Textile is a markup language written originally in PHP. Textile's source code can be found at https://code.google.com/p/textpattern/source/browse/development/4.0/textpattern/lib/classTextile.php

A small PHP programm will call this class and pass the contents of a wiki file to it. The Html formatted output will be saved with the file's name and the extension .html

Then you just enter in the "Make" field of your project properties:

  php textile.php %f

If you are editing in Geany a file in Textile format, e.g. //test.txl//, then you a click on the menu entry "Make" will create the file //test.html//.

The file //textile.php// could look like this:
<code>
<?php

// takes a filename from the commandline and converts its contents
// to a html format

require_once('classTextile.php');

$textile = new Textile;

$file_parts = pathinfo($argv[1]);

$wiki = file_get_contents($file_parts['basename']);

$html = $textile->TextileThis($wiki);

file_put_contents($file_parts['filename'].".html", $html);

// For untrusted user input, use TextileRestricted instead:
// echo $textile->TextileRestricted($in);

?>
</code>