[PATCH] Fix for gnome-canvas-image seg fault

[Erik Andersen <andersen xmission com>]

Quoting Erik Andersen <andersen@xmission.com>:
> With your change in place:
> 
>   map_width = COLNO * ghack_glyph_width();
>   map_height = ROWNO * ghack_glyph_height();
> 
> I still get the same seg fault.  
> 

To follow up to my follow up... In GnomeHackMapWindow.c there are
exactly two calls to gnome_canvas_item_new(). One of them was not
supplying any "image", so the following (using the image already defined
above) "fixes" the problem. 

                  ghack_map.map[i] = GNOME_CANVAS_IMAGE(
                          gnome_canvas_item_new (
			  group,
			  gnome_canvas_image_get_type (),
			  "x",      (double) x1,
                          "y",      (double) y1,
                          "width",  (double) ghack_glyph_height(),
                          "height", (double) ghack_glyph_width(),
+                          "image",  im,
                          NULL) );

I think the real problem is with gnome-canvas-image.c in
gnome_canvas_image_update() at line 406 where it assumes image->im is
a non-NULL pointer and de-references it without checking like at other
places in gnome-canvas-image.c. This is a live bug and not one of our
doing this time.  Patch to gnome-canvas-image.c enclosed.

 -Erik

--
Erik B. Andersen   Web:    http://www.xmission.com/~andersen/ 
                   email:  andersee@debian.org
--This message was written using 73% post-consumer electrons--



--- gnome-canvas-image.c.virgin	Tue Jan 12 22:28:38 1999
+++ gnome-canvas-image.c	Tue Jan 12 22:30:56 1999
@@ -403,12 +403,14 @@
 
 	gnome_canvas_update_bbox (item, c_bbox.x0, c_bbox.y0, c_bbox.x1, c_bbox.y1);
 
-	image->affine[0] = (affine[0] * image->width) / image->im->rgb_width;
-	image->affine[1] = (affine[1] * image->height) / image->im->rgb_height;
-	image->affine[2] = (affine[2] * image->width) / image->im->rgb_width;
-	image->affine[3] = (affine[3] * image->height) / image->im->rgb_height;
-	image->affine[4] = i_bbox.x0 * affine[0] + i_bbox.y0 * affine[2] + affine[4];
-	image->affine[5] = i_bbox.x0 * affine[1] + i_bbox.y0 * affine[3] + affine[5];
+	if (image->im) {
+	    image->affine[0] = (affine[0] * image->width) / image->im->rgb_width;
+	    image->affine[1] = (affine[1] * image->height) / image->im->rgb_height;
+	    image->affine[2] = (affine[2] * image->width) / image->im->rgb_width;
+	    image->affine[3] = (affine[3] * image->height) / image->im->rgb_height;
+	    image->affine[4] = i_bbox.x0 * affine[0] + i_bbox.y0 * affine[2] + affine[4];
+	    image->affine[5] = i_bbox.x0 * affine[1] + i_bbox.y0 * affine[3] + affine[5];
+	}
 #endif
 }