NAME
event, einit, estart, estartfn, etimer, eread, emouse, ekbd, ecanread, ecanmouse, ecankbd, ereadmouse, eatomouse, eresized, egetrect, edrawgetrect, emenuhit, eenter, emoveto, esetcursor, Event, Mouse, Menu – graphics events

SYNOPSIS

#include    <u.h>
#include    <libc.h>
#include    <draw.h>
#include    <event.h>
#include    <cursor.h>

void        einit(ulong keys)

ulong       event(Event *e)

Mouse       emouse(void)

int         ekbd(void)

int         ecanmouse(void)

int         ecankbd(void)

int         ereadmouse(Mouse *m)

int         eatomouse(Mouse *m, char *buf, int n)

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

ulong       estartfn(ulong key, int fd, int n,
int (*fn)(int, Event*, uchar*, int))

ulong       etimer(ulong key, int n)

ulong       eread(ulong keys, Event *e)

int         ecanread(ulong keys)

void        eresized(int new)

Rectangle egetrect(int but, Mouse *m)

void        edrawgetrect(Rectangle r, int up)

int         emenuhit(int but, Mouse *m, Menu *menu)

void        emoveto(Point p)

void        esetcursor(Cursor *c)

int         eenter(char *ask, char *buf, int len, Mouse *m)

extern Mouse      *mouse

enum{
Emouse = 1,
Ekeyboard = 2,
};

DESCRIPTION
These routines provide an interface to multiple sources of input for unthreaded programs. Threaded programs (see thread(2)) should instead use the threaded mouse and keyboard interface described in mouse(2) and keyboard(2).

Einit must be called first. If the argument to einit has the Emouse and Ekeyboard bits set, the mouse and keyboard events will be enabled; in this case, initdraw (see graphics(2)) must have already been called. The user must provide a function called eresized to be called whenever the window in which the process is running has been resized; the argument new is a flag specifying whether the program must call getwindow (see graphics(2)) to re–establish a connection to its window. After resizing (and perhaps calling getwindow), the global variable screen will be updated to point to the new window's Image structure.

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 complete rune is typed.

When the mouse moves or a mouse button is pressed 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 pressed, buttons&2 when the middle button is pressed, and buttons&4 when the right button is pressed. 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.

Ereadmouse reads the next mouse event from the file descriptor connected to the mouse, converts the textual data into a Mouse structure by calling eatomouse with the buffer and count from the read call, and returns the number of bytes read, or –1 for an error.

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, a key will be allocated and returned. Estartfn is similar to estart, but processes the data received by calling fn before returning the event to the user. The function fn is called with the id of the event; it should return id if the event is to be passed to the user, 0 if it is to be ignored. The variable Event.v can be used by fn to attach an arbitrary data item to the returned Event structure.    Ekeyboard and Emouse are the keyboard and mouse 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;
void    *v;
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 egetrect (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 pressed, marking the initial corner. If another button is pressed instead, egetrect returns a rectangle with zero for both corners, after waiting for all the buttons to be released. Otherwise, egetrect 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.

Egetrect uses successive calls to edrawgetrect to maintain the red rectangle showing the sweep–in–progress. The rectangle to be drawn is specified by rc and the up parameter says whether to draw (1) or erase (0) the rectangle.

Emenuhit displays a menu and returns a selected menu item number. It should be called with m holding the mouse event that triggered the emenuhit; 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.

Emoveto moves the mouse cursor to the position p on the screen.

Esetcursor changes the cursor image to that described by the Cursor c (see mouse(2)). If c is nil, it restores the image to the default arrow.

Eenter provides a simple method of text input in graphical programs. It displays a box at the current position of the mouse cursor (passed in the Mouse *m argument) in which text can be typed and edited. If the string argument ask is not nil, it is displayed as a static label before the input string. The buf parameter contains the null–terminated input string to be edited. The len argument specifies the length of buf in bytes including the terminating null byte. If buf or len is zero, no text can be entered. On success, eenter returns the number of bytes in the edited string buf or –1 on error.

SOURCE
/sys/src/libdraw

SEE ALSO
rio(1), graphics(2), plumb(2), cons(3), draw(3)