From 444ee8bc3674002d3aa315ad666638b00f145bed Mon Sep 17 00:00:00 2001
From: Matthias Melcher <github@matthiasm.com>
Date: Sat, 27 Jan 2024 17:54:49 +0100
Subject: [PATCH] Fix warning for out of range index.

---
 src/fl_boxtype.cxx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/fl_boxtype.cxx b/src/fl_boxtype.cxx
index 4f446c8ec..708635fbb 100644
--- a/src/fl_boxtype.cxx
+++ b/src/fl_boxtype.cxx
@@ -58,7 +58,9 @@ int Fl::box_shadow_width_ = 3;
 */
 int Fl::draw_box_active() { return draw_it_active; }
 
-const uchar *fl_gray_ramp() {return (draw_it_active?active_ramp:inactive_ramp)-'A';}
+// Note: the pointer that is returned by this function works only with indexes
+//       between 65 ('A') and including 88 ('X').
+const uchar *fl_gray_ramp() {return (static_cast<const uchar*>(draw_it_active?active_ramp:inactive_ramp))-'A';}
 
 /**
   Gets the drawing color to be used for the background of a box.