merge with event system

.cargo/config.toml

@@ -1,3 +1,17 @@
+# we use tokio_unstable to enable runtime::Handle::id so we can seperate
+# gloablsfrom mul1tiple parallel tests. If that function ever does get removed
+# its possible to replace (with some additional overhead and effort)
+# Annoyingly build.rustflags doesn't work here because it gets overwritten
+# if people have their own global target.<..> config (for examble to enable mold)
+# specificying flags this way is more robust as they get merged
+# This still gets overwritten by RUST_FLAGS tough, luckily it shouldn't be necessary
+# to set those most of the time. If downstream does overwrite this its not a huge
+# deal since it will only break tests anyway
+[target."cfg(all())"]
+rustflags = ["--cfg", "tokio_unstable", "-C", "target-feature=-crt-static"]
+
+
 [alias]
 xtask = "run --package xtask --"
 integration-test = "test --features integration --profile integration --workspace --test integration"
+

Cargo.lock

@@ -1410,6 +1410,15 @@ version = "0.12.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8a9ee70c43aaf417c914396645a0fa852624801b24ebb7ae78fe8272889ac888"
 
+[[package]]
+name = "hashbrown"
+version = "0.13.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "43a3c133739dddd0d2990f9a4bdf8eb4b21ef50e4851ca85ab661199821d510e"
+dependencies = [
+ "ahash",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.14.0"
@@ -1475,6 +1484,12 @@ dependencies = [
 name = "helix-event"
 version = "0.6.0"
 dependencies = [
+ "ahash",
+ "anyhow",
+ "futures-executor",
+ "hashbrown 0.13.2",
+ "log",
+ "once_cell",
  "parking_lot",
  "tokio",
 ]

book/src/configuration.md

@@ -51,7 +51,8 @@ Its settings will be merged with the configuration directory `config.toml` and t
 | `auto-completion` | Enable automatic pop up of auto-completion | `true` |
 | `auto-format` | Enable automatic formatting on save | `true` |
 | `auto-save` | Enable automatic saving on the focus moving away from Helix. Requires [focus event support](https://github.com/helix-editor/helix/wiki/Terminal-Support) from your terminal | `false` |
-| `idle-timeout` | Time in milliseconds since last keypress before idle timers trigger. Used for autocompletion, set to 0 for instant | `400` |
+| `idle-timeout` | Time in milliseconds since last keypress before idle timers trigger. | `250` |
+| `completion-timeout` | Time in milliseconds after typing a word character before completions are shown, set to 5 for instant.  | `250` |
 | `preview-completion-insert` | Whether to apply completion item instantly when selected | `true` |
 | `completion-trigger-len` | The min-length of word under cursor to trigger autocompletion | `2` |
 | `completion-replace` | Set to `true` to make completions always replace the entire word and not just the part before the cursor | `false` |

helix-event/Cargo.toml

@@ -11,5 +11,18 @@ homepage = "https://helix-editor.com"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-tokio = { version = "1", features = ["rt", "rt-multi-thread", "time", "sync", "parking_lot"] }
-parking_lot = { version = "0.12", features = ["send_guard"] }
+ahash = "0.8.3"
+hashbrown = "0.13.2"
+tokio = { version = "1", features = ["rt", "rt-multi-thread", "time", "sync", "parking_lot", "macros"] }
+# the event registry is essentially read only but must be an rwlock so we can
+# setup new events on intalization, hardware-lock-elision hugnly benefits this case
+# as is essentially makes the lock entirely free as long as there is no writes 
+parking_lot = { version = "0.12", features = ["hardware-lock-elision"] }
+once_cell = "1.18"
+
+anyhow = "1"
+log = "0.4"
+futures-executor = "0.3.28"
+
+[features]
+integration_test = []

helix-event/src/cancel.rs

@@ -0,0 +1,19 @@
+use std::future::Future;
+
+pub use oneshot::channel as cancelation;
+use tokio::sync::oneshot;
+
+pub type CancelTx = oneshot::Sender<()>;
+pub type CancelRx = oneshot::Receiver<()>;
+
+pub async fn cancelable_future<T>(future: impl Future<Output = T>, cancel: CancelRx) -> Option<T> {
+    tokio::select! {
+        biased;
+        _ = cancel => {
+            None
+        }
+        res = future => {
+            Some(res)
+        }
+    }
+}

helix-event/src/debounce.rs

@@ -0,0 +1,67 @@
+//! Utilities for declaring an async (usually debounced) hook
+
+use std::time::Duration;
+
+use futures_executor::block_on;
+use tokio::sync::mpsc::{self, error::TrySendError, Sender};
+use tokio::time::Instant;
+
+/// Async hooks provide a convenient framework for implementing (debounced)
+/// async event handlers. Most synchronous event hooks will likely need to
+/// debounce their events, coordinate multiple different hooks and potentially
+/// track some state. `AsyncHooks` facilitate these usecases by running as
+/// a background tokio task that waits for events (usually an enum) to be
+/// sent trough a channel.
+pub trait AsyncHook: Sync + Send + 'static + Sized {
+    type Event: Sync + Send + 'static;
+    /// Called immediately whenever an event is received, this function can
+    /// consume the event immediately or debounce it. In case of debouncing,
+    /// it can either define a new debounce timeout or continue the current one
+    fn handle_event(&mut self, event: Self::Event, timeout: Option<Instant>) -> Option<Instant>;
+
+    /// Called whenever the debounce timeline is reached
+    fn finish_debounce(&mut self);
+
+    fn spawn(self) -> mpsc::Sender<Self::Event> {
+        // the capacity doesn't matter too much here, unless the cpu is totally overwhelmed
+        // the cap will never be reached sine we always immediately drain the channel
+        // so it should only be reached in case of total CPU overload.
+        // However, a bounded channel is much more efficient so its nice to use here
+        let (tx, rx) = mpsc::channel(128);
+        tokio::spawn(run(self, rx));
+        tx
+    }
+}
+
+async fn run<Hook: AsyncHook>(mut hook: Hook, mut rx: mpsc::Receiver<Hook::Event>) {
+    let mut deadline = None;
+    loop {
+        let event = match deadline {
+            Some(deadline_) => {
+                let res = tokio::time::timeout_at(deadline_, rx.recv()).await;
+                match res {
+                    Ok(event) => event,
+                    Err(_) => {
+                        hook.finish_debounce();
+                        deadline = None;
+                        continue;
+                    }
+                }
+            }
+            None => rx.recv().await,
+        };
+        let Some(event) = event else {
+            break;
+        };
+        deadline = hook.handle_event(event, deadline);
+    }
+}
+
+pub fn send_blocking<T>(tx: &Sender<T>, data: T) {
+    // block_on has some ovherhead and in practice the channel should basically
+    // never be full anyway so first try sending without blocking
+    if let Err(TrySendError::Full(data)) = tx.try_send(data) {
+        // set a timeout so that we just drop a message instead of freezing the editor in the worst case
+        let _ = block_on(tx.send_timeout(data, Duration::from_millis(10)));
+    }
+}

helix-event/src/hook.rs

@@ -0,0 +1,91 @@
+//! rust dynamic dispatch is extremely limited so we have to build our
+//! own vtable implementation. Otherwise implementing the event system would not be possible.
+//! A nice bonus of this approach is that we can optimize the vtable a bit more. Normally
+//! a dyn Trait fat pointer contains two pointers: A pointer to the data itself and a
+//! pointer to a global (static) vtable entry which itself contains multiple other pointers
+//! (the various functions of the trait, drop, size annd align). That makes dynamic
+//! dispatch pretty slow (double pointer indirections). However, we only have a single function
+//! in the hook trait and don't need a drop implementation (event system is global anyway
+//! and never dropped) so we can just store the entire vtable inline.
+
+use anyhow::Result;
+use std::ptr::{self, NonNull};
+
+use crate::Event;
+
+/// Opaque handle type that represents an erased type parameter.
+///
+/// If extern types were stable, this could be implemented as `extern { pub type Opaque; }` but
+/// until then we can use this.
+///
+/// Care should be taken that we don't use a concrete instance of this. It should only be used
+/// through a reference, so we can maintain something else's lifetime.
+struct Opaque(());
+
+pub(crate) struct ErasedHook {
+    data: NonNull<Opaque>,
+    call: unsafe fn(NonNull<Opaque>, NonNull<Opaque>, NonNull<Opaque>),
+}
+
+impl ErasedHook {
+    pub(crate) fn new_dynamic<H: Fn() -> Result<()> + 'static + Send + Sync>(
+        hook: H,
+    ) -> ErasedHook {
+        unsafe fn call<F: Fn() -> Result<()> + 'static + Send + Sync>(
+            hook: NonNull<Opaque>,
+            _event: NonNull<Opaque>,
+            result: NonNull<Opaque>,
+        ) {
+            let hook: NonNull<F> = hook.cast();
+            let result: NonNull<Result<()>> = result.cast();
+            let hook: &F = hook.as_ref();
+            let res = hook();
+            ptr::write(result.as_ptr(), res)
+        }
+
+        unsafe {
+            ErasedHook {
+                data: NonNull::new_unchecked(Box::into_raw(Box::new(hook)) as *mut Opaque),
+                call: call::<H>,
+            }
+        }
+    }
+
+    pub(crate) fn new<E: Event, F: Fn(&mut E) -> Result<()>>(hook: F) -> ErasedHook {
+        unsafe fn call<E: Event, F: Fn(&mut E) -> Result<()>>(
+            hook: NonNull<Opaque>,
+            event: NonNull<Opaque>,
+            result: NonNull<Opaque>,
+        ) {
+            let hook: NonNull<F> = hook.cast();
+            let mut event: NonNull<E> = event.cast();
+            let result: NonNull<Result<()>> = result.cast();
+            let hook: &F = hook.as_ref();
+            let res = hook(event.as_mut());
+            ptr::write(result.as_ptr(), res)
+        }
+
+        unsafe {
+            ErasedHook {
+                data: NonNull::new_unchecked(Box::into_raw(Box::new(hook)) as *mut Opaque),
+                call: call::<E, F>,
+            }
+        }
+    }
+
+    pub(crate) unsafe fn call<E: Event>(&self, event: &mut E) -> Result<()> {
+        let mut res = Ok(());
+
+        unsafe {
+            (self.call)(
+                self.data,
+                NonNull::from(event).cast(),
+                NonNull::from(&mut res).cast(),
+            );
+        }
+        res
+    }
+}
+
+unsafe impl Sync for ErasedHook {}
+unsafe impl Send for ErasedHook {}

