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lib/mesa/docs/codingstyle.rst

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+Coding Style
+============
+
+Mesa is over 20 years old and the coding style has evolved over time.
+Some old parts use a style that's a bit out of date. Different sections
+of mesa can use different coding style as set in the local EditorConfig
+(.editorconfig) and/or Emacs (.dir-locals.el) file. Alternatively the
+following is applicable. If the guidelines below don't cover something,
+try following the format of existing, neighboring code.
+
+Basic formatting guidelines
+
+-  3-space indentation, no tabs.
+-  Limit lines to 78 or fewer characters. The idea is to prevent line
+   wrapping in 80-column editors and terminals. There are exceptions,
+   such as if you're defining a large, static table of information.
+-  Opening braces go on the same line as the if/for/while statement. For
+   example:
+
+   .. code-block:: c
+
+      if (condition) {
+         foo;
+      } else {
+         bar;
+      }
+
+-  Put a space before/after operators. For example, ``a = b + c;`` and
+   not ``a=b+c;``
+-  This GNU indent command generally does the right thing for
+   formatting:
+
+   .. code-block:: console
+
+      indent -br -i3 -npcs --no-tabs infile.c -o outfile.c
+
+-  Use comments wherever you think it would be helpful for other
+   developers. Several specific cases and style examples follow. Note
+   that we roughly follow `Doxygen <http://www.doxygen.nl>`__
+   conventions.
+
+   Single-line comments:
+
+   .. code-block:: c
+
+      /* null-out pointer to prevent dangling reference below */
+      bufferObj = NULL;
+
+   Or,
+
+   .. code-block:: c
+
+      bufferObj = NULL;  /* prevent dangling reference below */
+
+   Multi-line comment:
+
+   .. code-block:: c
+
+      /* If this is a new buffer object id, or one which was generated but
+       * never used before, allocate a buffer object now.
+       */
+
+   We try to quote the OpenGL specification where prudent:
+
+   .. code-block:: c
+
+      /* Page 38 of the PDF of the OpenGL ES 3.0 spec says:
+       *
+       *     "An INVALID_OPERATION error is generated for any of the following
+       *     conditions:
+       *
+       *     * <length> is zero."
+       *
+       * Additionally, page 94 of the PDF of the OpenGL 4.5 core spec
+       * (30.10.2014) also says this, so it's no longer allowed for desktop GL,
+       * either.
+       */
+
+   Function comment example:
+
+   .. code-block:: c
+
+      /**
+       * Create and initialize a new buffer object.  Called via the
+       * ctx->Driver.CreateObject() driver callback function.
+       * \param  name  integer name of the object
+       * \param  type  one of GL_FOO, GL_BAR, etc.
+       * \return  pointer to new object or NULL if error
+       */
+      struct gl_object *
+      _mesa_create_object(GLuint name, GLenum type)
+      {
+         /* function body */
+      }
+
+-  Put the function return type and qualifiers on one line and the
+   function name and parameters on the next, as seen above. This makes
+   it easy to use ``grep ^function_name dir/*`` to find function
+   definitions. Also, the opening brace goes on the next line by itself
+   (see above.)
+-  Function names follow various conventions depending on the type of
+   function:
+
+   +---------------------+------------------------------------------+
+   | Convention          | Explanation                              |
+   +=====================+==========================================+
+   | ``glFooBar()``      | a public GL entry point (in              |
+   |                     | :file:`glapi_dispatch.c`)                |
+   +---------------------+------------------------------------------+
+   | ``_mesa_FooBar()``  | the internal immediate mode function     |
+   +---------------------+------------------------------------------+
+   | ``save_FooBar()``   | retained mode (display list) function in |
+   |                     | :file:`dlist.c`                          |
+   +---------------------+------------------------------------------+
+   | ``foo_bar()``       | a static (private) function              |
+   +---------------------+------------------------------------------+
+   | ``_mesa_foo_bar()`` | an internal non-static Mesa function     |
+   +---------------------+------------------------------------------+
+
+-  Constants, macros and enum names are ``ALL_UPPERCASE``, with \_
+   between words.
+-  Mesa usually uses camel case for local variables (Ex:
+   ``localVarname``) while Gallium typically uses underscores (Ex:
+   ``local_var_name``).
+-  Global variables are almost never used because Mesa should be
+   thread-safe.
+-  Booleans. Places that are not directly visible to the GL API should
+   prefer the use of ``bool``, ``true``, and ``false`` over
+   ``GLboolean``, ``GL_TRUE``, and ``GL_FALSE``. In C code, this may
+   mean that ``#include <stdbool.h>`` needs to be added. The
+   ``try_emit_*`` method ``src/mesa/state_tracker/st_glsl_to_tgsi.cpp``
+   can serve as an example.