Comment 2 for bug 1513883

The problem with the "upload parameters that allow the (host) server to implement the desired functionality" approach is that I fear we end up solidifying into a C API ephemeral requirements coming from design.

The nested server being able to have full control over cursor state allow us to constrain all those Unity 8 specific UI design rules (such as screen edge barriers for mouse, that are overcome after some amount of pushing against them) into QML language, which is the perfect medium to codify such things.