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 <eowmob@exp-math.uni-
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 <H.Hanemaayer@inter.nl.net>.
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.