I use a custom Gtk theme along with the default Ambiance window controls. Using my theme, the Unity panel shows its very ugly default buttons when my window is maximized. Since I have the same window theme, I am assuming this comes from the Gtk theme. I tried copying and pasting a few things from Ambiance's gtkrc, but nothing has stuck so far.
What must a theme author do to gain pretty looking window buttons in Unity's panel?