[baobab/wip/cdavis/use-event-controllers: 1/3] chart: Use EventControllerScroll

[Christopher Davis <christopherdavis src gnome org>]

commit a23dab0f5d0ed3e5ab941017ec3f874137ccbc8e
Author: Christopher Davis <christopherdavis gnome org>
Date:   Tue Sep 21 17:49:58 2021 -0700

    chart: Use EventControllerScroll
    
    GTK4 doesn't have the `scroll_event` vfunc and uses
    EventControllers. To ease migration, we want to use
    event controllers where possible.

 src/baobab-chart.vala | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)
---
diff --git a/src/baobab-chart.vala b/src/baobab-chart.vala
index 8af189f..9702023 100644
--- a/src/baobab-chart.vala
+++ b/src/baobab-chart.vala
@@ -61,6 +61,8 @@ namespace Baobab {
 
         Gtk.Menu context_menu = null;
 
+        Gtk.EventControllerScroll scroll_controller;
+
         List<ChartItem> items;
 
         Location location_;
@@ -200,7 +202,10 @@ namespace Baobab {
         };
 
         construct {
-            add_events (Gdk.EventMask.EXPOSURE_MASK | Gdk.EventMask.ENTER_NOTIFY_MASK | 
Gdk.EventMask.LEAVE_NOTIFY_MASK | Gdk.EventMask.BUTTON_PRESS_MASK | Gdk.EventMask.POINTER_MOTION_MASK | 
Gdk.EventMask.SCROLL_MASK);
+            add_events (Gdk.EventMask.EXPOSURE_MASK | Gdk.EventMask.ENTER_NOTIFY_MASK | 
Gdk.EventMask.LEAVE_NOTIFY_MASK | Gdk.EventMask.BUTTON_PRESS_MASK | Gdk.EventMask.POINTER_MOTION_MASK);
+
+            scroll_controller = new Gtk.EventControllerScroll (this, 
Gtk.EventControllerScrollFlags.BOTH_AXES);
+            scroll_controller.scroll.connect (scroll_cb);
 
             action_group = new SimpleActionGroup ();
             action_group.add_action_entries (action_entries, this);
@@ -498,24 +503,14 @@ namespace Baobab {
             return false;
         }
 
-        protected override bool scroll_event (Gdk.EventScroll event) {
-            Gdk.EventMotion e = (Gdk.EventMotion) event;
-            switch (event.direction) {
-            case Gdk.ScrollDirection.LEFT:
-            case Gdk.ScrollDirection.UP:
+        void scroll_cb (double dx, double dy) {
+            // Up or to the left
+            if (dx > 0.0 || dy < 0.0) {
                 zoom_out ();
-                motion_notify_event (e);
-                break;
-            case Gdk.ScrollDirection.RIGHT:
-            case Gdk.ScrollDirection.DOWN:
+            // Down or to the right
+            } else if (dx < 0.0 || dy > 0.0) {
                 zoom_in ();
-                motion_notify_event (e);
-                break;
-            case Gdk.ScrollDirection.SMOOTH:
-                break;
             }
-
-            return false;
         }
 
         public void open_file () {