--- ray/src/px/x11image.c	1993/10/27 16:57:28	2.30
+++ ray/src/px/x11image.c	1993/11/15 10:55:33	2.34
@@ -119,9 +119,11 @@ extern long  ftell();
 Display  *thedisplay;
 Atom  closedownAtom, wmProtocolsAtom;
 
-int  noop() {}
+int  sigrecv;
 
+int  onsig() { sigrecv++; }
 
+
 main(argc, argv)
 int  argc;
 char  *argv[];
@@ -179,6 +181,8 @@ char  *argv[];
 	if (i > argc)
 		goto userr;
 	while (i < argc-1) {
+		sigrecv = 0;
+		signal(SIGCONT, onsig);
 		if ((pid=fork()) == 0) {	/* a child for each picture */
 			parent = -1;
 			break;
@@ -186,17 +190,15 @@ char  *argv[];
 		if (pid < 0)
 			quiterr("fork failed");
 		parent++;
-		signal(SIGCONT, noop);
-		pause();		/* wait for wake-up call */
+		while (!sigrecv)
+			pause();	/* wait for wake-up call */
 		i++;
 	}
 	if (i < argc) {			/* open picture file */
 		fname = argv[i];
 		fin = fopen(fname, "r");
-		if (fin == NULL) {
-			sprintf(errmsg, "cannot open file \"%s\"", fname);
-			quiterr(errmsg);
-		}
+		if (fin == NULL)
+			quiterr("cannot open picture file");
 	}
 				/* get header */
 	getheader(fin, headline, NULL);
@@ -213,9 +215,10 @@ char  *argv[];
 
 	init(argc, argv);			/* get file and open window */
 
-	if (parent < 0)
+	if (parent < 0) {
 		kill(getppid(), SIGCONT);	/* signal parent if child */
-
+		sigrecv--;
+	}
 	for ( ; ; )
 		getevent();		/* main loop */
 userr:
@@ -311,10 +314,11 @@ char **argv;
 		quiterr("cannot create window");
 	width = xmax;
 	height = ymax;
-	xgcv.foreground = ourblack;
-	xgcv.background = ourwhite;
+	/* prepare graphics drawing context */
 	if ((xgcv.font = XLoadFont(thedisplay, FONTNAME)) == 0)
 		quiterr("cannot get font");
+	xgcv.foreground = ourblack;
+	xgcv.background = ourwhite;
 	ourgc = XCreateGC(thedisplay, wind, GCForeground|GCBackground|
 			GCFont, &xgcv);
 	xgcv.function = GXinvert;
@@ -350,16 +354,23 @@ char **argv;
 quiterr(err)		/* print message and exit */
 char  *err;
 {
-	if (err != NULL)
+	register int  es;
+	int  cs;
+
+	if (es = err != NULL)
 		fprintf(stderr, "%s: %s: %s\n", progname, 
 				fname==NULL?"<stdin>":fname, err);
-	if (wind) {
+	if (parent > 0 & wind != 0) {
 		XDestroyWindow(thedisplay, wind);
 		XFlush(thedisplay);
-	}
-	while (parent > 0 && wait(0) != -1)	/* wait for any children */
+	} else if (parent < 0 & sigrecv == 0)
+		kill(getppid(), SIGCONT);
+	while (parent > 0 && wait(&cs) != -1) {	/* wait for any children */
+		if (es == 0)
+			es = cs>>8 & 0xff;
 		parent--;
-	exit(err != NULL);
+	}
+	exit(es);
 }
 
 
@@ -661,9 +672,16 @@ XKeyPressedEvent  *ekey;
 	case '@':				/* adaptation level */
 		if (avgbox(cval) == -1)
 			return(-1);
-		comp = com=='@'
-		? 106./pow(1.219+pow(luminance(cval)/exposure,.4),2.5)/exposure
-		: .5/bright(cval) ;
+		comp = bright(cval);
+		if (comp < 1e-20) {
+			XBell(thedisplay, 0);
+			return(-1);
+		}
+		if (com == '@')
+			comp = 106./exposure/
+			pow(1.219+pow(comp*WHTEFFICACY/exposure,.4),2.5);
+		else
+			comp = .5/comp;
 		comp = log(comp)/.69315 - scale;
 		n = comp < 0 ? comp-.5 : comp+.5 ;	/* round */
 		if (n == 0)