From ncurses.h
typedef struct
{
short id; /* ID to distinguish multiple devices */
int x, y, z; /* event coordinates (character-cell) */
mmask_t bstate; /* button state bits */
}
MEVENT;
What does the z coordinate represent?
From the curs_mouse man page:
The z member in the event structure is not presently used. It is intended for use with touch screens (which may be pressure- sensitive) or with 3D-mice/trackballs/power gloves.
Also, if you search lib_mouse.c in the ncurses source code for ->z and .z, you will find that it is only ever set to zero.