Avoid division by zero crash observed by Yuan MEI.

See http://lists.gnu.org/archive/html/emacs-devel/2015-11/msg00194.html.

* src/dispnew.c (required_matrix_height, required_matrix_width):
Avoid division by zero.
* src/xterm.c (x_term_init): Init dpyinfo->smallest_font_height and
dpyinfo->smallest_char_width to 1.

2 files changed, 8 insertions, 2 deletions

diff --git a/src/dispnew.c b/src/dispnew.c
index 91640769838..1a822f06365 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -1694,7 +1694,8 @@ required_matrix_height (struct window *w)
 
   if (FRAME_WINDOW_P (f))
     {
-      int ch_height = FRAME_SMALLEST_FONT_HEIGHT (f);
+      /* http://lists.gnu.org/archive/html/emacs-devel/2015-11/msg00194.html  */
+      int ch_height = max (FRAME_SMALLEST_FONT_HEIGHT (f), 1);
       int window_pixel_height = window_box_height (w) + eabs (w->vscroll);
 
       return (((window_pixel_height + ch_height - 1)
@@ -1720,7 +1721,8 @@ required_matrix_width (struct window *w)
   struct frame *f = XFRAME (w->frame);
   if (FRAME_WINDOW_P (f))
     {
-      int ch_width = FRAME_SMALLEST_CHAR_WIDTH (f);
+      /* http://lists.gnu.org/archive/html/emacs-devel/2015-11/msg00194.html  */
+      int ch_width = max (FRAME_SMALLEST_CHAR_WIDTH (f), 1);
 
       /* Compute number of glyphs needed in a glyph row.  */
       return (((WINDOW_PIXEL_WIDTH (w) + ch_width - 1)
diff --git a/src/xterm.c b/src/xterm.c
index 691ad05efe1..5e9c16b8af4 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -11963,6 +11963,10 @@ x_term_init (Lisp_Object display_name, char *xrm_option, char *resource_name)
   dpyinfo->display = dpy;
   dpyinfo->connection = ConnectionNumber (dpyinfo->display);
 
+  /* http://lists.gnu.org/archive/html/emacs-devel/2015-11/msg00194.html  */
+  dpyinfo->smallest_font_height = 1;
+  dpyinfo->smallest_char_width = 1;
+
   /* Set the name of the terminal. */
   terminal->name = xlispstrdup (display_name);