.conf are read as configuration_ files.  Proposal: allow
  ~/.docutils to be a a configuration *directory*, along with
  /etc/docutils/ and ./docutils.conf/.  Within these directories,
  check for config.txt files.  We can also have subdirectories here,
  for plugins, S5 themes, components (readers/writers/parsers) etc.

  Docutils will continue to support configuration files for backwards
  compatibility.

* Add support for document decorations other than headers & footers?
  For example, top/bottom/side navigation bars for web pages.  Generic
  decorations?

  Seems like a bad idea as long as it isn't independent from the output
  format (for example, navigation bars are only useful for web pages).

* docutils_update: Check for a ``Makefile`` in a directory, and run
  ``make`` if found?  This would allow for variant processing on
  specific source files, such as running ``rst2s5`` instead of
  ``rst2html``.

* Add a "disable table of contents" setting?  The S5 writer could set
  it as a default.  Rationale:

      The ``contents`` (table of contents) directive must not be used
      [in S5/HTML documents].  It changes the CSS class of headings
      and they won't show up correctly in the screen presentation.

      -- `Easy Slide Shows With reStructuredText & S5
      <../user/slide-shows.html>`_

  Analogue to the ``sectnum_xform`` setting, it could be used by the
  latex writer to switch to a LaTeX generated ToC (currently, the latex
  writer calls it "use_latex_toc").

object numbering and object references
--------------------------------------

For equations, tables & figures.

These would be the equivalent of DocBook's "formal" elements.

In LaTeX, automatic counters are implemented for sections, equations and
floats (figures, tables) (configurable via stylesheets or in the
latex-preamble). Objects can be given `reference names`_ with the
``\label{<refname}`` command, ``\ref{<refname>}`` inserts the
corresponding number.

No such mechanism exists in HTML.

* We need _`persistent sequences`, similar to chapter and footnote
  numbers. See `OpenOffice.org XML`_ "fields".

  - Should the sequences be automatic or manual (user-specifyable)?

* It is already possible to give `reference names`_ to objects via
  internal hyperlink targets or the "name" directive option::

      .. _figure name:

      .. figure:: image.png

  or ::

      .. figure:: image.png
         :name: figure name

  Improve the mapping of "phrase references" to IDs/labels with Literal
  transcription (i.e. ü -> ue, ß -> ss, å -> aa) instead of just
  stripping the accents and other non-ASCII chars. See also the feature
  request `allow more characters when transforming "names" to "ids"`__.

  A "table" directive has been implemented, supporting table titles.

  Perhaps the name could derive from the title/caption?

  .. _reference names: ../ref/rst/restructuredtext.html#reference-names
  __ https://sourceforge.net/p/docutils/feature-requests/66/

* We need syntax for object references.  Cf. `OpenOffice.org XML`_
  "reference fields":

  - Parameterized substitutions are too complicated
    (cf. `or not to do`: `object references`_)

  - An interpreted text approach is simpler and better::

      See Figure :ref:`figure name` and Equation :ref:`eq:identity`.

  - "equation", "figure", and "page" roles could generate appropriate
    boilerplate text::

        See :figure:`figure name` on :page:`figure name`.

    See `Interpreted Text`_ below.

    Reference boilerplate could be specified in the document
    (defaulting to nothing)::

        .. fignum::
           :prefix-ref: "Figure "
           :prefix-caption: "Fig. "
           :suffix-caption: :

    The position of the role (prefix or suffix) could also be utilized

  .. _OpenOffice.org XML: http://xml.openoffice.org/
  .. _object references: rst/alternatives.html#object-references


Documentation
=============

User Docs
---------

* Add a FAQ entry about using Docutils (with reStructuredText) on a
  server and that it's terribly slow.  See the first paragraphs in
  <http://article.gmane.org/gmane.text.docutils.user/1584>.

* Add document about what Docutils has previously been used for
  (web/use-cases.txt?).

* Improve index in docs/user/config.txt.


Developer Docs
--------------

* Improve the internal module documentation (docstrings in the code).
  Specific deficiencies listed below.

  - docutils.parsers.rst.states.State.build_table: data structure
    required (including StringList).

  - docutils.parsers.rst.states: more complete documentation of parser
    internals.

* docs/ref/doctree.txt: DTD element structural relationships,
  semantics, and attributes.  In progress; element descriptions to be
  completed.

* Document the ``pending`` elements, how they're generated and what
  they do.

* Document the transforms_ (perhaps in docstrings?): how they're used,
  what they do, dependencies & order considerations.

* Document the HTML classes used by html4css1.py.

* Write an overview of the Docutils architecture, as an introduction
  for developers.  What connects to what, why, and how.  Either update
  PEP 258 (see PEPs_ below) or as a separate doc.

* Give information about unit tests.  Maybe as a howto?

* Document the docutils.nodes APIs.

* Complete the docs/api/publisher.txt docs.


How-Tos
-------

* Creating Docutils Writers

* Creating Docutils Readers

* Creating Docutils Transforms_

* Creating Docutils Parsers

* Using Docutils as a Library


PEPs
----

* Complete PEP 258 Docutils Design Specification.

  - Fill in the blanks in API details.

  - Specify the nodes.py internal data structure implementation?

        [Tibs:] Eventually we need to have direct documentation in
        there on how it all hangs together - the DTD is not enough
        (indeed, is it still meant to be correct?  [Yes, it is.
        --DG]).

* Rework PEP 257, separating style from spec from tools, wrt Docutils?
  See Doc-SIG from 2001-06-19/20.


Python Source Reader
====================

General:

* Analyze Tony Ibbs' PySource code.

* Analyze Doug Hellmann's HappyDoc project.

* Investigate how POD handles literate programming.

* Take the best ideas and integrate them into Docutils.

Miscellaneous ideas:

* Ask Python-dev for opinions (GvR for a pronouncement) on special
  variables (__author__, __version__, etc.): convenience vs. namespace
  pollution.  Ask opinions on whether or not Docutils should recognize
  & use them.

* If we can detect that a comment block begins with ``##``, a la
  JavaDoc, it might be useful to indicate interspersed section headers
  & explanatory text in a module.  For example::

      """Module docstring."""

      ##
      # Constants
      # =========

      a = 1
      b = 2

      ##
      # Exception Classes
      # =================

      class MyException(Exception): pass

      # etc.

* Should standalone strings also become (module/class) docstrings?
  Under what conditions?  We want to prevent arbitrary strings from
  becoming docstrings of prior attribute assignments etc.  Assume
  that there must be no blank lines between attributes and attribute
  docstrings?  (Use lineno of NEWLINE token.)

  Triple-quotes are sometimes used for multi-line comments (such as
  commenting out blocks of code).  How to reconcile?

* HappyDoc's idea of using comment blocks when there's no docstring
  may be useful to get around the conflict between `additional
  docstrings`_ and ``from __future__ import`` for module docstrings.
  A module could begin like this::

      #!/usr/bin/env python
      # :Author: Me
      # :Copyright: whatever

      """This is the public module docstring (``__doc__``)."""

      # More docs, in comments.
      # All comments at the beginning of a module could be
      # accumulated as docstrings.
      # We can't have another docstring here, because of the
      # ``__future__`` statement.

      from __future__ import division

  Using the JavaDoc convention of a doc-comment block beginning with
  ``##`` is useful though.  It allows doc-comments and implementation
  comments.

  .. _additional docstrings:
     ../peps/pep-0258.html#additional-docstrings

* HappyDoc uses an initial comment block to set "parser configuration
  values".  Do the same thing for Docutils, to set runtime settings on
  a per-module basis?  I.e.::

      # Docutils:setting=value

  Could be used to turn on/off function parameter comment recognition
  & other marginal features.  Could be used as a general mechanism to
  augment config files and command-line options (but which takes
  precedence?).

* Multi-file output should be divisible at arbitrary level.

* Support all forms of ``import`` statements:

  - ``import module``: listed as "module"
  - ``import module as alias``: "alias (module)"
  - ``from module import identifier``: "identifier (from module)"
  - ``from module import identifier as alias``: "alias (identifier
    from module)"
  - ``from module import *``: "all identifiers (``*``) from module"

* Have links to colorized Python source files from API docs?  And
  vice-versa: backlinks from the colorized source files to the API
  docs!

* In summaries, use the first *sentence* of a docstring if the first
  line is not followed by a blank line.


reStructuredText Parser
=======================

Also see the `... Or Not To Do?`__ list.

__ rst/alternatives.html#or-not-to-do

Bugs
----

* A container directive with ``:class:`` option gets the spurious
  class value "class".

