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| <title>Coding Style</title> |
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| <div class="header"> |
| <h1>The Mesa 3D Graphics Library</h1> |
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| <h1>Coding Style</h1> |
| |
| <p> |
| 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| Some old parts use a style that's a bit out of date.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. |
| </p> |
| |
| <p> |
| Basic formatting guidelines |
| </p> |
| |
| <ul> |
| <li>3-space indentation, no tabs. |
| <li>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. |
| <li>Opening braces go on the same line as the if/for/while statement. |
| For example: |
| <pre> |
| if (condition) { |
| foo; |
| } else { |
| bar; |
| } |
| </pre> |
| |
| <li>Put a space before/after operators. For example, <tt>a = b + c;</tt> |
| and not <tt>a=b+c;</tt> |
| |
| <li>This GNU indent command generally does the right thing for formatting: |
| <pre> |
| indent -br -i3 -npcs --no-tabs infile.c -o outfile.c |
| </pre> |
| |
| <li>Use comments wherever you think it would be helpful for other developers. |
| Several specific cases and style examples follow. Note that we roughly |
| follow <a href="http://www.stack.nl/~dimitri/doxygen/">Doxygen</a> conventions. |
| <br> |
| <br> |
| Single-line comments: |
| <pre> |
| /* null-out pointer to prevent dangling reference below */ |
| bufferObj = NULL; |
| </pre> |
| Or, |
| <pre> |
| bufferObj = NULL; /* prevent dangling reference below */ |
| </pre> |
| Multi-line comment: |
| <pre> |
| /* If this is a new buffer object id, or one which was generated but |
| * never used before, allocate a buffer object now. |
| */ |
| </pre> |
| We try to quote the OpenGL specification where prudent: |
| <pre> |
| /* 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. |
| */ |
| </pre> |
| Function comment example: |
| <pre> |
| /** |
| * 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 */ |
| } |
| </pre> |
| |
| <li>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 |
| <code>grep ^function_name dir/*</code> to find function definitions. Also, |
| the opening brace goes on the next line by itself (see above.) |
| |
| <li>Function names follow various conventions depending on the type of function: |
| <pre> |
| 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 |
| </pre> |
| |
| <li>Constants, macros and enumerant names are ALL_UPPERCASE, with _ between |
| words. |
| <li>Mesa usually uses camel case for local variables (Ex: "localVarname") |
| while gallium typically uses underscores (Ex: "local_var_name"). |
| <li>Global variables are almost never used because Mesa should be thread-safe. |
| |
| <li>Booleans. Places that are not directly visible to the GL API |
| should prefer the use of <tt>bool</tt>, <tt>true</tt>, and |
| <tt>false</tt> over <tt>GLboolean</tt>, <tt>GL_TRUE</tt>, and |
| <tt>GL_FALSE</tt>. In C code, this may mean that |
| <tt>#include <stdbool.h></tt> needs to be added. The |
| <tt>try_emit_</tt>* methods in src/mesa/program/ir_to_mesa.cpp and |
| src/mesa/state_tracker/st_glsl_to_tgsi.cpp can serve as examples. |
| |
| </ul> |
| </p> |
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