helix-event/src/lib.rs

@@ -1,8 +1,164 @@
 //! `helix-event` contains systems that allow (often async) communication between
-//! different editor components without strongly coupling them. Currently this
-//! crate only contains some smaller facilities but the intend is to add more
-//! functionality in the future ( like a generic hook system)
+//! different editor components without strongly coupling them. Specifically
+//! it allows defining synchronous hooks that run when certain editor events
+//! occur.
+//!
+//! The core of the event system are hook callbacks and the [`Event`] trait. A
+//! hook is essentially just a closure `Fn(event: &mut impl Event) -> Result<()>`
+//! that gets called every time an approriate event is dispatched. The implementation
+//! details of the [`Event`] trait are considered private. The [`events`] macro is
+//! provided which automatically declares event types. Similarly the `register_hook`
+//! macro should be used to (safely) declare event hooks.
+//!
+//! Hooks run synchronously which can be advantageous since they can modify the
+//! current editor state right away (for example to immediately hide the completion
+//! popup). However, they can not contain their own state without locking since
+//! they only receive immutable references. For handler that want to track state, do
+//! expensive background computations or debouncing an [`AsyncHook`] is preferable.
+//! Async hooks are based around a channels that receive events specific to
+//! that `AsyncHook` (usually an enum). These events can be sent by synchronous
+//! hooks. Due to some limtations around tokio channels the [`send_blocking`]
+//! function exported in this crate should be used instead of the builtin
+//! `blocking_send`.
+//!
+//! In addition to the core event system, this crate contains some message queues
+//! that allow transfer of data back to the main event loop from async hooks and
+//! hooks that may not have access to all application data (for example in helix-view).
+//! This include the ability to control rendering ([`lock_frame`], [`request_redraw`]) and
+//! display status messages ([`status`]).
+//!
+//! Hooks declared in helix-term can furthermore dispatch synchronous jobs to be run on the
+//! main loop (including access to the compositor). Ideally that queue will be moved
+//! to helix-view in the future if we manage to detach the compositor from its rendering backend.
 
+use anyhow::Result;
+pub use cancel::{cancelable_future, cancelation, CancelRx, CancelTx};
+pub use debounce::{send_blocking, AsyncHook};
 pub use redraw::{lock_frame, redraw_requested, request_redraw, start_frame, RenderLockGuard};
+pub use registry::Event;
 
+mod cancel;
+mod debounce;
+mod hook;
 mod redraw;
+mod registry;
+#[doc(hidden)]
+pub mod runtime;
+pub mod status;
+
+#[cfg(test)]
+mod test;
+
+pub fn register_event<E: Event + 'static>() {
+    registry::with_mut(|registry| registry.register_event::<E>())
+}
+
+/// Registers a hook that will be called when an event of type `E` is dispatched.
+/// This function should usually not be used directly, use the [`register_hook`]
+/// macro instead.
+///
+///
+/// # Safety
+///
+/// `hook` must be totally generic over all lifetime parameters of `E`. For
+/// example if `E` was a known type `Foo<'a, 'b>`, then the correct trait bound
+/// would be `F: for<'a, 'b, 'c> Fn(&'a mut Foo<'b, 'c>)`, but there is no way to
+/// express that kind of constraint for a generic type with the Rust type system
+/// as of this writing.
+pub unsafe fn register_hook_raw<E: Event>(
+    hook: impl Fn(&mut E) -> Result<()> + 'static + Send + Sync,
+) {
+    registry::with_mut(|registry| registry.register_hook(hook))
+}
+
+/// Register a hook solely by event name
+pub fn register_dynamic_hook(
+    hook: impl Fn() -> Result<()> + 'static + Send + Sync,
+    id: &str,
+) -> Result<()> {
+    registry::with_mut(|reg| reg.register_dynamic_hook(hook, id))
+}
+
+pub fn dispatch(e: impl Event) {
+    registry::with(|registry| registry.dispatch(e));
+}
+
+/// Macro to delclare events
+///
+/// # Examples
+///
+/// ``` no-compile
+/// events! {
+///     FileWrite(&Path)
+///     ViewScrolled{ view: View, new_pos: ViewOffset }
+///     DocumentChanged<'a> { old_doc: &'a Rope, doc: &'a mut Document, changes: &'a ChangeSet  }
+/// }
+///
+/// fn init() {
+///    register_event::<FileWrite>();
+///    register_event::<ViewScrolled>();
+///    register_event::<InsertChar>();
+///    register_event::<DocumentChanged>();
+/// }
+///
+/// fn save(path: &Path, content: &str){
+///     std::fs::write(path, content);
+///     dispatch(FileWrite(path));
+/// }
+/// ```
+#[macro_export]
+macro_rules! events {
+    ($name: ident<$($lt: lifetime),*> { $($data:ident : $data_ty:ty),* } $($rem:tt)*) => {
+        pub struct $name<$($lt),*> { $(pub $data: $data_ty),* }
+        impl<$($lt),*> $crate::Event for $name<$($lt),*> {
+            const ID: &'static str = stringify!($name);
+            const LIFETIMES: usize = $crate::events!(@sum $(1, $lt),*);
+            type Static = $crate::events!(@replace_lt $name, $('static, $lt),*);
+        }
+        $crate::events!{ $($rem)* }
+    };
+    ($name: ident { $($data:ident : $data_ty:ty),* } $($rem:tt)*) => {
+        pub struct $name { $(pub $data: $data_ty),* }
+        impl $crate::Event for $name {
+            const ID: &'static str = stringify!($name);
+            const LIFETIMES: usize = 0;
+            type Static = Self;
+        }
+        $crate::events!{ $($rem)* }
+    };
+    () => {};
+    (@replace_lt $name: ident, $($lt1: lifetime, $lt2: lifetime),* ) => {$name<$($lt1),*>};
+    (@sum $($val: expr, $lt1: lifetime),* ) => {0 $(+ $val)*};
+}
+
+/// Safely register statically typed event hooks
+#[macro_export]
+macro_rules! register_hook {
+    // Safety: this is safe because we fully control the type of the event here and
+    // ensure all lifetime arguments are fully generic and the correct number of lifetime arguments
+    // is present
+    (move |$event:ident: &mut $event_ty: ident<$($lt: lifetime),*>| $body: expr) => {
+        let val = move |$event: &mut $event_ty<$($lt),*>| $body;
+        unsafe {
+            #[allow(unused)]
+            const ASSERT: () = {
+                if <$event_ty as $crate::Event>::LIFETIMES != 0 + $crate::events!(@sum $(1, $lt),*){
+                    panic!("invalid type alias");
+                }
+            };
+            $crate::register_hook_raw::<$crate::events!(@replace_lt $event_ty, $('static, $lt),*)>(val);
+        }
+    };
+    (move |$event:ident: &mut $event_ty: ident| $body: expr) => {
+        let val = move |$event: &mut $event_ty| $body;
+        unsafe {
+            #[allow(unused)]
+            const ASSERT: () = {
+                if <$event_ty as $crate::Event>::LIFETIMES != 0{
+                    panic!("invalid type alias");
+                }
+            };
+            $crate::register_hook_raw::<$event_ty>(val);
+        }
+    };
+}

helix-event/src/redraw.rs

@@ -5,6 +5,9 @@ use std::future::Future;
 use parking_lot::{RwLock, RwLockReadGuard};
 use tokio::sync::Notify;
 
+use crate::runtime_local;
+
+runtime_local! {
     /// A `Notify` instance that can be used to (asynchronously) request
     /// the editor the render a new frame.
     static REDRAW_NOTIFY: Notify = Notify::const_new();
@@ -15,6 +18,7 @@ static REDRAW_NOTIFY: Notify = Notify::const_new();
     /// locks (read) to prevent the next frame from being drawn
     /// until a certain computation has finished.
     static RENDER_LOCK: RwLock<()> = RwLock::new(());
+}
 
 pub type RenderLockGuard = RwLockReadGuard<'static, ()>;
 