Misc
----

* Another list problem::

      * foo
            * bar
            * baz

  This ends up as a definition list.  This is more of a usability
  issue.

* This case is probably meant to be a nested list, but it ends up as a
  list inside a block-quote without an error message::

      - foo

       - bar

  It should probably just be an error.

  The problem with this is that you don't notice easily in HTML that
  it's not a nested list but a block-quote -- there's not much of a
  visual difference.

* Treat enumerated lists that are not arabic and consist of only one
  item in a single line as ordinary paragraphs.  See
  <http://article.gmane.org/gmane.text.docutils.user/2635>.

* The citation syntax could use some improvements.  See
  <http://thread.gmane.org/gmane.text.docutils.user/2499> (and the
  sub-thread at
  <http://thread.gmane.org/gmane.text.docutils.user/2499/focus=3028>,
  and the follow-ups at
  <http://thread.gmane.org/gmane.text.docutils.user/3087>,
  <http://thread.gmane.org/gmane.text.docutils.user/3110>,
  <http://thread.gmane.org/gmane.text.docutils.user/3114>),
  <http://thread.gmane.org/gmane.text.docutils.user/2443>,
  <http://thread.gmane.org/gmane.text.docutils.user/2715>,
  <http://thread.gmane.org/gmane.text.docutils.user/3027>,
  <http://thread.gmane.org/gmane.text.docutils.user/3120>,
  <http://thread.gmane.org/gmane.text.docutils.user/3253>.

* The current list-recognition logic has too many false positives, as
  in ::

      * Aorta
      * V. cava superior
      * V. cava inferior

  Here ``V.`` is recognized as an enumerator, which leads to
  confusion.  We need to find a solution that resolves such problems
  without complicating the spec to much.

  See <http://thread.gmane.org/gmane.text.docutils.user/2524>.

* Add indirect links via citation references & footnote references.
  Example::

      `Goodger (2005)`_ is helpful.

      .. _Goodger (2005): [goodger2005]_
      .. [goodger2005] citation text

  See <http://thread.gmane.org/gmane.text.docutils.user/2499>.

* Complain about bad URI characters
  (http://article.gmane.org/gmane.text.docutils.user/2046) and
  disallow internal whitespace
  (http://article.gmane.org/gmane.text.docutils.user/2214).

* Create ``info``-level system messages for unnecessarily
  backslash-escaped characters (as in ``"\something"``, rendered as
  "something") to allow checking for errors which silently slipped
  through.

* Add (functional) tests for untested roles.

* Add test for ":figwidth: image" option of "figure" directive.  (Test
  code needs to check if PIL is available on the system.)

* Add support for CJK double-width whitespace (indentation) &
  punctuation characters (markup; e.g. double-width "*", "-", "+")?

* Add motivation sections for constructs in spec.

* Support generic hyperlink references to _`targets in other
  documents`?  Not in an HTML-centric way, though (it's trivial to say
  ``https://www.example.org/doc#name``, and useless in non-HTML
  contexts).  XLink/XPointer?  ``.. baseref::``?  See Doc-SIG
  2001-08-10.

* Implement the header row separator modification to table.el.  (Wrote
  to Takaaki Ota & the table.el mailing list on 2001-08-12, suggesting
  support for "=====" header rows.  On 2001-08-17 he replied, saying
  he'd put it on his to-do list, but "don't hold your breath".)

* Fix the parser's indentation handling to conform with the stricter
  definition in the spec.  (Explicit markup blocks should be strict or
  forgiving?)

  .. XXX What does this mean?  Can you elaborate, David?

* Make the parser modular.  Allow syntax constructs to be added or
  disabled at run-time.  Subclassing is probably not enough because it
  makes it difficult to apply multiple extensions.

* Generalize the "doctest block" construct (which is overly
  Python-centric) to other interactive sessions?  "Doctest block"
  could be renamed to "I/O block" or "interactive block", and each of
  these could also be recognized as such by the parser:

  - Shell sessions::

        $ cat example1.txt
        A block beginning with a "$ " prompt is interpreted as a shell
        session interactive block.  As with Doctest blocks, the
        interactive block ends with the first blank line, and wouldn't
        have to be indented.

  - Root shell sessions::

        # cat example2.txt
        A block beginning with a "# " prompt is interpreted as a root
        shell session (the user is or has to be logged in as root)
        interactive block.  Again, the block ends with a blank line.

  Other standard (and unambiguous) interactive session prompts could
  easily be added (such as "> " for WinDOS).

  Tony Ibbs spoke out against this idea (2002-06-14 Doc-SIG thread
  "docutils feedback").

* Add support for pragma (syntax-altering) directives.

  Some pragma directives could be local-scope unless explicitly
  specified as global/pragma using ":global:" options.

* Support whitespace in angle-bracketed standalone URLs according to
  Appendix E ("Recommendations for Delimiting URI in Context") of `RFC
  2396`_.

  .. _RFC 2396: https://www.rfc-editor.org/rfc/rfc2396.txt

* Use the vertical spacing of the source text to determine the
  corresponding vertical spacing of the output?

* [From Mark Nodine]  For cells in simple tables that comprise a
  single line, the justification can be inferred according to the
  following rules:

  1. If the text begins at the leftmost column of the cell,
     then left justification, ELSE
  2. If the text begins at the rightmost column of the cell,
     then right justification, ELSE
  3. Center justification.

  The onus is on the author to make the text unambiguous by adding
  blank columns as necessary.  There should be a parser setting to
  turn off justification-recognition (normally on would be fine).

  Decimal justification?

  All this shouldn't be done automatically.  Only when it's requested
  by the user, e.g. with something like this::

      .. table::
         :auto-indent:

         (Table goes here.)

  Otherwise it will break existing documents.

* Generate a warning or info message for paragraphs which should have
  been lists, like this one::

      1. line one
      3. line two

* Generalize the "target-notes" directive into a command-line option
  somehow?  See docutils-develop 2003-02-13.

* Allow a "::"-only paragraph (first line, actually) to introduce a
  _`literal block without a blank line`?  (Idea from Paul Moore.) ::

      ::
          This is a literal block

  Is indentation enough to make the separation between a paragraph
  which contains just a ``::`` and the literal text unambiguous?
  (There's one problem with this concession: If one wants a definition
  list item which defines the term "::", we'd have to escape it.)  It
  would only be reasonable to apply it to "::"-only paragraphs though.
  I think the blank line is visually necessary if there's text before
  the "::"::

      The text in this paragraph needs separation
      from the literal block following::
          This doesn't look right.

* Add new syntax for _`nested inline markup`?  Or extend the parser to
  parse nested inline markup somehow?  See the `collected notes
  <rst/alternatives.html#nested-inline-markup>`__.

* Drop the backticks from embedded URIs with omitted reference text?
  Should the angle brackets be kept in the output or not? ::

      <file_name>_

  Probably not worth the trouble.

* How about a syntax for alternative hyperlink behavior, such as "open
  in a new window" (as in HTML's ``<a target="_blank">``)?

  The MoinMoin wiki uses a caret ("^") at the beginning of the URL
  ("^" is not a legal URI character).  That could work for both inline
  and explicit targets::

      The `reference docs <^url>`__ may be handy.

      .. _name: ^url

  This may be too specific to HTML.  It hasn't been requested very
  often either.

* Add an option to add URI schemes at runtime.

* _`Segmented lists`::

      : segment : segment : segment
      : segment : segment : very long
        segment
      : segment : segment : segment

  The initial colon (":") can be thought of as a type of bullet

  We could even have segment titles::

      :: title  : title   : title
      : segment : segment : segment
      : segment : segment : segment

  This would correspond well to DocBook's SegmentedList.  Output could
  be tabular or "name: value" pairs, as described in DocBook's docs.

* Enable grid _`tables inside XML comments`, where "``--``" ends comments.

  Implementation possibilities:

  1. Make the table syntax characters into "table" directive options.
     This is the most flexible but most difficult, and we probably
     don't need that much flexibility.

  2. Substitute "~" for "-" with a specialized directive option
     (e.g. ":tildes:").

  3. Make the standard table syntax recognize "~" as well as "-", even
     without a directive option.  Individual tables would have to be
     internally consistent.

  4. Allow Unicode box characters for table markup
     (`feature request [6]`_)

  Directive options are preferable to configuration settings, because
  tables are document-specific.  A pragma directive would be another
  approach, to set the syntax once for a whole document.

  Unicode box character markup would kill two birds with one stone.

