feat: Add pre-events and inner events to OnEventView

src/event.rs

@@ -87,6 +87,17 @@ impl EventResult {
             cb(s);
         }
     }
+
+    /// Returns `self` if it is not `Event::Ignored`, otherwise returns `f()`.
+    pub fn or_else<F>(self, f: F) -> Self
+    where
+        F: FnOnce() -> EventResult,
+    {
+        match self {
+            EventResult::Ignored => f(),
+            other => other,
+        }
+    }
 }
 
 /// A non-character key on the keyboard

src/views/on_event_view.rs

@@ -1,10 +1,10 @@
-
-
 use Cursive;
+use With;
 use event::{Callback, Event, EventResult};
 use std::collections::HashMap;
+
+use std::rc::Rc;
 use view::{View, ViewWrapper};
-use With;
 
 /// A simple wrapper view that catches some ignored event from its child.
 ///
@@ -20,15 +20,37 @@ use With;
 ///                         .on_event(event::Key::Esc, |s| s.quit());
 /// ```
 pub struct OnEventView<T: View> {
-    content: T,
-    callbacks: HashMap<Event, Callback>,
+    inner: T,
+    callbacks: HashMap<Event, Action<T>>,
+}
+
+type InnerCallback<T> = Rc<Box<Fn(&mut T) -> Option<EventResult>>>;
+
+struct Action<T> {
+    phase: TriggerPhase,
+    callback: InnerCallback<T>,
+}
+
+impl<T> Clone for Action<T> {
+    fn clone(&self) -> Self {
+        Action {
+            phase: self.phase.clone(),
+            callback: self.callback.clone(),
+        }
+    }
+}
+
+#[derive(PartialEq, Clone)]
+enum TriggerPhase {
+    BeforeChild,
+    AfterChild,
 }
 
 impl<T: View> OnEventView<T> {
     /// Wraps the given view in a new OnEventView.
     pub fn new(view: T) -> Self {
         OnEventView {
-            content: view,
+            inner: view,
             callbacks: HashMap::new(),
         }
     }
@@ -36,32 +58,144 @@ impl<T: View> OnEventView<T> {
     /// Registers a callback when the given event is ignored by the child.
     ///
     /// Chainable variant.
-    pub fn on_event<F, E: Into<Event>>(self, event: E, cb: F) -> Self
-        where F: Fn(&mut Cursive) + 'static
+    pub fn on_event<F, E>(self, event: E, cb: F) -> Self
+    where
+        E: Into<Event>,
+        F: Fn(&mut Cursive) + 'static,
     {
         self.with(|s| s.set_on_event(event, cb))
     }
 
