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.