bug#16738: Errors while resizing vertically

[Paul Eggert <eggert@cs.ucla.edu>]

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My change adjusted set-window-new-pixel so that it rejects attempts to 
set the new pixel size to a negative value. Here, new-pixel is currently 
0, so (set-window-new-pixel window-17 t) is attempting to change 
new-pixel to be -17.

Are negative new-pixel values allowed?  If so, the attached patch should 
fix the problem.  If not, the problem's probably in the caller.



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=== modified file 'src/window.c'
--- src/window.c	2014-02-21 08:02:05 +0000
+++ src/window.c	2014-02-21 20:25:41 +0000
@@ -3702,8 +3702,9 @@
   (Lisp_Object window, Lisp_Object size, Lisp_Object add)
 {
   struct window *w = decode_valid_window (window);
-  EMACS_INT size_min = NILP (add) ? 0 : - XINT (w->new_pixel);
-  EMACS_INT size_max = size_min + min (INT_MAX, MOST_POSITIVE_FIXNUM);
+  EMACS_INT new_pixel = NILP (add) ? 0 : XINT (w->new_pixel);
+  EMACS_INT size_min = max (INT_MIN, MOST_NEGATIVE_FIXNUM) - new_pixel;
+  EMACS_INT size_max = min (INT_MAX, MOST_POSITIVE_FIXNUM) - new_pixel;
 
   CHECK_RANGED_INTEGER (size, size_min, size_max);
   if (NILP (add))