Hi Guys,
One problem I just came across with the latest Mesa sources is that
the Mesa version of GL/gl.h includes function prototypes for all the
extension functions. Ie there is the:
GLAPI void GLAPIENTRY glBlendEquationEXT( GLenum mode );
It is a bad thing for the OpenGL headers to be declaring extension
functions directly (and especially to be exported!), because that
allows application developers to circumvent the proper extension
mechanism. This can lead to portability problems down the trace.
What is needed is to define function *pointer* prototypes in the
GL/gl.h header file, which will be used by apps to declare pointers
to the functions that it will be calling. In our header files we
include the following (not found in the Mesa headers):
typedef void (APIENTRYP PFNGLBLENDEQUATIONEXTPROC)(GLenum mode);
The above macros are taken from the way that the SGI and Microsoft
headers define this stuff in their header files.
Hence I proprose that we have a GL/gl_ext.h header file that contains
all the internal prototypes for extension functions. Obviously it is
important for binary compatibility that all implementations declare
and export functions that have the same prototypes for common
extensions.
There is also the need for vendor specific OpenGL extensions to be
included, that should not be in the common header files. Hence I also
propose that the last line of GL/gl.h should go ahead and include
GL/gl_vendor.h. The default provided with Mesa should be either
empty, or contain Mesa specific stuff. We will have a version that we
ship that does stuff we need to allow for auto-switching of OpenGL
implementations under Windows at runtime.
Regards,
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