Extension:ConTeXtXML

TODO: This page documents the situation that will become active in a few days/a week when the newly developed wiki extension will be ported over from the test wiki. This page is written in preparation. Soon, this todo block will be deleted. We have a heatwave right now, and even though there are some things in the extension that I still want to improve on, it is too hot in the actual office to do any programming. Instead, I am on the couch in front of a fan. --Taco (talk) 19:48, 10 August 2020 (CEST) (See: To-Do List)

An extension for editing /Command subpages

The ConTeXtXML extension is a new wiki feature specifically designed to edit the ConTeXt command referencs pages (the ones that live under the /Command/ URL.

It does this by intercepting the creation of new wiki pages below /Command/, and using a ContentHandler extension to maintain those pages. The text model of those pages is contextxml, which is a special XML format developed for documenting ConTeXt commands that is based in the interface XML files by Wolfgang Schuster.

For details of the XML format and the subtree structure below /Command/, see the pages Command and Help:Command. This page documents some features of the wiki extension itself.

Building on wikitext

The core of the extension is made up of two connected php classes:

• ConTeXtXMLContentHandler, which extends WikitextContentHandler
• ConTeXtXMLContent, which extends WikitextContent

Together they ensure that even though the declared page format is CONTENT_FORMAT_XML (which expands to the mime-type text/xml) and the page model is contextxml instead of wikitext, it remains possible to use wiki code. The extension achieves this by using a preprocessor on the XML data that converts it to wiki code that can then be used by the normal mediawiki page viewing and parser code. At the same time, it keeps the XML format available for edits to take place on, so that any documentation text that is added by the user(s) can be easily extracted and exported for other uses outside of the wiki.

It turns out that for this to work, some tweaks have to be made. Either I have not understood the mediawiki documentation well, or there are issues with extending WikitextContent, or perhaps even both. Anyway:

• The content_models mediawiki SQL database table needed an extra row with the values 4,contextxml. Added manually as I could not figure out how to do this automatically at extension registration time.
• WikitextContent does not like being subclassed, so some functions from the parent:: needed to be copied wholesale instead of just wrapping a bit of code around the parent implementation.

Building on Article

When a user loads an existing page, that page is normally of class Article (except for some special cases). The Article class sets the page content model to wikitext, which makes it use the standard WikitextContent and WikitextContenthandler. Because that would not work for the ConTeXtXML pages, there is a third class:

• CmdPage, which extends Article

This class is really small. It only exists are a coatrack for using ConTeXtXMLContent. It may not even be really needed in the current implementation, but it could prove useful for future further extensions.

And then the Hooks

The extension uses a set of hooks to link into the mediawiki processing:

ArticleFromTitle

Creates a CmdPage if the wiki page title starts with /Command.

ContentHandlerDefaultModelFor

Sets the content model to contextxml if the wiki page title starts with /Command.

PageContentSave

On save, this saves contextxml pages to a designated harddisk location as well as in the wiki database.

ArticleAfterFetchContentObject

On load, this checks whether the page content on the designated harddisk location has changed. If yes, it will replace the text of the mediawiki revision with the content of the file on the harddisk. This is so that there is an easy interface for integrating updated versions of the interface xml files from Wolfgang.

EditFormPreloadText

This fills the edit area for newly created /Command pages from the file on the harddisk

EditPageNoSuchSection

Error hook that is triggered if the user tried to edit a section that is generated from wiki code instead of from the XML data. This is an error because it is quite hard to extract the right block of text in that case and still keep track of where it is in relation to the XML data.

EditPage::showEditForm:fields

Prints a simple help message at the top of the edit field for /Command pages.

TODO: more later --Taco (talk) 19:48, 10 August 2020 (CEST) (See: To-Do List)