[gtk+] Range: Fix inverted horizontal scroll wheel events

[Daniel Boles <dboles src gnome org>]

commit 29b8cfc95250f31570f39a0d14688a8ba21c505d
Author: Daniel Boles <dboles src gnome org>
Date:   Sat Oct 14 18:45:20 2017 +0100

    Range: Fix inverted horizontal scroll wheel events
    
    Bug 737175 aimed to ensure that scrolling up on a horizontal range would
    result in its value increasing, as that’s what users intuitively expect.
    However, its commit 416c370da1d2eff2458e4a0c5b8e504cd8061559 meant that,
    if the event gives scroll deltas, we inverted our delta unconditionally.
    
    So it broke horizontal scrolling: scrolling left moved the slider right…
    
    We must only invert if using dy as delta. dx already has the right sign,
    so inverting it was wrong.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=788905

 gtk/gtkrange.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkrange.c b/gtk/gtkrange.c
index 8539674..b9ddad5 100644
--- a/gtk/gtkrange.c
+++ b/gtk/gtkrange.c
@@ -2313,7 +2313,7 @@ gtk_range_scroll_controller_scroll (GtkEventControllerScroll *scroll,
 #endif
 
   if (gtk_orientable_get_orientation (GTK_ORIENTABLE (range)) == GTK_ORIENTATION_HORIZONTAL)
-    delta = - (dx ? dx : dy) * scroll_unit;
+    delta = (dx ? dx : -dy) * scroll_unit;
   else
     delta = dy * scroll_unit;