From 34415c4557400f6706d06a533d61db2fcfc7b754 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <icculus@icculus.org>
Date: Fri, 20 Mar 2015 12:23:53 -0400
Subject: [PATCH] Windows: support for OpenGL extension
 WGL_ARB_context_flush_control.

---
 src/video/windows/SDL_windowsopengl.c | 24 ++++++++++++++++++++++--
 src/video/windows/SDL_windowsopengl.h |  1 +
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/video/windows/SDL_windowsopengl.c b/src/video/windows/SDL_windowsopengl.c
index 71855c87418e9..bab97fae0dd42 100644
--- a/src/video/windows/SDL_windowsopengl.c
+++ b/src/video/windows/SDL_windowsopengl.c
@@ -74,6 +74,13 @@
 #define WGL_FRAMEBUFFER_SRGB_CAPABLE_ARB                0x20A9
 #endif
 
+#ifndef WGL_ARB_context_flush_control
+#define WGL_ARB_context_flush_control
+#define WGL_CONTEXT_RELEASE_BEHAVIOR_ARB   0x2097
+#define WGL_CONTEXT_RELEASE_BEHAVIOR_NONE_ARB           0x0000
+#define WGL_CONTEXT_RELEASE_BEHAVIOR_FLUSH_ARB          0x2098
+#endif
+
 typedef HGLRC(APIENTRYP PFNWGLCREATECONTEXTATTRIBSARBPROC) (HDC hDC,
                                                             HGLRC
                                                             hShareContext,
@@ -405,6 +412,11 @@ WIN_GL_InitExtensions(_THIS)
         _this->gl_data->HAS_WGL_EXT_create_context_es2_profile = SDL_TRUE;
     }
 
+    /* Check for GLX_ARB_context_flush_control */
+    if (HasExtension("WGL_ARB_context_flush_control", extensions)) {
+        _this->gl_data->HAS_WGL_ARB_context_flush_control = SDL_TRUE;
+    }
+
     _this->gl_data->wglMakeCurrent(hdc, NULL);
     _this->gl_data->wglDeleteContext(hglrc);
     ReleaseDC(hwnd, hdc);
@@ -648,8 +660,8 @@ WIN_GL_CreateContext(_THIS, SDL_Window * window)
             SDL_SetError("GL 3.x is not supported");
             context = temp_context;
         } else {
-        /* max 8 attributes plus terminator */
-            int attribs[9] = {
+        /* max 10 attributes plus terminator */
+            int attribs[11] = {
                 WGL_CONTEXT_MAJOR_VERSION_ARB, _this->gl_config.major_version,
                 WGL_CONTEXT_MINOR_VERSION_ARB, _this->gl_config.minor_version,
                 0
@@ -668,6 +680,14 @@ WIN_GL_CreateContext(_THIS, SDL_Window * window)
         attribs[iattr++] = _this->gl_config.flags;
         }
 
+        /* only set if wgl extension is available */
+        if( _this->gl_data->HAS_WGL_ARB_context_flush_control ) {
+            attribs[iattr++] = WGL_CONTEXT_RELEASE_BEHAVIOR_ARB;
+            attribs[iattr++] = _this->gl_config.release_behavior ?
+                                    WGL_CONTEXT_RELEASE_BEHAVIOR_FLUSH_ARB :
+                                    WGL_CONTEXT_RELEASE_BEHAVIOR_NONE_ARB;
+        }
+
         attribs[iattr++] = 0;
 
             /* Create the GL 3.x context */
diff --git a/src/video/windows/SDL_windowsopengl.h b/src/video/windows/SDL_windowsopengl.h
index b96e0ac1e4a38..b95b90f742aa5 100644
--- a/src/video/windows/SDL_windowsopengl.h
+++ b/src/video/windows/SDL_windowsopengl.h
@@ -30,6 +30,7 @@ struct SDL_GLDriverData
     SDL_bool HAS_WGL_ARB_pixel_format;
     SDL_bool HAS_WGL_EXT_swap_control_tear;
     SDL_bool HAS_WGL_EXT_create_context_es2_profile;
+    SDL_bool HAS_WGL_ARB_context_flush_control;
 
     void *(WINAPI * wglGetProcAddress) (const char *proc);
       HGLRC(WINAPI * wglCreateContext) (HDC hdc);