Comment 1 for bug 1588237

The described behavior matches the way keyboard mapping is handled within mir right now. Unity8 configures keymaps for each client surface. Each client surface then has its own independent key state. Key state here means the set of active modifier keys, including toggles like Caps Lock, Num Lock. So it depends on which client sees

Mir 0.24 will change this behavior. It will default to have a per keyboard device key state tracked and updated inside a mir server like Unity8. Thus Num Lock will stay active after you switch between surfaces. BUT: For that to work Unity8 need to configure its own server side per device keymaps (they only default to us). Additionally we still allow client side per surface keymaps. As of now the solution inside of lp:mir and the presumptive 0.24 would not be capable of transfering the current toggle state of Caps Lock or Num Lock when switching to an application with a client side keymap. We already identified that problem, and I plan to address that soon. But it might not make it into 0.24

As a short term fix I suggest to switch unity8 to only use server side keymaps with 0.24, until this last problem is also addressed.