fix(status-area): forward SNI scroll events (#1431)

StatusNotifierItems can expose a Scroll(int delta, string orientation) method for tray hosts to call when the user wheels over an item. The status-area applet handled activation and context menus, but did not forward wheel events to that method.

Track the hovered tray item only while the pointer is over an icon, ignore wheel events already captured by widgets, accumulate fine-grained wheel deltas into discrete scroll steps, and call Scroll on the item proxy. Add unit coverage for the delta/orientation mapping and pixel accumulation.

Signed-off-by: William Fish <william.michael.fish@gmail.com>

cosmic-applet-status-area/src/components/app.rs

@@ -9,11 +9,14 @@ use cosmic::{
     },
     cctk::sctk::reexports::calloop,
     iced::{
-        self, Length, Subscription,
+        self,
+        Event::Mouse,
+        Length, Subscription, event,
+        mouse::{self, ScrollDelta},
         platform_specific::shell::commands::popup::{destroy_popup, get_popup},
-        theme::Style,
         window,
     },
+    scroll::{DiscreteScrollDelta, DiscreteScrollState},
     surface,
     widget::{container, mouse_area},
 };
@@ -33,7 +36,8 @@ pub enum Msg {
     StatusMenu((usize, status_menu::Msg)),
     StatusNotifier(status_notifier_watcher::Event),
     TogglePopup(usize),
-    Hovered(usize),
+    Hovered(Option<usize>),
+    WheelScrolled(ScrollDelta),
     Surface(surface::Action),
     ToggleOverflow,
     HoveredOverflow,
@@ -49,6 +53,8 @@ pub(crate) struct App {
     max_menu_id: usize,
     popup: Option<window::Id>,
     overflow_popup: Option<window::Id>,
+    hovered_menu: Option<usize>,
+    scroll_states: BTreeMap<usize, DiscreteScrollState>,
     token_tx: Option<calloop::channel::Sender<TokenRequest>>,
 }
 
@@ -103,9 +109,10 @@ impl App {
         let overflow_index = self.overflow_index().unwrap_or(0);
         let children = self.menus.iter().skip(overflow_index).map(|(id, menu)| {
             mouse_area(
-                menu_icon_button(&self.core.applet, &menu).on_press_down(Msg::TogglePopup(*id)),
+                menu_icon_button(&self.core.applet, menu).on_press_down(Msg::TogglePopup(*id)),
             )
-            .on_enter(Msg::Hovered(*id))
+            .on_enter(Msg::Hovered(Some(*id)))
+            .on_exit(Msg::Hovered(None))
             .into()
         });
 
@@ -210,6 +217,7 @@ impl cosmic::Application for App {
                     {
                         let id = *id;
                         self.menus.remove(&id);
+                        self.scroll_states.remove(&id);
                         if self.open_menu == Some(id) {
                             self.open_menu = None;
                             if let Some(popup_id) = self.popup {
@@ -312,6 +320,10 @@ impl cosmic::Application for App {
                 }
             },
             Msg::Hovered(id) => {
+                self.hovered_menu = id;
+                let Some(id) = id else {
+                    return Task::none();
+                };
                 let mut cmds = Vec::new();
                 if let Some(old_id) = self.open_menu.take() {
                     if old_id != id {
@@ -361,6 +373,19 @@ impl cosmic::Application for App {
                 cmds.push(get_popup(popup_settings));
                 Task::batch(cmds)
             }
+            Msg::WheelScrolled(delta) => {
+                let Some(id) = self.hovered_menu else {
+                    return Task::none();
+                };
+                let discrete_delta = self.scroll_states.entry(id).or_default().update(delta);
+                let Some((delta, orientation)) = discrete_scroll_delta(discrete_delta) else {
+                    return Task::none();
+                };
+                let Some(menu) = self.menus.get(&id) else {
+                    return Task::none();
+                };
+                scroll(id, menu.item.item_proxy().clone(), delta, orientation)
+            }
             Msg::Surface(a) => {
                 return cosmic::task::message(cosmic::Action::Cosmic(
                     cosmic::app::Action::Surface(a),
@@ -405,6 +430,7 @@ impl cosmic::Application for App {
                 }
             }
             Msg::HoveredOverflow => {
+                self.hovered_menu = None;
                 let mut cmds = Vec::new();
                 if self.overflow_popup.is_some() {
                     // If we already have an overflow popup, do nothing
@@ -460,6 +486,12 @@ impl cosmic::Application for App {
             subscriptions.push(menu.subscription(is_open).with(*id).map(Msg::StatusMenu));
         }
         subscriptions.push(activation_token_subscription(0).map(Msg::Token));
+        subscriptions.push(event::listen_with(|e, status, _| match (e, status) {
+            (Mouse(mouse::Event::WheelScrolled { delta }), event::Status::Ignored) => {
+                Some(Msg::WheelScrolled(delta))
+            }
+            _ => None,
+        }));
 
