From f728a26f645d9d30404ef77debf4add06775b566 Mon Sep 17 00:00:00 2001
From: "J?rgen P. Tjern?" <jorgen@valvesoftware.com>
Date: Tue, 9 Jul 2013 12:58:54 -0700
Subject: [PATCH] SDL_GL_MakeCurrent: Only no-op redundant calls on *same*
 thread.

This ensures that we only no-op redundant calls if they're made on the
same thread as the last MakeCurrent with those arguments. This should
maek SDL behave better with multithreaded environments.
---
 src/video/SDL_sysvideo.h | 2 ++
 src/video/SDL_video.c    | 5 ++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/video/SDL_sysvideo.h b/src/video/SDL_sysvideo.h
index 45ca74507..cd3fa2717 100644
--- a/src/video/SDL_sysvideo.h
+++ b/src/video/SDL_sysvideo.h
@@ -25,6 +25,7 @@
 
 #include "SDL_messagebox.h"
 #include "SDL_shape.h"
+#include "SDL_thread.h"
 
 /* The SDL video driver */
 
@@ -301,6 +302,7 @@ struct SDL_VideoDevice
     /* Cache current GL context; don't call the OS when it hasn't changed. */
     SDL_Window *current_glwin;
     SDL_GLContext current_glctx;
+    SDL_threadID current_glthread;
 
     /* * * */
     /* Data private to this driver */
diff --git a/src/video/SDL_video.c b/src/video/SDL_video.c
index d5d0a7556..801fa5e3e 100644
--- a/src/video/SDL_video.c
+++ b/src/video/SDL_video.c
@@ -2730,6 +2730,7 @@ SDL_GL_CreateContext(SDL_Window * window)
     /* Creating a context is assumed to make it current in the SDL driver. */
     _this->current_glwin = window;
     _this->current_glctx = ctx;
+    _this->current_glthread = SDL_ThreadID();
 
     return ctx;
 }
@@ -2738,6 +2739,7 @@ int
 SDL_GL_MakeCurrent(SDL_Window * window, SDL_GLContext ctx)
 {
     int retval;
+    SDL_threadID thread = SDL_ThreadID();
 
     if (!ctx) {
         window = NULL;
@@ -2749,13 +2751,14 @@ SDL_GL_MakeCurrent(SDL_Window * window, SDL_GLContext ctx)
         }
     }
 
-    if ((window == _this->current_glwin) && (ctx == _this->current_glctx)) {
+    if ((window == _this->current_glwin) && (ctx == _this->current_glctx) && (thread == _this->current_glthread)) {
         retval = 0;  /* we're already current. */
     } else {
         retval = _this->GL_MakeCurrent(_this, window, ctx);
         if (retval == 0) {
             _this->current_glwin = window;
             _this->current_glctx = ctx;
+            _this->current_glthread = thread;
         }
     }