[libshumate] view: Fix scroll-to-zoom direction

[Marcus Lundblad <mlundblad src gnome org>]

commit ee1dac0d6a9fa465aa8ad31af32f8b4c8938b567
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Tue Mar 9 17:28:29 2021 -0300

    view: Fix scroll-to-zoom direction
    
    The check for the scroll deltas is reversed, correct that. It's worth
    noticing that we don't have to care about natural scroll, the values
    are reversed when it's enabled.
    
    Also make sure to not zoom out when dy is zero.
    
    Fixes: https://gitlab.gnome.org/GNOME/libshumate/-/issues/4

 shumate/shumate-view.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/shumate/shumate-view.c b/shumate/shumate-view.c
index 57fbb4d..9ff75fc 100644
--- a/shumate/shumate-view.c
+++ b/shumate/shumate-view.c
@@ -534,9 +534,9 @@ on_scroll_controller_scroll (ShumateView              *self,
       scroll_latitude = shumate_viewport_widget_y_to_latitude (priv->viewport, GTK_WIDGET (self), 
priv->current_y);
     }
 
-  if (dy > 0)
+  if (dy < 0)
     shumate_viewport_zoom_in (priv->viewport);
-  else
+  else if (dy > 0)
     shumate_viewport_zoom_out (priv->viewport);
 
   if (map_source)