EVENT(2) System Calls Manual EVENT(2)
NAME
event, einit, estart, etimer, eread, emouse, ekbd, ecanread, ecanmouse, ecankbd, ereshaped, getrect, menuhit, Event, Mouse, Menu - graphics
events
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <libg.h>
void einit(ulong keys)
ulong event(Event *e)
Mouse emouse(void)
int ekbd(void)
int ecanmouse(void)
int ecankbd(void)
ulong estart(ulong key, int fd, int n)
ulong etimer(ulong key, int n)
ulong eread(ulong keys, Event *e)
int ecanread(ulong keys)
void ereshaped(Rectangle r)
Rectangle getrect(int but, Mouse *m)
int menuhit(int but, Mouse *m, Menu *menu)
enum{
Emouse = 1,
Ekeyboard = 2,
};
/* Alef only */
adt Menu
{
/* ... */
(int, Mouse) hit(*Menu, int but, chan(Mouse), Mouse);
};
DESCRIPTION
These routines provide an interface to multiple sources of input. To use them, einit must be called. If the argument to einit has the
Emouse and Ekeyboard bits set, the mouse and keyboard events will be enabled; in this case, binit (see graphics(2)) must have already been
called. The user must provide a function called ereshaped to be called whenever the window in which the process is running has been
reshaped; the argument will be the Rectangle for the new window shape, including the border.
As characters are typed on the keyboard, they are read by the event mechanism and put in a queue. Ekbd returns the next rune from the
queue, blocking until the queue is non-empty. The characters are read in raw mode (see cons(3)), so they are available as soon as a com-
plete rune is typed.
When the mouse moves or a mouse button is depressed or released, a new mouse event is queued by the event mechanism. Emouse returns the
next mouse event from the queue, blocking until the queue is non-empty. Emouse returns a Mouse structure:
struct Mouse
{
int buttons;
Point xy;
ulong msec;
};
Buttons&1 is set when the left mouse button is depressed, buttons&2 when the middle button is depressed, and buttons&4 when the right but-
ton is depressed. The current mouse position is always returned in xy. Msec is a time stamp in units of milliseconds.
Ecankbd and ecanmouse return non-zero when there are keyboard or mouse events available to be read.
Estart can be used to register additional file descriptors to scan for input. It takes as arguments the file descriptor to register, the
maximum length of an event message on that descriptor, and a key to be used in accessing the event. The key must be a power of 2 and must
not conflict with any previous keys. If a zero key is given, one will be allocated and returned. Ekeyboard and Emouse are the mouse and
keyboard event keys.
Etimer starts a repeating timer with a period of n milliseconds; it returns the timer event key, or zero if it fails. Only one timer can
be started. Extra timer events are not queued and the timer channel has no associated data.
Eread waits for the next event specified by the mask keys of event keys submitted to estart. It fills in the appropriate field of the
argument Event structure, which looks like:
struct Event
{
int kbdc;
Mouse mouse;
int n;
uchar data[EMAXMSG];
};
Data is an array which is large enough to hold a 9P message. Eread returns the key for the event which was chosen. For example, if a
mouse event was read, Emouse will be returned.
Event waits for the next event of any kind. The return is the same as for eread.
As described in graphics(2), the graphics functions are buffered. Event, eread, emouse, and ekbd all cause a buffer flush unless there is
an event of the appropriate type already queued.
Ecanread checks whether a call to eread(keys) would block, returning 0 if it would, 1 if it would not.
Getrect prompts the user to sweep a rectangle. It should be called with m holding the mouse event that triggered the getrect (or, if none,
a Mouse with buttons set to 7). It changes to the sweep cursor, waits for the buttons all to be released, and then waits for button number
but to be depressed, marking the initial corner. If another button is depressed instead, getrect returns a rectangle with zero for both
corners, after waiting for all the buttons to be released. Otherwise, getrect continually draws the swept rectangle until the button is
released again, and returns the swept rectangle. The mouse structure pointed to by m will contain the final mouse event.
Menuhit displays a menu and returns a selected menu item number. It should be called with m holding the mouse event that triggered the
menuhit; it will call emouse to update it. A Menu is a structure:
struct Menu
{
char **item;
char *(*gen)(int);
int lasthit;
};
If item is nonzero, it should be a null-terminated array of the character strings to be displayed as menu items. Otherwise, gen should be
a function that, given an item number, returns the character string for that item, or zero if the number is past the end of the list.
Items are numbered starting at zero. Menuhit waits until but is released, and then returns the number of the selection, or -1 for no
selection. The m argument is filled in with the final mouse event.
Alef
Alef has none of the event software, since the language encourages a different approach using processes to convert mouse and keyboard
activity into messages. In this vein, a function called hit, analogous to menuhit, exists as a part of the Menu adt; it takes as argument
a chan of type Mouse and a Mouse-valued argument reflecting the current state. It returns the selection and the new state of the mouse.
SOURCE
/sys/src/libg
SEE ALSO
81/2(1), graphics(2), cons(3), bit(3)
BUGS
There should be an official Alef interface to the mouse and keyboard.
EVENT(2)