Regarding the documentation effort (not specifically 2geom) - I have recently checked in some XML tree documentation, including the observer and (deprecated) listener API. I hope it will be useful. However, there are a few widespread problems with the doxygen docs in Inkscape:
1. Malformed file comments. There are 2 compound problems: forgetting @file, so the comment doesn't document the file but the first thing in it (usually the Inkscape namespace - see the docs to witness how pervasive this mistake is), and putting legal / credits stuff in the doxygen comments. I think it doesn't belong in the documentation. Here is a template that corrects both errors:
/** @file * @brief Brief description of what this file contains * * Some more detailed description if you wish. */ /* Authors: * Some author * * (C) 2008 Authors * Released under GNU GPL, see file 'COPYING' for details */
#ifndef INCLUDE_GUARD #define INCLUDE_GUARD
... rest of file ...
2. Class descriptions in file comments. Obviously it's better to put class descriptions in class comments. 3. Skimpy descriptions of important things. Generally it's better to be overly verbose than to miss crucial details. The most important thing missing documentation right now is probably the GC system. 4. Unnecessary jargon. At first I had trouble understanding what "repr" is. The full word "representation" almost never appears. 5. A minor but related problem: newlines after Vim modeline, which break its function. 6. No attribution or legal notice in the file.
Fortunately most of those problems are easy to fix.