  In the meantime, the list-table_ directive is a good replacement for
  grid tables inside XML comments.

  .. _feature request [6]:
      https://sourceforge.net/p/docutils/feature-requests/6
  .. _list-table: ../ref/rst/directives.html#list-table


* Generalize docinfo contents (bibliographic fields): remove specific
  fields, and have only a single generic "field"?

* _`Line numbers` and "source" in system messages:

  - Add "source" and "line" keyword arguments to all Reporter calls?
    This would require passing source/line arguments along all
    intermediate functions (where currently only `line` is used).

    Or rather specify "line" only if actually needed?

    Currently, `document.reporter` uses a state machine instance to
    determine the "source" and "line" info from
    `statemachine.input_lines` if not given explicitly. Except for
    special cases, the "line" argument is not needed because,
    `document.statemachine` keeps record of the current line number.

  - For system messages generated after the parsing is completed (i.e. by
    transforms or the writer) "line" info must be present in the doctree
    elements.

    Elements' .line assignments should be checked.  (Assign to .source
    too?  Add a set_info method?  To what?)

    The "source" (and line number in the source) can either be added
    explicitly to the elements or determined from the “raw” line
    number by `document.statemachine.get_source_and_line`.

  - Some line numbers in elements are not being set properly
    (explicitly), just implicitly/automatically.  See rev. 1.74 of
    docutils/parsers/rst/states.py for an example of how to set.

  - The line numbers of definition list items are wrong::

        $ rst2pseudoxml --expose-internal-attribute line
        1
          2
          3

        5
          6
          7

        <document source="<stdin>">
            <definition_list>
                <definition_list_item internal:line="3">
                    <term>
                        1
                    <definition>
                        <paragraph internal:line="2">
                            2
                            3
                <definition_list_item internal:line="6">
                    <term>
                        5
                    <definition>
                        <paragraph internal:line="6">
                            6
                            7

* .. _none source:

  Quite a few nodes are getting a "None" source attribute as well.  In
  particular, see the bodies of definition lists.


Adaptable file extensions
-------------------------

Questions
`````````

Should Docutils support adaptable file extensions in hyperlinks?

  In the rST source, sister documents are ".txt" files. If we're
  generating HTML, then ".html" is appropriate; if PDF, then ".pdf";
  etc.

Handle documents only, or objects (images, etc.) also?

  Different output formats support different sets of image formats (HTML
  supports ".svg" but not ".pdf", pdfLaTeX supports ".pdf" but not ".svg",
  LaTeX supports only ".eps").

  This is less urgent 2020 than 2004, as `pdflatex` and `lualatex` are
  now standard and support most image formats. Also, a wrapper like
  `rubber`__ that provides on-the-fly image conversion depends on the
  "wrong" extension in the LaTeX source.

  __ https://pypi.org/project/rubber/

At what point should the extensions be substituted?

  Transforms_:
    Fits well in the `Reader → Transformer → Writer`__ processing framework.

    * Filename/URL extension replacement can be done walking over the
      Document tree transforming the document tree from a valid state
      to another valid state.

    * Writer-specific configuration is still possible in the
      respective sections of the configuration_ file.

    __ ../peps/pep-0258.html#id24

  Pre- or post-processing:
    Can be implemented independent of Docutils -- keeps Docutils simple.

      ... those who need more sophisticated filename extension
      tweaking can simply use regular expressions, which isn't too
      difficult due to the determinability of the writers.  So there
      is no need to add a complex filename-extension-handling feature
      to Docutils.

      --- `Lea Wiemann in docutils-users 2004-06-04`__

  __ https://sourceforge.net/p/docutils/mailman/message/6918089/


Proposals
`````````

How about using ".*" to indicate "choose the most appropriate filename
extension"?  For example::

    .. _Another Document: another.*

* My point about using ``.*`` is that any other mechanism inside reST
  leads to too many ambiguities in reading reST documents; at least
  with ``.*`` it's clear that some kind of substitution is going on.

  --- Aahz

* What is to be done for output formats that don't *have* hyperlinks?
  For example, LaTeX targeted at print.  Hyperlinks may be "called
  out", as footnotes with explicit URLs.  (Don't convert the links.)

  But then there's also LaTeX targeted at PDFs, which *can* have
  links.  Perhaps a runtime setting for "*" could explicitly provide
  the extension, defaulting to the output file's extension.

* If this handles images also, how to differentiate between document
  and image links?  Element context (within "image")?  Which image
  extension to use for which document format? For HTML output, there
  is no reliable way of determining which extension to use (svg, png,
  jpg, jpeg, gif, ...).

  Should the system check for existing files?  No, not practical (the
  image files may be not available when the document is processed to HTML).

  Mailing list threads: `Images in both HTML and LaTeX`__ (especially
  `this summary of Lea's objections`__).

  __ https://sourceforge.net/p/docutils/mailman/docutils-users/thread/40BAA4B7.5020801%40python.org/#msg6918066
  __ https://sourceforge.net/p/docutils/mailman/message/6918089/

Chris Liechti suggests a new ``:link:`` role in `more-universal
links?`__::

    .. role:: link(rewrite)
       :transform: .txt|.html

  and then to use it::

    for more information see :link:`README.txt`

  it would be useful if it supported an additional option
  ``:format: html`` so that separate rules for each format can be
  defined. (like the "raw" role)

__ https://sourceforge.net/p/docutils/mailman/message/6919484/


Idea from Jim Fulton: an external lookup table of targets:

    I would like to specify the extension (e.g. .txt) [in the
    source, rather than ``filename.*``], but tell the converter to
    change references to the files anticipating that the files will
    be converted too.

    For example::

      .. _Another Document: another.txt

      rst2html --convert-links "another.txt bar.txt" foo.txt

    That is, name the files for which extensions should be converted.

    Note that I want to refer to original files in the original text
    (another.txt rather than another.*) because I want the
    unconverted text to stand on its own.

    Note that in most cases, people will be able to use globs::

      rst2html --convert-link-extensions-for "`echo *.txt`" foo.txt

    It might be nice to be able to use multiple arguments, as in::

      rst2html --convert-link-extensions-for *.txt -- foo.txt

    > Handle documents only, or objects (images, etc.) also?

    No, documents only, but there really is no need for guesswork.
    Just get the file names as command-line arguments.  EIBTI
    [explicit is better than implicit].

In `Patch #169`__ `Hyperlink extension rewriting`, John L. Clark
suggests command line options that map to-be-changed file extensions, e.g.::

     rst2html --map-extension rst html --map-extension jpg png \
        input-filename.rst

__ https://sourceforge.net/p/docutils/patches/169/

  Specifying the mapping as regular expressions would make this
  approach more generic and easier to implement (use ``re.replace``
  and refer to the "re" module's documentation instead of coding and
  documenting a home-grown extraction and mapping procedure).


Math Markup
-----------

Since Docutils 0.8, a "math" role and directive using LaTeX math
syntax as input format is part of reStructuredText.

Open issues:

* Use a "Transform" for math format conversions as extensively discussed in
  the "math directive issues" thread in May 2008
  (http://osdir.com/ml/text.docutils.devel/2008-05/threads.html)?

* Generic `math-output setting`_ (currently specific to HTML).
  (List of math-output preferences?)

* Try to be compatible with `Math support in Sphinx`_?

  * The ``:label:`` option selects a label for the equation, by which it
    can be cross-referenced, and causes an equation number to be issued.
    In Docutils, the option ``:name:`` sets the label.
    Equation numbering is not implemented yet.

  * Option ``:nowrap:`` prevents wrapping of the given math in a
    math environment (you have to specify the math environment in the
    content).

  .. _Math support in Sphinx: http://sphinx.pocoo.org/ext/math.html

* Equation numbering and references. (see the section on
  `object numbering and object references` for equations,
  formal tables, and images.)

