Add scoped overlay hosts

core/src/event/controller.rs

@@ -14,6 +14,10 @@ impl ControllerId {
     pub fn host(self) -> WidgetId {
         self.host
     }
+
+    pub fn is<C: 'static>(self) -> bool {
+        self.kind == TypeId::of::<C>()
+    }
 }
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
@@ -44,6 +48,10 @@ pub trait Controller<Rsc>: ControllerValue {
     fn command(&mut self, _command: Command, _rsc: &mut Rsc) -> CommandResult {
         CommandResult::Unused
     }
+
+    fn blocks_prior_input(&self) -> bool {
+        false
+    }
 }
 
 pub struct ControllerManager<Rsc> {
@@ -206,6 +214,16 @@ impl<Rsc: 'static> ControllerManager<Rsc> {
         self.command_target
     }
 
+    pub fn command_target_blocks_input(&self) -> bool {
+        let Some(id) = self.command_target else {
+            return false;
+        };
+        self.by_widget
+            .get(&id.host)
+            .and_then(|controllers| controllers.get(&id.kind))
+            .is_some_and(|controller| controller.blocks_prior_input())
+    }
+
     pub(crate) fn command_target_revision(&self) -> u64 {
         self.command_target_revision
     }
@@ -214,6 +232,18 @@ impl<Rsc: 'static> ControllerManager<Rsc> {
         self.command_boundary
     }
 
+    pub(crate) fn is_below(&self, mut widget: WidgetId, ancestor: WidgetId) -> bool {
+        loop {
+            let Some(parent) = self.parents.get(&widget).copied().flatten() else {
+                return false;
+            };
+            if parent == ancestor {
+                return true;
+            }
+            widget = parent;
+        }
+    }
+
     pub(crate) fn set_command_boundary(&mut self, boundary: Option<WidgetId>) {
         self.command_boundary = boundary;
     }