helix-event/src/registry.rs

@@ -0,0 +1,127 @@
+//! A global registry where events are registered and can be
+//! subscribed to by registering hooks. The registry identifies event
+//! types using their type name so multiple event with the same type name
+//! may not be registered (will cause a panic to ensure soundness)
+
+use std::any::TypeId;
+
+use anyhow::{bail, Result};
+use hashbrown::hash_map::Entry;
+use hashbrown::HashMap;
+use parking_lot::RwLock;
+
+use crate::hook::ErasedHook;
+use crate::runtime_local;
+
+pub struct Registry {
+    events: HashMap<&'static str, TypeId, ahash::RandomState>,
+    handlers: HashMap<&'static str, Vec<ErasedHook>, ahash::RandomState>,
+}
+
+impl Registry {
+    pub fn register_event<E: Event + 'static>(&mut self) {
+        let ty = TypeId::of::<E>();
+        assert_eq!(ty, TypeId::of::<E::Static>());
+        match self.events.entry(E::ID) {
+            Entry::Occupied(entry) => {
+                if entry.get() == &ty {
+                    // don't warn during tests to avoid log spam
+                    #[cfg(not(feature = "integration_test"))]
+                    panic!("Event {} was registered multiple times", E::ID);
+                } else {
+                    panic!("Multiple events with ID {} were registered", E::ID);
+                }
+            }
+            Entry::Vacant(ent) => {
+                ent.insert(ty);
+                self.handlers.insert(E::ID, Vec::new());
+            }
+        }
+    }
+
+    /// # Safety
+    ///
+    /// `hook` must be totally generic over all lifetime parameters of `E`. For
+    /// example if `E` was a known type `Foo<'a, 'b> then the correct trait bound
+    /// would be `F: for<'a, 'b, 'c> Fn(&'a mut Foo<'b, 'c>)` but there is no way to
+    /// express that kind of constraint for a generic type with the rust type system
+    /// right now.
+    pub unsafe fn register_hook<E: Event>(
+        &mut self,
+        hook: impl Fn(&mut E) -> Result<()> + 'static + Send + Sync,
+    ) {
+        // ensure event type ids match so we can rely on them always matching
+        let id = E::ID;
+        let Some(&event_id) = self.events.get(id) else {
+            panic!("Tried to register handler for unknown event {id}");
+        };
+        assert!(
+            TypeId::of::<E::Static>() == event_id,
+            "Tried to register invalid hook for event {id}"
+        );
+        let hook = ErasedHook::new(hook);
+        self.handlers.get_mut(id).unwrap().push(hook);
+    }
+
+    pub fn register_dynamic_hook(
+        &mut self,
+        hook: impl Fn() -> Result<()> + 'static + Send + Sync,
+        id: &str,
+    ) -> Result<()> {
+        // ensure event type ids match so we can rely on them always matching
+        if self.events.get(id).is_none() {
+            bail!("Tried to register handler for unknown event {id}");
+        };
+        let hook = ErasedHook::new_dynamic(hook);
+        self.handlers.get_mut(id).unwrap().push(hook);
+        Ok(())
+    }
+
+    pub fn dispatch<E: Event>(&self, mut event: E) {
+        let Some(hooks) = self.handlers.get(E::ID) else {
+            log::error!("Dispatched unknown event {}", E::ID);
+            return;
+        };
+        let event_id = self.events[E::ID];
+
+        assert_eq!(
+            TypeId::of::<E::Static>(),
+            event_id,
+            "Tried to dispatch invalid event {}",
+            E::ID
+        );
+
+        for hook in hooks {
+            // safety: event type is the same
+            if let Err(err) = unsafe { hook.call(&mut event) } {
+                log::error!("{} hook failed: {err:#?}", E::ID);
+                crate::status::report_blocking(err);
+            }
+        }
+    }
+}
+
+runtime_local! {
+    static REGISTRY: RwLock<Registry> = RwLock::new(Registry {
+        // hardcoded random number is good enough here we don't care about DOS resistance
+        // and avoids the additional complexity of `Option<Registry>`
+        events: HashMap::with_hasher(ahash::RandomState::with_seeds(423, 9978, 38322, 3280080)),
+        handlers: HashMap::with_hasher(ahash::RandomState::with_seeds(423, 99078, 382322, 3282938)),
+    });
+}
+
+pub(crate) fn with<T>(f: impl FnOnce(&Registry) -> T) -> T {
+    f(&REGISTRY.read())
+}
+
+pub(crate) fn with_mut<T>(f: impl FnOnce(&mut Registry) -> T) -> T {
+    f(&mut REGISTRY.write())
+}
+
+pub trait Event: Sized {
+    /// Globally unique (case sensitive)  string that identifies this type.
+    /// A good candidate is the events type name
+    const ID: &'static str;
+    const LIFETIMES: usize;
+    type Static: Event + 'static;
+}

helix-event/src/runtime.rs

@@ -0,0 +1,88 @@
+//! The event system makes use of global to decouple different systems.
+//! However, this can cause problems for the integration test system because
+//! it runs multiple helix applications in parallel. Making the globals
+//! thread-local does not work because a applications can/does have multiple
+//! runtime threads. Instead this crate implements a similar notion to a thread
+//! local but instead of being local to a single thread, the statics are local to
+//! a single tokio-runtime. The implementation requires locking so its not exactly efficient.
+//!
+//! Therefore this function is only enabled during integration tests and behaves like
+//! a normal static otherwise. I would prefer this module to be fully private and to only
+//! export the macro but the macro still need to construct these internals so its marked
+//! `doc(hidden)` instead
+
+use std::ops::Deref;
+
+#[cfg(not(feature = "integration_test"))]
+pub struct RuntimeLocal<T: 'static> {
+    /// inner API used in the macro, not part of public API
+    #[doc(hidden)]
+    pub __data: T,
+}
+
+#[cfg(not(feature = "integration_test"))]
+impl<T> Deref for RuntimeLocal<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.__data
+    }
+}
+
+#[cfg(not(feature = "integration_test"))]
+#[macro_export]
+macro_rules! runtime_local {
+    ($($(#[$attr:meta])* $vis: vis static $name:ident: $ty: ty = $init: expr;)*) => {
+        $($(#[$attr])* $vis static $name: $crate::runtime::RuntimeLocal<$ty> = $crate::runtime::RuntimeLocal {
+            __data: $init
+        };)*
+    };
+}
+
+#[cfg(feature = "integration_test")]
+pub struct RuntimeLocal<T: 'static> {
+    data:
+        parking_lot::RwLock<hashbrown::HashMap<tokio::runtime::Id, &'static T, ahash::RandomState>>,
+    init: fn() -> T,
+}
+
+#[cfg(feature = "integration_test")]
+impl<T> RuntimeLocal<T> {
+    /// inner API used in the macro, not part of public API
+    #[doc(hidden)]
+    pub const fn __new(init: fn() -> T) -> Self {
+        Self {
+            data: parking_lot::RwLock::new(hashbrown::HashMap::with_hasher(
+                ahash::RandomState::with_seeds(423, 9978, 38322, 3280080),
+            )),
+            init,
+        }
+    }
+}
+
+#[cfg(feature = "integration_test")]
+impl<T> Deref for RuntimeLocal<T> {
+    type Target = T;
+    fn deref(&self) -> &T {
+        let id = tokio::runtime::Handle::current().id();
+        let guard = self.data.read();
+        match guard.get(&id) {
+            Some(res) => res,
+            None => {
+                drop(guard);
+                let data = Box::leak(Box::new((self.init)()));
+                let mut guard = self.data.write();
+                guard.insert(id, data);
+                data
+            }
+        }
+    }
+}
+
+#[cfg(feature = "integration_test")]
+#[macro_export]
+macro_rules! runtime_local {
+    ($($(#[$attr:meta])* $vis: vis static $name:ident: $ty: ty = $init: expr;)*) => {
+         $($(#[$attr])* $vis static $name: $crate::runtime::RuntimeLocal<$ty> = $crate::runtime::RuntimeLocal::__new(|| $init);)*
+    };
+}

helix-event/src/status.rs

@@ -0,0 +1,68 @@
+//! A queue of async messages/errors that will be shown in the editor
+
+use std::borrow::Cow;
+use std::time::Duration;
+
+use crate::{runtime_local, send_blocking};
+use once_cell::sync::OnceCell;
+use tokio::sync::mpsc::{Receiver, Sender};
+
+/// Describes the severity level of a [`StatusMessage`].
+#[derive(Debug, Clone, Copy, Eq, PartialEq, PartialOrd, Ord)]
+pub enum Severity {
+    Hint,
+    Info,
+    Warning,
+    Error,
+}
+
+pub struct StatusMessage {
+    pub severity: Severity,
+    pub message: Cow<'static, str>,
+}
+
+impl From<anyhow::Error> for StatusMessage {
+    fn from(err: anyhow::Error) -> Self {
+        StatusMessage {
+            severity: Severity::Error,
+            message: err.to_string().into(),
+        }
+    }
+}
+
+impl From<&'static str> for StatusMessage {
+    fn from(msg: &'static str) -> Self {
+        StatusMessage {
+            severity: Severity::Info,
+            message: msg.into(),
+        }
+    }
+}
+
+runtime_local! {
+    static MESSAGES: OnceCell<Sender<StatusMessage>> = OnceCell::new();
+}
+
+pub async fn report(msg: impl Into<StatusMessage>) {
+    // if the error channel overflows just ignore it
+    let _ = MESSAGES
+        .wait()
+        .send_timeout(msg.into(), Duration::from_millis(10))
+        .await;
+}
+
+pub fn report_blocking(msg: impl Into<StatusMessage>) {
+    let messages = MESSAGES.wait();
+    send_blocking(messages, msg.into())
+}
+
+/// Must be called once during editor startup exactly once
+/// before any of the messages in this module can be used
+///
+/// # Panics
+/// If called multiple times
+pub fn setup() -> Receiver<StatusMessage> {
+    let (tx, rx) = tokio::sync::mpsc::channel(128);
+    let _ = MESSAGES.set(tx);
+    rx
+}

helix-event/src/test.rs

@@ -0,0 +1,90 @@
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Arc;
+use std::time::Duration;
+
+use parking_lot::Mutex;
+
+use crate::{dispatch, events, register_dynamic_hook, register_event, register_hook};
+#[test]
+fn smoke_test() {
+    events! {
+        Event1 { content: String }
+        Event2 { content: usize }
+    }
+    register_event::<Event1>();
+    register_event::<Event2>();
+
+    // setup hooks
+    let res1: Arc<Mutex<String>> = Arc::default();
+    let acc = Arc::clone(&res1);
+    register_hook!(move |event: &mut Event1| {
+        acc.lock().push_str(&event.content);
+        Ok(())
+    });
+    let res2: Arc<AtomicUsize> = Arc::default();
+    let acc = Arc::clone(&res2);
+    register_hook!(move |event: &mut Event2| {
+        acc.fetch_add(event.content, Ordering::Relaxed);
+        Ok(())
+    });
+
+    // triggers events
+    let thread = std::thread::spawn(|| {
+        for i in 0..1000 {
+            dispatch(Event2 { content: i });
+        }
+    });
+    std::thread::sleep(Duration::from_millis(1));
+    dispatch(Event1 {
+        content: "foo".to_owned(),
+    });
+    dispatch(Event2 { content: 42 });
+    dispatch(Event1 {
+        content: "bar".to_owned(),
+    });
+    dispatch(Event1 {
+        content: "hello world".to_owned(),
+    });
+    thread.join().unwrap();
+
+    // check output
+    assert_eq!(&**res1.lock(), "foobarhello world");
+    assert_eq!(
+        res2.load(Ordering::Relaxed),
+        42 + (0..1000usize).sum::<usize>()
+    );
+}
+
+#[test]
+fn dynamic() {
+    events! {
+        Event3 {}
+        Event4 { count: usize }
+    };
+    register_event::<Event3>();
+    register_event::<Event4>();
+
+    let count = Arc::new(AtomicUsize::new(0));
+    let count1 = count.clone();
+    let count2 = count.clone();
+    register_dynamic_hook(
+        move || {
+            count1.fetch_add(2, Ordering::Relaxed);
+            Ok(())
+        },
+        "Event3",
+    )
+    .unwrap();
+    register_dynamic_hook(
+        move || {
+            count2.fetch_add(3, Ordering::Relaxed);
+            Ok(())
+        },
+        "Event4",
+    )
+    .unwrap();
+    dispatch(Event3 {});
+    dispatch(Event4 { count: 0 });
+    dispatch(Event3 {});
+    assert_eq!(count.load(Ordering::Relaxed), 7)
+}

helix-lsp/src/client.rs

@@ -8,7 +8,7 @@ use helix_core::{find_workspace, path, syntax::LanguageServerFeature, ChangeSet,
 use helix_loader::{self, VERSION_AND_GIT_HASH};
 use lsp::{
     notification::DidChangeWorkspaceFolders, CodeActionCapabilityResolveSupport,
-    DidChangeWorkspaceFoldersParams, OneOf, PositionEncodingKind, WorkspaceFolder,
+    DidChangeWorkspaceFoldersParams, OneOf, PositionEncodingKind, SignatureHelp, WorkspaceFolder,
     WorkspaceFoldersChangeEvent,
 };
 use lsp_types as lsp;
@@ -924,6 +924,7 @@ impl Client {
         text_document: lsp::TextDocumentIdentifier,
         position: lsp::Position,
         work_done_token: Option<lsp::ProgressToken>,
+        context: lsp::CompletionContext,
     ) -> Option<impl Future<Output = Result<Value>>> {
         let capabilities = self.capabilities.get().unwrap();
 