         iced::Subscription::batch(subscriptions)
     }
@@ -472,9 +504,10 @@ impl cosmic::Application for App {
             .iter()
             .take(overflow_index.unwrap_or(self.menus.len()))
             .map(|(id, menu)| {
-                mouse_area(menu_icon_button(&self.core.applet, &menu).on_press(Msg::Activate(*id)))
+                mouse_area(menu_icon_button(&self.core.applet, menu).on_press(Msg::Activate(*id)))
                     .on_right_press(Msg::TogglePopup(*id))
-                    .on_enter(Msg::Hovered(*id))
+                    .on_enter(Msg::Hovered(Some(*id)))
+                    .on_exit(Msg::Hovered(None))
                     .into()
             });
 
@@ -570,6 +603,33 @@ fn activate(
     })
 }
 
+fn scroll(
+    id: usize,
+    item_proxy: crate::subscriptions::status_notifier_item::StatusNotifierItemProxy<'static>,
+    delta: i32,
+    orientation: &'static str,
+) -> Task<cosmic::Action<Msg>> {
+    Task::future(async move {
+        match item_proxy.scroll(delta, orientation).await {
+            Ok(_) => cosmic::action::app(Msg::None),
+            Err(err) => {
+                tracing::error!("Scroll failed for {}: {}", id, err);
+                cosmic::action::app(Msg::None)
+            }
+        }
+    })
+}
+
+fn discrete_scroll_delta(delta: DiscreteScrollDelta) -> Option<(i32, &'static str)> {
+    if delta.y != 0 {
+        Some((delta.y as i32, "vertical"))
+    } else if delta.x != 0 {
+        Some((delta.x as i32, "horizontal"))
+    } else {
+        None
+    }
+}
+
 fn menu_icon_button<'a>(
     applet: &'a cosmic::applet::Context,
     menu: &'a status_menu::State,
@@ -614,3 +674,43 @@ fn menu_icon_button<'a>(
 pub fn main() -> iced::Result {
     cosmic::applet::run::<App>(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn discrete_scroll_prefers_vertical_delta() {
+        assert_eq!(
+            discrete_scroll_delta(cosmic::scroll::DiscreteScrollDelta { x: 4, y: -2 }),
+            Some((-2, "vertical"))
+        );
+    }
+
+    #[test]
+    fn discrete_scroll_uses_horizontal_delta_when_vertical_is_zero() {
+        assert_eq!(
+            discrete_scroll_delta(cosmic::scroll::DiscreteScrollDelta { x: 3, y: 0 }),
+            Some((3, "horizontal"))
+        );
+    }
+
+    #[test]
+    fn discrete_scroll_ignores_zero_delta() {
+        assert_eq!(
+            discrete_scroll_delta(cosmic::scroll::DiscreteScrollDelta { x: 0, y: 0 }),
+            None
+        );
+    }
+
+    #[test]
+    fn pixel_scroll_accumulates_before_emitting_discrete_delta() {
+        let mut state = cosmic::scroll::DiscreteScrollState::default();
+
+        let first = state.update(ScrollDelta::Pixels { x: 0.0, y: 12.0 });
+        assert_eq!(discrete_scroll_delta(first), None);
+
+        let second = state.update(ScrollDelta::Pixels { x: 0.0, y: 12.0 });
+        assert_eq!(discrete_scroll_delta(second), Some((1, "vertical")));
+    }
+}

cosmic-applet-status-area/src/subscriptions/status_notifier_item.rs

@@ -202,6 +202,8 @@ pub trait StatusNotifierItem {
     fn activate(&self, x: i32, y: i32) -> zbus::Result<()>;
 
     fn secondary_activate(&self, x: i32, y: i32) -> zbus::Result<()>;
+
+    fn scroll(&self, delta: i32, orientation: &str) -> zbus::Result<()>;
 }
 
 #[derive(Clone, Debug)]