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docs: update the coding style information 

This hasn't been updated in a long time and from recent discussion on
the mailing list, it's not always clear what's expected.  Hopefully,
this will help a bit.

v2: document function brace placement, per Thomas Helland.

Reviewed-by: Thomas Helland <thomashelland90@gmail.com>
This commit is contained in:
Brian Paul 2015-05-25 10:18:35 -06:00
parent d959885b91
commit c6184f84b7
1 changed files with 93 additions and 72 deletions
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docs/devinfo.html
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@ -28,97 +28,118 @@
<h2 id="style">Coding Style</h2>
<p>
Mesa's code style has changed over the years. Here's the latest.
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Some old parts use a style that's a bit out of date.
If the guidelines below don't cover something, try following the format of
existing, neighboring code.
</p>
<p>
Comment your code! It's extremely important that open-source code be
well documented. Also, strive to write clean, easily understandable code.
Basic formatting guidelines
</p>
<p>
3-space indentation
</p>
<p>
If you use tabs, set them to 8 columns
</p>
<p>
Line width: the preferred width to fill comments and code in Mesa is 78
columns. Exceptions are sometimes made for clarity (e.g. tabular data is
sometimes filled to a much larger width so that extraneous carriage returns
don't obscure the table).
</p>
<p>
Brace example:
</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;
}
switch (condition) {
case 0:
foo();
break;
case 1: {
...
break;
}
default:
...
break;
}
if (condition) {
foo;
} else {
bar;
}
</pre>
<p>
Here's the GNU indent command which will best approximate my preferred style:
(Note that it won't format switch statements in the preferred way)
</p>
<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
indent -br -i3 -npcs --no-tabs infile.c -o outfile.c
</pre>
<p>
Local variable name example: localVarName (no underscores)
</p>
<p>
Constants and macros are ALL_UPPERCASE, with _ between words
</p>
<p>
Global variables are not allowed.
</p>
<p>
Function name examples:
</p>
<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>
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
/* 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>
<p>
Places that are not directly visible to the GL API should prefer the use
of <tt>bool</tt>, <tt>true</tt>, and
<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.
</p>
</ul>
<h2 id="submitting">Submitting patches</h2>