Discussion on: What's the Most Unusual Thing You've Discovered While Coding?

[José Pablo Ramírez Vargas]

While maintaining a BHO (Browser Helper Object) for IE7+ over a decade ago, I found out that:

1. Invisible windows CAN get the keyboard focus.
2. Changing focus is a kernel-mode operation, subject to deadlocks.
3. Microsoft does not consider that invisible windows can have the keyboard focus, a waste, or a bug.