Adds eshutdown(2) to allow programs to stop event processing before exiting.

There is currently no way for programs using event(2) to stop event processing.
Device files and memory are held by the library.  This prevents programs using
event(2) from returning to console mode cleanly without exiting.

This patch adds eshutdown(2) to provide that function.  Existing programs using
event(2) should not be affected by this change.  I have recompiled and run
clock(1) and tweak(1) for testing, both of which behave unchanged.

Notes:
Wed Mar 19 15:07:39 EDT 2008 geoff
    Please (re)read style(6) and edit your code to conform,
    then resubmit this patch.  Thanks.


Reference: /n/sources/patch/sorry/eshutdown
Date: Sat Mar 15 19:14:56 CET 2008
Signed-off-by: stefanha@gmail.com
Reviewed-by: geoff

--- /sys/include/event.h	Sat Mar 15 19:13:58 2008
+++ /sys/include/event.h	Sat Mar 15 19:13:54 2008
@@ -44,6 +44,7 @@
  * Events
  */
 extern void	 einit(ulong);
+extern void	 eshutdown(void);
 extern ulong	 estart(ulong, int, int);
 extern ulong	 estartfn(ulong, int, int, int (*fn)(int, Event*, uchar*, int));
 extern ulong	 etimer(ulong, int);
--- /sys/src/libdraw/event.c	Sat Mar 15 19:14:12 2008
+++ /sys/src/libdraw/event.c	Sat Mar 15 19:14:08 2008
@@ -10,7 +10,7 @@
 struct Slave
 {
 	int	pid;
-	Ebuf	*head;		/* ueue of messages for this descriptor */
+	Ebuf	*head;		/* queue of messages for this descriptor */
 	Ebuf	*tail;
 	int	(*fn)(int, Event*, uchar*, int);
 };
@@ -37,6 +37,8 @@
 static	int	enote(void *, char *);
 static	int	mousefd;
 static	int	cursorfd;
+static	int	consfd;
+static	int	ctlfd;
 
 static
 Ebuf*
@@ -228,13 +230,15 @@
 void
 einit(ulong keys)
 {
-	int ctl, fd;
+	int firstinit;
 	char buf[256];
 
+	firstinit = (parentpid == 0);
 	parentpid = getpid();
 	if(pipe(epipe) < 0)
 		drawerror(display, "events: einit pipe");
-	atexit(ekill);
+	if(firstinit)
+		atexit(ekill);
 	atnotify(enote, 1);
 	snprint(buf, sizeof buf, "%s/mouse", display->devdir);
 	mousefd = open(buf, ORDWR|OCEXEC);
@@ -246,17 +250,17 @@
 		drawerror(display, "einit: can't open cursor\n");
 	if(keys&Ekeyboard){
 		snprint(buf, sizeof buf, "%s/cons", display->devdir);
-		fd = open(buf, OREAD);
-		if(fd < 0)
+		consfd = open(buf, OREAD);
+		if(consfd < 0)
 			drawerror(display, "events: can't open console");
 		snprint(buf, sizeof buf, "%s/consctl", display->devdir);
-		ctl = open("/dev/consctl", OWRITE|OCEXEC);
-		if(ctl < 0)
+		ctlfd = open("/dev/consctl", OWRITE|OCEXEC);
+		if(ctlfd < 0)
 			drawerror(display, "events: can't open consctl");
-		write(ctl, "rawon", 5);
+		write(ctlfd, "rawon", 5);
 		for(Skeyboard=0; Ekeyboard & ~(1<<Skeyboard); Skeyboard++)
 			;
-		ekeyslave(fd);
+		ekeyslave(consfd);
 	}
 	if(keys&Emouse){
 		estart(Emouse, mousefd, 1+4*12);
@@ -266,6 +270,69 @@
 }
 
