Coding Style
+ ++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 +Some old parts use a style that's a bit out of date.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 +
+ +-
+
- 3-space indentation, no tabs. +
- 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. +
- Opening braces go on the same line as the if/for/while statement.
+For example:
+
+ if (condition) { + foo; + } else { + bar; + } ++ + - Put a space before/after operators. For example, a = b + c; +and not a=b+c; + +
- This GNU indent command generally does the right thing for formatting:
+
+ indent -br -i3 -npcs --no-tabs infile.c -o outfile.c +
+ + - Use comments wherever you think it would be helpful for other developers.
+Several specific cases and style examples follow. Note that we roughly
+follow Doxygen conventions.
+
+
+Single-line comments: ++ /* null-out pointer to prevent dangling reference below */ + bufferObj = NULL; +
+Or, ++ 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: + * + * *
+Function comment example: +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. + */ + + /** + * 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 */ + } ++ + - 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
+
grep ^function_name dir/*to find function definitions. Also, +the opening brace goes on the next line by itself (see above.) + + - 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 +
+ + - Constants, macros and enumerant names are ALL_UPPERCASE, with _ between +words. +
- Mesa usually uses camel case for local variables (Ex: "localVarname") +while gallium typically uses underscores (Ex: "local_var_name"). +
- Global variables are almost never used because Mesa should be thread-safe. + +
- Booleans. Places that are not directly visible to the GL API +should prefer the use of bool, true, and +false over GLboolean, GL_TRUE, and +GL_FALSE. In C code, this may mean that +#include <stdbool.h> needs to be added. The +try_emit_* methods in src/mesa/program/ir_to_mesa.cpp and +src/mesa/state_tracker/st_glsl_to_tgsi.cpp can serve as examples. + +