Ensure positive number of glyphs for margins of positive width

* src/dispnew.c (margin_glyphs_to_reserve): Always return a
positive value when a non-zero width of the marginal area was
requested.  (Bug#22356)

1 files changed, 3 insertions, 1 deletions

diff --git a/src/dispnew.c b/src/dispnew.c
index 8d671f82e47..3e1557fa3b9 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -320,7 +320,9 @@ margin_glyphs_to_reserve (struct window *w, int total_glyphs, int margin)
       int width = w->total_cols;
       double d = max (0, margin);
       d = min (width / 2 - 1, d);
-      return (int) ((double) total_glyphs / width * d);
+      /* Since MARGIN is positive, we cannot possibly have less than
+         one glyph for the marginal area.  */
+      return max (1, (int) ((double) total_glyphs / width * d));
     }
   return 0;
 }