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<title>Coding Style</title>
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<h1>The Mesa 3D Graphics Library</h1>
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<h1>Coding Style</h1>
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Some old parts use a style that's a bit out of date.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.
Basic formatting guidelines
<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:
if (condition) {
} else {
<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:
indent -br -i3 -npcs --no-tabs infile.c -o outfile.c
<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="">Doxygen</a> conventions.
Single-line comments:
/* null-out pointer to prevent dangling reference below */
bufferObj = NULL;
bufferObj = NULL; /* prevent dangling reference below */
Multi-line comment:
/* If this is a new buffer object id, or one which was generated but
* never used before, allocate a buffer object now.
We try to quote the OpenGL specification where prudent:
/* 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.
Function comment example:
* 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 */
<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:
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
<li>Constants, macros and enumerant names are ALL_UPPERCASE, with _ between
<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.