The “XEventProc” thing is now implemented in Ardour
So I’ve tried implementing it in Redux ´too to check if it’s working, but it’s not. Not exactly sure why. I’ll need to build and debug Ardour from sources to find out more info here. This unfortunately will take a longer while.
Basically, the reason why the keyboard in Redux is working in Carla, Renoise, Bitwig and Co, but not in Reaper and Ardour, is because the latter hosts are embedding the plugin window into child window frame. In order to receive/handle keys, the Redux window needs to gain focus.
The highlights in the Hex keyboard are generated by polling the global keyboard state. So they always work, even when the window is not focused.