[mutter] backends/x11: if the scroll button is nonzero, enable button scrolling

[Florian Müllner <fmuellner src gnome org>]

commit 48243bfcbc62a9b277a6086f1756586a1d1885fa
Author: Peter Hutterer <peter hutterer who-t net>
Date:   Tue Sep 8 16:28:33 2020 +1000

    backends/x11: if the scroll button is nonzero, enable button scrolling
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1431

 src/backends/x11/meta-input-settings-x11.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/backends/x11/meta-input-settings-x11.c b/src/backends/x11/meta-input-settings-x11.c
index c9ca787883..5c22dffeeb 100644
--- a/src/backends/x11/meta-input-settings-x11.c
+++ b/src/backends/x11/meta-input-settings-x11.c
@@ -377,6 +377,7 @@ meta_input_settings_x11_set_scroll_button (MetaInputSettings  *settings,
                                            ClutterInputDevice *device,
                                            guint               button)
 {
+  change_scroll_method (device, SCROLL_METHOD_FIELD_BUTTON, button != 0);
   change_property (device, "libinput Button Scrolling Button",
                    XA_CARDINAL, 32, &button, 1);
 }