@@ -935,13 +936,12 @@ impl Client {
                 text_document,
                 position,
             },
+            context: Some(context),
             // TODO: support these tokens by async receiving and updating the choice list
             work_done_progress_params: lsp::WorkDoneProgressParams { work_done_token },
             partial_result_params: lsp::PartialResultParams {
                 partial_result_token: None,
             },
-            context: None,
-            // lsp::CompletionContext { trigger_kind: , trigger_character: Some(), }
         };
 
         Some(self.call::<lsp::request::Completion>(params))
@@ -988,7 +988,7 @@ impl Client {
         text_document: lsp::TextDocumentIdentifier,
         position: lsp::Position,
         work_done_token: Option<lsp::ProgressToken>,
-    ) -> Option<impl Future<Output = Result<Value>>> {
+    ) -> Option<impl Future<Output = Result<Option<SignatureHelp>>>> {
         let capabilities = self.capabilities.get().unwrap();
 
         // Return early if the server does not support signature help.
@@ -1004,7 +1004,8 @@ impl Client {
             // lsp::SignatureHelpContext
         };
 
-        Some(self.call::<lsp::request::SignatureHelpRequest>(params))
+        let res = self.call::<lsp::request::SignatureHelpRequest>(params);
+        Some(async move { Ok(serde_json::from_value(res.await?)?) })
     }
 
     pub fn text_document_range_inlay_hints(

helix-term/Cargo.toml

@@ -15,7 +15,7 @@ rust-version = "1.65"
 [features]
 default = ["git", "steel"] # Remove steel if you don't want it
 unicode-lines = ["helix-core/unicode-lines"]
-integration = []
+integration = ["helix-event/integration_test"]
 git = ["helix-vcs/git"]
 steel = ["dep:steel-core", "helix-core/steel", "helix-view/steel", "tui/steel"]
 

helix-term/src/application.rs

@@ -1,7 +1,7 @@
 use arc_swap::{access::Map, ArcSwap};
 use futures_util::Stream;
 use helix_core::{
-    diagnostic::{DiagnosticTag, NumberOrString},
+    diagnostic::{DiagnosticTag, NumberOrString, Severity},
     path::get_relative_path,
     pos_at_coords, syntax, Selection,
 };
@@ -27,6 +27,7 @@ use crate::{
     commands::apply_workspace_edit,
     compositor::{Compositor, Event},
     config::Config,
+    handlers,
     job::Jobs,
     keymap::Keymaps,
     ui::{self, overlay::overlaid},
@@ -141,6 +142,7 @@ impl Application {
         let area = terminal.size().expect("couldn't get terminal size");
         let mut compositor = Compositor::new(area);
         let config = Arc::new(ArcSwap::from_pointee(config));
+        let handlers = handlers::setup(config.clone());
         let mut editor = Editor::new(
             area,
             theme_loader.clone(),
@@ -148,6 +150,7 @@ impl Application {
             Arc::new(Map::new(Arc::clone(&config), |config: &Config| {
                 &config.editor
             })),
+            handlers,
         );
 
         let keys = Box::new(Map::new(Arc::clone(&config), |config: &Config| {
@@ -331,10 +334,21 @@ impl Application {
                 Some(event) = input_stream.next() => {
                     self.handle_terminal_events(event).await;
                 }
-                Some(callback) = self.jobs.futures.next() => {
-                    self.jobs.handle_callback(&mut self.editor, &mut self.compositor, callback);
+                Some(callback) = self.jobs.callbacks.recv() => {
+                    self.jobs.handle_callback(&mut self.editor, &mut self.compositor, Ok(Some(callback)));
                     self.render().await;
                 }
+                Some(msg) = self.jobs.status_messages.recv() => {
+                    let severity = match msg.severity{
+                        helix_event::status::Severity::Hint => Severity::Hint,
+                        helix_event::status::Severity::Info => Severity::Info,
+                        helix_event::status::Severity::Warning => Severity::Warning,
+                        helix_event::status::Severity::Error => Severity::Error,
+                    };
+                    // TODO: show multiple status messages at once to avoid clobbering
+                    self.editor.status_msg = Some((msg.message, severity));
+                    helix_event::request_redraw();
+                }
                 Some(callback) = self.jobs.wait_futures.next() => {
                     self.jobs.handle_callback(&mut self.editor, &mut self.compositor, callback);
                     self.render().await;

helix-term/src/commands.rs

@@ -36,7 +36,7 @@ use helix_core::{
 };
 use helix_view::{
     document::{FormatterError, Mode, SCRATCH_BUFFER_NAME},
-    editor::{Action, CompleteAction},
+    editor::Action,
     info::Info,
     input::KeyEvent,
     keyboard::KeyCode,
@@ -55,14 +55,10 @@ use crate::{
     filter_picker_entry,
     job::Callback,
     keymap::ReverseKeymap,
-    ui::{
-        self, editor::InsertEvent, lsp::SignatureHelp, overlay::overlaid, CompletionItem, Picker,
-        Popup, Prompt, PromptEvent,
-    },
+    ui::{self, overlay::overlaid, Picker, Popup, Prompt, PromptEvent},
 };
 
 use crate::job::{self, Jobs};
-use futures_util::{stream::FuturesUnordered, TryStreamExt};
 use std::{collections::HashMap, fmt, future::Future};
 use std::{collections::HashSet, num::NonZeroUsize};
 
@@ -86,7 +82,7 @@ pub struct Context<'a> {
     pub count: Option<NonZeroUsize>,
     pub editor: &'a mut Editor,
 
-    pub callback: Option<crate::compositor::Callback>,
+    pub callback: Vec<crate::compositor::Callback>,
     pub on_next_key_callback: Option<OnKeyCallback>,
     pub jobs: &'a mut Jobs,
 }
@@ -94,14 +90,16 @@ pub struct Context<'a> {
 impl<'a> Context<'a> {
     /// Push a new component onto the compositor.
     pub fn push_layer(&mut self, component: Box<dyn Component>) {
-        self.callback = Some(Box::new(|compositor: &mut Compositor, _| {
+        self.callback
+            .push(Box::new(|compositor: &mut Compositor, _| {
                 compositor.push(component)
             }));
     }
 
     /// Call `replace_or_push` on the Compositor
     pub fn replace_or_push_layer<T: Component>(&mut self, id: &'static str, component: T) {
-        self.callback = Some(Box::new(move |compositor: &mut Compositor, _| {
+        self.callback
+            .push(Box::new(move |compositor: &mut Compositor, _| {
                 compositor.replace_or_push(id, component);
             }));
     }
@@ -2776,7 +2774,6 @@ fn delete_by_selection_insert_mode(
         );
     }
     doc.apply(&transaction, view.id);
-    lsp::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
 }
 
 fn delete_selection(cx: &mut Context) {
@@ -2850,10 +2847,6 @@ fn insert_mode(cx: &mut Context) {
         .transform(|range| Range::new(range.to(), range.from()));
 
     doc.set_selection(view.id, selection);
-
-    // [TODO] temporary workaround until we're not using the idle timer to
-    //        trigger auto completions any more
-    cx.editor.clear_idle_timer();
 }
 
 // inserts at the end of each selection
@@ -3125,7 +3118,7 @@ pub fn command_palette(cx: &mut Context) {
     let register = cx.register;
     let count = cx.count;
 
-    cx.callback = Some(Box::new(
+    cx.callback.push(Box::new(
         move |compositor: &mut Compositor, cx: &mut compositor::Context| {
             let keymap = compositor.find::<ui::EditorView>().unwrap().keymaps.map()
                 [&cx.editor.mode]
@@ -3145,7 +3138,7 @@ pub fn command_palette(cx: &mut Context) {
                     register,
                     count,
                     editor: cx.editor,
-                    callback: None,
+                    callback: Vec::new(),
                     on_next_key_callback: None,
                     jobs: cx.jobs,
                 };
@@ -3173,7 +3166,7 @@ pub fn command_palette(cx: &mut Context) {
 
 fn last_picker(cx: &mut Context) {
     // TODO: last picker does not seem to work well with buffer_picker
-    cx.callback = Some(Box::new(|compositor, cx| {
+    cx.callback.push(Box::new(|compositor, cx| {
         if let Some(picker) = compositor.last_picker.take() {
             compositor.push(picker);
         } else {
@@ -3681,9 +3674,10 @@ fn hunk_range(hunk: Hunk, text: RopeSlice) -> Range {
 }
 
 pub mod insert {
+    use crate::events::PostInsertChar;
+
     use super::*;
     pub type Hook = fn(&Rope, &Selection, char) -> Option<Transaction>;
-    pub type PostHook = fn(&mut Context, char);
 
     /// Exclude the cursor in range.
     fn exclude_cursor(text: RopeSlice, range: Range, cursor: Range) -> Range {
@@ -3697,88 +3691,6 @@ pub mod insert {
         }
     }
 
