[gimp/gimp-2-10] app: fix offset handling in spiral gradients

[Ell <ell src gnome org>]

commit 6a1474677dac92d77978157fb8a98fb5fb895aa1
Author: Ell <ell_se yahoo com>
Date:   Fri Sep 27 16:05:41 2019 +0300

    app: fix offset handling in spiral gradients
    
    In gimp:gradient, properly scale the "offset" property in spiral
    graidnets.
    
    (cherry picked from commit 04280690b2d778fcd4ac753117eb6599ec24ab40)

 app/operations/gimpoperationgradient.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/app/operations/gimpoperationgradient.c b/app/operations/gimpoperationgradient.c
index 9bbc294e1b..2dbb74666d 100644
--- a/app/operations/gimpoperationgradient.c
+++ b/app/operations/gimpoperationgradient.c
@@ -777,6 +777,8 @@ gradient_calc_spiral_factor (gdouble   dist,
       gdouble ang;
       double  r;
 
+      offset = offset / 100.0;
+
       ang0 = atan2 (axis[0], axis[1]) + G_PI;
       ang1 = atan2 (x, y) + G_PI;