Doxygen not listing nested namespaces

In general, you have to document anything for Doxygen to decide that it's important. Namespaces in included. But you don't have to document them particularly well; just a brief notation of what they're for is sufficient for Doxygen to document them.

If you set the EXTRACT_ALL Build flag (see http://www.doxygen.nl/manual/config.html#cfg_extract_all) this will extract information from nested namespace information without you needing to specifically document them.

I had a similar problem where Doxygen wasn't seeing that the namespace was nested. I fixed it by specifying the scope:

Before:

/**
* @namespace outer
* @brief the outer namespace
*/
namespace outer
{
  /**
  * @namespace inner
  * @brief the inner namespace
  */
  namespace inner
  {
  }
}

After:

/**
* @namespace outer
* @brief the outer namespace
*/
namespace outer
{
  /**
  * @namespace outer::inner
  * @brief the inner namespace
  */
  namespace inner
  {
  }
}