.. _math-output setting: ../user/config.html#math-output


alternative input formats
`````````````````````````

Use a directive option to specify an alternative input format, e.g. (but not
limited to):

MathML_
  Not for hand-written code but maybe useful when pasted in (or included
  from a file)

  For an overview of MathML implementations and tests, see, e.g.,
  the `mathweb wiki`_ or the `ConTeXT MathML page`_.

  .. _MathML: https://www.w3.org/TR/MathML2/
  .. _mathweb wiki: http://www.mathweb.org/wiki/MathML
  .. _ConTeXT MathML page: http://wiki.contextgarden.net/MathML

  A MathML to LaTeX XSLT sheet:
  https://github.com/davidcarlisle/web-xslt/tree/master/pmml2tex


ASCIIMath_
  Simple, ASCII based math input language (see also `ASCIIMath tutorial`_).

  * The Python module ASCIIMathML_ translates a string with ASCIIMath into a
    MathML tree. Used, e.g., by MultiMarkdown__.

    A more comprehensive implementation is ASCIIMathPython_ by
    Paul Trembley (also used in his sandbox projects).

  * For conversion to LaTeX, there is

    - a JavaScript script at
      http://dlippman.imathas.com/asciimathtex/ASCIIMath2TeX.js

    - The javascript `asciimath-to-latex` AsciiMath to LaTex converter at
      the node package manager
      https://www.npmjs.com/package/asciimath-to-latex
      and at GitHub https://github.com/tylerlong/asciimath-to-latex

    - a javascript and a PHP converter script at GitHub
      https://github.com/asciimath/asciimathml/tree/master/asciimath-based

  .. _ASCIIMath: http://www1.chapman.edu/~jipsen/mathml/asciimath.html
  .. _ASCIIMath tutorial:
     http://www.wjagray.co.uk/maths/ASCIIMathTutorial.html
  .. _ASCIIMathML: http://pypi.python.org/pypi/asciimathml/
  .. _ASCIIMathPython: https://github.com/paulhtremblay/asciimathml
  __ http://fletcherpenney.net/multimarkdown/

`Unicode Nearly Plain Text Encoding of Mathematics`_
   format for lightly marked-up representation of mathematical
   expressions in Unicode.

   (Unicode Technical Note. Sole responsibility for its contents rests
   with the author(s). Publication does not imply any endorsement by
   the Unicode Consortium.)

   .. _Unicode Nearly Plain Text Encoding of Mathematics:
      https://www.unicode.org/notes/tn28/

itex
  See `the culmination of a relevant discussion in 2003
  <http://article.gmane.org/gmane.text.docutils.user/118>`__.



LaTeX output
````````````

Which equation environments should be supported by the math directive?

* one line:

  + numbered: `equation`
  + unnumbered: `equation*`

* multiline (test for ``\\`` outside of a nested environment
  (e.g. `array` or `cases`)

  + numbered: `align` (number every line)

    (To give one common number to all lines, put them in a `split`
    environment. Docutils then places it in an `equation` environment.)

  + unnumbered: `align*`

  + Sphinx math also supports `gather` (checking for blank lines in
    the content). Docutils puts content blocks separated by blank
    lines in separate math-block doctree nodes. (The only difference of
    `gather` to two consecutive "normal" environments seems to be that
    page-breaks between the two are prevented.)

See http://www.math.uiuc.edu/~hildebr/tex/displays.html.


HTML output
```````````

There is no native math support in HTML4. HTML5 has built-in support for
MathML. MathML is supported by all major browsers since 2023.

For supported math output variants see the `math-output setting`_.

MathML_
  Additional converters from LaTeX to MathML

  * TeX4ht_ (TeX based)
  * `MathJax for Node`_

  .. _MathML: https://www.w3.org/TR/MathML2/
  .. _TeX4ht: http://www.tug.org/applications/tex4ht/mn.html
  .. _MathJax for Node: https://github.com/mathjax/MathJax-node


HTML/CSS
  format math in standard HTML enhanced by CSS rules
  (`Examples and experiments`__).
  The ``math-output=html`` option uses the converter from eLyXer_
  (included with Docutils).

  Alternatives: LaTeX-math to HTML/CSS converters include

  * Hevea_ (Objective Caml)
  * `MathJax for Node`_
  * KaTeX_

  __ http://www.zipcon.net/~swhite/docs/math/math.html
  .. _elyxer: http://elyxer.nongnu.org/
  .. _Hevea: http://para.inria.fr/~maranget/hevea/
  .. _KaTeX: https://katex.org

client side JavaScript conversion
  Use TeX notation in the web page and JavaScript in the displaying browser.
  (implemented as `math-output setting`_ "mathjax").

  * jqMath_ (faster and lighter than MathJax_)

  .. _MathJax: http://www.mathjax.org/
  .. _jqMath: http://mathscribe.com/author/jqmath.html

OpenOffice output
`````````````````

* The `OpenDocument standard`_ version 1.1 says:

    Mathematical content is represented by MathML 2.0

  However, putting MathML into an ODP file seems tricky as these
  (maybe outdated) links suppose:
  http://idippedut.dk/post/2008/01/25/Do-your-math-ODF-and-MathML.aspx
  http://idippedut.dk/post/2008/03/03/Now-I-get-it-ODF-and-MathML.aspx

  .. _OpenDocument standard:
    http://www.oasis-open.org/standards#opendocumentv1.1

* OOoLaTeX__:  "a set of macros designed to bring the power of LaTeX
  into OpenOffice."

  __ http://ooolatex.sourceforge.net/


Directives
----------

Directives below are often referred to as "module.directive", the
directive function.  The "module." is not part of the directive name
when used in a document.

* Allow for field lists in list tables.  See
  <http://thread.gmane.org/gmane.text.docutils.devel/3392>.

* .. _unify tables:

  Unify table implementations and unify options of table directives
  (http://article.gmane.org/gmane.text.docutils.user/1857).

* Allow directives to be added at run-time?

* Use the language module for directive option names?

* Add "substitution_only" and "substitution_ok" function attributes,
  and automate context checking?

* Implement options or features on existing directives:

  - All directives that produce titled elements should grow implicit
    reference names based on the titles.

  - Allow the _`:trim:` option for all directives when they occur in a
    substitution definition, not only the unicode_ directive.

    .. _unicode: ../ref/rst/directives.html#unicode-character-codes

  - Add the "class" option to the unicode_ directive.  For example, you
    might want to get characters or strings with borders around them.

  - _`images.figure`: "title" and "number", to indicate a formal
    figure?

  - _`parts.sectnum`: "local"?, "refnum"

    A "local" option could enable numbering for sections from a
    certain point down, and sections in the rest of the document are
    not numbered.  For example, a reference section of a manual might
    be numbered, but not the rest.  OTOH, an all-or-nothing approach
    would probably be enough.

    The "sectnum" directive should be usable multiple times in a
    single document.  For example, in a long document with "chapter"
    and "appendix" sections, there could be a second "sectnum" before
    the first appendix, changing the sequence used (from 1,2,3... to
    A,B,C...).  This is where the "local" concept comes in.  This part
    of the implementation can be left for later.

    A "refnum" option (better name?) would insert reference names
    (targets) consisting of the reference number.  Then a URL could be
    of the form ``http://host/document.html#2.5`` (or "2-5"?).  Allow
    internal references by number?  Allow name-based *and*
    number-based ids at the same time, or only one or the other (which
    would the table of contents use)?  Usage issue: altering the
    section structure of a document could render hyperlinks invalid.

  - _`parts.contents`: Add a "suppress" or "prune" option?  It would
    suppress contents display for sections in a branch from that point
    down.  Or a new directive, like "prune-contents"?

    Add an option to include topics in the TOC?  Another for sidebars?
    The "topic" directive could have a "contents" option, or the
    "contents" directive" could have an "include-topics" option.  See
    docutils-develop 2003-01-29.

  - _`parts.header` & _`parts.footer`: Support multiple, named headers
    & footers?  For example, separate headers & footers for odd, even,
    and the first page of a document.

    This may be too specific to output formats which have a notion of
    "pages".

  - _`misc.class`:

    - Add a ``:parent:`` option for setting the parent's class
      (http://article.gmane.org/gmane.text.docutils.devel/3165).

  - _`misc.include`:

    - Option to label lines?

    - How about an environment variable, say RSTINCLUDEPATH or
      RSTPATH, for standard includes (as in ``.. include:: <name>``)?
      This could be combined with a setting/option to allow
      user-defined include directories.

    - Add support for inclusion by URL? ::

          .. include::
             :url: https://www.example.org/inclusion.txt

    - Strip blank lines from begin and end of a literal included file or
      file section. This would correspond to the way a literal block is
      handled.

      As nodes.literal_block expects (and we have) the text as a string
      (rather than a list of lines), using a regexp seems the way.

  - _`misc.raw`: add a "destination" option to the "raw" directive? ::

        .. raw:: html
           :destination: head

           <link ...>

    It needs thought & discussion though, to come up with a consistent
    set of destination labels and consistent behavior.

    And placing HTML code inside the <head> element of an HTML
    document is rather the job of a templating system.

  - _`body.sidebar`: Allow internal section structure?  Adornment
    styles would be independent of the main document.

    That is really complicated, however, and the document model
    greatly benefits from its simplicity.

