This blog is updated daily.
A general description is here.
Package help is now converted from Rd by the R-based converters that were first introduced in 2.9.0. This means
- Packages that were installed by R-devel after 2009-08-09 should not be used with earlier versions of R, and some aspects of package help will be missing if there are so used. (Text, HTML and latex help and the runnable examples.)
- Text, HTML and latex help and examples for packages installed under the new system is converted on-demand from stored parsed Rd files. (Conversions stored in R < 2.10.0 are used if no parsed Rd files are found.)
HTML help is now generated dynamically using a HTTP server running in the R process and listening on the loopback interface.
- The implementation is not quite complete.
- Those who need to worry about security implications of such a server can disable it by setting the environment variable R_DISABLE_HTTPD to a non-empty value. They may want to build static HTML pages, which is done by the configure option --enable-prebuilt-html (which adds --html to the default for installing packages).
- If the server is disabled and there are no static HTML pages, a HTML help page wthout links is generated as a file:// URLis disables help.start() and HTML help (so text help is shown instead).
- The Java/Javascript search engine has been replaced by an HTML interface to help.search(): this means tha. help.start() no longer has an argument 'search from HTML is only available if the HTTP server is used. help.start() no longer has an argument 'searchEngine' as it is no longer neededEngine' as it is no longer needed.
- The dynamic help can now locate cross-references of the form \link[pkg]{foo} and \link[pkg:foo]{bar} where 'foo' is an alias in the package, rather than the documented (base of a) filename.
- Details may change before release.
help(offline = TRUE) now calls a function
offline_help_helper() if this exists in the workspace or
further down the search path, otherwise the function of that
name in the 'utils' name space.
For the default helper, options(offline_PDF = TRUE) will select PDF output rather than the default PostScript.
help() has a new argument 'help_type' (with default set by the option of that name) to supersede 'offline', 'htmlhelp' and 'chmhelp' (although for now they still work if 'help_type' is unset). There is a new type, "PDF" to allow offline PDF (rather than PostScript).
A function offline_help_helper() will be used if this exists in the workspace or further down the search path, otherwise the function of that name in the 'utils' name space.
help.start() no longer sets options(htmlhelp = TRUE) (it used to on Unix but not on Windows). Nor does it on Unix reset the "browser" option if given an argument of that name.
Arguments 'update' and 'remote' are now available on all platforms.