I created a new class based on the book class. In this class I use the package fancyhdr in order to define some heading content.
In my document, I load my new class and then I set the page dimensions with the geometry package. The problem is that the heading do not span all the page width. I did already observed that for example if you defined heading before you load geometry package. But here, as heading are defined in the class I cannot load geometry before. How can I fix this ?