* Implement directives.  Each of the list items below begins with an
  identifier of the form, "module_name.directive_function_name".  The
  directive name itself could be the same as the
  directive_function_name, or it could differ.

  - _`html.imagemap`

    It has the disadvantage that it's only easily implementable for
    HTML, so it's specific to one output format.

    (For non-HTML writers, the imagemap would have to be replaced with
    the image only.)

  - _`parts.endnotes` (or "footnotes"): See `Footnote & Citation Gathering`_.

  - _`parts.citations`: See `Footnote & Citation Gathering`_.

  - _`misc.language`: Specify (= change) the language of a document at
    parse time?

    * The misc.settings_ directive suggested below offers a more generic
      approach.

    * The language of document parts can be indicated by the "special class
      value" ``"language-"`` + `BCP 47`_ language code. Class arguments to
      the title are attached to the document's base node - hence titled
      documents can be given a different language at parse time. However,
      "language by class attribute" does not change parsing (localized
      directives etc.), only supporting writers.

    .. _BCP 47: https://www.rfc-editor.org/rfc/bcp/bcp47.txt


  - _`misc.settings`: Set any(?) Docutils runtime setting from within
    a document?  Needs much thought and discussion.

    Security concerns need to be taken into account (it shouldn't be
    possible to enable ``file_insertion_enabled`` from within a
    document), and settings that only would have taken effect before
    the directive (like ``tab-width``) shouldn't be accessible either.

    See this sub-thread:
    <http://thread.gmane.org/gmane.text.docutils.user/3620/focus=3649>

  - _`misc.gather`: Gather (move, or copy) all instances of a specific
    element.  A generalization of the `Footnote & Citation Gathering`_
    ideas.

  - Add a custom "directive" directive, equivalent to "role"?  For
    example::

        .. directive:: incr

           .. class:: incremental

        .. incr::

        "``.. incr::``" above is equivalent to "``.. class:: incremental``".

    Another example::

        .. directive:: printed-links

           .. topic:: Links
              :class: print-block

              .. target-notes::
                 :class: print-inline

    This acts like macros.  The directive contents will have to be
    evaluated when referenced, not when defined.

    * Needs a better name?  "Macro", "substitution"?
    * What to do with directive arguments & options when the
      macro/directive is referenced?

  - Make the meaning of block quotes overridable?  Only a 1-shot
    though; doesn't solve the general problem.

  - _`conditional directives`:

    .. note:: See also the implementation in Sphinx_.

    Docutils already has the ability to say "use this content for
    Writer X" via the "raw" directive. It also does have the ability
    to say "use this content for any Writer other than X" via the
    "strip-elements with class" config value.  However, using "raw"
    input just to select a special writer is inconvenient in many
    cases.
    It wouldn't be difficult to get more straightforward support, though.

    My first idea would be to add a set of conditional directives.
    Let's call them "writer-is" and "writer-is-not" for discussion
    purposes (don't worry about implementation details).  We might
    have::

         .. writer-is:: text-only

            ::

                +----------+
                |   SNMP   |
                +----------+
                |   UDP    |
                +----------+
                |    IP    |
                +----------+
                | Ethernet |
                +----------+

         .. writer-is:: pdf

            .. figure:: protocol_stack.eps

         .. writer-is-not:: text-only pdf

            .. figure:: protocol_stack.png

    This could be an interface to the Filter transform
    (docutils.transforms.components.Filter).

    The ideas in the `adaptable file extensions`_ section above may
    also be applicable here.

    SVG's "switch" statement may provide inspiration.

    Here's an example of a directive that could produce multiple
    outputs (*both* raw troff pass-through *and* a GIF, for example)
    and allow the Writer to select. ::

        .. eqn::

           .EQ
           delim %%
           .EN
           %sum from i=o to inf c sup i~=~lim from {m -> inf}
           sum from i=0 to m sup i%
           .EQ
           delim off
           .EN

  - _`body.example`: Examples; suggested by Simon Hefti.  Semantics as
    per Docbook's "example"; admonition-style, numbered, reference,
    with a caption/title.

  - _`body.index`: Index targets.

    See `Index Entries & Indexes
    <./rst/alternatives.html#index-entries-indexes>`__.

  - _`body.literal`: Literal block, possibly "formal" (see `object
    numbering and object references`_ above).  Possible options:

    - "highlight" a range of lines

    - include only a specified range of lines

    - "number" or "line-numbers"? (since 0.9 available with "code" directive)

    - "styled" could indicate that the directive should check for
      style comments at the end of lines to indicate styling or
      markup.

      Specific derivatives (i.e., a "python-interactive" directive)
      could interpret style based on cues, like the ">>> " prompt and
      "input()"/"raw_input()" calls.

    See docutils-users 2003-03-03.

  - _`body.listing`: Code listing with title (to be numbered
    eventually), equivalent of "figure" and "table" directives.

  - _`pysource.usage`: Extract a usage message from the program,
    either by running it at the command line with a ``--help`` option
    or through an exposed API.  [Suggestion for Optik.]

  - _`body.float`: Generic float that can be used for figures, tables,
    code listings, flowcharts, ...

    There is a Sphinx extension by Ignacio Fernández Galván <jellby@gmail.com>

       I implemented something for generic floats in sphinx, and submitted a
       pull request that is still waiting::

        .. float::
           :type: figure
           :caption: My caption

      https://github.com/sphinx-doc/sphinx/pull/1858


Interpreted Text
----------------

Interpreted text is entirely a reStructuredText markup construct, a
way to get around built-in limitations of the medium.  Some roles are
intended to introduce new doctree elements, such as "title-reference".
Others are merely convenience features, like "RFC".

All supported interpreted text roles must already be known to the
Parser when they are encountered in a document.  Whether pre-defined
in core/client code, or in the document, doesn't matter; the roles
just need to have already been declared.  Adding a new role may
involve adding a new element to the DTD and may require extensive
support, therefore such additions should be well thought-out.  There
should be a limited number of roles.

The only place where no limit is placed on variation is at the start,
at the Reader/Parser interface.  Transforms are inserted by the Reader
into the Transformer's queue, where non-standard elements are
converted.  Once past the Transformer, no variation from the standard
Docutils doctree is possible.

An example is the Python Source Reader, which will use interpreted
text extensively.  The default role will be "Python identifier", which
will be further interpreted by namespace context into <class>,
<method>, <module>, <attribute>, etc. elements (see pysource.dtd),
which will be transformed into standard hyperlink references, which
will be processed by the various Writers.  No Writer will need to have
any knowledge of the Python-Reader origin of these elements.

* Add explicit interpreted text roles for the rest of the implicit
  inline markup constructs: named-reference, anonymous-reference,
  footnote-reference, citation-reference, substitution-reference,
  target, uri-reference (& synonyms).

* Add directives for each role as well?  This would allow indirect
  nested markup::

      This text contains |nested inline markup|.

      .. |nested inline markup| emphasis::

         nested ``inline`` markup

* Implement roles:

  - "_`raw-wrapped`" (or "_`raw-wrap`"): Base role to wrap raw text
    around role contents.

    For example, the following reStructuredText source ... ::

        .. role:: red(raw-formatting)
           :prefix:
               :html: <font color="red">
               :latex: {\color{red}
           :suffix:
               :html: </font>
               :latex: }

        colored :red:`text`

    ... will yield the following document fragment::

        <paragraph>
            colored
            <inline classes="red">
                <raw format="html">
                    <font color="red">
                <raw format="latex">
                    {\color{red}
                <inline classes="red">
                    text
                <raw format="html">
                    </font>
                <raw format="latex">
                    }

    Possibly without the intermediate "inline" node.

  - _`"acronym" and "abbreviation"`: Associate the full text with a
    short form.  Jason Diamond's description:

        I want to translate ```reST`:acronym:`` into ``<acronym
        title='reStructuredText'>reST</acronym>``.  The value of the
        title attribute has to be defined out-of-band since you can't
        parameterize interpreted text.  Right now I have them in a
        separate file but I'm experimenting with creating a directive
        that will use some form of reST syntax to let you define them.

    Should Docutils complain about undefined acronyms or
    abbreviations?

    What to do if there are multiple definitions?  How to
    differentiate between CSS (Content Scrambling System) and CSS
    (Cascading Style Sheets) in a single document?  David Priest
    responds,

        The short answer is: you don't.  Anyone who did such a thing
        would be writing very poor documentation indeed.  (Though I
        note that `somewhere else in the docs`__, there's mention of
        allowing replacement text to be associated with the
        abbreviation.  That takes care of the duplicate
        acronyms/abbreviations problem, though a writer would be
        foolish to ever need it.)

