.TH showextensions 7 "May 2007" BUGLE "User manual"
.SH NAME
showextensions \- show that extensions utilised by an OpenGL application
.SH SYNOPSIS
.nf
filterset showextensions
.fi
.SH DESCRIPTION
The
.B showextensions
filter-set can be used to determine what version of OpenGL and what
extensions are used by a particular application. It can be used to
check that an application does not accidentally depend on an OpenGL
version that is not targetted. The most common error is calling a core
OpenGL function (for a recent version of OpenGL) when one intended to
use an older and more widely supported extension.

Note that it can only report what is used, not what is required, which
may be different if the application uses certain features only after
detecting them. It also only tests the run-time usage; the compile-time
usage may be different.

Two methods are used for detection: the functions called and the
enumerants passed to functions. The former is quite reliable, since
different entry points are used for the core and extension versions of
the same function. The latter is necessary to detect extensions such as
.B GL_SGIS_generate_mipmap
which do not introduce new function calls, but it is less reliable as
many enumerants share values. Some extensions are not detected at all:
GL_ARB_texture_non_power_of_two does not introduce any tokens or
functions, and some promoted extensions (like
GL_ARB_pixel_buffer_object) have additional semantics to their
predecessors but again introduce no new tokens or functions.
.SH OUTPUT
A typical output is the following:
.IP
.nf
Min GL version: GL_VERSION_1_5
Min GLX version: GLX_VERSION_1_2
Used extensions: GL_ARB_shader_objects GL_ARB_vertex_shader
.fi
.P
This indicates that the application used OpenGL 1.5 and GLX 1.2 (and
possibly some extensions that are incorporated into OpenGL 1.5), as
well as the extensions listed.
.SH BUGS
The enumerant detection is not entirely reliable.

Sometimes extensions are listed even though they are already part of
the core version listed.

It is assumed that OpenGL 1.1 and GLX 1.2 are used; there is no way to
detect whether an application would work on OpenGL 1.0 or GLX 1.1.
.SH AUTHOR
.B gldb
and the
.B bugle
library are written and maintained by Bruce Merry
<bmerry@users.sourceforge.net>.
.SH SEE ALSO
.BR bugle (3)