SDL: video: add NOT_AN_OPENGL_WINDOW define (similar to NOT_A_VULKAN_WINDOW)

SDL Commits
1 
From b71d9274291d38df68254b236448e3933a8c4eb3 Mon Sep 17 00:00:00 2001
From: pionere <[EMAIL REDACTED]>
Date: Fri, 11 Nov 2022 12:09:15 +0100
Subject: [PATCH] video: add NOT_AN_OPENGL_WINDOW define (similar to
 NOT_A_VULKAN_WINDOW)

---
 src/video/SDL_video.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/video/SDL_video.c b/src/video/SDL_video.c
index ff4602f95c53..24a42a4ce517 100644
--- a/src/video/SDL_video.c
+++ b/src/video/SDL_video.c
@@ -4067,6 +4067,8 @@ SDL_GL_GetAttribute(SDL_GLattr attr, int *value)
 #endif /* SDL_VIDEO_OPENGL */
 }
 
+#define NOT_AN_OPENGL_WINDOW "The specified window isn't an OpenGL window"
+
 SDL_GLContext
 SDL_GL_CreateContext(SDL_Window * window)
 {
@@ -4074,7 +4076,7 @@ SDL_GL_CreateContext(SDL_Window * window)
     CHECK_WINDOW_MAGIC(window, NULL);
 
     if (!(window->flags & SDL_WINDOW_OPENGL)) {
-        SDL_SetError("The specified window isn't an OpenGL window");
+        SDL_SetError(NOT_AN_OPENGL_WINDOW);
         return NULL;
     }
 
@@ -4111,7 +4113,7 @@ SDL_GL_MakeCurrent(SDL_Window * window, SDL_GLContext ctx)
         CHECK_WINDOW_MAGIC(window, -1);
 
         if (!(window->flags & SDL_WINDOW_OPENGL)) {
-            return SDL_SetError("The specified window isn't an OpenGL window");
+            return SDL_SetError(NOT_AN_OPENGL_WINDOW);
         }
     } else if (!_this->gl_allow_no_surface) {
         return SDL_SetError("Use of OpenGL without a window is not supported on this platform");
@@ -4192,7 +4194,7 @@ SDL_GL_SwapWindowWithResult(SDL_Window * window)
     CHECK_WINDOW_MAGIC(window, -1);
 
     if (!(window->flags & SDL_WINDOW_OPENGL)) {
-        return SDL_SetError("The specified window isn't an OpenGL window");
+        return SDL_SetError(NOT_AN_OPENGL_WINDOW);
     }
 
     if (SDL_GL_GetCurrentWindow() != window) {