        __ `inline parameter syntax`_

    How to define the full text?  Possibilities:

    1. With a directive and a definition list? ::

           .. acronyms::

              reST
                  reStructuredText
              DPS
                  Docstring Processing System

       Would this list remain in the document as a glossary, or would
       it simply build an internal lookup table?  A "glossary"
       directive could be used to make the intention clear.
       Acronyms/abbreviations and glossaries could work together.

       Then again, a glossary could be formed by gathering individual
       definitions from around the document.

    2. Some kind of `inline parameter syntax`_? ::

           `reST <reStructuredText>`:acronym: is `WYSIWYG <what you
           see is what you get>`:acronym: plaintext markup.

       .. _inline parameter syntax:
          rst/alternatives.html#parameterized-interpreted-text

    3. A combination of 1 & 2?

       The multiple definitions issue could be handled by establishing
       rules of priority.  For example, directive-based lookup tables
       have highest priority, followed by the first inline definition.
       Multiple definitions in directive-based lookup tables would
       trigger warnings, similar to the rules of `implicit hyperlink
       targets`__.

       __ ../ref/rst/restructuredtext.html#implicit-hyperlink-targets

    4. Using substitutions? ::

           .. |reST| acronym:: reST
              :text: reStructuredText

    What do we do for other formats than HTML which do not support
    tool tips?  Put the full text in parentheses?

  - "figure", "table", "listing", "chapter", "page", etc: See `object
    numbering and object references`_ above.

  - "glossary-term": This would establish a link to a glossary.  It
    would require an associated "glossary-entry" directive, whose
    contents could be a definition list::

        .. glossary-entry::

           term1
               definition1
           term2
               definition2

    This would allow entries to be defined anywhere in the document,
    and collected (via a "glossary" directive perhaps) at one point.


Doctree pruning
---------------

[DG 2017-01-02: These are not definitive to-dos, just one developer's
opinion. Added 2009-10-13 by Günter Milde, in r6178.]
[Updated by GM 2017-02-04]

The number of doctree nodes can be reduced by "normalizing" some related
nodes. This makes the document model and the writers somewhat simpler.

* The "doctest" element can be replaced by literal blocks with a class
  attribute (similar to the "code" directive output).
  The syntax shall be left in reST.

  [DG 2017-01-02:] +0.

  Discussion
    The syntax could be left in reST (for a set period of time?).

    [DG 2017-01-02:] The syntax must be left in reST, practically
    forever. Removing it would introduce a huge backwards
    incompatibility. Any syntax removal must be preceded by a thorough
    review and planning, including a deprecation warning process. My
    opinion: it's not worth it.

* "Normalize" special admonitions (note, hint, warning, ...) during parsing
  (similar to _`transforms.writer_aux.Admonitions`). There is no need to
  keep them as distinct elements in the doctree specification.

  [DG 2017-01-02:] -1: <note>{body}</> is much more concise and
  expressive than <admonition><title>Note</>{body}</>, and the title
  translation can be put off until much later in the process.

  [GM 2017-02-04]:

  -0 for <admonition class=note><title>Note</>... instead of <note>:
     a document is rarely printed/used as doctree or XML.

  +1 reduce the complexity of the doctree
     (there is no 1:1 rST syntax element <-> doctree node mapping anyway).

  +2 every writer needs 9 visit_*/depart_* method pairs to handle the 9
     subtypes of an admonition, i.e. we could but also remove 36 redundant
     methods (HTML, LaTeX, Manpage, ODF).

  -1 the most unfortunately named of these directives will survive. [#]_

     .. [#] with "biblical touch" and hard to translate:

            :admonition: | Ermahnung; Verweis; Warnung; Rüge
                         | (exhortation; censure; warning; reprimand, rebuke)


  Keep the special admonition directives in reStructuredText syntax.

  [DG 2017-01-02:] We must definitely keep the syntax. Removing it
  would introduce a huge backwards incompatibility.


Unimplemented Transforms
========================

* _`Footnote & Citation Gathering`

  Collect and move footnotes & citations to the end of a document or the
  place of a "footnotes" or "citations" directive
  (see `<./ref/rst/directives.html>_`)

  Footnotes:
    Collect all footnotes that are referenced in the document before the
    directive (and after an eventually preceding ``.. footnotes::``
    directive) and insert at this place.

    Allows "endnotes" at a configurable place.

  Citations:
    Collect citations that are referenced ...

    Citations can be:

    a) defined in the document as citation elements

    b) auto-generated from entries in a bibliographic database.

       + based on bibstuff_?
       + also have a look at

         * CrossTeX_, a backwards-compatible, improved bibtex
           re-implementation in Python (including HTML export).
           (development stalled since 2 years)

         * Pybtex_,a drop-in replacement for BibTeX written in Python.

           * BibTeX styles & (experimental) pythonic style API.
           * Database in BibTeX, BibTeXML and YAML formats.
           * full Unicode support.
           * Write to TeX, HTML and plain text.

         * `Zotero plain <http://e6h.org/%7Eegh/hg/zotero-plain/>`__
           supports Zotero databases and CSL_ styles with Docutils with an
           ``xcite`` role.

         * `sphinxcontrib-bibtex`_ Sphinx extension with "bibliography"
           directive and "cite" role supporting BibTeX databases.

         * `Modified rst2html
           <http://www.loria.fr/~rougier/coding/article/rst2html.py>`__ by
           Nicolas Rougier.


    * Automatically insert a "References" heading?

.. _CrossTeX: http://www.cs.cornell.edu/people/egs/crosstex/
.. _Pybtex:   http://pybtex.sourceforge.net/
.. _CSL: http://www.citationstyles.org/
.. _sphinxcontrib-bibtex: http://sphinxcontrib-bibtex.readthedocs.org/

* _`Reference Merging`

  When merging two or more subdocuments (such as docstrings),
  conflicting references may need to be resolved.  There may be:

  * duplicate reference and/or substitution names that need to be made
    unique; and/or
  * duplicate footnote numbers that need to be renumbered.

  Should this be done before or after reference-resolving transforms
  are applied?  What about references from within one subdocument to
  inside another?

* _`Document Splitting`

  If the processed document is written to multiple files (possibly in
  a directory tree), it will need to be split up.  Internal references
  will have to be adjusted.

  (HTML only?  Initially, yes.  Eventually, anything should be
  splittable.)

  Ideas:

  - Insert a "destination" attribute into the root element of each
    split-out document, containing the path/filename.  The Output
    object or Writer will recognize this attribute and split out the
    files accordingly.  Must allow for common headers & footers,
    prev/next, breadcrumbs, etc.

  - Transform a single-root document into a document containing
    multiple subdocuments, recursively.  The content model of the
    "document" element would have to change to::

        <!ELEMENT document
            ( (title, subtitle?)?,
              decoration?,
              (docinfo, transition?)?,
              %structure.model;,
              document* )>

    (I.e., add the last line -- 0 or more document elements.)

    Let's look at the case of hierarchical (directories and files)
    HTML output.  Each document element containing further document
    elements would correspond to a directory (with an index.html file
    for the content preceding the subdocuments).  Each document
    element containing no subdocuments (i.e., structure model elements
    only) corresponds to a concrete file with no directory.

    The natural transform would be to map sections to subdocuments,
    but possibly only a given number of levels deep.

* _`Navigation`

  If a document is split up, each segment will need navigation links:
  parent, children (small TOC), previous (preorder), next (preorder).
  Part of `Document Splitting`_?

* _`List of System Messages`

  The ``system_message`` elements are inserted into the document tree,
  adjacent to the problems themselves where possible.  Some (those
  generated post-parse) are kept until later, in
  ``document.messages``, and added as a special final section,
  "Docutils System Messages".

  Docutils could be made to generate hyperlinks to all known
  system_messages and add them to the document, perhaps to the end of
  the "Docutils System Messages" section.

  Fred L. Drake, Jr. wrote:

      I'd like to propose that both parse- and transformation-time
      messages are included in the "Docutils System Messages" section.
      If there are no objections, I can make the change.

  The advantage of the current way of doing things is that parse-time
  system messages don't require a transform; they're already in the
  document.  This is valuable for testing (unit tests,
  tools/dev/quicktest.py).  So if we do decide to make a change, I think
  the insertion of parse-time system messages ought to remain as-is
  and the Messages transform ought to move all parse-time system
  messages (remove from their originally inserted positions, insert in
  System Messages section).

