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EVENT(2)										 EVENT(2)

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

       #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)

		 Emouse = 1,
		 Ekeyboard = 2,

       /* Alef only */

       adt Menu
		 /* ... */
		 (int, Mouse) hit(*Menu, int but, chan(Mouse), Mouse);

       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 Rectan-
       gle 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, block-
       ing 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 button is depressed.  The current mouse posi-
       tion 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

	      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

       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

       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 rec-
       tangle 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 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.


       81/2(1), graphics(2), cons(3), bit(3)

       There should be an official Alef interface to the mouse and keyboard.

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