video: SDL_GL_GetAttribute gets correct SDL_GL_CONTEXT_RELEASE_BEHAVIOR value.

Original patch was from @ramezgerges (thanks!).

Fixes #11697.

src/video/SDL_video.c

@@ -51,10 +51,14 @@
 #include <SDL3/SDL_opengles2.h>
 #endif // SDL_VIDEO_OPENGL_ES2 && !SDL_VIDEO_OPENGL
 
-#ifndef SDL_VIDEO_OPENGL
-#ifndef GL_CONTEXT_RELEASE_BEHAVIOR_KHR
-#define GL_CONTEXT_RELEASE_BEHAVIOR_KHR 0x82FB
+// GL_CONTEXT_RELEASE_BEHAVIOR and GL_CONTEXT_RELEASE_BEHAVIOR_KHR have the same number.
+#ifndef GL_CONTEXT_RELEASE_BEHAVIOR
+#define GL_CONTEXT_RELEASE_BEHAVIOR 0x82FB
 #endif
+
+// GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH and GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH_KHR have the same number.
+#ifndef GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH
+#define GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH 0x82FC
 #endif
 
 #ifdef SDL_PLATFORM_EMSCRIPTEN
@@ -4820,11 +4824,7 @@ bool SDL_GL_GetAttribute(SDL_GLAttr attr, int *value)
         attrib = GL_SAMPLES;
         break;
     case SDL_GL_CONTEXT_RELEASE_BEHAVIOR:
-#ifdef SDL_VIDEO_OPENGL
         attrib = GL_CONTEXT_RELEASE_BEHAVIOR;
-#else
-        attrib = GL_CONTEXT_RELEASE_BEHAVIOR_KHR;
-#endif
         break;
     case SDL_GL_BUFFER_SIZE:
     {
@@ -4969,6 +4969,12 @@ bool SDL_GL_GetAttribute(SDL_GLAttr attr, int *value)
         }
         return SDL_SetError("OpenGL error: %08X", error);
     }
+
+    // convert GL_CONTEXT_RELEASE_BEHAVIOR values back to SDL_GL_CONTEXT_RELEASE_BEHAVIOR values
+    if (attr == SDL_GL_CONTEXT_RELEASE_BEHAVIOR) {
+        *value = (*value == GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH) ? SDL_GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH : SDL_GL_CONTEXT_RELEASE_BEHAVIOR_NONE;
+    }
+
     return true;
 #else
     return SDL_Unsupported();