-    // It trigger completion when idle timer reaches deadline
-    // Only trigger completion if the word under cursor is longer than n characters
-    pub fn idle_completion(cx: &mut Context) {
-        let config = cx.editor.config();
-        let (view, doc) = current!(cx.editor);
-        let text = doc.text().slice(..);
-        let cursor = doc.selection(view.id).primary().cursor(text);
-
-        use helix_core::chars::char_is_word;
-        let mut iter = text.chars_at(cursor);
-        iter.reverse();
-        for _ in 0..config.completion_trigger_len {
-            match iter.next() {
-                Some(c) if char_is_word(c) => {}
-                _ => return,
-            }
-        }
-        super::completion(cx);
-    }
-
-    fn language_server_completion(cx: &mut Context, ch: char) {
-        let config = cx.editor.config();
-        if !config.auto_completion {
-            return;
-        }
-
-        use helix_lsp::lsp;
-        // if ch matches completion char, trigger completion
-        let doc = doc_mut!(cx.editor);
-        let trigger_completion = doc
-            .language_servers_with_feature(LanguageServerFeature::Completion)
-            .any(|ls| {
-                // TODO: what if trigger is multiple chars long
-                matches!(&ls.capabilities().completion_provider, Some(lsp::CompletionOptions {
-                    trigger_characters: Some(triggers),
-                    ..
-                }) if triggers.iter().any(|trigger| trigger.contains(ch)))
-            });
-
-        if trigger_completion {
-            cx.editor.clear_idle_timer();
-            super::completion(cx);
-        }
-    }
-
-    fn signature_help(cx: &mut Context, ch: char) {
-        use helix_lsp::lsp;
-        // if ch matches signature_help char, trigger
-        let doc = doc_mut!(cx.editor);
-        // TODO support multiple language servers (not just the first that is found), likely by merging UI somehow
-        let Some(language_server) = doc
-            .language_servers_with_feature(LanguageServerFeature::SignatureHelp)
-            .next()
-        else {
-            return;
-        };
-
-        let capabilities = language_server.capabilities();
-
-        if let lsp::ServerCapabilities {
-            signature_help_provider:
-                Some(lsp::SignatureHelpOptions {
-                    trigger_characters: Some(triggers),
-                    // TODO: retrigger_characters
-                    ..
-                }),
-            ..
-        } = capabilities
-        {
-            // TODO: what if trigger is multiple chars long
-            let is_trigger = triggers.iter().any(|trigger| trigger.contains(ch));
-            // lsp doesn't tell us when to close the signature help, so we request
-            // the help information again after common close triggers which should
-            // return None, which in turn closes the popup.
-            let close_triggers = &[')', ';', '.'];
-
-            if is_trigger || close_triggers.contains(&ch) {
-                super::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
-            }
-        }
-    }
-
     // The default insert hook: simply insert the character
     #[allow(clippy::unnecessary_wraps)] // need to use Option<> because of the Hook signature
     fn insert(doc: &Rope, selection: &Selection, ch: char) -> Option<Transaction> {
@@ -3808,12 +3720,7 @@ pub mod insert {
             doc.apply(&t, view.id);
         }
 
-        // TODO: need a post insert hook too for certain triggers (autocomplete, signature help, etc)
-        // this could also generically look at Transaction, but it's a bit annoying to look at
-        // Operation instead of Change.
-        for hook in &[language_server_completion, signature_help] {
-            hook(cx, c);
-        }
+        helix_event::dispatch(PostInsertChar { c, cx });
     }
 
     pub fn insert_string(cx: &mut Context, string: String) {
@@ -4049,8 +3956,6 @@ pub mod insert {
             });
         let (view, doc) = current!(cx.editor);
         doc.apply(&transaction, view.id);
-
-        lsp::signature_help_impl(cx, SignatureHelpInvoked::Automatic);
     }
 
     pub fn delete_char_forward(cx: &mut Context) {
@@ -4687,151 +4592,14 @@ fn remove_primary_selection(cx: &mut Context) {
 }
 
 pub fn completion(cx: &mut Context) {
-    use helix_lsp::{lsp, util::pos_to_lsp_pos};
-
     let (view, doc) = current!(cx.editor);
+    let range = doc.selection(view.id).primary();
+    let text = doc.text().slice(..);
+    let cursor = range.cursor(text);
 
-    let savepoint = if let Some(CompleteAction::Selected { savepoint }) = &cx.editor.last_completion
-    {
-        savepoint.clone()
-    } else {
-        doc.savepoint(view)
-    };
-
-    let text = savepoint.text.clone();
-    let cursor = savepoint.cursor();
-
-    let mut seen_language_servers = HashSet::new();
-
-    let mut futures: FuturesUnordered<_> = doc
-        .language_servers_with_feature(LanguageServerFeature::Completion)
-        .filter(|ls| seen_language_servers.insert(ls.id()))
-        .map(|language_server| {
-            let language_server_id = language_server.id();
-            let offset_encoding = language_server.offset_encoding();
-            let pos = pos_to_lsp_pos(&text, cursor, offset_encoding);
-            let doc_id = doc.identifier();
-            let completion_request = language_server.completion(doc_id, pos, None).unwrap();
-
-            async move {
-                let json = completion_request.await?;
-                let response: Option<lsp::CompletionResponse> = serde_json::from_value(json)?;
-
-                let items = match response {
-                    Some(lsp::CompletionResponse::Array(items)) => items,
-                    // TODO: do something with is_incomplete
-                    Some(lsp::CompletionResponse::List(lsp::CompletionList {
-                        is_incomplete: _is_incomplete,
-                        items,
-                    })) => items,
-                    None => Vec::new(),
-                }
-                .into_iter()
-                .map(|item| CompletionItem {
-                    item,
-                    language_server_id,
-                    resolved: false,
-                })
-                .collect();
-
-                anyhow::Ok(items)
-            }
-        })
-        .collect();
-
-    // setup a channel that allows the request to be canceled
-    let (tx, rx) = oneshot::channel();
-    // set completion_request so that this request can be canceled
-    // by setting completion_request, the old channel stored there is dropped
-    // and the associated request is automatically dropped
-    cx.editor.completion_request_handle = Some(tx);
-    let future = async move {
-        let items_future = async move {
-            let mut items = Vec::new();
-            // TODO if one completion request errors, all other completion requests are discarded (even if they're valid)
-            while let Some(mut lsp_items) = futures.try_next().await? {
-                items.append(&mut lsp_items);
-            }
-            anyhow::Ok(items)
-        };
-        tokio::select! {
-            biased;
-            _ = rx => {
-                Ok(Vec::new())
-            }
-            res = items_future => {
-                res
-            }
-        }
-    };
-
-    let trigger_offset = cursor;
-
-    // TODO: trigger_offset should be the cursor offset but we also need a starting offset from where we want to apply
-    // completion filtering. For example logger.te| should filter the initial suggestion list with "te".
-
-    use helix_core::chars;
-    let mut iter = text.chars_at(cursor);
-    iter.reverse();
-    let offset = iter.take_while(|ch| chars::char_is_word(*ch)).count();
-    let start_offset = cursor.saturating_sub(offset);
-
-    let trigger_doc = doc.id();
-    let trigger_view = view.id;
-
-    // FIXME: The commands Context can only have a single callback
-    // which means it gets overwritten when executing keybindings
-    // with multiple commands or macros. This would mean that completion
-    // might be incorrectly applied when repeating the insertmode action
-    //
-    // TODO: to solve this either make cx.callback a Vec of callbacks or
-    // alternatively move `last_insert` to `helix_view::Editor`
-    cx.callback = Some(Box::new(
-        move |compositor: &mut Compositor, _cx: &mut compositor::Context| {
-            let ui = compositor.find::<ui::EditorView>().unwrap();
-            ui.last_insert.1.push(InsertEvent::RequestCompletion);
-        },
-    ));
-
-    cx.jobs.callback(async move {
-        let items = future.await?;
-        let call = move |editor: &mut Editor, compositor: &mut Compositor| {
-            let (view, doc) = current_ref!(editor);
-            // check if the completion request is stale.
-            //
-            // Completions are completed asynchronously and therefore the user could
-            //switch document/view or leave insert mode. In all of thoise cases the
-            // completion should be discarded
-            if editor.mode != Mode::Insert || view.id != trigger_view || doc.id() != trigger_doc {
-                return;
-            }
-
-            if items.is_empty() {
-                // editor.set_error("No completion available");
-                return;
-            }
-            let size = compositor.size();
-            let ui = compositor.find::<ui::EditorView>().unwrap();
-            let completion_area = ui.set_completion(
-                editor,
-                savepoint,
-                items,
-                start_offset,
-                trigger_offset,
-                size,
-            );
-            let size = compositor.size();
-            let signature_help_area = compositor
-                .find_id::<Popup<SignatureHelp>>(SignatureHelp::ID)
-                .map(|signature_help| signature_help.area(size, editor));
-            // Delete the signature help popup if they intersect.
-            if matches!((completion_area, signature_help_area),(Some(a), Some(b)) if a.intersects(b))
-            {
-                compositor.remove(SignatureHelp::ID);
-            }
-        };
-        Ok(Callback::EditorCompositor(Box::new(call)))
-    });
+    cx.editor
+        .handlers
+        .trigger_completions(cursor, doc.id(), view.id);
 }
 
 // comments
@@ -5010,10 +4778,6 @@ fn move_node_bound_impl(cx: &mut Context, dir: Direction, movement: Movement) {
             );
 
             doc.set_selection(view.id, selection);
-
-            // [TODO] temporary workaround until we're not using the idle timer to
-            //        trigger auto completions any more
-            editor.clear_idle_timer();
         }
     };
 
@@ -5994,7 +5758,7 @@ fn replay_macro(cx: &mut Context) {
     cx.editor.macro_replaying.push(reg);
 
     let count = cx.count();
-    cx.callback = Some(Box::new(move |compositor, cx| {
+    cx.callback.push(Box::new(move |compositor, cx| {
         for _ in 0..count {
             for &key in keys.iter() {
                 compositor.handle_event(&compositor::Event::Key(key), cx);

helix-term/src/commands/lsp.rs

@@ -1,4 +1,4 @@
-use futures_util::{future::BoxFuture, stream::FuturesUnordered, FutureExt};
+use futures_util::{stream::FuturesUnordered, FutureExt};
 use helix_lsp::{
     block_on,
     lsp::{
@@ -8,21 +8,21 @@ use helix_lsp::{
     util::{diagnostic_to_lsp_diagnostic, lsp_range_to_range, range_to_lsp_range},
     Client, OffsetEncoding,
 };
-use serde_json::Value;
 use tokio_stream::StreamExt;
 use tui::{
     text::{Span, Spans},
     widgets::Row,
 };
 