-    /// Registers a callback when the given event is ignored by the child.
-    pub fn set_on_event<F, E: Into<Event>>(&mut self, event: E, cb: F)
-        where F: Fn(&mut Cursive) + 'static
+    /// Registers a callback when the given event is received.
+    ///
+    /// The child will never receive this event.
+    ///
+    /// Chainable variant.
+    pub fn on_pre_event<F, E>(self, event: E, cb: F) -> Self
+    where
+        E: Into<Event>,
+        F: Fn(&mut Cursive) + 'static,
     {
-        self.callbacks.insert(event.into(), Callback::from_fn(cb));
+        self.with(|s| s.set_on_pre_event(event, cb))
+    }
+
+    /// Registers a callback when the given event is received.
+    ///
+    /// The given callback will be run before the child view sees the event.
+    /// If the result is `None`, then the child view is given the event as usual.
+    /// Otherwise, it bypasses the child view and directly processes the result.
+    ///
+    /// Chainable variant.
+    pub fn on_pre_event_inner<F, E>(self, event: E, cb: F) -> Self
+    where
+        E: Into<Event>,
+        F: Fn(&mut T) -> Option<EventResult> + 'static,
+    {
+        self.with(|s| s.set_on_pre_event_inner(event, cb))
+    }
+
+    /// Registers a callback when the given event is ignored by the child.
+    ///
+    /// If the child view ignores the event, `cb` will be called with the
+    /// child view as argument.
+    /// If the result is not `None`, it will be processed as well.
+    ///
+    /// Chainable variant.
+    pub fn on_event_inner<F, E>(self, event: E, cb: F) -> Self
+    where
+        E: Into<Event>,
+        F: Fn(&mut T) -> Option<EventResult> + 'static,
+    {
+        self.with(|s| s.set_on_event_inner(event, cb))
+    }
+
+    /// Registers a callback when the given event is ignored by the child.
+    pub fn set_on_event<F, E>(&mut self, event: E, cb: F)
+    where
+        E: Into<Event>,
+        F: Fn(&mut Cursive) + 'static,
+    {
+        let cb = Callback::from_fn(cb);
+        let action =
+            move |_: &mut T| Some(EventResult::Consumed(Some(cb.clone())));
+
+        self.set_on_event_inner(event, action);
+    }
+
+    /// Registers a callback when the given event is received.
+    ///
+    /// The child will never receive this event.
+    pub fn set_on_pre_event<F, E>(&mut self, event: E, cb: F)
+    where
+        E: Into<Event>,
+        F: Fn(&mut Cursive) + 'static,
+    {
+        let cb = Callback::from_fn(cb);
+        let action =
+            move |_: &mut T| Some(EventResult::Consumed(Some(cb.clone())));
+
+        self.set_on_pre_event_inner(event, action);
+    }
+
+    /// Registers a callback when the given event is received.
+    ///
+    /// The given callback will be run before the child view sees the event.
+    /// If the result is `None`, then the child view is given the event as usual.
+    /// Otherwise, it bypasses the child view and directly processes the result.
+    pub fn set_on_pre_event_inner<F, E>(&mut self, event: E, cb: F)
+    where
+        E: Into<Event>,
+        F: Fn(&mut T) -> Option<EventResult> + 'static,
+    {
+        self.callbacks.insert(
+            event.into(),
+            Action {
+                phase: TriggerPhase::BeforeChild,
+                callback: Rc::new(Box::new(cb)),
+            },
+        );
+    }
+
+    /// Registers a callback when the given event is ignored by the child.
+    ///
+    /// If the child view ignores the event, `cb` will be called with the
+    /// child view as argument.
+    /// If the result is not `None`, it will be processed as well.
+    pub fn set_on_event_inner<F, E>(&mut self, event: E, cb: F)
+    where
+        E: Into<Event>,
+        F: Fn(&mut T) -> Option<EventResult> + 'static,
+    {
+        self.callbacks.insert(
+            event.into(),
+            Action {
+                phase: TriggerPhase::AfterChild,
+                callback: Rc::new(Box::new(cb)),
+            },
+        );
     }
 }
 
 impl<T: View> ViewWrapper for OnEventView<T> {
-    wrap_impl!(self.content: T);
+    wrap_impl!(self.inner: T);
 
     fn wrap_on_event(&mut self, event: Event) -> EventResult {
-        match self.content.on_event(event.clone()) {
-            EventResult::Ignored => {
-                match self.callbacks.get(&event) {
-                    None => EventResult::Ignored,
-                    Some(cb) => EventResult::Consumed(Some(cb.clone())),
-                }
-            }
-            res => res,
+        let action = self.callbacks.get(&event).cloned();
+        let pre_child = action
+            .as_ref()
+            .map(|a| a.phase == TriggerPhase::BeforeChild)
+            .unwrap_or(false);
+
+        if pre_child {
+            action
+                .and_then(|a| (*a.callback)(&mut self.inner))
+                .unwrap_or_else(|| self.inner.on_event(event))
+        } else {
+            self.inner.on_event(event).or_else(|| {
+                action
+                    .and_then(|a| (*a.callback)(&mut self.inner))
+                    .unwrap_or(EventResult::Ignored)
+            })
         }
     }
 }