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+=========
+LibFormat
+=========
+
+LibFormat is a library that implements automatic source code formatting based
+on Clang. This documents describes the LibFormat interface and design as well
+as some basic style discussions.
+
+If you just want to use `clang-format` as a tool or integrated into an editor,
+checkout :doc:`ClangFormat`.
+
+Design
+------
+
+FIXME: Write up design.
+
+
+Interface
+---------
+
+The core routine of LibFormat is ``reformat()``:
+
+.. code-block:: c++
+
+  tooling::Replacements reformat(const FormatStyle &Style, Lexer &Lex,
+                                 SourceManager &SourceMgr,
+                                 std::vector<CharSourceRange> Ranges);
+
+This reads a token stream out of the lexer ``Lex`` and reformats all the code
+ranges in ``Ranges``. The ``FormatStyle`` controls basic decisions made during
+formatting. A list of options can be found under :ref:`style-options`. 
+
+
+.. _style-options:
+
+Style Options
+-------------
+
+The style options describe specific formatting options that can be used in
+order to make `ClangFormat` comply with different style guides. Currently,
+two style guides are hard-coded:
+
+.. code-block:: c++
+
+  /// \brief Returns a format style complying with the LLVM coding standards:
+  /// http://llvm.org/docs/CodingStandards.html.
+  FormatStyle getLLVMStyle();
+
+  /// \brief Returns a format style complying with Google's C++ style guide:
+  /// http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml.
+  FormatStyle getGoogleStyle();
+
+These options are also exposed in the :doc:`standalone tools <ClangFormat>`
+through the `-style` option.
+
+In the future, we plan on making this configurable.