mutter/tests/tools/disable-npots.c

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/*
* This file can be build as a shared library and then used as an
* LD_PRELOAD to fake a system where NPOTs is not supported. It simply
* overrides glGetString and removes the extension strings.
*/
/* This is just included to get the right GL header */
#include <cogl/cogl.h>
#include <dlfcn.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <stdlib.h>
/* If RTLD_NEXT isn't available then try just using NULL */
#ifdef RTLD_NEXT
#define LIB_HANDLE RTLD_NEXT
#else
#define LIB_HANDLE NULL
#endif
typedef const GLubyte * (* GetStringFunc) (GLenum name);
static const char * const bad_strings[]
= { "GL_ARB_texture_non_power_of_two",
"GL_ARB_texture_rectangle",
"GL_EXT_texture_rectangle",
NULL };
static gboolean
get_gl_version (const gchar *version_string,
int *major_out, int *minor_out)
{
const char *major_end, *minor_end;
int major = 0, minor = 0;
if (version_string == NULL)
return FALSE;
/* Extract the major number */
for (major_end = version_string; *major_end >= '0'
&& *major_end <= '9'; major_end++)
major = (major * 10) + *major_end - '0';
/* If there were no digits or the major number isn't followed by a
dot then it is invalid */
if (major_end == version_string || *major_end != '.')
return FALSE;
/* Extract the minor number */
for (minor_end = major_end + 1; *minor_end >= '0'
&& *minor_end <= '9'; minor_end++)
minor = (minor * 10) + *minor_end - '0';
/* If there were no digits or there is an unexpected character then
it is invalid */
if (minor_end == major_end + 1
|| (*minor_end && *minor_end != ' ' && *minor_end != '.'))
return FALSE;
*major_out = major;
*minor_out = minor;
return TRUE;
}
const GLubyte *
glGetString (GLenum name)
{
const gchar *ret = NULL;
static GetStringFunc func = NULL;
static gchar *extensions = NULL;
static gchar *version = NULL;
if (func == NULL
&& (func = (GetStringFunc) dlsym (LIB_HANDLE, "glGetString")) == NULL)
fprintf (stderr, "dlsym: %s\n", dlerror ());
else if (func == glGetString)
fprintf (stderr, "dlsym returned the wrapper of glGetString\n");
else
{
ret = (const gchar *) (* func) (name);
if (name == GL_EXTENSIONS)
{
if (extensions == NULL)
{
if ((extensions = strdup ((char *) ret)) == NULL)
fprintf (stderr, "strdup: %s\n", strerror (errno));
else
{
gchar *dst = extensions, *src = extensions;
while (1)
{
const char * const *str = bad_strings;
gchar *end;
while (isspace (*src))
*(dst++) = *(src++);
if (*src == 0)
break;
for (end = src + 1; *end && !isspace (*end); end++);
while (*str && strncmp ((char *) src, *str, end - src))
str++;
if (*str == NULL)
{
memcpy (dst, src, end - src);
dst += end - src;
}
src = end;
}
*dst = '\0';
}
}
ret = extensions;
}
else if (name == GL_VERSION)
{
int gl_major, gl_minor;
/* If the GL version is >= 2.0 then Cogl will assume it
supports NPOT textures anyway so we need to tweak it */
if (get_gl_version ((const gchar *) ret,
&gl_major, &gl_minor) && gl_major >= 2)
{
if (version == NULL)
{
const gchar *tail = strchr (ret, ' ');
if (tail)
{
version = malloc (3 + strlen (tail) + 1);
if (version)
{
strcpy (version + 3, tail);
memcpy (version, "1.9", 3);
}
}
else
version = strdup ("1.9");
}
ret = version;
}
}
}
return (const GLubyte *) ret;
}