| Emil Velikov | e561737 | 2016-11-16 00:31:26 +0000 | [diff] [blame] | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| 2 | <html lang="en"> |
| 3 | <head> |
| 4 | <meta http-equiv="content-type" content="text/html; charset=utf-8"> |
| 5 | <title>Coding Style</title> |
| 6 | <link rel="stylesheet" type="text/css" href="mesa.css"> |
| 7 | </head> |
| 8 | <body> |
| 9 | |
| 10 | <div class="header"> |
| 11 | <h1>The Mesa 3D Graphics Library</h1> |
| 12 | </div> |
| 13 | |
| 14 | <iframe src="contents.html"></iframe> |
| 15 | <div class="content"> |
| 16 | |
| 17 | <h1>Coding Style</h1> |
| 18 | |
| 19 | <p> |
| 20 | Mesa is over 20 years old and the coding style has evolved over time. |
| 21 | Some old parts use a style that's a bit out of date. |
| 22 | |
| 23 | Different sections of mesa can use different coding style as set in the local |
| 24 | EditorConfig (.editorconfig) and/or Emacs (.dir-locals.el) file. |
| 25 | |
| 26 | Alternatively the following is applicable. |
| 27 | |
| 28 | If the guidelines below don't cover something, try following the format of |
| 29 | existing, neighboring code. |
| 30 | </p> |
| 31 | |
| 32 | <p> |
| 33 | Basic formatting guidelines |
| 34 | </p> |
| 35 | |
| 36 | <ul> |
| 37 | <li>3-space indentation, no tabs. |
| 38 | <li>Limit lines to 78 or fewer characters. The idea is to prevent line |
| 39 | wrapping in 80-column editors and terminals. There are exceptions, such |
| 40 | as if you're defining a large, static table of information. |
| 41 | <li>Opening braces go on the same line as the if/for/while statement. |
| 42 | For example: |
| 43 | <pre> |
| 44 | if (condition) { |
| 45 | foo; |
| 46 | } else { |
| 47 | bar; |
| 48 | } |
| 49 | </pre> |
| 50 | |
| 51 | <li>Put a space before/after operators. For example, <tt>a = b + c;</tt> |
| 52 | and not <tt>a=b+c;</tt> |
| 53 | |
| 54 | <li>This GNU indent command generally does the right thing for formatting: |
| 55 | <pre> |
| 56 | indent -br -i3 -npcs --no-tabs infile.c -o outfile.c |
| 57 | </pre> |
| 58 | |
| 59 | <li>Use comments wherever you think it would be helpful for other developers. |
| 60 | Several specific cases and style examples follow. Note that we roughly |
| 61 | follow <a href="http://www.stack.nl/~dimitri/doxygen/">Doxygen</a> conventions. |
| 62 | <br> |
| 63 | <br> |
| 64 | Single-line comments: |
| 65 | <pre> |
| 66 | /* null-out pointer to prevent dangling reference below */ |
| 67 | bufferObj = NULL; |
| 68 | </pre> |
| 69 | Or, |
| 70 | <pre> |
| 71 | bufferObj = NULL; /* prevent dangling reference below */ |
| 72 | </pre> |
| 73 | Multi-line comment: |
| 74 | <pre> |
| 75 | /* If this is a new buffer object id, or one which was generated but |
| 76 | * never used before, allocate a buffer object now. |
| 77 | */ |
| 78 | </pre> |
| 79 | We try to quote the OpenGL specification where prudent: |
| 80 | <pre> |
| 81 | /* Page 38 of the PDF of the OpenGL ES 3.0 spec says: |
| 82 | * |
| 83 | * "An INVALID_OPERATION error is generated for any of the following |
| 84 | * conditions: |
| 85 | * |
| 86 | * * <length> is zero." |
| 87 | * |
| 88 | * Additionally, page 94 of the PDF of the OpenGL 4.5 core spec |
| 89 | * (30.10.2014) also says this, so it's no longer allowed for desktop GL, |
| 90 | * either. |
| 91 | */ |
| 92 | </pre> |
| 93 | Function comment example: |
| 94 | <pre> |
| 95 | /** |
| 96 | * Create and initialize a new buffer object. Called via the |
| 97 | * ctx->Driver.CreateObject() driver callback function. |
| 98 | * \param name integer name of the object |
| 99 | * \param type one of GL_FOO, GL_BAR, etc. |
| 100 | * \return pointer to new object or NULL if error |
| 101 | */ |
| 102 | struct gl_object * |
| 103 | _mesa_create_object(GLuint name, GLenum type) |
| 104 | { |
| 105 | /* function body */ |
| 106 | } |
| 107 | </pre> |
| 108 | |
| 109 | <li>Put the function return type and qualifiers on one line and the function |
| 110 | name and parameters on the next, as seen above. This makes it easy to use |
| 111 | <code>grep ^function_name dir/*</code> to find function definitions. Also, |
| 112 | the opening brace goes on the next line by itself (see above.) |
| 113 | |
| 114 | <li>Function names follow various conventions depending on the type of function: |
| 115 | <pre> |
| 116 | glFooBar() - a public GL entry point (in glapi_dispatch.c) |
| 117 | _mesa_FooBar() - the internal immediate mode function |
| 118 | save_FooBar() - retained mode (display list) function in dlist.c |
| 119 | foo_bar() - a static (private) function |
| 120 | _mesa_foo_bar() - an internal non-static Mesa function |
| 121 | </pre> |
| 122 | |
| 123 | <li>Constants, macros and enumerant names are ALL_UPPERCASE, with _ between |
| 124 | words. |
| 125 | <li>Mesa usually uses camel case for local variables (Ex: "localVarname") |
| 126 | while gallium typically uses underscores (Ex: "local_var_name"). |
| 127 | <li>Global variables are almost never used because Mesa should be thread-safe. |
| 128 | |
| 129 | <li>Booleans. Places that are not directly visible to the GL API |
| 130 | should prefer the use of <tt>bool</tt>, <tt>true</tt>, and |
| 131 | <tt>false</tt> over <tt>GLboolean</tt>, <tt>GL_TRUE</tt>, and |
| 132 | <tt>GL_FALSE</tt>. In C code, this may mean that |
| 133 | <tt>#include <stdbool.h></tt> needs to be added. The |
| 134 | <tt>try_emit_</tt>* methods in src/mesa/program/ir_to_mesa.cpp and |
| 135 | src/mesa/state_tracker/st_glsl_to_tgsi.cpp can serve as examples. |
| 136 | |
| 137 | </ul> |
| 138 | </p> |
| 139 | |
| 140 | </div> |
| 141 | </body> |
| 142 | </html> |