From 8d66e7eaa131f868c8a41826e5ed3a9fbcf91083 Mon Sep 17 00:00:00 2001
From: Michael Natterer <mitch@gimp.org>
Date: Wed, 13 Jun 2018 15:20:21 +0200
Subject: [PATCH] libgimpwidgets: improve gimp_scroll_adjustment_values()

so it works for very small adjustment page sizes. Same as GTK+ commit
c0ba041c73214f82d2c32b2ca1fa8f3c388c6170
---
 libgimpwidgets/gimpscrolledpreview.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/libgimpwidgets/gimpscrolledpreview.c b/libgimpwidgets/gimpscrolledpreview.c
index 2b801ad58d..da9f648269 100644
--- a/libgimpwidgets/gimpscrolledpreview.c
+++ b/libgimpwidgets/gimpscrolledpreview.c
@@ -966,12 +966,22 @@ gimp_scroll_adjustment_values (GdkEventScroll *sevent,
     }
 
   if (adj_x)
-    scroll_unit_x = pow (gtk_adjustment_get_page_size (adj_x), 2.0 / 3.0);
+    {
+      gdouble page_size = gtk_adjustment_get_page_size (adj_x);
+      gdouble pow_unit  = pow (page_size, 2.0 / 3.0);
+
+      scroll_unit_x = MIN (page_size / 2.0, pow_unit);
+    }
   else
     scroll_unit_x = 1.0;
 
   if (adj_y)
-    scroll_unit_y = pow (gtk_adjustment_get_page_size (adj_y), 2.0 / 3.0);
+    {
+      gdouble page_size = gtk_adjustment_get_page_size (adj_y);
+      gdouble pow_unit  = pow (page_size, 2.0 / 3.0);
+
+      scroll_unit_y = MIN (page_size / 2.0, pow_unit);
+    }
   else
     scroll_unit_y = 1.0;