Manual Reference Pages - VGA_WAITEVENT (3)
vga_waitevent - wait for various I/O events
int vga_waitevent(int which, fd_set *input, fd_set *output
, fd_set *except, struct timeval *timeout)
This is the only function allowing you to wait for keyboard
AND mouse events. It is based on the
so for deep understanding of
vga_waitevent() look at
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
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.
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
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
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
timeout is passed the remaining time is written into it on return.
If it is 0 a timeout occured. (again: cf.
Therefore, depending on context,
may return 0 if only special, non svgalib, events occured.
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
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
though. There is no such counterpart for the first example.
Finally, there is a very nice
demo showing most capabilities of
This function was introduced in 1.2.10. Unfortunately there was a typo in the first
implementation which broke the case where
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.
This manual page was edited by Michael Weller <email@example.com>. The
exact source of the referenced function as well as of the original documentation is
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.
|Svgalib (>= 1.2.11) ||VGA_WAITEVENT (3) ||27 July 1997 |
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