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 Some old parts use a style that's a bit out of date.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 `__ 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: * * * 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: :: glFooBar() - a public GL entry point (in glapi_dispatch.c) _mesa_FooBar() - the internal immediate mode function save_FooBar() - retained mode (display list) function in 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 `` needs to be added. The ``try_emit_*`` methods in ``src/mesa/program/ir_to_mesa.cpp`` and ``src/mesa/state_tracker/st_glsl_to_tgsi.cpp`` can serve as examples.