 static void
+_eshutdown(int exiting)
+{
+	int i;
+	int nalive;
+	Ebuf *eb;
+	Ebuf *next;
+	Waitmsg *wt;
+
+	atnotify(enote, 0);
+	close(epipe[0]);
+	epipe[0] = -1;
+	close(epipe[1]);
+	epipe[1] = -1;
+	for(i=0; i<nslave; i++){
+		if(parentpid == eslave[i].pid)
+			continue;	/* don't kill myself */
+		postnote(PNPROC, eslave[i].pid, "die");
+	}
+	/* returning leaves mousefd open so that the display is closed before the kernel closes mousefd. */
+	/* this ensures that rio redraws the console. */
+	if(exiting)
+		return;
+	nalive = nslave;
+	while(nalive > 0){
+		wt = wait();
+		if(!wt)
+			break;
+		for(i=0; i<nslave; i++){
+			if(eslave[i].pid == wt->pid){
+				nalive--;
+			}
+		}
+		free(wt);
+	}
+	for(i=0; i<nslave; i++){
+		for(eb=eslave[i].head; eb; eb=next){
+			next = eb->next;
+			free(eb);
+		}
+		memset(&eslave[i], 0, sizeof(eslave[i]));
+	}
+	nslave = 0;
+	Skeyboard = -1;
+	Smouse = -1;
+	Stimer = -1;
+	write(ctlfd, "rawoff", 6);
+	close(ctlfd);
+	ctlfd = -1;
+	close(consfd);
+	consfd = -1;
+	close(cursorfd);
+	cursorfd = -1;
+	close(mousefd);
+	mousefd = -1;
+}
+
+void
+eshutdown(void)
+{
+	_eshutdown(0);
+}
+
+static void
 extract(void)
 {
 	Slave *s;
@@ -372,22 +439,15 @@
 		}
 		return 0;
 	}
-	close(epipe[0]);
-	epipe[0] = -1;
-	close(epipe[1]);
-	epipe[1] = -1;
-	for(i=0; i<nslave; i++){
-		if(pid == eslave[i].pid)
-			continue;	/* don't kill myself */
-		postnote(PNPROC, eslave[i].pid, "die");
-	}
+	_eshutdown(1);
 	return 0;
 }
 
 static void
 ekill(void)
 {
-	enote(0, 0);
+	if(epipe[0] != -1)
+		enote(0, 0);
 }
 
 Mouse
--- /sys/src/ape/lib/draw/libc.h	Sat Mar 15 19:14:19 2008
+++ /sys/src/ape/lib/draw/libc.h	Sat Mar 15 19:14:16 2008
@@ -126,6 +126,7 @@
 #define readn _READN
 #define mallocz _MALLOCZ
 #define iounit	_IOUNIT
+#define wait _WAIT
 
 /* assume being called as in event.c */
 #define postnote(x, pid, msg) kill(pid, SIGTERM)
--- /sys/man/2/event	Sat Mar 15 19:14:29 2008
+++ /sys/man/2/event	Sat Mar 15 19:14:23 2008
@@ -1,6 +1,6 @@
 .TH EVENT 2
 .SH NAME
-event, einit, estart, estartfn, etimer, eread, emouse, ekbd, ecanread, ecanmouse, ecankbd, ereadmouse, eatomouse, eresized, egetrect, edrawgetrect, emenuhit, emoveto, esetcursor, Event, Mouse, Menu \- graphics events
+event, einit, eshutdown, estart, estartfn, etimer, eread, emouse, ekbd, ecanread, ecanmouse, ecankbd, ereadmouse, eatomouse, eresized, egetrect, edrawgetrect, emenuhit, emoveto, esetcursor, Event, Mouse, Menu \- graphics events
 .SH SYNOPSIS
 .nf
 .PP
@@ -20,6 +20,9 @@
 void	einit(ulong keys)
 .PP
 .B
+void	eshutdown(void)
+.PP
+.B
 ulong	event(Event *e)
 .PP
 .B
@@ -132,6 +135,11 @@
 will be updated to point to the new window's
 .B Image
 structure.
+.PP
+.I Eshutdown
+stops collecting events and frees resources.  This happens
+automatically on program exit but is available for programs
+wishing to stop event processing before exiting.
 .PP
 As characters are typed on the keyboard, they are read by the
 event mechanism and put in a queue.