[shotwell] Wayland: Fix scroll and zoom

[Jens Georg <jensgeorg src gnome org>]

commit a54c9b6f48d5451c877aff02056b73328e7e512e
Author: Jens Georg <mail jensge org>
Date:   Fri Nov 10 16:28:47 2017 +0100

    Wayland: Fix scroll and zoom
    
    Scroll and zoom with mouse wheel did not work anymore on Wayland
    
    https://bugzilla.gnome.org/show_bug.cgi?id=781472

 src/Page.vala |   19 ++++++++++++++++++-
 1 files changed, 18 insertions(+), 1 deletions(-)
---
diff --git a/src/Page.vala b/src/Page.vala
index a47b37e..ea8606e 100644
--- a/src/Page.vala
+++ b/src/Page.vala
@@ -174,7 +174,7 @@ public abstract class Page : Gtk.ScrolledWindow {
         event_source.add_events(Gdk.EventMask.BUTTON_PRESS_MASK | Gdk.EventMask.BUTTON_RELEASE_MASK
             | Gdk.EventMask.POINTER_MOTION_MASK | Gdk.EventMask.POINTER_MOTION_HINT_MASK
             | Gdk.EventMask.BUTTON_MOTION_MASK | Gdk.EventMask.LEAVE_NOTIFY_MASK
-            | Gdk.EventMask.SCROLL_MASK);
+            | Gdk.EventMask.SCROLL_MASK | Gdk.EventMask.SMOOTH_SCROLL_MASK);
         event_source.button_press_event.connect(on_button_pressed_internal);
         event_source.button_release_event.connect(on_button_released_internal);
         event_source.motion_notify_event.connect(on_motion_internal);
@@ -1026,6 +1026,23 @@ public abstract class Page : Gtk.ScrolledWindow {
 
             case Gdk.ScrollDirection.RIGHT:
                 return on_mousewheel_right(event);
+
+            case Gdk.ScrollDirection.SMOOTH:
+                {
+                    double dx, dy;
+                    event.get_scroll_deltas(out dx, out dy);
+
+                    if (dy < 0)
+                        return on_mousewheel_up(event);
+                    else if (dy > 0)
+                        return on_mousewheel_down(event);
+                    else if (dx < 0)
+                        return on_mousewheel_left(event);
+                    else if (dx > 0)
+                        return on_mousewheel_right(event);
+                    else
+                        return false;
+                }
            
             default:
                 return false;