如何在使用自定义窗口镶边时向WPF标题栏添加按钮？

I'm attempting to create a simple button template in which the button normally looks like a single horizontal line, but when moused over, the button will display a "rectangle" color fill behind it. This is the code I have, but I can't seem to get the triggers to fire. I'm attempting to create a simple button templa