-use super::{align_view, push_jump, Align, Context, Editor, Open};
+use super::{align_view, push_jump, Align, Context, Editor};
 
 use helix_core::{
     path, syntax::LanguageServerFeature, text_annotations::InlineAnnotation, Selection,
 };
 use helix_view::{
-    document::{DocumentInlayHints, DocumentInlayHintsId, Mode},
+    document::{DocumentInlayHints, DocumentInlayHintsId},
     editor::Action,
+    handlers::lsp::SignatureHelpInvoked,
     theme::Style,
     Document, View,
 };
@@ -30,10 +30,7 @@ use helix_view::{
 use crate::{
     compositor::{self, Compositor},
     job::Callback,
-    ui::{
-        self, lsp::SignatureHelp, overlay::overlaid, DynamicPicker, FileLocation, Picker, Popup,
-        PromptEvent,
-    },
+    ui::{self, overlay::overlaid, DynamicPicker, FileLocation, Picker, Popup, PromptEvent},
 };
 
 use std::{
@@ -42,7 +39,6 @@ use std::{
     fmt::Write,
     future::Future,
     path::PathBuf,
-    sync::Arc,
 };
 
 /// Gets the first language server that is attached to a document which supports a specific feature.
@@ -1134,146 +1130,10 @@ pub fn goto_reference(cx: &mut Context) {
     );
 }
 
-#[derive(PartialEq, Eq, Clone, Copy)]
-pub enum SignatureHelpInvoked {
-    Manual,
-    Automatic,
-}
-
 pub fn signature_help(cx: &mut Context) {
-    signature_help_impl(cx, SignatureHelpInvoked::Manual)
-}
-
-pub fn signature_help_impl(cx: &mut Context, invoked: SignatureHelpInvoked) {
-    let (view, doc) = current!(cx.editor);
-
-    // TODO merge multiple language server signature help into one instead of just taking the first language server that supports it
-    let future = doc
-        .language_servers_with_feature(LanguageServerFeature::SignatureHelp)
-        .find_map(|language_server| {
-            let pos = doc.position(view.id, language_server.offset_encoding());
-            language_server.text_document_signature_help(doc.identifier(), pos, None)
-        });
-
-    let Some(future) = future else {
-        // Do not show the message if signature help was invoked
-        // automatically on backspace, trigger characters, etc.
-        if invoked == SignatureHelpInvoked::Manual {
     cx.editor
-                .set_error("No configured language server supports signature-help");
-        }
-        return;
-    };
-    signature_help_impl_with_future(cx, future.boxed(), invoked);
-}
-
-pub fn signature_help_impl_with_future(
-    cx: &mut Context,
-    future: BoxFuture<'static, helix_lsp::Result<Value>>,
-    invoked: SignatureHelpInvoked,
-) {
-    cx.callback(
-        future,
-        move |editor, compositor, response: Option<lsp::SignatureHelp>| {
-            let config = &editor.config();
-
-            if !(config.lsp.auto_signature_help
-                || SignatureHelp::visible_popup(compositor).is_some()
-                || invoked == SignatureHelpInvoked::Manual)
-            {
-                return;
-            }
-
-            // If the signature help invocation is automatic, don't show it outside of Insert Mode:
-            // it very probably means the server was a little slow to respond and the user has
-            // already moved on to something else, making a signature help popup will just be an
-            // annoyance, see https://github.com/helix-editor/helix/issues/3112
-            if invoked == SignatureHelpInvoked::Automatic && editor.mode != Mode::Insert {
-                return;
-            }
-
-            let response = match response {
-                // According to the spec the response should be None if there
-                // are no signatures, but some servers don't follow this.
-                Some(s) if !s.signatures.is_empty() => s,
-                _ => {
-                    compositor.remove(SignatureHelp::ID);
-                    return;
-                }
-            };
-            let doc = doc!(editor);
-            let language = doc.language_name().unwrap_or("");
-
-            let signature = match response
-                .signatures
-                .get(response.active_signature.unwrap_or(0) as usize)
-            {
-                Some(s) => s,
-                None => return,
-            };
-            let mut contents = SignatureHelp::new(
-                signature.label.clone(),
-                language.to_string(),
-                Arc::clone(&editor.syn_loader),
-            );
-
-            let signature_doc = if config.lsp.display_signature_help_docs {
-                signature.documentation.as_ref().map(|doc| match doc {
-                    lsp::Documentation::String(s) => s.clone(),
-                    lsp::Documentation::MarkupContent(markup) => markup.value.clone(),
-                })
-            } else {
-                None
-            };
-
-            contents.set_signature_doc(signature_doc);
-
-            let active_param_range = || -> Option<(usize, usize)> {
-                let param_idx = signature
-                    .active_parameter
-                    .or(response.active_parameter)
-                    .unwrap_or(0) as usize;
-                let param = signature.parameters.as_ref()?.get(param_idx)?;
-                match &param.label {
-                    lsp::ParameterLabel::Simple(string) => {
-                        let start = signature.label.find(string.as_str())?;
-                        Some((start, start + string.len()))
-                    }
-                    lsp::ParameterLabel::LabelOffsets([start, end]) => {
-                        // LS sends offsets based on utf-16 based string representation
-                        // but highlighting in helix is done using byte offset.
-                        use helix_core::str_utils::char_to_byte_idx;
-                        let from = char_to_byte_idx(&signature.label, *start as usize);
-                        let to = char_to_byte_idx(&signature.label, *end as usize);
-                        Some((from, to))
-                    }
-                }
-            };
-            contents.set_active_param_range(active_param_range());
-
-            let old_popup = compositor.find_id::<Popup<SignatureHelp>>(SignatureHelp::ID);
-            let mut popup = Popup::new(SignatureHelp::ID, contents)
-                .position(old_popup.and_then(|p| p.get_position()))
-                .position_bias(Open::Above)
-                .ignore_escape_key(true);
-
-            // Don't create a popup if it intersects the auto-complete menu.
-            let size = compositor.size();
-            if compositor
-                .find::<ui::EditorView>()
-                .unwrap()
-                .completion
-                .as_mut()
-                .map(|completion| completion.area(size, editor))
-                .filter(|area| area.intersects(popup.area(size, editor)))
-                .is_some()
-            {
-                return;
-            }
-
-            compositor.replace_or_push(SignatureHelp::ID, popup);
-        },
-    );
+        .handlers
+        .trigger_signature_help(SignatureHelpInvoked::Manual, cx.editor)
 }
 
 pub fn hover(cx: &mut Context) {

helix-term/src/events.rs

@@ -0,0 +1,20 @@
+use helix_event::{events, register_event};
+use helix_view::document::Mode;
+use helix_view::events::{DocumentDidChange, SelectionDidChange};
+
+use crate::commands;
+use crate::keymap::MappableCommand;
+
+events! {
+    OnModeSwitch<'a, 'cx> { old_mode: Mode, new_mode: Mode, cx: &'a mut commands::Context<'cx> }
+    PostInsertChar<'a, 'cx> { c: char, cx: &'a mut commands::Context<'cx> }
+    PostCommand<'a, 'cx> { command: & 'a MappableCommand, cx: &'a mut commands::Context<'cx> }
+}
+
+pub fn register() {
+    register_event::<OnModeSwitch>();
+    register_event::<PostInsertChar>();
+    register_event::<PostCommand>();
+    register_event::<DocumentDidChange>();
+    register_event::<SelectionDidChange>();
+}

helix-term/src/handlers.rs

@@ -0,0 +1,40 @@
+use std::sync::Arc;
+
+use arc_swap::ArcSwap;
+use helix_core::RopeSlice;
+use helix_event::AsyncHook;
+
+use crate::config::Config;
+use crate::events;
+use crate::handlers::completion::CompletionHandler;
+use crate::handlers::signature_help::SignatureHelpHandler;
+
+pub use completion::trigger_auto_completion;
+pub use helix_view::handlers::lsp::SignatureHelpInvoked;
+pub use helix_view::handlers::Handlers;
+
+fn rope_ends_with(text: &str, rope: RopeSlice<'_>) -> bool {
+    let len = rope.len_bytes();
+    if len < text.len() {
+        return false;
+    }
+    rope.get_byte_slice(len - text.len()..)
+        .map_or(false, |end| end == text)
+}
+
+mod completion;
+mod signature_help;
+
+pub fn setup(config: Arc<ArcSwap<Config>>) -> Handlers {
+    events::register();
+
+    let completions = CompletionHandler::new(config).spawn();
+    let signature_hints = SignatureHelpHandler::new().spawn();
+    let handlers = Handlers {
+        completions,
+        signature_hints,
+    };
+    completion::register_hooks(&handlers);
+    signature_help::register_hooks(&handlers);
+    handlers
+}

