summaryrefslogtreecommitdiff
path: root/docs/codingstyle.html
blob: 4dfb0cc02f0bbb84e1729ea1ef98647632f2ff52 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html lang="en">
<head>
  <meta http-equiv="content-type" content="text/html; charset=utf-8">
  <title>Coding Style</title>
  <link rel="stylesheet" type="text/css" href="mesa.css">
</head>
<body>

<div class="header">
  <h1>The Mesa 3D Graphics Library</h1>
</div>

<iframe src="contents.html"></iframe>
<div class="content">

<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Some old parts use a style that's a bit out of date.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 &lt;stdbool.h&gt;</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>

</div>
</body>
</html>