For a touch system to be multi-user, that is, more than one touch can be processed at a time such that there is no direct relationship between the various touches and the touches do not interfere with each other, you need to use an appropriate touch interface that caters for this requirement.
For example, Windows 10 allows for independent touches on each touch monitor so this caters for multi-user at a monitor level when using the standard HID driver to support the touch screen.
For most other OS if the desktop or application touch control is via an operating system interface (mouse or HID) then it will be restricted to a single user use as all touches have a direct relationship.
To achieve multi-user functionality you normally need to bypass the OS touch interfaces and implement another form of touch control as described below.
Independent touch interface
If you utilise a method of direct control over the touch interface, bypassing the OS interface, then you can create true multi-user touch applications.
Instead of using native touch events in your application you could, for example, use the UPDD API or the TUIO interface to receive touch data into your application via the touch driver, or in the case of TUIO, via a TUIO server.
The application will receive all raw touches and can handle as appropriate.
Our UPDD Test program is a UPDD API and TUIO Client program so you can run up as many copies as needed and draw simultaneously within each copy of the program. This will show multi-touch / multi-user in action, all be it in a relatively simple use. Source code of the test program is available at the link.
Multi-seat
This is a term use to refer to the configuration of individual users all using the resources of a single PC.
Each user can have their own monitor, keyboard, mouse and other hardware, such as touchscreen, and they all operate independently of each other.
Linux multi-seat is discussed here. Our current Linux driver and touch configuration methods should in theory support Linux multi-seat configurations.
With our previous driver, UPDD V5, we did have support for various multi-seat layers available for Windows such as Friendly Seats, Microsoft MultiPoint, SoftXpand, Dicolab, BeTwin. There may be others. We could consider adding support for these systems if required in UPDD V6.
Using the above methods or system extensions, you should, in theory, be able to configure a touchscreen as a multi-seat device such that is has full independence from other touch devices.