helix-term/src/handlers/completion.rs

@@ -0,0 +1,465 @@
+use std::collections::HashSet;
+use std::sync::Arc;
+use std::time::Duration;
+
+use arc_swap::ArcSwap;
+use futures_util::stream::FuturesUnordered;
+use helix_core::chars::char_is_word;
+use helix_core::syntax::LanguageServerFeature;
+use helix_event::{
+    cancelable_future, cancelation, register_hook, send_blocking, CancelRx, CancelTx,
+};
+use helix_lsp::lsp;
+use helix_lsp::util::pos_to_lsp_pos;
+use helix_view::document::{Mode, SavePoint};
+use helix_view::handlers::lsp::CompletionEvent;
+use helix_view::{DocumentId, Editor, ViewId};
+use tokio::sync::mpsc::Sender;
+use tokio::time::Instant;
+use tokio_stream::StreamExt;
+
+use crate::commands;
+use crate::compositor::Compositor;
+use crate::config::Config;
+use crate::events::{OnModeSwitch, PostCommand, PostInsertChar};
+use crate::handlers::rope_ends_with;
+use crate::job::{dispatch, dispatch_blocking};
+use crate::keymap::MappableCommand;
+use crate::ui::editor::InsertEvent;
+use crate::ui::lsp::SignatureHelp;
+use crate::ui::{self, CompletionItem, Popup};
+
+use super::Handlers;
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+enum TriggerKind {
+    Auto,
+    TriggerChar,
+    Manual,
+}
+
+#[derive(Debug, Clone, Copy)]
+struct Trigger {
+    pos: usize,
+    view: ViewId,
+    doc: DocumentId,
+    kind: TriggerKind,
+}
+
+#[derive(Debug)]
+pub(super) struct CompletionHandler {
+    /// currently active trigger which will cause a
+    /// completion request after the timeout
+    trigger: Option<Trigger>,
+    /// A handle for currently active completion request.
+    /// This can be used to determine whether the current
+    /// request is still active (and new triggers should be
+    /// ignored) and can also be used to abort the current
+    /// request (by dropping the handle)
+    request: Option<CancelTx>,
+    config: Arc<ArcSwap<Config>>,
+}
+
+impl CompletionHandler {
+    pub fn new(config: Arc<ArcSwap<Config>>) -> CompletionHandler {
+        Self {
+            config,
+            request: None,
+            trigger: None,
+        }
+    }
+}
+
+impl helix_event::AsyncHook for CompletionHandler {
+    type Event = CompletionEvent;
+
+    fn handle_event(
+        &mut self,
+        event: Self::Event,
+        _old_timeout: Option<Instant>,
+    ) -> Option<Instant> {
+        match event {
+            CompletionEvent::AutoTrigger {
+                cursor: trigger_pos,
+                doc,
+                view,
+            } => {
+                // techically it shouldn't be possible to switch views/documents in insert mode
+                // but peoble may create weird keymaps/use the mouse so lets be extra careful
+                if self
+                    .trigger
+                    .as_ref()
+                    .map_or(true, |trigger| trigger.doc != doc || trigger.view != view)
+                {
+                    self.trigger = Some(Trigger {
+                        pos: trigger_pos,
+                        view,
+                        doc,
+                        kind: TriggerKind::Auto,
+                    });
+                }
+            }
+            CompletionEvent::TriggerChar { cursor, doc, view } => {
+                // immediately request completions and drop all auto completion requests
+                self.request = None;
+                self.trigger = Some(Trigger {
+                    pos: cursor,
+                    view,
+                    doc,
+                    kind: TriggerKind::TriggerChar,
+                });
+                // stop debouncing immidietly and request the completion
+                self.finish_debounce();
+                return None;
+            }
+            CompletionEvent::ManualTrigger { cursor, doc, view } => {
+                // immediately request completions and drop all auto completion requests
+                self.request = None;
+                self.trigger = Some(Trigger {
+                    pos: cursor,
+                    view,
+                    doc,
+                    kind: TriggerKind::Manual,
+                });
+                // stop debouncing immidietly and request the completion
+                self.finish_debounce();
+                return None;
+            }
+            CompletionEvent::Cancel => {
+                self.trigger = None;
+                self.request = None;
+            }
+            CompletionEvent::DeleteText { cursor } => {
+                // if we deleted the original trigger, abort the completion
+                if matches!(self.trigger, Some(Trigger{ pos, .. }) if cursor < pos) {
+                    self.trigger = None;
+                    self.request = None;
+                }
+            }
+        }
+        self.trigger.map(|trigger| {
+            // if the current request was closed forget about it
+            // otherwise immediately restart the completion request
+            let canceled = self.request.take().map_or(false, |req| !req.is_closed());
+            let timeout = if trigger.kind == TriggerKind::Auto && !canceled {
+                self.config.load().editor.completion_timeout
+            } else {
+                // we want almost instant completions for trigger chars
+                // and restarting completion requests. The small timeout here mainly
+                // serves to better handle cases where the completion handler
+                // may fall behind (so multiple events in the channel) and macros
+                Duration::from_millis(5)
+            };
+            Instant::now() + timeout
+        })
+    }
+
+    fn finish_debounce(&mut self) {
+        let trigger = self.trigger.take().expect("debounce always has a trigger");
+        let (tx, rx) = cancelation();
+        self.request = Some(tx);
+        dispatch_blocking(move |editor, compositor| {
+            request_completion(trigger, rx, editor, compositor)
+        });
+    }
+}
+
+fn request_completion(
+    mut trigger: Trigger,
+    cancel: CancelRx,
+    editor: &mut Editor,
+    compositor: &mut Compositor,
+) {
+    let (view, doc) = current!(editor);
+
+    if compositor
+        .find::<ui::EditorView>()
+        .unwrap()
+        .completion
+        .is_some()
+        || editor.mode != Mode::Insert
+    {
+        return;
+    }
+
+    let text = doc.text();
+    let cursor = doc.selection(view.id).primary().cursor(text.slice(..));
+    if trigger.view != view.id || trigger.doc != doc.id() || cursor < trigger.pos {
+        return;
+    }
+    // this looks odd... Why are we not using the trigger position from
+    // the `trigger` here? Won't that mean that the trigger char doesn't get
+    // send to the LS if we type fast enougn? Yes that is true but it's
+    // not actually a problem. The LSP will resolve the completion to the identifier
+    // anyway (in fact sending the later position is necessary to get the right results
+    // from LSPs that provide incomplete completion list). We rely on trigger offset
+    // and primary cursor matching for multi-cursor completions so this is definitely
+    // necessary from our side too.
+    trigger.pos = cursor;
+    let trigger_text = text.slice(..cursor);
+
+    let mut seen_language_servers = HashSet::new();
+    let mut futures: FuturesUnordered<_> = doc
+        .language_servers_with_feature(LanguageServerFeature::Completion)
+        .filter(|ls| seen_language_servers.insert(ls.id()))
+        .map(|ls| {
+            let language_server_id = ls.id();
+            let offset_encoding = ls.offset_encoding();
+            let pos = pos_to_lsp_pos(text, cursor, offset_encoding);
+            let doc_id = doc.identifier();
+            let context = if trigger.kind == TriggerKind::Manual {
+                lsp::CompletionContext {
+                    trigger_kind: lsp::CompletionTriggerKind::INVOKED,
+                    trigger_character: None,
+                }
+            } else {
+                let trigger_char =
+                    ls.capabilities()
+                        .completion_provider
+                        .as_ref()
+                        .and_then(|provider| {
+                            provider
+                                .trigger_characters
+                                .as_deref()?
+                                .iter()
+                                .find(|&trigger| rope_ends_with(trigger, trigger_text))
+                        });
+                lsp::CompletionContext {
+                    trigger_kind: lsp::CompletionTriggerKind::TRIGGER_CHARACTER,
+                    trigger_character: trigger_char.cloned(),
+                }
+            };
+
+            let completion_response = ls.completion(doc_id, pos, None, context).unwrap();
+            async move {
+                let json = completion_response.await?;
+                let response: Option<lsp::CompletionResponse> = serde_json::from_value(json)?;
+                let items = match response {
+                    Some(lsp::CompletionResponse::Array(items)) => items,
+                    // TODO: do something with is_incomplete
+                    Some(lsp::CompletionResponse::List(lsp::CompletionList {
+                        is_incomplete: _is_incomplete,
+                        items,
+                    })) => items,
+                    None => Vec::new(),
+                }
+                .into_iter()
+                .map(|item| CompletionItem {
+                    item,
+                    language_server_id,
+                    resolved: false,
+                })
+                .collect();
+                anyhow::Ok(items)
+            }
+        })
+        .collect();
+
+    let future = async move {
+        let mut items = Vec::new();
+        while let Some(lsp_items) = futures.next().await {
+            match lsp_items {
+                Ok(mut lsp_items) => items.append(&mut lsp_items),
+                Err(err) => {
+                    log::debug!("completion request failed: {err:?}");
+                }
+            };
+        }
+        items
+    };
+
+    let savepoint = doc.savepoint(view);
+
+    let ui = compositor.find::<ui::EditorView>().unwrap();
+    ui.last_insert.1.push(InsertEvent::RequestCompletion);
+    tokio::spawn(async move {
+        let items = cancelable_future(future, cancel).await.unwrap_or_default();
+        if items.is_empty() {
+            return;
+        }
+        dispatch(move |editor, compositor| {
+            show_completion(editor, compositor, items, trigger, savepoint)
+        })
+        .await
+    });
+}
+
+fn show_completion(
+    editor: &mut Editor,
+    compositor: &mut Compositor,
+    items: Vec<CompletionItem>,
+    trigger: Trigger,
+    savepoint: Arc<SavePoint>,
+) {
+    let (view, doc) = current_ref!(editor);
+    // check if the completion request is stale.
+    //
+    // Completions are completed asynchronously and therefore the user could
+    //switch document/view or leave insert mode. In all of thoise cases the
+    // completion should be discarded
+    if editor.mode != Mode::Insert || view.id != trigger.view || doc.id() != trigger.doc {
+        return;
+    }
+
+    let size = compositor.size();
+    let ui = compositor.find::<ui::EditorView>().unwrap();
+    if ui.completion.is_some() {
+        return;
+    }
+
+    let completion_area = ui.set_completion(editor, savepoint, items, trigger.pos, size);
+    let signature_help_area = compositor
+        .find_id::<Popup<SignatureHelp>>(SignatureHelp::ID)
+        .map(|signature_help| signature_help.area(size, editor));
+    // Delete the signature help popup if they intersect.
+    if matches!((completion_area, signature_help_area),(Some(a), Some(b)) if a.intersects(b)) {
+        compositor.remove(SignatureHelp::ID);
+    }
+}
+
+pub fn trigger_auto_completion(
+    tx: &Sender<CompletionEvent>,
+    editor: &Editor,
+    trigger_char_only: bool,
+) {
+    let config = editor.config.load();
+    if config.auto_completion {
+        let (view, doc): (&helix_view::View, &helix_view::Document) = current_ref!(editor);
+        let mut text = doc.text().slice(..);
+        let cursor = doc.selection(view.id).primary().cursor(text);
+        text = doc.text().slice(..cursor);
+
+        let is_trigger_char = doc
+            .language_servers_with_feature(LanguageServerFeature::Completion)
+            .any(|ls| {
+                matches!(&ls.capabilities().completion_provider, Some(lsp::CompletionOptions {
+                        trigger_characters: Some(triggers),
+                        ..
+                    }) if triggers.iter().any(|trigger| rope_ends_with(trigger, text)))
+            });
+        if is_trigger_char {
+            send_blocking(
+                tx,
+                CompletionEvent::TriggerChar {
+                    cursor,
+                    doc: doc.id(),
+                    view: view.id,
+                },
+            );
+            return;
+        }
+
+        let is_auto_trigger = !trigger_char_only
+            && doc
+                .text()
+                .chars_at(cursor)
+                .reversed()
+                .take(config.completion_trigger_len as usize)
+                .all(char_is_word);
+
+        if is_auto_trigger {
+            send_blocking(
+                tx,
+                CompletionEvent::AutoTrigger {
+                    cursor,
+                    doc: doc.id(),
+                    view: view.id,
+                },
+            );
+        }
+    }
+}
+
+fn update_completions(cx: &mut commands::Context, c: Option<char>) {
+    cx.callback.push(Box::new(move |compositor, cx| {
+        let editor_view = compositor.find::<ui::EditorView>().unwrap();
+        if let Some(completion) = &mut editor_view.completion {
+            completion.update_filter(c);
+            if completion.is_empty() {
+                editor_view.clear_completion(cx.editor);
+                // clearing completions might mean we want to immediately rerequest them (usually
+                // this occurs if typing a trigger char)
+                if c.is_some() {
+                    trigger_auto_completion(&cx.editor.handlers.completions, cx.editor, false);
+                }
+            }
+        }
+    }))
+}
+
+fn clear_completions(cx: &mut commands::Context) {
+    cx.callback.push(Box::new(|compositor, cx| {
+        let editor_view = compositor.find::<ui::EditorView>().unwrap();
+        editor_view.clear_completion(cx.editor);
+    }))
+}
+
+fn completion_post_command_hook(
+    tx: &Sender<CompletionEvent>,
+    PostCommand { command, cx }: &mut PostCommand<'_, '_>,
+) -> anyhow::Result<()> {
+    if cx.editor.mode == Mode::Insert {
+        if cx.editor.last_completion.is_some() {
+            match command {
+                MappableCommand::Static {
+                    name: "delete_word_forward" | "delete_char_forward" | "completion",
+                    ..
+                } => (),
+                MappableCommand::Static {
+                    name: "delete_char_backward",
+                    ..
+                } => update_completions(cx, None),
+                _ => clear_completions(cx),
+            }
+        } else {
+            let event = match command {
+                MappableCommand::Static {
+                    name: "delete_char_backward" | "delete_word_forward" | "delete_char_forward",
+                    ..
+                } => {
+                    let (view, doc) = current!(cx.editor);
+                    let primary_cursor = doc
+                        .selection(view.id)
+                        .primary()
+                        .cursor(doc.text().slice(..));
+                    CompletionEvent::DeleteText {
+                        cursor: primary_cursor,
+                    }
+                }
+                // if we cancel completions here it would always cancel the manual request
+                MappableCommand::Static {
+                    name: "completion", ..
+                } => return Ok(()),
+                _ => CompletionEvent::Cancel,
+            };
+            send_blocking(tx, event);
+        }
+    }
+    Ok(())
+}
+
+pub(super) fn register_hooks(handlers: &Handlers) {
+    let tx = handlers.completions.clone();
+    register_hook!(move |event: &mut PostCommand<'_, '_>| completion_post_command_hook(&tx, event));
+
+    let tx = handlers.completions.clone();
+    register_hook!(move |event: &mut OnModeSwitch<'_, '_>| {
+        if event.old_mode == Mode::Insert {
+            send_blocking(&tx, CompletionEvent::Cancel);
+            clear_completions(event.cx);
+        } else if event.new_mode == Mode::Insert {
+            trigger_auto_completion(&tx, event.cx.editor, false)
+        }
+        Ok(())
+    });
+
+    let tx = handlers.completions.clone();
+    register_hook!(move |event: &mut PostInsertChar<'_, '_>| {
+        if event.cx.editor.last_completion.is_some() {
+            update_completions(event.cx, Some(event.c))
+        } else {
+            trigger_auto_completion(&tx, event.cx.editor, false);
+        }
+        Ok(())
+    });
+}

