ev_open(S)

Syntax

#include  <sys/types.h>
#include  <sys/param.h>
#include  <sys/sysmacros.h>
#include  <sys/page.h>
#include  <sys/event.h>
#include  <mouse.h>

int ev_open (dmask)
dmask_t *dmaskp;

Description

The bitmask is made of one or more of four classes of devices. The four classes are D_STRING, D_REL, D_ABS, or D_OTHER. D_STRING refers to character stream devices like the keyboard. D_REL refers to relative locator devices like mice. D_ABS refers to absolute locator devices like bitpads. These values are defined in <mouse.h>.

ev_open attempts to open devices of the types indicated in the argument and sets the mask to indicate the devices successfully opened. If no devices can be successfully opened, ev_open returns -1 as an error condition.

If ev_open succeeds in opening an event queue and devices, it returns a file descriptor for the event queue. The file descriptor is for use with the select system call and should not be used for reading or writing.

This is a program fragment that opens an event queue with a mouse and the keyboard attached:

   main()
   {
   dmask_t dmask;			/* device mask */
   int qfd;			/* event queue file descriptor */
   

   ev_init();			/* initialize event manager */
   			
   dmask = D_REL|D_STRING;		/* device mask for mouse & kbd */
   qfd = ev_open(&dmask);		/* try to open event queue */
   if ( qfd < 0 )
   	exit(1);		/* error on open */
   

   if (dmask != (D_REL | D_STRING))
   	exit(2);		/* could not attach both devices */
   				/* event queue is open */
   ...
   }

Diagnostics

It returns -1 if there was a configuration error in the configuration files (see ev_init(S)). ev_open returns -2 if it does not find any devices to attach. It returns -3 if it is unable to open devices it finds. It returns -4 if it is unable to open an event queue.

See also

Standards conformance