EVENT(3G)

NAME
event, einit, estart, etimer, eread, emouse, ekbd, ecanread, ecanmouse, ecankbd, ereshaped, getrect, menuhit, Event, Mouse, Menu - graphics events

SYNOPSIS
#include <libc.h>
#include <libg.h>

void	einit(ulong keys)

unsigned long	event(Event *e)

Mouse	emouse(void)

int	ekbd(void)

int	ecanmouse(void)

int	ecankbd(void)

unsigned long	estart(ulong key, int fd, int n)

unsigned long	etimer(ulong key, int n)

unsigned long	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,
}

DESCRIPTION
These routines provide an interface to multiple sources of input. To use them, einit must be called. If the argument to enit has the Emouse and Ekeyboard bits set, the mouse and keyboard events will be enabled; in this case, xtbinit (see graphics(3)) must have already been called. The user must provide a function called ereshaped, which will 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 character from the queue, blocking until the queue is non-empty. The characters are read by the event mechanism from the keyboard so they are available as soon as they are 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;
        	unsigned long msec;
        };

Buttons is a bit field; 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 button is depressed. The current mouse position is always returned in xy. Msec is the time stamp of the mouse event in units of milliseconds.

Ecankbd and ecanmouse return non-zero when there are keyboard or mouse events to available to be read.

Estart can be used to register additional file descriptors. 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 confilict with any previous keys. If a zero key is given, one which is not used will be chosen and returned. Ekeyboard and Emouse are the mouse and keyboard event keys.

Etimer starts a repeating timer with a period of n milliseconds (default 1 second). 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 plan 9 protocol 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(3), the graphics functions are buffered. Event, eread, emouse, and ekbd all cause a buffer flush unless there is an event of the appropriate type ready to return.

Getrect is used to prompt 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 to all go up, 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 x-coordinates, 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 seleced menu item number. It should be called with m holding the mouse event that triggered the menuhit . 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.

SEE ALSO
graphics(3).