That sounds interesting! The mouse.xr is the standard mouse for the EP?
I would like to support the 1 or 2 most important EP mouse devices in SymbOS.
Yes (and No).
As far as I know, EP does not use mouses, generally.
There are only a VERY few programs which use mouse.
I can name only two of them: PAINTBOX (it is an graphical image editing (pixel painting) program) and EGI (it is a windowing GUI program written on the top of the EXOS, targeting to be the GUI of the (never released) next version of the EXOS).
So (almost) there are only these two programs on EP, using a mouse.
But Yes, these programs use a mouse through a piece of software, which is in a file called mouse.xr.
These two programs get mouse position from this mouse.xr software.
This mouse.xr software (as far as I know) works only with a hardware called the boxsoft mouse interface, which connect a NEOS mouse to the EP control and serial ports.
In the past, there were some other PC mouse hardware interfaces to the EP, but these used custom softwares for driver or application, and these almost disappear for now.
NEOS mouse or the boxsoft mouse interface are extreme rare, too. Almost nobody have those. (Zozosoft has one of those, for example.)
So EP almost does not have a mouse, at all.
As far as I know, there are two pieces of software applications worth to take into account with mouse, are PAINTBOX and EGI, using a NEOS mouse through the boxsoft mouse interface hardware through the mouse.xr "driver" software.
Mouses (almost) exist in the EP world in the meaning of these two programs only ...
Maybe Zozo could verify my statements, or add to it ... Zozo ?