From: Andrew Apted <ajapted@netspace.net.au>
  To  : ggi-develop@eskimo.com
  Date: Fri, 17 Jul 1998 23:20:20 +1000

Re: display-tile buglet

Hartmut writes:

>  Hi!
>  I tried againa wrong display, tile, this time:
>  
>   export LIBGGI_DISPLAY="tile:0,0,600,300,(x):0,300,600,300,(x):600,0,300,600"
>  > a.out 
>  display-tile: Opening of target rox/mystique-8-15-16-32.so failed.

Same problem here (same name too: rox/mystique... !).

The problem appears to be something not-nice about sscanf.  In
display/tile/visual.c there is :

    if(sscanf(args, "%d,%d,%d,%d,%n", &sx, &sy, &vx, &vy, &n)!=4)

The manpage for sscanf says that the number of successful conversions is
returned.  What happens (I suspect) is that even missing the last comma
still returns 4 -- but there really was an error and the %n never gets
set (which shoots us off into lala land).

Checking it now...

Yep, that was it.  Below is a patch that fixes the problem.  Steve, look
alright to you ?

Cheers,
_____________________________________________  ____
                                               \  /
  Andrew Apted   <andrew@ggi-project.org>       \/
  

--- display/tile/visual.c.old	Fri Jul 17 23:05:31 1998
+++ display/tile/visual.c	Fri Jul 17 23:06:12 1998
@@ -63,7 +63,9 @@
 
 		sx = sy = vx = vy = 0;
 
-		if(sscanf(args, "%d,%d,%d,%d,%n", &sx, &sy, &vx, &vy, &n)!=4) {
+		if ((sscanf(args, "%d,%d,%d,%d%n", &sx, &sy,
+		     &vx, &vy, &n) != 4) || (args+=n, *args != ',')) {
+
 			fprintf(stderr, "display-tile: The argument format is \"offx,offy,sizex,sizey,(subdisplay):...\",\n"
 					"              where offx and offy are the tile's offset from the main display,\n"
 					"                    sizex and sizey are the size of the tile,\n"
@@ -72,7 +74,7 @@
 			return GGI_DL_ERROR;
 		}
 		
-		args+=n;
+		args++;  /* skip comma */
 
 		tilehook->vis_origins[i].x = sx;
 		tilehook->vis_origins[i].y = sy;
--- display/common/parsing.inc.old	Fri Jul 17 23:09:35 1998
+++ display/common/parsing.inc	Fri Jul 17 23:11:43 1998
@@ -38,6 +38,12 @@
 	int bracketized=0;
 	int bracket_count=0;
 
+	if (*str == 0) {
+		fprintf(stderr, "libggi: Missing target descriptor !\n");
+		*target = 0;
+		return NULL;
+	}
+
 	if (*str == '(') {
 		bracketized=1;
 		bracket_count++;