It is possible for a shell process to open the touch panel device and acquire exclusive access using EVIOCGRAB. It can then read the input_event stream and forward it while resolving conflicts with injected touch events.
I'm not familiar with xtmapper's internal implementation, so I'm not sure how difficult this feature would be to add.
I also have a working proof of concept if that would be helpful.
This is also how Panda Mouse Pro managed to recently add support for simultaneous real and injected touch events for unrooted devices.
It is possible for a shell process to open the touch panel device and acquire exclusive access using EVIOCGRAB. It can then read the input_event stream and forward it while resolving conflicts with injected touch events.
I'm not familiar with xtmapper's internal implementation, so I'm not sure how difficult this feature would be to add.
I also have a working proof of concept if that would be helpful.
This is also how Panda Mouse Pro managed to recently add support for simultaneous real and injected touch events for unrooted devices.