From da0309545e6fbe091920f2c8b979d179c3aede26 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Wed, 13 Dec 2017 13:46:28 +0530
Subject: [PATCH] Ensure bounds in add_line()

---
 kitty/fonts/render.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kitty/fonts/render.py b/kitty/fonts/render.py
index 774ec6d2f..0ee85254f 100644
--- a/kitty/fonts/render.py
+++ b/kitty/fonts/render.py
@@ -73,7 +73,7 @@ def resize_fonts(new_sz):
 
 def add_line(buf, cell_width, position, thickness, cell_height):
     y = position - thickness // 2
-    while thickness:
+    while thickness > 0 and y > -1 and y < cell_height - 1:
         thickness -= 1
         ctypes.memset(ctypes.addressof(buf) + (cell_width * y), 255, cell_width)
         y += 1