Guest touchscreen support

[Jo-Taylor]

While Qubes technically does support touchscreen devices it currently does so through XFCE interpreting touchscreen events and generating mouse events from them. This severely limits Qubes utility to, say, host drawing software for stylus supporting devices in GuestVMs, or to utilise the much more developed touchscreen support present in GUIs such as Windows or Gnome.

It seems like it would be fairly simple to add to the Qubes GUI protocol to let it directly grab and pass through touchscreen events rather than relying on Xfce to generate mouse events. This would allow, say, a full screen Windows VM to run OneNote with full palm rejection, or support for automatic detection of text fields and providing a touch keyboard inside of a fullscreen VM, or any number of other touchscreen based use cases on fully touchscreen supporting OSs like Windows or even native Fedora in a HVM, with minimal additional code in the Qubes GUI protocol. This would be particularly useful in the increasingly common 2 in 1 device market, enabling Qubes users to access the same touchscreen features available on other operating systems by simply passing through the appropriate inputs to a VM providing the software intended to receive touchscreen input.