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vga_waitevent(3)              Svgalib User Manual             vga_waitevent(3)

NAME
       vga_waitevent - wait for various I/O events

SYNOPSIS
       #include <sys/time.h>
       #include <sys/types.h>
       #include <unistd.h>
       #include <vga.h>

       int vga_waitevent(int which, fd_set *input, fd_set *output , fd_set
       *except, struct timeval *timeout)

DESCRIPTION
       This is the only function allowing you to wait for keyboard AND mouse
       events. It is based on the select(2) library function, so for deep
       understanding of vga_waitevent() look at select(2) as well.

       which can be 0 or logical ored together from VGA_MOUSEEVENT and
       VGA_KEYEVENT.  If you are interested in waiting for file descriptors
       having input available or being ready for new write data or being in an
       exceptional condition (urgent data arrived on a TCP stream) set the
       corresponding bits in the fd_set structures passed (see select(3)).  If
       you want vga_waitevent() to return after a timeout value pass a struct
       timeval with the desired value. If you are not interested in the
       corresponding events you may pass NULL for any of the pointers.

       If NULL is passed for timeout vga_waitevent() will not time out but
       block until any of the other events occurs.  If the integer returned is
       < 0 an error occurred. Check the global variable errno for details. If
       a value >= 0 is returned it is a bitmask constructed using
       VGA_MOUSEEVENT and VGA_KEYEVENT to show which of these events occured.

       If any of these two occured the appropriate update functions are
       already called by vga_waitevent().vga_waitevent() operates in raw as
       well as non-raw keyboard mode. In the latter case use vga_getch(3) not
       vga_getkey(3) to read the newly arrived keys.

       Any of the file related conditions being met will be signalled by
       setting exactly the bits for files that met the conditions in the
       corresponding fd_set structures. If a non-NULL timeout is passed the
       remaining time is written into it on return.  If it is 0 a timeout
       occured. (again: cf.  select(2)) Therefore, depending on context,
       vga_waitkey(3) may return 0 if only special, non svgalib, events
       occured.

EXAMPLES
       If you want to wait blocking for a keypress OR a mouse event use:
       vga_waitevent(VGA_MOUSEEVENT | VGA_KEYEVENT, NULL, NULL, NULL, NULL);

       If you want to wait for a keypress OR a mouse event but non-blocking
       use:

       #include <sys/time.h>
       #include <sys/types.h>
       #include <unistd.h>
       #include <vga.h>

       struct timeval timeout;
       timeout.tv_sec = 0;
       timeout.tv_usec = 0;
       vga_waitevent(VGA_MOUSEEVENT | VGA_KEYEVENT, NULL, NULL, NULL,
       &timeout);

       You could do a similar thing by just calling

       mouse_update();
       keyboard_update();

       though. There is no such counterpart for the first example.

       Finally, there is a very nice eventtest(6) demo showing most
       capabilities of vga_waitevent().

BUGS
       This function was introduced in 1.2.10. Unfortunately there was a typo
       in the first implementation which broke the case where input was NULL.
       Though fixed in 1.2.11 for optimal portability pass an empty fd_set
       instead of NULL as first argument.

       When not running in background mode, that is, the svgalib applcation is
       suspended while the VC is switched away, it seems vga_waitevent gets
       stuck and does no longer timeout. It is not clear if this is an svgalib
       bug, kernel bug or general problem.

SEE ALSO
       svgalib(7), vgagl(7), libvga.config(5), eventtest(6),
       mouse_getposition_6d(3), mouse_getx(3), mouse_update(3),
       mouse_waitforupdate(3), vga_getkey(3), vga_getch(3)

AUTHOR
       This manual page was edited by Michael Weller <[email protected]
       essen.de>. The exact source of the referenced function as well as of
       the original documentation is unknown.

       It is very likely that both are at least to some extent are due to Harm
       Hanemaayer <[email protected]>.

       Occasionally this might be wrong. I hereby asked to be excused by the
       original author and will happily accept any additions or corrections to
       this first version of the svgalib manual.

Svgalib (>= 1.2.11)              27 July 1997                 vga_waitevent(3)
Command Section