gtkD's current documentation scripts are not working as they should, probably because there's a mix of doxygen, ddoc and other styles of documentation comments in the source code. It'd be wise to settle for a single (officially supported) style.
Currently I'm unable to get doxygen to run past 'computing class inheritance relations' (seems to sit there indefinitely). DDoc, on the other hand, successfully builds a couple of pages, but some are blank (probably due to parameter lists being in the wrong syntax).
I think doxygen is the right choice for the task, if only I could get it to produce some output. It'd be fairly simple, then, to write a short script that could make the necessary changes to files in the wrong syntax.