It is safe to call any mouse routine even when a mouse is not present.

If a mouse is present, the Carry flag is set. If %1 is provided, a jump to %1 will be performed as well.

When a mouse is detected, it is automatically initialized at program startup. It is just not automatically made visible. This macro is to provide a simple way for the program to alter it's behaviour or messages based on the presence of a mouse.

See also: MouseUnavailable and MouseShow.