Respect natural-scroll for workspace switch gesture

src/input.rs

@@ -1156,11 +1156,20 @@ impl State {
         );
     }
 
-    fn on_gesture_swipe_update<I: InputBackend>(&mut self, event: I::GestureSwipeUpdateEvent) {
-        let res = self
-            .niri
-            .layout
-            .workspace_switch_gesture_update(event.delta_y());
+    fn on_gesture_swipe_update<I: InputBackend>(&mut self, event: I::GestureSwipeUpdateEvent)
+    where
+        I::Device: 'static,
+    {
+        let mut delta_y = event.delta_y();
+
+        let device = event.device();
+        if let Some(device) = (&device as &dyn Any).downcast_ref::<input::Device>() {
+            if device.config_scroll_natural_scroll_enabled() {
+                delta_y = -delta_y;
+            }
+        }
+
+        let res = self.niri.layout.workspace_switch_gesture_update(delta_y);
         if let Some(output) = res {
             if let Some(output) = output {
                 self.niri.queue_redraw(output);

src/layout/mod.rs

@@ -1462,7 +1462,7 @@ impl<W: LayoutElement> Layout<W> {
         for monitor in monitors {
             if let Some(WorkspaceSwitch::Gesture(gesture)) = &mut monitor.workspace_switch {
                 // Normalize like GNOME Shell's workspace switching.
-                let delta_y = -delta_y / 400.;
+                let delta_y = delta_y / 400.;
 
                 let min = gesture.center_idx.saturating_sub(1) as f64;
                 let max = (gesture.center_idx + 1).min(monitor.workspaces.len() - 1) as f64;