gistfile1.txt

            nk_layout_row_dynamic(ctx, 20, 1);
            nk_label(ctx, "background:", NK_TEXT_LEFT);
            nk_layout_row_dynamic(ctx, 25, 1);
            if (nk_combo_begin_color(ctx, nk_rgb_cf(bg), nk_vec2(nk_widget_width(ctx),400)))
             {
             nk_layout_row_dynamic(ctx, 120, 1);
             bg = nk_color_picker(ctx, bg, NK_RGBA);
             nk_layout_row_dynamic(ctx, 25, 1);
             bg.r = nk_propertyf(ctx, "#R:", 0, bg.r, 1.0f, 0.01f,0.005f);
             bg.g = nk_propertyf(ctx, "#G:", 0, bg.g, 1.0f, 0.01f,0.005f);
             bg.b = nk_propertyf(ctx, "#B:", 0, bg.b, 1.0f, 0.01f,0.005f);
             bg.a = nk_propertyf(ctx, "#A:", 0, bg.a, 1.0f, 0.01f,0.005f);
             nk_combo_end(ctx);
             }
        }
        nk_end(ctx);

        /* 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);

        glLineWidth(2);

        glBegin(GL_LINES);
         glVertex2f(30, 30);
         glVertex2f(20, 20);
        glEnd();

        glColor3f(0.80, 0.0, 0.0);
        glBegin(GL_LINES);
        glVertex2i(10,10);
        glVertex2i(200,320);
        glEnd();

        glColor3f(0.0, 0.0, 0.0);
        glBegin(GL_POINTS);
        glVertex2i(50, 50);
        glEnd();

        glFlush();

        /* IMPORTANT: `nk_sdl_render` modifies some global OpenGL state
         * with blending, scissor, face culling, depth test and viewport and
         * defaults everything back into a default state.
         * Make sure to either a.) save and restore or b.) reset your own state after
         * rendering the UI. */
        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);
    SDL_Quit();
    return 0;
}