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# doctools::toc::export(n) 0.2.2 tcllib "Documentation tools"

## Name

doctools::toc::export - Exporting tables of contents

## Synopsis

- package require doctools::toc::export ?0.2.2?
- package require Tcl 8.5 9
- package require struct::map
- package require doctools::toc::structure
- package require snit
- package require pluginmgr

- ::doctools::toc::export objectName
- objectName method ?arg arg ...?
- objectName destroy
- objectName export serial serial ?format?
- objectName export object object ?format?
- objectName config names
- objectName config get
- objectName config set name ?value?
- objectName config unset pattern...
- export serial configuration

## Description

This package provides a class to manage the plugins for the export of tables of contents to other formats, i.e. their conversion to, for example doctoc, HTML, etc.

This is one of the three public pillars the management of tables of contents resides on. The other two pillars are

1. Importing tables of contents, and

2. Holding tables of contents

For information about the Concepts of tables of contents, and their parts, see the same-named section. For information about the data structure which is the major input to the manager objects provided by this package see the section ToC serialization format.

The plugin system of our class is based on the package pluginmgr, and configured to look for plugins using

1. the environment variable DOCTOOLS_TOC_EXPORT_PLUGINS,

2. the environment variable DOCTOOLS_TOC_PLUGINS,

3. the environment variable DOCTOOLS_PLUGINS,

4. the path "~/.doctools/toc/export/plugin"

5. the path "~/.doctools/toc/plugin"

6. the path "~/.doctools/plugin"

7. the path "~/.doctools/toc/export/plugins"

8. the path "~/.doctools/toc/plugins"

9. the path "~/.doctools/plugins"

10. the registry entry "HKEY_CURRENT_USER\SOFTWARE\DOCTOOLS\TOC\EXPORT\PLUGINS"

11. the registry entry "HKEY_CURRENT_USER\SOFTWARE\DOCTOOLS\TOC\PLUGINS"

12. the registry entry "HKEY_CURRENT_USER\SOFTWARE\DOCTOOLS\PLUGINS"

The last three are used only when the package is run on a machine using Windows(tm) operating system.

The whole system is delivered with six predefined export plugins, namely

doctoc

  See doctoc export plugin for details.

html

  See html export plugin for details.

json

  See json export plugin for details.

nroff

  See nroff export plugin for details.

text

  See text export plugin for details.

wiki

  See wiki export plugin for details.

Readers wishing to write their own export plugin for some format, i.e. plugin writers reading and understanding the section containing the Export plugin API v2 reference is an absolute necessity, as it specifies the interaction between this package and its plugins in detail.

## Concepts

1. A table of contents consists of a (possibly empty) list of elements.

2. Each element in the list is identified by its label.

3. Each element is either a reference, or a division.

4. Each reference has an associated document, identified by a symbolic id, and a textual description.

5. Each division may have an associated document, identified by a symbolic id.

6. Each division consists consists of a (possibly empty) list of elements, with each element following the rules as specified in item 2 and above.

A few notes

1. The above rules span up a tree of elements, with references as the leaf nodes, and divisions as the inner nodes, and each element representing an entry in the whole table of contents.

2. The identifying labels of any element E are unique within their division (or toc), and the full label of any element E is the list of labels for all nodes on the unique path from the root of the tree to E, including E.

## API

### Package commands

::doctools::toc::export objectName

  This command creates a new export manager object with an associated Tcl command whose name is objectName. This object command is explained in full detail in the sections Object command and Object methods. The object command will be created under the current namespace if the objectName is not fully qualified, and in the specified namespace otherwise.

### Object command

All objects created by the ::doctools::toc::export command have the following general form:

objectName method ?arg arg ...?

  The method method and its arg'uments determine the exact behavior of the command. See section Object methods for the detailed specifications.

### Object methods

objectName destroy

  This method destroys the object it is invoked for.

objectName export serial serial ?format?

  This method takes the canonical serialization of a table of contents stored in serial and converts it to the specified format, using the export plugin for the format. An error is thrown if no plugin could be found for the format. The string generated by the conversion process is returned as the result of this method.

  If no format is specified the method defaults to doctoc.

  The specification of what a canonical serialization is can be found in the section ToC serialization format.

  The plugin has to conform to the interface specified in section Export plugin API v2 reference.

objectName export object object ?format?

  This method is a convenient wrapper around the export serial method described by the previous item. It expects that object is an object command supporting a serialize method returning the canonical serialization of a table of contents. It invokes that method, feeds the result into export serial and returns the resulting string as its own result.

objectName config names

  This method returns a list containing the names of all configuration variables currently known to the object.

objectName config get

  This method returns a dictionary containing the names and values of all configuration variables currently known to the object.

objectName config set name ?value?

  This method sets the configuration variable name to the specified value and returns the new value of the variable.

  If no value is specified it simply returns the current value, without changing it.

