Hide toggle hamburguer button when drawer is closed?

[kpagcha]

I am using a different button to toggle the drawer, but I want to keep the X button (which is also the hamburguer) to close it. I am trying to hide it on drawer.closed but the animation looks bad.

The best choice would be any built in option to deal with this scenario.

If there is none, I would need the "on close" event (when the animation start) and try to time hiding the hamburguer with some fading out effect. But how can I access that event?