[gimp] app: fix off-by-one error in last commit

[N/A <ell src gnome org>]

commit 709c929d4f0a2be7f4c770790e05f735b5b22a7b
Author: Ell <ell_se yahoo com>
Date:   Sat Dec 9 05:21:55 2017 -0500

    app: fix off-by-one error in last commit

 app/display/gimpdisplayshell-draw.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/app/display/gimpdisplayshell-draw.c b/app/display/gimpdisplayshell-draw.c
index 819517a..68270e2 100644
--- a/app/display/gimpdisplayshell-draw.c
+++ b/app/display/gimpdisplayshell-draw.c
@@ -176,7 +176,7 @@ gimp_display_shell_draw_image (GimpDisplayShell *shell,
     {
       gdouble a = shell->rotate_angle * G_PI / 180.0;
 
-      chunk_width = chunk_height = MIN (chunk_width, chunk_height)   /
+      chunk_width = chunk_height = (MIN (chunk_width, chunk_height) - 1.0) /
                                    (fabs (sin (a)) + fabs (cos (a)));
     }