Custom macros used in "description of document":http://www.redmine.org/projects/redmine/wiki/RedmineDocuments don't receive a defined "@obj@" parameter:

in "document view":http://www.redmine.org/projects/redmine/repository/entry/trunk/app/views/documents/show.html.erb#L15, "@object@" parameter is not used when "@textilizable@" is called, so¶

"@obj@" variable is "not defined":http://www.redmine.org/projects/redmine/repository/entry/trunk/app/helpers/application_helper.rb#L477 and any macro is called with a not defined "@obj@"¶

macros can not access to the document that is rendered¶

For testing, here is a macro:

Redmine::WikiFormatting::Macros.register do
  desc "test macro"
  macro :viewer do |obj, args|
    if obj
      'ok'
    else
      'nok'
    end
  end
end