Window - vurtun/nuklear GitHub Wiki

        if (nk_begin(ctx, "Nuklear", nk_rect(WINDOW_WIDTH/2 - 110, WINDOW_HEIGHT/2 - 110, 220, 220),
                     NK_WINDOW_BORDER|NK_WINDOW_MOVABLE|NK_WINDOW_CLOSABLE))
        {
            // Widgets code here
        }
        nk_end(ctx);

If you use the NK_WINDOW_CLOSABLE flag the end user will be able to close the window, you can check to see if a window has been closed and even re-open (or show) a window.

This trivial example add to a counter when the window has been closed by the user, after a short while the window is then shown again.

        if (nk_window_is_hidden(&ctx, "Nuklear")) {
		closeCount++;
		if (closeCount > 120) {
			closeCount = 0;
			nk_window_show(&ctx, "Nuklear", NK_SHOWN);
		}
	}