--- a/src/video/x11/SDL_x11gl.c	Thu Apr 27 07:59:16 2006 +0000
+++ b/src/video/x11/SDL_x11gl.c	Thu Apr 27 08:39:51 2006 +0000
@@ -43,6 +43,47 @@
 #define GLX_SAMPLES_ARB                    100001
 #endif
 
+#ifndef GLX_EXT_visual_rating
+#define GLX_EXT_visual_rating
+#define GLX_VISUAL_CAVEAT_EXT              0x20
+#define GLX_SLOW_VISUAL_EXT                0x8001
+#define GLX_NON_CONFORMANT_VISUAL_EXT      0x800D
+#endif
+
+#if SDL_VIDEO_OPENGL_GLX
+static int glXExtensionSupported(_THIS, const char *extension)
+{
+	const char *extensions;
+	const char *start;
+	const char *where, *terminator;
+
+	/* Extension names should not have spaces. */
+	where = SDL_strchr(extension, ' ');
+	if ( where || *extension == '\0' ) {
+	      return 0;
+	}
+
+	extensions = this->gl_data->glXQueryExtensionsString(GFX_Display,SDL_Screen);
+	/* It takes a bit of care to be fool-proof about parsing the
+	 * OpenGL extensions string. Don't be fooled by sub-strings, etc.
+	 */
+	
+	start = extensions;
+	
+	for (;;) {
+		where = SDL_strstr(start, extension);
+		if (!where) break;
+		
+		terminator = where + strlen(extension);
+		if (where == start || *(where - 1) == ' ')
+	        if (*terminator == ' ' || *terminator == '\0') return 1;
+						  
+		start = terminator;
+	}
+	return 0;
+}
+#endif /* SDL_VIDEO_OPENGL_GLX */
+
 XVisualInfo *X11_GL_GetVisual(_THIS)
 {
 #if SDL_VIDEO_OPENGL_GLX
@@ -138,6 +179,12 @@
 		attribs[i++] = this->gl_config.multisamplesamples;
 	}
 
+	if( this->gl_config.accelerated >= 0 &&
+	    glXExtensionSupported(this, "GLX_EXT_visual_rating") ) {
+		attribs[i++] = GLX_VISUAL_CAVEAT_EXT;
+		attribs[i++] = this->gl_config.accelerated ? GLX_NONE : GLX_DONT_CARE;
+	}
+
 #ifdef GLX_DIRECT_COLOR /* Try for a DirectColor visual for gamma support */
 	if ( !SDL_getenv("SDL_VIDEO_X11_NODIRECTCOLOR") ) {
 		attribs[i++] = GLX_X_VISUAL_TYPE;
@@ -205,7 +252,6 @@
 {
 	int retval;
 #if SDL_VIDEO_OPENGL_GLX
-	const char *glXext;
 
 	/* We do this to create a clean separation between X and GLX errors. */
 	XSync( SDL_Display, False );
@@ -222,12 +268,10 @@
 	}
 	gl_active = 1;
 
-	/* The use of strstr here should be safe */
-	glXext = this->gl_data->glXQueryExtensionsString(GFX_Display, DefaultScreen(GFX_Display));
-	if ( !SDL_strstr(glXext, "SGI_swap_control") ) {
+	if ( !glXExtensionSupported(this, "SGI_swap_control") ) {
 		this->gl_data->glXSwapIntervalSGI = NULL;
 	}
-	if ( !SDL_strstr(glXext, "GLX_MESA_swap_control") ) {
+	if ( !glXExtensionSupported(this, "GLX_MESA_swap_control") ) {
 		this->gl_data->glXSwapIntervalMESA = NULL;
 		this->gl_data->glXGetSwapIntervalMESA = NULL;
 	}
@@ -340,11 +384,25 @@
  	    case SDL_GL_MULTISAMPLESAMPLES:
  		glx_attrib = GLX_SAMPLES_ARB;
  		break;
+ 	    case SDL_GL_ACCELERATED_VISUAL:
+		if ( glXExtensionSupported(this, "GLX_EXT_visual_rating") ) {
+			glx_attrib = GLX_VISUAL_CAVEAT_EXT;
+			retval = this->gl_data->glXGetConfig(GFX_Display, glx_visualinfo, glx_attrib, value);
+			if ( *value == GLX_SLOW_VISUAL_EXT ) {
+				*value = SDL_FALSE;
+			} else {
+				*value = SDL_TRUE;
+			}
+			return retval;
+		} else {
+			return(-1);
+		}
+		break;
 	    case SDL_GL_SWAP_CONTROL:
 		if ( this->gl_data->glXGetSwapIntervalMESA ) {
 			return this->gl_data->glXGetSwapIntervalMESA();
 		} else {
-			return -1 /*(this->gl_config.swap_control > 0)*/;
+			return(-1)/*(this->gl_config.swap_control > 0)*/;
 		}
 		break;
 	    default: