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Some old parts use a style that's a bit out of date.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