INT 33,18 - Set alternate subroutine call mask and address

AX = 18h

DX = offset to function

CX = user interrupt mask:

¦F-8¦7¦6¦5¦4¦3¦2¦1¦0¦ user interrupt mask in CX

¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ +--- alt key pressed during event

¦ ¦ ¦ ¦ ¦ ¦ ¦ +---- ctrl key pressed during event

¦ ¦ ¦ ¦ ¦ ¦ +----- shift key pressed during event

¦ ¦ ¦ ¦ ¦ +------ right button up event

¦ ¦ ¦ ¦ +------- right button down event

¦ ¦ ¦ +-------- left button up event

¦ ¦ +--------- left button down event

¦ +---------- cursor moved

+------------ unused

- entire mask is set to zero when ~INT 33,0~ is called

- up to three handlers may be defined with this call

- mask should be cleared before program exit

- when handler is called it receives parameters in the following

registers:

AX = condition mask causing call

CX = horizontal cursor position

DX = vertical cursor position

DI = horizontal counts

SI = vertical counts

DS = mouse driver data segment

BX = button state:

¦F-2¦1¦0¦

¦ ¦ +--- left button (1 = pressed)

¦ +---- right button (1 = pressed)

+------ unused