sctk: Fixes for cursor icon

* With multiple windows, `SetCursor` is only sent for the focused
  window. Fixing a flicker between icons when two windows are using
  different cursors.
* If there is a drag surface, let that surface set the cursor. And not
  any other.
* Set cursor on `enter`, and when switching between CSDs and app area.

Fixes pop-os/libcosmic#533.

sctk/src/application.rs

@@ -929,7 +929,7 @@ where
 
                 // just draw here immediately and never again for dnd icons
                 // TODO handle scale factor?
-                let _new_mouse_interaction = user_interface.draw(
+                let new_mouse_interaction = user_interface.draw(
                     &mut renderer,
                     state.theme(),
                     &Style {
@@ -940,6 +940,13 @@ where
                     state.cursor(),
                 );
 
+                mouse_interaction = new_mouse_interaction;
+                ev_proxy.send_event(Event::SetCursor(mouse_interaction));
+                // Pre-emptively remove cursor focus from other surface so they won't set cursor
+                for state in states.values_mut() {
+                    state.cursor_position = None;
+                }
+
                 let subsurfaces = crate::subsurface_widget::take_subsurfaces();
                 if let Some(subsurface_state) = subsurface_state.as_mut() {
                     subsurface_state.update_subsurfaces(
@@ -1439,7 +1446,11 @@ where
                     }
 
                     debug.draw_finished();
-                    if new_mouse_interaction != mouse_interaction {
+
+                    // Set cursor if mouse interaction has changed, and surface has pointer focus
+                    if state.cursor_position.is_some()
+                        && new_mouse_interaction != mouse_interaction
+                    {
                         mouse_interaction = new_mouse_interaction;
                         ev_proxy
                             .send_event(Event::SetCursor(mouse_interaction));

sctk/src/event_loop/mod.rs

@@ -838,9 +838,10 @@ where
                         },
                     },
                     Event::SetCursor(iced_icon) => {
-                        if let Some(ptr) = self.state.seats.get(0).and_then(|s| s.ptr.as_ref()) {
+                        if let Some(seat) = self.state.seats.get_mut(0) {
                             let icon = conversion::cursor_icon(iced_icon);
-                            let _ = ptr.set_cursor(self.wayland_dispatcher.as_source_ref().connection(), icon);
+                            seat.icon = Some(icon);
+                            seat.set_cursor(self.wayland_dispatcher.as_source_ref().connection(), icon);
                         }
 
                     }

sctk/src/event_loop/state.rs

@@ -98,9 +98,21 @@ pub(crate) struct SctkSeat {
     pub(crate) last_touch_down: Option<(u32, i32, u32)>, // (time, point, serial)
     pub(crate) _modifiers: Modifiers,
     pub(crate) data_device: DataDevice,
+    // Cursor icon currently set (by CSDs, or application)
+    pub(crate) active_icon: Option<CursorIcon>,
+    // Cursor icon set by applicationb
     pub(crate) icon: Option<CursorIcon>,
 }
 
+impl SctkSeat {
+    pub(crate) fn set_cursor(&mut self, conn: &Connection, icon: CursorIcon) {
+        if let Some(ptr) = self.ptr.as_ref() {
+            ptr.set_cursor(conn, icon);
+            self.active_icon = Some(icon);
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct SctkWindow<T> {
     pub(crate) id: window::Id,

sctk/src/handlers/seat/pointer.rs

@@ -94,41 +94,24 @@ impl<T: Debug> PointerHandler for SctkState<T> {
                         return;
                     }
                     PointerEventKind::Motion { .. } => {
-                        if my_seat.icon != Some(icon) {
-                            let _ = my_seat
-                                .ptr
-                                .as_ref()
-                                .unwrap()
-                                .set_cursor(conn, icon);
-                            my_seat.icon = Some(icon);
+                        if my_seat.active_icon != Some(icon) {
+                            let _ = my_seat.set_cursor(conn, icon);
                         }
                         return;
                     }
-                    PointerEventKind::Enter { .. } => {
-                        my_seat.ptr_focus.replace(e.surface.clone());
-                        if my_seat.icon != Some(icon) {
-                            let _ = my_seat
-                                .ptr
-                                .as_ref()
-                                .unwrap()
-                                .set_cursor(conn, icon);
-                            my_seat.icon = Some(icon);
-                        }
-                    }
-                    PointerEventKind::Leave { .. } => {
-                        my_seat.ptr_focus.take();
-                        my_seat.icon = None;
-                    }
+                    PointerEventKind::Enter { .. } => {}
+                    PointerEventKind::Leave { .. } => {}
                     _ => {}
                 }
-                let _ = my_seat.ptr.as_ref().unwrap().set_cursor(conn, icon);
-            } else if my_seat.icon.is_some() {
-                let _ = my_seat
-                    .ptr
-                    .as_ref()
-                    .unwrap()
-                    .set_cursor(conn, CursorIcon::Default);
-                my_seat.icon = None;
+                if my_seat.active_icon != Some(icon) {
+                    my_seat.set_cursor(conn, icon);
+                }
+            } else if my_seat.active_icon != my_seat.icon {
+                // Restore cursor that was set by appliction, or default
+                my_seat.set_cursor(
+                    conn,
+                    my_seat.icon.unwrap_or(CursorIcon::Default),
+                );
             }
 
             if is_active {
@@ -144,7 +127,7 @@ impl<T: Debug> PointerHandler for SctkState<T> {
                 }
                 PointerEventKind::Leave { .. } => {
                     my_seat.ptr_focus.take();
-                    my_seat.icon = None;
+                    my_seat.active_icon = None;
                 }
                 PointerEventKind::Press {
                     time,

sctk/src/handlers/seat/seat.rs

@@ -43,6 +43,7 @@ where
             last_kbd_press: None,
             last_touch_down: None,
             icon: None,
+            active_icon: None,
         });
     }
 
@@ -71,6 +72,7 @@ where
                     last_kbd_press: None,
                     last_touch_down: None,
                     icon: None,
+                    active_icon: None,
                 });
                 self.seats.last_mut().unwrap()
             }