2018-10-23 00:35:32 -06:00
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html lang="en">
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<head>
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<meta http-equiv="content-type" content="text/html; charset=utf-8">
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<title>Coding Style</title>
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<link rel="stylesheet" type="text/css" href="mesa.css">
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</head>
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<body>
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<div class="header">
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<h1>The Mesa 3D Graphics Library</h1>
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</div>
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<iframe src="contents.html"></iframe>
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<div class="content">
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<h1>Coding Style</h1>
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<p>
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Mesa is over 20 years old and the coding style has evolved over time.
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Some old parts use a style that's a bit out of date.
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Different sections of mesa can use different coding style as set in the local
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EditorConfig (.editorconfig) and/or Emacs (.dir-locals.el) file.
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Alternatively the following is applicable.
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If the guidelines below don't cover something, try following the format of
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existing, neighboring code.
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</p>
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<p>
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Basic formatting guidelines
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</p>
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<ul>
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<li>3-space indentation, no tabs.
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<li>Limit lines to 78 or fewer characters. The idea is to prevent line
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wrapping in 80-column editors and terminals. There are exceptions, such
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as if you're defining a large, static table of information.
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<li>Opening braces go on the same line as the if/for/while statement.
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For example:
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<pre>
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if (condition) {
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foo;
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} else {
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bar;
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}
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</pre>
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<li>Put a space before/after operators. For example, <tt>a = b + c;</tt>
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and not <tt>a=b+c;</tt>
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<li>This GNU indent command generally does the right thing for formatting:
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<pre>
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indent -br -i3 -npcs --no-tabs infile.c -o outfile.c
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</pre>
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<li>Use comments wherever you think it would be helpful for other developers.
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Several specific cases and style examples follow. Note that we roughly
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follow <a href="https://www.stack.nl/~dimitri/doxygen/">Doxygen</a> conventions.
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<br>
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<br>
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Single-line comments:
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<pre>
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/* null-out pointer to prevent dangling reference below */
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bufferObj = NULL;
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</pre>
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Or,
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<pre>
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bufferObj = NULL; /* prevent dangling reference below */
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</pre>
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Multi-line comment:
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<pre>
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/* If this is a new buffer object id, or one which was generated but
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* never used before, allocate a buffer object now.
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*/
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</pre>
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We try to quote the OpenGL specification where prudent:
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<pre>
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/* Page 38 of the PDF of the OpenGL ES 3.0 spec says:
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*
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* "An INVALID_OPERATION error is generated for any of the following
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* conditions:
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*
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2019-01-29 04:52:04 -07:00
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* * <length> is zero."
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2018-10-23 00:35:32 -06:00
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*
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* Additionally, page 94 of the PDF of the OpenGL 4.5 core spec
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* (30.10.2014) also says this, so it's no longer allowed for desktop GL,
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* either.
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*/
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</pre>
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Function comment example:
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<pre>
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/**
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* Create and initialize a new buffer object. Called via the
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* ctx->Driver.CreateObject() driver callback function.
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2018-10-23 00:35:32 -06:00
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* \param name integer name of the object
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* \param type one of GL_FOO, GL_BAR, etc.
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* \return pointer to new object or NULL if error
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*/
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struct gl_object *
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_mesa_create_object(GLuint name, GLenum type)
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{
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/* function body */
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}
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</pre>
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<li>Put the function return type and qualifiers on one line and the function
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name and parameters on the next, as seen above. This makes it easy to use
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<code>grep ^function_name dir/*</code> to find function definitions. Also,
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the opening brace goes on the next line by itself (see above.)
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<li>Function names follow various conventions depending on the type of function:
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<pre>
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glFooBar() - a public GL entry point (in glapi_dispatch.c)
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_mesa_FooBar() - the internal immediate mode function
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save_FooBar() - retained mode (display list) function in dlist.c
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foo_bar() - a static (private) function
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_mesa_foo_bar() - an internal non-static Mesa function
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</pre>
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<li>Constants, macros and enum names are ALL_UPPERCASE, with _ between
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words.
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<li>Mesa usually uses camel case for local variables (Ex: "localVarname")
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while gallium typically uses underscores (Ex: "local_var_name").
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<li>Global variables are almost never used because Mesa should be thread-safe.
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<li>Booleans. Places that are not directly visible to the GL API
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should prefer the use of <tt>bool</tt>, <tt>true</tt>, and
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<tt>false</tt> over <tt>GLboolean</tt>, <tt>GL_TRUE</tt>, and
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<tt>GL_FALSE</tt>. In C code, this may mean that
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<tt>#include <stdbool.h></tt> needs to be added. The
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<tt>try_emit_</tt>* methods in src/mesa/program/ir_to_mesa.cpp and
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src/mesa/state_tracker/st_glsl_to_tgsi.cpp can serve as examples.
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</ul>
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</p>
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</div>
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</body>
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</html>
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