Implemented pre-C99 support for macro expansion for callbacks.

Note: not tested with a pre-C99 compiler as I (the author) don't have any compiler that doesn't C99.

Fixed copyright too.

git-svn-id: https://svn.code.sf.net/p/freeglut/code/trunk@1814 7f0cb862-5218-0410-a997-914c9d46530a
This commit is contained in:
dcnieho 2017-06-30 23:21:40 +00:00
parent 0209cd1ef5
commit dbbf2e5f08

View File

@ -3,9 +3,8 @@
* *
* The freeglut library callback macro file. * The freeglut library callback macro file.
* *
* Copyright (c) 1999-2000 Pawel W. Olszta. All Rights Reserved. * Copyright (C) 2016 Vincent Simonetti
* Written by Pawel W. Olszta, <olszta@sourceforge.net> * Creation date: Sat Jan 16 2016
* Creation date: Thu Dec 2 1999
* *
* Permission is hereby granted, free of charge, to any person obtaining a * Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"), * copy of this software and associated documentation files (the "Software"),
@ -38,20 +37,65 @@
* FG_COMPILER_SUPPORTS_VA_ARGS: if the compiler supports varadic macros * FG_COMPILER_SUPPORTS_VA_ARGS: if the compiler supports varadic macros
*/ */
/*
* Info:
*
* This took a while to figure out, so be sure try to understand what is happening so that you can ensure that whatever you
* change won't break other areas.
*
* If you are just adding a new callback/changing it's argument count, just go to the bottom of the file.
*
* This whole file exists purely for the sake of preventing the need to implement additional parsing logic for each callback
* to pass user arguments. Of course, the necessity to support older compilers means that, as seen in the line above, there
* is still a requirement to add/modify code to handle callbacks. If freeglut ever requires newer compilers (at minimum, ones
* that support C99 or higher), code can very slowly be removed from this file. Even better would be if the C standard eventually
* supports something similar to what GCC has implemented or offers an alternative. Another option is if C++ would be "allowed" by
* project maintaners, as then templates can be used and function overloading. Ironically, the template would probably look worse
* then the GCC macro, so maybe it's good to stay as is.
*
* Onto the different "versions" of macros:
*
* There is one for GCC/Clang(/and supposedly the Intel compiler) which supports the non-standard ##__VA_ARGS__ token. The code may
* look ugly, but the result is, if this was standard, no one would ever need to open this file unless they were curious (or needed
* more then 5 arguments for a callback, but that's trivial to add). It works by adding many fake macros to a "picker" macro
* (PP_HAS_ARGS_IMPL2) which then indictaes which macro counter to use. As we can already use varadic macros (the VA in __VA_ARGS__),
* this just becomes a "reuse the arguments*.
*
* The next is for any non-GCC/Clang/etc. compiler *cough* MSVC/compiler you probably shouldn't be using *cough* that supports C99
* by default. It requires each callback to have a specific argument count passthrough macro. The only reason there are specific
* count macros is so that (see paraghraph below) don't need have their own set of callback macros. Ideally, there would only be
* ZERO and ONE_OR_MORE. This works by having callback-specific macros call a specific handler macro to return user data (ZERO) or
* return one or more arguments along with userData (ONE_OR_MORE) where, with varadic macros, it just reuses the arguments.
*
* The last set is for the poor individual who has to use a compiler that doesn't support C99 by default, or may not support it at
* all. Stuff like MSVC6... It works by having a specific-count macro that "extracts" each argument to have them reused without the
* parathesis.
*
* A note on parathesis, as earlier mentioned, if the GCC varadic macro element was standard, then instead of needing:
*
* func EXPAND_WCB(Mouse)(( (GLUT_LEFT_BUTTON, GLUT_DOWN, 10, 30), userData));
*
* ...you can do the following:
*
* func EXPAND_WCB (GLUT_LEFT_BUTTON, GLUT_DOWN, 10, 30);
*
* Wow... so much nice and easier to understand. Sub-note: I have not worked on a version that explicitly takes userData, so for now
* if you can get to that version, look in the version control change history for this file and you'll find that version which
* implicitly passes "userData" and only works on GCC vardiac macro supporting compilers.
*/
#ifdef FG_COMPILER_SUPPORTS_GCC_VA_ARGS_HACK #ifdef FG_COMPILER_SUPPORTS_GCC_VA_ARGS_HACK
/* /*
* EXPAND_WCB() is used as: * EXPAND_WCB() is used as:
* *
* EXPAND_WCB arg_list * EXPAND_WCB( cbname )(( arg_list, userData ))
* *
* ... where {(arg_list)} is the parameter list. * ... where {(arg_list)} is the parameter list and userData is user
* provided data.
* *
* This will take the arg_list and extend it by one argument, adding * All additional macros are to get around trailing ',' for zero-arg
* the argument "userData" to the end of the list. * callbacks.
*
* All additional args are to get around trailing ',', argument counts,
* and not needing a GCC extension to make this work.
* *
* Modification of: * Modification of:
* http://stackoverflow.com/questions/5355241/generating-function-declaration-using-a-macro-iteration/5355946#5355946 * http://stackoverflow.com/questions/5355241/generating-function-declaration-using-a-macro-iteration/5355946#5355946
@ -115,7 +159,6 @@
* #define EXPAND_WCB_SUB_Entry(args) EXPAND_WCB_ONE args * #define EXPAND_WCB_SUB_Entry(args) EXPAND_WCB_ONE args
*/ */
#define FG_COMPILER_SUPPORTS_VA_ARGS //XXX (should be compiler defined)
#ifdef FG_COMPILER_SUPPORTS_VA_ARGS #ifdef FG_COMPILER_SUPPORTS_VA_ARGS
#define EXPAND_WCB_UNPARAN(...) __VA_ARGS__ #define EXPAND_WCB_UNPARAN(...) __VA_ARGS__
@ -129,8 +172,17 @@
#else #else
//TODO #define EXTRACT_ONE_ARGS(arg1) arg1
#error "Compiler does not support varadic argument macros" #define EXTRACT_TWO_ARGS(arg1, arg2) arg1, arg2
#define EXTRACT_THREE_ARGS(arg1, arg2, arg3) arg1, arg2, arg3
#define EXTRACT_FOUR_ARGS(arg1, arg2, arg3, arg4) arg1, arg2, arg3, arg4
#define EXTRACT_FIVE_ARGS(arg1, arg2, arg3, arg4, arg5) arg1, arg2, arg3, arg4, arg5
#define EXPAND_WCB_ONE(args, userData) (EXTRACT_ONE_ARGS args, userData)
#define EXPAND_WCB_TWO(args, userData) (EXTRACT_TWO_ARGS args, userData)
#define EXPAND_WCB_THREE(args, userData) (EXTRACT_THREE_ARGS args, userData)
#define EXPAND_WCB_FOUR(args, userData) (EXTRACT_FOUR_ARGS args, userData)
#define EXPAND_WCB_FIVE(args, userData) (EXTRACT_FIVE_ARGS args, userData)
#endif #endif