* _`Index Generation`


HTML Writer
===========

* Make the _`list compacting` logic more generic: For example, allow
  for literal blocks or line blocks inside of compact list items.

  This is not implementable as long as list compacting is done by
  omitting ``<p>`` tags.  List compacting would need to be done by
  adjusting CSS margins instead.

  :2015-04-02: The new html writer no longer strips <p> tags but adds the
               class value ``simple`` to the list.
               Formatting is done by CSS --- configurable by a custom style
               sheet.

               Auto-compactization can be overridden by the ``open`` vs.
               ``compact`` class arguments.

* Idea for field-list rendering: hanging indent::

      Field name (bold): First paragraph of field body begins
          with the field name inline.

          If the first item of a field body is not a paragraph,
          it would begin on the following line.

  :2015-04-02: The new html writer writes field-lists as definition lists
               with class ``field-list``.
               Formatting is done by CSS --- configurable by a custom style
               sheet. The default style sheet has some examples, including a
               run-in field-list style.

* Add more support for <link> elements, especially for navigation
  bars.

  The framework does not have a notion of document relationships, so
  probably raw.destination_ should be used.

  We'll have framework support for document relationships when support
  for `multiple output files`_ is added.  The HTML writer could
  automatically generate <link> elements then.

  .. _raw.destination: misc.raw_

* Base list compaction on the spacing of source list?  Would require
  parser support.  (Idea: fantasai, 16 Dec 2002, doc-sig.)

* Add a tool tip ("title" attribute?) to footnote back-links
  identifying them as such.  Text in Docutils language module.

* Set HTML "width" and "height" attributes with the original size (read
  from the image) to prevent *layout shifts*:

    Layout shifts are very disrupting to the user, especially if you have
    already started reading the article and suddenly you are thrown off
    by a jolt of movement, and you have to find your place again.

    -- `Setting Height And Width On Images Is Important Again`__

  - If there are no size options (``:widht:``, ``:height:``, ``:scale:``)
    in the "image" directive and
    the image is *local* and can be read and interpreted by PIM.
    (if not, silently skip).

  - Alternatively, if the only size option is ``:scale: 100%`` and the
    image can be read with urllib (*opt-in* for the "costly" variant).

__ https://www.smashingmagazine.com/2020/03/setting-height-width-images-important-again/.


PEP/HTML Writer
===============

* Remove the generic style information (duplicated from html4css1.css)
  from pep.css to avoid redundancy.

  Set ``stylesheet-path`` to "html4css.css,pep.css" and the
  ``stylesheet-dirs`` accordingly instead. (See the xhtml11 writer for an
  example.)


S5/HTML Writer
==============

* Add a way to begin an untitled slide.

* Add a way to begin a new slide, continuation, using the same title
  as the previous slide?  (Unnecessary?)  You need that if you have a
  lot of items in one section which don't fit on one slide.

  Maybe either this item or the previous one can be realized using
  transitions.

* Have a timeout on incremental items, so the colour goes away after 1
  second.

* Add an empty, black last slide (optionally).  Currently the handling
  of the last slide is not very nice, it re-cycles through the
  incremental items on the last slide if you hit space-bar after the
  last item.

* Add a command-line option to disable advance-on-click.

* Add a speaker's master document, which would contain a small version
  of the slide text with speaker's notes interspersed.  The master
  document could use ``target="whatever"`` to direct links to a
  separate window on a second monitor (e.g., a projector).

  .. Note:: This item and the following items are partially
     accomplished by the S5 1.2 code (currently in alpha), which has
     not yet been integrated into Docutils.

* Speaker's notes -- how to intersperse?  Could use reST comments
  (".."), but make them visible in the speaker's master document.  If
  structure is necessary, we could use a "comment" directive (to avoid
  nonsensical DTD changes, the "comment" directive could produce an
  untitled topic element).

  The speaker's notes could (should?) be separate from S5's handout
  content.

* The speaker's master document could use frames for easy navigation:
  TOC on the left, content on the right.

  - It would be nice if clicking in the TOC frame simultaneously
    linked to both the speaker's notes frame and to the slide window,
    synchronizing both.  Needs JavaScript?

  - TOC would have to be tightly formatted -- minimal indentation.

  - TOC auto-generated, as in the PEP Reader.  (What if there already
    is a "contents" directive in the document?)

  - There could be another frame on the left (top-left or bottom-left)
    containing a single "Next" link, always pointing to the next slide
    (synchronized, of course).  Also "Previous" link?  FF/Rew go to
    the beginning of the next/current parent section?  First/Last
    also?  Tape-player-style buttons like ``|<<  <<  <  >  >>  >>|``?

Epub/HTML Writer
================

Add epub as an output format.

  epub is an open file format for ebooks based on HTML, specified by the
  `International Digital Publishing Forum`_. Thus, documents in epub
  format are suited to be read with `electronic reading devices`_.

Pack the output of a HTML writer and supporting files (e.g. images)
into one single epub document.

There are `links to two 3rd party ePub writers`__ in the Docutils link list.
Test and consider moving the better one into the docutils core.

__ ../user/links.html#ePub
.. _International Digital Publishing Forum: http://www.idpf.org/
.. _electronic reading devices:
   https://en.wikipedia.org/wiki/List_of_e-book_readers


LaTeX writer
============

Also see the Problems__ section in the `latex writer documentation`_.

__ ../user/latex.html#problems

.. _latex writer documentation: ../user/latex.html

.. _latex-variants:
   ../../../sandbox/latex-variants/README.html

Bug fixes
---------

* Too deeply nested lists fail: generate a warning and provide
  a workaround.

  2017-02-09 this is fixed for enumeration in 0.13.1

  for others, cf. sandbox/latex-variants/tests/rst-levels.txt

* File names of included graphics (see also `grffile` package).

* Paragraph following field-list or table in compound is indented.

  This is a problem with the current DUfieldlist definition and with the
  use of "longtable" for tables. See `other LaTeX constructs and packages
  instead of re-implementations`_ for alternatives.


Generate clean and configurable LaTeX source
----------------------------------------------

Which packages do we want to use?

+ base and "recommended" packages

  (packages that should be in a "reasonably sized and reasonably modern
  LaTeX installation like the `texlive-latex-recommended` Debian package,
  say):

+ No "fancy" or "exotic" requirements.

+ pointers to advanced packages and their use in the `latex writer
  documentation`_.

Configurable placement of figure and table floats
`````````````````````````````````````````````````

* Special class argument to individually place figures?

  Example::

    .. figure:: foo.pdf
       :class: place-here-if-possible place-top place-bottom

  would be written as ``\figure[htb]{...}`` with
  the optional args:

  :H: place-here
  :h: place-here-if-possible
  :t: place-top
  :b: place-bottom
  :p: place-on-extra-page

  Alternative: class value = "place-" + optional arg, e.g. ``:class:
  place-htb``.

Footnotes
`````````

+ True footnotes with LaTeX auto-numbering (as option ``--latex-footnotes``)
  (also for target-footnotes):
  Write ``\footnote{<footnote content>}`` at the place of the
  ``<footnote_reference>`` node.

+ Open questions:

  - Load hyperref_ with option "hyperfootnotes" and/or
    package footnotebackref_ or leave this to the user?

  - Consider cases where LaTeX does not support footnotes
    (inside tables__, headings__, caption, ...).
    Use ftnxtra_, tabularx_, tabulary_, longtable_?

    __ http://www.tex.ac.uk/cgi-bin/texfaq2html?label=footintab
    __ http://www.tex.ac.uk/cgi-bin/texfaq2html?label=ftnsect

  - Consider `multiple footnote refs to common footnote text`__.

    KOMA-script classes and the KOMA scrextend_ package provide
    ``\footref`` that can be used for additional references to a
    ``\label``-ed footnote. Since 2021-05-01, ``\footref`` is provided
    by the LaTeX core, too.

    __ http://www.tex.ac.uk/cgi-bin/texfaq2html?label=multfoot

  - Consider numbered vs. symbolic footnotes.

+ document customization (links to how-to and packages)

.. Footnote packages at CTAN (www.ctan.org/pkg/<packagename>):

   :footnote: provides a "savenotes" environment which collects all
              footnotes and emits them at ``end{savenotes}``
              (texlive-latex-recommended)

   :ftnxtra_: fixes the issue of footnote inside \caption{},
             tabular environment and \section{} like commands.

   :footnotebackref_: bidirectional links to/from footnote mark to
                      footnote text.

