Merge branch 'ogl-driver-error' into 'next'

Add error message when the GDI Generic OpenGL renderer is encountered in Windows

See merge request STJr/SRB2!1172

src/sdl/ogl_sdl.c

@@ -167,6 +167,18 @@ boolean OglSdlSurface(INT32 w, INT32 h)
 		GL_DBG_Printf("OpenGL %s\n", gl_version);
 		GL_DBG_Printf("GPU: %s\n", gl_renderer);
 		GL_DBG_Printf("Extensions: %s\n", gl_extensions);
+
+		if (strcmp((const char*)gl_renderer, "GDI Generic") == 0 &&
+			strcmp((const char*)gl_version, "1.1.0") == 0)
+		{
+			// Oh no... Windows gave us the GDI Generic rasterizer, so something is wrong...
+			// The game will crash later on when unsupported OpenGL commands are encountered.
+			// Instead of a nondescript crash, show a more informative error message.
+			// Also set the renderer variable back to software so the next launch won't
+			// repeat this error.
+			CV_StealthSet(&cv_renderer, "Software");
+			I_Error("OpenGL Error: Failed to access the GPU. There may be an issue with your graphics drivers.");
+		}
 	}
 	first_init = true;