How draw on a background?

       /* ------- /nuklear/demo/sdl_opengl3 but must working on every backend ------ */

        /* Draw */
        SDL_GetWindowSize(win, &win_width, &win_height);
        glViewport(0, 0, win_width, win_height);
        glClear(GL_COLOR_BUFFER_BIT);
        glClearColor(bg.r, bg.g, bg.b, bg.a);


        nk_stroke_line( (struct nk_command_buffer *)&((ctx->current)->buffer), 0, 0, 1280, 800, 2, nk_rgb(255,0,0));



        nk_sdl_render(NK_ANTI_ALIASING_ON, MAX_VERTEX_MEMORY, MAX_ELEMENT_MEMORY);
        SDL_GL_SwapWindow(win);
    }

cleanup:
    nk_sdl_shutdown();
    SDL_GL_DeleteContext(glContext);
    SDL_DestroyWindow(win);