From c2b5cdcef2e70b493559398e222e380743a811af Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <icculus@icculus.org>
Date: Tue, 29 Sep 2009 13:50:33 +0000
Subject: [PATCH] Make SDL_GL_GetAttribute(SDL_GL_SWAP_CONTROL) work with
 GLX_SGI_swap_control.

  Fixes Bugzilla #697.
---
 src/video/x11/SDL_x11gl.c    | 9 +++++++--
 src/video/x11/SDL_x11gl_c.h  | 1 +
 src/video/x11/SDL_x11video.c | 2 ++
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/video/x11/SDL_x11gl.c b/src/video/x11/SDL_x11gl.c
index 78e9982bd..ca7c6a1a5 100644
--- a/src/video/x11/SDL_x11gl.c
+++ b/src/video/x11/SDL_x11gl.c
@@ -289,7 +289,9 @@ int X11_GL_CreateContext(_THIS)
 		if ( this->gl_data->glXSwapIntervalMESA ) {
 			this->gl_data->glXSwapIntervalMESA(this->gl_config.swap_control);
 		} else if ( this->gl_data->glXSwapIntervalSGI ) {
-			this->gl_data->glXSwapIntervalSGI(this->gl_config.swap_control);
+			if (this->gl_data->glXSwapIntervalSGI(this->gl_config.swap_control) != 0) {
+				this->gl_data->sgi_swap_interval = this->gl_config.swap_control;
+			}
 		}
 	}
 #else
@@ -412,7 +414,10 @@ int X11_GL_GetAttribute(_THIS, SDL_GLattr attrib, int* value)
 	    case SDL_GL_SWAP_CONTROL:
 		if ( this->gl_data->glXGetSwapIntervalMESA ) {
 			*value = this->gl_data->glXGetSwapIntervalMESA();
-			return(0);
+			return 0;
+		} else if ( this->gl_data->glXSwapIntervalSGI ) {
+			*value = this->gl_data->sgi_swap_interval;
+			return 0;
 		} else {
 			unsupported = 1;
 		}
diff --git a/src/video/x11/SDL_x11gl_c.h b/src/video/x11/SDL_x11gl_c.h
index 50a9a5f11..48143abe6 100644
--- a/src/video/x11/SDL_x11gl_c.h
+++ b/src/video/x11/SDL_x11gl_c.h
@@ -75,6 +75,7 @@ struct SDL_PrivateGLData {
     GLint (*glXSwapIntervalMESA) ( unsigned interval );
     GLint (*glXGetSwapIntervalMESA) ( void );
 
+    int sgi_swap_interval;
 #endif /* SDL_VIDEO_OPENGL_GLX */
 };
 
diff --git a/src/video/x11/SDL_x11video.c b/src/video/x11/SDL_x11video.c
index 22d125a01..7484c5f7a 100644
--- a/src/video/x11/SDL_x11video.c
+++ b/src/video/x11/SDL_x11video.c
@@ -121,6 +121,8 @@ static SDL_VideoDevice *X11_CreateDevice(int devindex)
 		SDL_memset(device->hidden, 0, (sizeof *device->hidden));
 		SDL_memset(device->gl_data, 0, (sizeof *device->gl_data));
 
+		device->gl_data->sgi_swap_interval = 1;
+
 		/* Set the driver flags */
 		device->handles_any_size = 1;