Since the beginning, Markdown was developed to be used as a text filter for various text editors. I thought that it was probably possible to do the same with wiki2xhtml, the "engine" driving the wiki syntax of Dotclear.
To do this, it is necessary to install PHP 5 locally. The most simple is to trust the specialist of that kind of tools for Mac, Marc Liyanage. The installation is really simple.
Once PHP 5 installed, we need a script to send the text to the engine, and return the result to the text editor.
BBedit
Download the file wiki2xhtml.php.zip, unpack it then move the resulting file wiki2xhtml.php in the folder ~/Library/Application Support/BBEdit/Unix Support/Unix Filters/. You may need to modify line 9 to the location of the file class.wiki2xhtml.php on you machine.
The command will be available in the menu #! -> Unix Filters -> wiki2xhtml.php
TextWrangler
Download the file wiki2xhtml.php.zip, unpack it then move the resulting file wiki2xhtml.php in the folder ~/Library/Application Support/TextWrangler/Unix Support/Unix Filters/. You may need to modify line 9 to the location of the file class.wiki2xhtml.php on you machine.
The command will be available in the menu #! -> Unix Filters -> wiki2xhtml.php
MarsEdit
Download the file wiki2xhtml.zip, unpack it then move the resulting folder wiki2xhtml in the folder ~/Library/Application Support/MarsEdit/TextFilters/. You may need to modify line 9 to the location of the file class.wiki2xhtml.php on you machine.
In the editing windows, click on the Preview button. At the bottom of this windows, you can select wiki2xhtml in the formatting menu.
Update 20090406 : change to the MarsEdit URL. It was about time...