From 71819202385f9090dacddce16cbaa35abf10baf8 Mon Sep 17 00:00:00 2001
From: Bruce Evans <bde@FreeBSD.org>
Date: Fri, 26 Apr 2019 13:04:10 +0000
Subject: [PATCH] Fix an off-by-1 error for copying overlapping bitmaps in
 r346416.  For nonzero height, the first line in the original order was not
 copied, and for zero height, garbage lines before the first were copied until
 a crash occurred.

---
 lib/libvgl/bitmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/libvgl/bitmap.c b/lib/libvgl/bitmap.c
index eafced3cc7e0..0a7f049d9fa0 100644
--- a/lib/libvgl/bitmap.c
+++ b/lib/libvgl/bitmap.c
@@ -207,7 +207,7 @@ __VGLBitmapCopy(VGLBitmap *src, int srcx, int srcy,
   yextra = 0;
   ystep = 1;
   if (src->Bitmap == dst->Bitmap && srcy < dsty) {
-    yend = srcy;
+    yend = srcy - 1;
     yextra = hight - 1;
     ystep = -1;
   }