docs/codingstyle.html

   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   The Mesa 3D Graphics Library
  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  21 Some old parts use a style that's a bit out of date.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, <code>a = b + c;</code>
  52 and not <code>a=b+c;</code>
  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>
  60 <p>Use comments wherever you think it would be helpful for other developers.
  61 Several specific cases and style examples follow.  Note that we roughly
  62 follow <a href="http://www.doxygen.nl">Doxygen</a> conventions.
  63 </p>
  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  *     * &lt;length&gt; 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-&gt;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 enum names are <code>ALL_UPPERCASE</code>, with _
 124 between words.
 125 <li>Mesa usually uses camel case for local variables (Ex:
 126 <code>localVarname</code>) while gallium typically uses underscores (Ex:
 127 <code>local_var_name</code>).
 128 <li>Global variables are almost never used because Mesa should be thread-safe.
 129
 130 <li>Booleans.  Places that are not directly visible to the GL API
 131 should prefer the use of <code>bool</code>, <code>true</code>, and
 132 <code>false</code> over <code>GLboolean</code>, <code>GL_TRUE</code>, and
 133 <code>GL_FALSE</code>.  In C code, this may mean that
 134 <code>#include &lt;stdbool.h&gt;</code> needs to be added.  The
 135 <code>try_emit_*</code> methods in <code>src/mesa/program/ir_to_mesa.cpp</code>
 136 and <code>src/mesa/state_tracker/st_glsl_to_tgsi.cpp</code> can serve as
 137 examples.
 138
 139 </ul>
 140
 141 </div>
 142 </body>
 143 </html>