How do plugins work when providing several custom keys in a plugin-specific window?

Question

I'm referring to plugins like gundo and nerdtree, which offer a whole lot of key bindings only when the cursor is their window.

Therefore, I was wandering if there's a common or preferred way to accoplish something like this.

The intuitive way, to me, seems pretty obvious: create a autocmd that is triggered when the cursor moves into that window, and another one when it moves away from that windows. The two autocmds should activate the plugin-specific mappings and revert the original mappings/functionalities respectively.

However, I can't see how the latter can be done without having to write a list of "mappings to be recovered or removed".

The motivation for this question is that I'm considering writing a small plugin to make all window-related actions (like moving them, moving across them, opening them, closing them, ...) easier to perform, as described here.