.. Footnote Discussion:

   `German tutorial
   <http://www2.informatik.hu-berlin.de/~ahamann/studies/footnotes.pdf>`__

   `wikibooks: footnote workarounds
   <https://en.wikibooks.org/wiki/LaTeX/Footnotes_and_Margin_Notes#Common_problems_and_workarounds>`__

.. _footnotebackref: https://www.ctan.org/pkg/footnotebackref
.. _ftnxtra: https://www.ctan.org/pkg/ftnxtra
.. _hyperref: https://www.ctan.org/pkg/hyperref
.. _longtable: https://www.ctan.org/pkg/longtable
.. _scrextend: https://www.ctan.org/pkg/longtable
.. _tabularx: https://www.ctan.org/pkg/tabularx


Other LaTeX constructs and packages instead of re-implementations
`````````````````````````````````````````````````````````````````

* Check the generated source with package `nag`.

* enumitem_ (texlive-latex-extra) for field-lists?

.. _enumitem: https://www.ctan.org/pkg/enumitem

Default layout
--------------

* Use italic instead of slanted for titlereference?

* Start a new paragraph after lists (as currently)
  or continue (no blank line in source, no parindent in output)?

  Overriding:

  * continue if the `compound paragraph`_ directive is used (as currently),
    or
  * force a new paragraph with an empty comment.

* Sidebar handling (environment with `framed`, `marginnote`, `wrapfig`,
  ...)?

* Use optionlist for docinfo?

* Keep literal-blocks together on a page, avoid pagebreaks.

  Failed experiments up to now: samepage, minipage, pagebreak 1 to 4 before
  the block.

  Should be possible with ``--literal-block-env==lstlistings`` and some
  configuration...

* More space between title and subtitle? ::

     -  \\ % subtitle%
     +  \\[0.5em] % subtitle%

.. _compound paragraph:
   ../ref/rst/directives.html#compound-paragraph

Tables
``````

* Improve/simplify logic to set the column width in the output.

  + Assumed reST line length for table width setting configurable, or
  + use `ltxtable` (a combination of `tabularx` (auto-width) and
    `longtable` (page breaks)), or
  + use tabularx column type ``X`` and let LaTeX decide width, or
  + use tabulary_?

  .. _tabulary: https://www.ctan.org/pkg/tabulary

* From comp.text.tex (13. 4. 2011):

    When using fixed width columns, you should ensure that the total
    width does not exceed \linewidth: if the first column is p{6cm}
    the second one should be p{\dimexpr\linewidth-6cm-4\tabcolsep}
    because the glue \tabcolsep is added twice at every column edge.
    You may also consider to set \tabcolsep to a different value...

* csv-tables do not have a colwidth.

* Add more classes or options, e.g. for

  + horizontal alignment and rules.
  + long table vs. tabular (see next item).

* Use tabular instead of longtable for tables in legends or generally
  inside a float?

  Alternatively, default to tabular and use longtable only if specified
  by config setting or class argument (analogue to booktable)?

* Table heads and footer for longtable (firstpage lastpage ..)?

* In tools.txt the option tables right column, there should be some more
  spacing between the description and the next paragraph "Default:".

* Paragraph separation in tables is hairy.
  see http://www.tex.ac.uk/cgi-bin/texfaq2html?label=struttab

  - The strut solution did not work.
  - setting extrarowheight added ad top of row not between paragraphs in
    a cell. ALTHOUGH i set it to 2pt because, text is too close to the topline.
  - baselineskip/stretch does not help.

* Should there be two hlines after table head and on table end?

* Place titled tables in a float ('table' environment)?

  The 'table', 'csv-table', and 'list-table' directives support an (optional)
  table title. In analogy to the 'figure' directive this should map to a
  table float.

Image and figure directives
```````````````````````````

* compare the test case in:

  + `<../../test/functional/input/data/standard.txt>`__
  + `<../../test/functional/expected/standalone_rst_html4css1.html>`__
  + `<../../test/functional/expected/standalone_rst_latex.tex>`__

* The default CSS styling for HTML output (plain.css, default.css) lets
  text following a right- or left-aligned image float to the side of the
  image/figure.

  + Use this default also for LaTeX?

  + Wrap text around figures/images with class argument "wrap"
    (like the odt writer)?

  Use `wrapfig` (or other recommended) package.

* support more graphic formats (especially SVG, the only standard
  vector format for HTML)


Missing features
----------------

* support "figwidth" argument for figures.

  As the 'figwidth' argument is still ignored and the "natural width" of
  a figure in LaTeX is 100 % of the text width, setting the 'align'
  argument has currently no effect on the LaTeX output.

* Multiple author entries in docinfo (same thing as in html).

* Consider supporting the "compact" option and class argument (from
  rst2html) as some lists look better compact and others need the space.

* Better citation support
  (see `Footnote & Citation Gathering`_).

* If ``use-latex-citations`` is used, a bibliography is inserted right at the
  end of the document.

  Put in place of the to-be-implemented "citations" directive
  (see `Footnote & Citation Gathering`_).


Unicode to LaTeX
````````````````

The `LyX <http://www.lyx.org>`_ document processor has a comprehensive
Unicode to LaTeX conversion feature with a file called ``unicodesymbols``
that lists LaTeX counterparts for a wide range of Unicode characters.

* Use this in the LaTeXTranslator?
  Think of copyright issues!

* The "ucs" package has many translations in ...doc/latex/ucs/config/

* The bibstuff_ tool ships a `latex_codec` Python module!

.. _bibstuff: http://code.google.com/p/bibstuff/


XeTeX writer
````````````

* Glyphs missing in the font are left out in the PDF without warning
  (e.g. ⇔ left-right double arrow in the functional test output).

* Disable word-wrap (hyphenation) in literal text locally with
  ``providecommand{\nohyphenation}{\addfontfeatures{HyphenChar=None}}``?


problematic URLs
````````````````

* ^^ LaTeX's special syntax for characters results in "strange" replacements
  (both with \href and \url).

  `file with ^^ <../strange^^name>`__:
  `<../strange^^name>`__

* Unbalanced braces, { or }, will fail (both with \href and \url)::

    `file with { <../strange{name>`__
    `<../strange{name>`__

Currently, a warning is written to the error output stream.

For correct printing, we can

* use the \href command with "normal" escaped name argument, or
* define a url-command in the preamble ::

    \urldef{\fragileURLi}\nolinkurl{myself%node@gateway.net}

but need to find a way to insert it as href argument.

The following fails::

    \href{https://www.w3.org/XML/Schema^^dev}{\fragileURLi}

Use %-replacement like http://nowhere/url_with%28parens%29 ?

-> does not work for file paths (with pdflatex and xpdf).


add-stylesheet option
`````````````````````

From http://article.gmane.org/gmane.text.docutils.devel/3429/

The problem is that since we have a default value, we have to
differentiate between adding another stylesheet and replacing the
default.  I suggest that the existing --stylesheet & --stylesheet-path
options keep their semantics to replace the existing settings.  We
could introduce new --add-stylesheet & --add-stylesheet-path options,
which accumulate; further --stylesheet/--stylesheet-path options would
clear these lists.  The stylesheet or stylesheet_path setting (only
one may be set), plus the added_stylesheets and added_stylesheet_paths
settings, describe the combined styles.

For example, this run will have only one custom stylesheet:

    rstpep2html.py --stylesheet-path custom.css ...

This run will use the default stylesheet, and the custom one:

    rstpep2html.py --add-stylesheet-path custom.css ...

This run will use the default stylesheet, a custom local stylesheet,
and an external stylesheet:

    rstpep2html.py --add-stylesheet-path custom.css \
        --add-stylesheet https://www.example.org/external.css ...

This run will use only the second custom stylesheet:

    rstpep2html.py --add-stylesheet-path custom.css \
        --stylesheet-path second.css ...




Front-End Tools
===============

* Parameterize help text & defaults somehow?  Perhaps a callback?  Or
  initialize ``settings_spec`` in ``__init__`` or ``init_options``?

* Disable common options that don't apply?
  (This should now be easier with ``frontend.filter_settings_spec``.)

* Add ``--section-numbering`` command line option.  The "sectnum"
  directive should override the ``--no-section-numbering`` command
  line option then.

* Implement the following suggestions from clig.dev?

     Display output on success, but keep it brief.
     provide a --quiet option to suppress all non-essential output.

     Consider chaining several args as input and use --output
     (or redirection) for output.

     -- https://clig.dev/#help

.. _partial parsing:
   https://docs.python.org/3/library/argparse.html#partial-parsing

.. _configuration: ../user/config.html
.. _transforms: ../api/transforms.html


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