  Note that while the user can set the predefined configuration variables user and format doing so will have no effect, these values will be internally overridden when invoking an import plugin.

objectName config unset pattern...

  This method unsets all configuration variables matching the specified glob patterns. If no pattern is specified it will unset all currently defined configuration variables.

## Export plugin API v2 reference

Plugins are what this package uses to manage the support for any output format beyond the ToC serialization format. Here we specify the API the objects created by this package use to interact with their plugins.

A plugin for this package has to follow the rules listed below:

1. A plugin is a package.

2. The name of a plugin package has the form doctools::toc::export::FOO, where FOO is the name of the format the plugin will generate output for. This name is also the argument to provide to the various export methods of export manager objects to get a string encoding a table of contents in that format.

3. The plugin can expect that the package doctools::toc::export::plugin is present, as indicator that it was invoked from a genuine plugin manager.

4. A plugin has to provide one command, with the signature shown below.

   export serial configuration

     Whenever an export manager of doctools::toc has to generate output for a table of contents it will invoke this command.

     string serial

       This argument will contain the canonical serialization of the table of contents for which to generate the output. The specification of what a canonical serialization is can be found in the section ToC serialization format.

     dictionary configuration

       This argument will contain the current configuration to apply to the generation, as a dictionary mapping from variable names to values.

       The following configuration variables have a predefined meaning all plugins have to obey, although they can ignore this information at their discretion. Any other other configuration variables recognized by a plugin will be described in the manpage for that plugin.

       user

         This variable is expected to contain the name of the user owning the process invoking the plugin.

       format

         This variable is expected to contain the name of the format whose plugin is invoked.

       file

         This variable, if defined by the user of the table object is expected to contain the name of the input file for which the plugin is generating its output for.

       map

         This variable, if defined by the user of the table object is expected to contain a dictionary mapping from symbolic document ids used in the table entries to actual paths (or urls). A plugin has to be able to handle the possibility that a document id is without entry in this mapping.

5. A single usage cycle of a plugin consists of the invokations of the command export. This call has to leave the plugin in a state where another usage cycle can be run without problems.

## ToC serialization format

Here we specify the format used by the doctools v2 packages to serialize tables of contents as immutable values for transport, comparison, etc.

We distinguish between regular and canonical serializations. While a table of contents may have more than one regular serialization only exactly one of them will be canonical.

regular serialization

  1. The serialization of any table of contents is a nested Tcl dictionary.

  2. This dictionary holds a single key, doctools::toc, and its value. This value holds the contents of the table of contents.

  3. The contents of the table of contents are a Tcl dictionary holding the title of the table of contents, a label, and its elements. The relevant keys and their values are

     title

       The value is a string containing the title of the table of contents.

     label

       The value is a string containing a label for the table of contents.

     items

       The value is a Tcl list holding the elements of the table, in the order they are to be shown.

       Each element is a Tcl list holding the type of the item, and its description, in this order. An alternative description would be that it is a Tcl dictionary holding a single key, the item type, mapped to the item description.

       The two legal item types and their descriptions are

       reference

         This item describes a single entry in the table of contents, referencing a single document. To this end its value is a Tcl dictionary containing an id for the referenced document, a label, and a longer textual description which can be associated with the entry. The relevant keys and their values are

         id

           The value is a string containing the id of the document associated with the entry.

         label

           The value is a string containing a label for this entry. This string also identifies the entry, and no two entries (references and divisions) in the containing list are allowed to have the same label.

         desc

           The value is a string containing a longer description for this entry.

       division

         This item describes a group of entries in the table of contents, inducing a hierarchy of entries. To this end its value is a Tcl dictionary containing a label for the group, an optional id to a document for the whole group, and the list of entries in the group. The relevant keys and their values are

         id

           The value is a string containing the id of the document associated with the whole group. This key is optional.

         label

           The value is a string containing a label for the group. This string also identifies the entry, and no two entries (references and divisions) in the containing list are allowed to have the same label.

         items

           The value is a Tcl list holding the elements of the group, in the order they are to be shown. This list has the same structure as the value for the keyword items used to describe the whole table of contents, see above. This closes the recusrive definition of the structure, with divisions holding the same type of elements as the whole table of contents, including other divisions.

canonical serialization

  The canonical serialization of a table of contents has the format as specified in the previous item, and then additionally satisfies the constraints below, which make it unique among all the possible serializations of this table of contents.

  1. The keys found in all the nested Tcl dictionaries are sorted in ascending dictionary order, as generated by Tcl's builtin command lsort -increasing -dict.

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category doctools of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

## Keywords

HTML, conversion, doctoc, documentation, export, formatting, generation, json, manpage, markup, nroff, plugin, reference, table, table of contents, tcler's wiki, text, url, wiki

## Category

Documentation tools

## Copyright

Copyright © 2009-2019 Andreas Kupries <andreas_kupries@users.sourceforge.net>