Checks for an OpenGL implementation. If a valid OpenGL implementation is found, this macro would set C preprocessor symbol HAVE_GL to 1.
If either a valid OpenGL header or library was not found, by default the configuration would exits on error. This behavior can be overwritten by providing a custom "ACTION-IF-NOT-FOUND" hook.
If the header, library was found, and been tested for compiling and linking the configuration would export the required compiler flags to "GL_CFLAGS" and "GL_LIBS". These two variables can also be overwritten by user from the command line if they want to link against the library they specified instead of having the configuration script to detect the flags automatically. Note that having "GL_CFLAGS" or "GL_LIBS" set doesn’t mean it can compile or link with the flags, since it could be overwritten by user. However the "HAVE_GL" symbol and "ACTION-IF-FOUND" hook is always guaranteed to reflect a valid OpenGL implementation.
If user didn’t specify the "ACTION-IF-FOUND" hook, the configuration would prepend "GL_CFLAGS" and "GL_LIBS" to "CFLAGS" and "LIBS", like many other autoconf macros do.
OpenGL is one of the libraries that has different header names on different platforms. This macro does the header detection, and will export the following symbol: "HAVE_GL_GL_H" for having "GL/gl.h" or "HAVE_OPENGL_GL_H" for having "OpenGL/gl.h". To write a portable OpenGL code, you should include OpenGL header like so:
#if defined(HAVE_WINDOWS_H) && defined(_WIN32) # include <windows.h> #endif #ifdef HAVE_GL_GL_H # include <GL/gl.h> #elif defined(HAVE_OPENGL_GL_H) # include <OpenGL/gl.h> #else # error no gl.h #endif
On the OSX platform, there’s two possible OpenGL implementation. One is the OpenGL that ships with OSX, the other comes with X11/XQuartz (http://www.xquartz.org). To use the xquartz variant, user can use the option –with-xquartz-gl[=path to xquartz root]. By default the configuration will check "/opt/X11", which is the default X11 install location on OSX.
Download the latest version of ax_check_gl.m4 or browse the macro’s revision history.
Copyright © 2009 Braden McDaniel firstname.lastname@example.org
Copyright © 2012 Bastien Roucaries email@example.com
Copyright © 2016 Felix Chern firstname.lastname@example.org
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