How to make widgets scale and look right in gtk window?

Question

GTK+

I made widgets, packed some of them into scroll_window, set their size with gtk_widget_set_size_request. Somehow I didn't do it right. how to do it right. For example, in unity, each widget seems to have its own size and it can be changed like. unity is also written in gtk. When the unity window is enlarged, then all widgets are scaled like. How can I do it right?