Date: Mon, 31 May 2004 15:03:05 +0900
From: ITO Nobuaki <banb@j-link.ne.jp>
Subject: [SDL] cannot enable OpenGL quadbuffer stereo mode on Linux

Hello.

I'm using SDL-1.2 on Linux box with Quadro 4 XGL.  Quadro has the VESA 3pin
stereo port, and I attached the stereo shutter glasses to the card.  Codes
written with GLUT could drive those glasses correctly, but SDL couldn't even
when SDL_GL_SetAttribute(SDL_GL_STEREO, 1) was called.

With some testing programs, finally I found that OpenGL stereo quadbuffer mode
would be enabled in case that glXMakeCurrent() is called properly after
glXCreateContext().  I know SDL_SetVideoMode() does call X11_GL_MakeCurrent(),
but I don't know the reason why it doesn't work.

Quick hack follows.  This patch works fine with SDL-1.2.7.

--- SDL-1.2.7/src/video/x11/SDL_x11gl.c.ste     2004-02-19 02:22:09.000000000 +0900
+++ SDL-1.2.7/src/video/x11/SDL_x11gl.c 2004-05-31 13:25:04.375053196+0900
@@ -126,7 +126,6 @@

        if( this->gl_config.stereo ) {
                attribs[i++] = GLX_STEREO;
-               attribs[i++] = this->gl_config.stereo;
        }

        if( this->gl_config.multisamplebuffers ) {
@@ -212,6 +211,13 @@
                return -1;
        }

+       if ( ! this->gl_data->glXMakeCurrent(GFX_Display,
+                                            SDL_Window, glx_context) ) {
+               SDL_SetError("Unable to make GL context current");
+               return -1;
+       }
+       XSync( GFX_Display, False );  
+
        gl_active = 1;
 #else   
        SDL_SetError("X11 driver not configured with OpenGL");