helix-term/src/handlers/signature_help.rs

@@ -0,0 +1,334 @@
+use std::sync::Arc;
+use std::time::Duration;
+
+use helix_core::syntax::LanguageServerFeature;
+use helix_event::{
+    cancelable_future, cancelation, register_hook, send_blocking, CancelRx, CancelTx,
+};
+use helix_lsp::lsp;
+use helix_view::document::Mode;
+use helix_view::events::{DocumentDidChange, SelectionDidChange};
+use helix_view::handlers::lsp::{SignatureHelpEvent, SignatureHelpInvoked};
+use helix_view::Editor;
+use tokio::sync::mpsc::Sender;
+use tokio::time::Instant;
+
+use crate::commands::Open;
+use crate::compositor::Compositor;
+use crate::events::{OnModeSwitch, PostInsertChar};
+use crate::handlers::{rope_ends_with, Handlers};
+use crate::ui::lsp::SignatureHelp;
+use crate::ui::Popup;
+use crate::{job, ui};
+
+#[derive(Debug)]
+enum State {
+    Open,
+    Closed,
+    Pending { request: CancelTx },
+}
+
+/// debounce timeout in ms, value taken from VSCode
+/// TODO: make this configurable?
+const TIMEOUT: u64 = 120;
+
+#[derive(Debug)]
+pub(super) struct SignatureHelpHandler {
+    trigger: Option<SignatureHelpInvoked>,
+    state: State,
+}
+
+impl SignatureHelpHandler {
+    pub fn new() -> SignatureHelpHandler {
+        SignatureHelpHandler {
+            trigger: None,
+            state: State::Closed,
+        }
+    }
+}
+
+impl helix_event::AsyncHook for SignatureHelpHandler {
+    type Event = SignatureHelpEvent;
+
+    fn handle_event(
+        &mut self,
+        event: Self::Event,
+        timeout: Option<tokio::time::Instant>,
+    ) -> Option<Instant> {
+        match event {
+            SignatureHelpEvent::Invoked => {
+                self.trigger = Some(SignatureHelpInvoked::Manual);
+                self.state = State::Closed;
+                self.finish_debounce();
+                return None;
+            }
+            SignatureHelpEvent::Trigger => {}
+            SignatureHelpEvent::ReTrigger => {
+                // don't retrigger if we aren't open/pending yet
+                if matches!(self.state, State::Closed) {
+                    return timeout;
+                }
+            }
+            SignatureHelpEvent::Cancel => {
+                self.state = State::Closed;
+                return None;
+            }
+            SignatureHelpEvent::RequestComplete { open } => {
+                // don't cancel rerequest that was already triggered
+                if let State::Pending { request } = &self.state {
+                    if !request.is_closed() {
+                        return timeout;
+                    }
+                }
+                self.state = if open { State::Open } else { State::Closed };
+                return timeout;
+            }
+        }
+        if self.trigger.is_none() {
+            self.trigger = Some(SignatureHelpInvoked::Automatic)
+        }
+        Some(Instant::now() + Duration::from_millis(TIMEOUT))
+    }
+
+    fn finish_debounce(&mut self) {
+        let invocation = self.trigger.take().unwrap();
+        let (tx, rx) = cancelation();
+        self.state = State::Pending { request: tx };
+        job::dispatch_blocking(move |editor, _| request_signature_help(editor, invocation, rx))
+    }
+}
+
+pub fn request_signature_help(
+    editor: &mut Editor,
+    invoked: SignatureHelpInvoked,
+    cancel: CancelRx,
+) {
+    let (view, doc) = current!(editor);
+
+    // TODO merge multiple language server signature help into one instead of just taking the first language server that supports it
+    let future = doc
+        .language_servers_with_feature(LanguageServerFeature::SignatureHelp)
+        .find_map(|language_server| {
+            let pos = doc.position(view.id, language_server.offset_encoding());
+            language_server.text_document_signature_help(doc.identifier(), pos, None)
+        });
+
+    let Some(future) = future else {
+        // Do not show the message if signature help was invoked
+        // automatically on backspace, trigger characters, etc.
+        if invoked == SignatureHelpInvoked::Manual {
+            editor
+                .set_error("No configured language server supports signature-help");
+        }
+        return;
+    };
+
+    tokio::spawn(async move {
+        match cancelable_future(future, cancel).await {
+            Some(Ok(res)) => {
+                job::dispatch(move |editor, compositor| {
+                    show_signature_help(editor, compositor, invoked, res)
+                })
+                .await
+            }
+            Some(Err(err)) => log::error!("signature help request failed: {err}"),
+            None => (),
+        }
+    });
+}
+
+pub fn show_signature_help(
+    editor: &mut Editor,
+    compositor: &mut Compositor,
+    invoked: SignatureHelpInvoked,
+    response: Option<lsp::SignatureHelp>,
+) {
+    let config = &editor.config();
+
+    if !(config.lsp.auto_signature_help
+        || SignatureHelp::visible_popup(compositor).is_some()
+        || invoked == SignatureHelpInvoked::Manual)
+    {
+        return;
+    }
+
+    // If the signature help invocation is automatic, don't show it outside of Insert Mode:
+    // it very probably means the server was a little slow to respond and the user has
+    // already moved on to something else, making a signature help popup will just be an
+    // annoyance, see https://github.com/helix-editor/helix/issues/3112
+    // For the most part this should not be needed as the request gets canceled automatically now
+    // but its technically possible for the mode change to just preempt this callback so better safe than sorry
+    if invoked == SignatureHelpInvoked::Automatic && editor.mode != Mode::Insert {
+        return;
+    }
+
+    let response = match response {
+        // According to the spec the response should be None if there
+        // are no signatures, but some servers don't follow this.
+        Some(s) if !s.signatures.is_empty() => s,
+        _ => {
+            send_blocking(
+                &editor.handlers.signature_hints,
+                SignatureHelpEvent::RequestComplete { open: false },
+            );
+            compositor.remove(SignatureHelp::ID);
+            return;
+        }
+    };
+    send_blocking(
+        &editor.handlers.signature_hints,
+        SignatureHelpEvent::RequestComplete { open: true },
+    );
+
+    let doc = doc!(editor);
+    let language = doc.language_name().unwrap_or("");
+
+    let signature = match response
+        .signatures
+        .get(response.active_signature.unwrap_or(0) as usize)
+    {
+        Some(s) => s,
+        None => return,
+    };
+    let mut contents = SignatureHelp::new(
+        signature.label.clone(),
+        language.to_string(),
+        Arc::clone(&editor.syn_loader),
+    );
+
+    let signature_doc = if config.lsp.display_signature_help_docs {
+        signature.documentation.as_ref().map(|doc| match doc {
+            lsp::Documentation::String(s) => s.clone(),
+            lsp::Documentation::MarkupContent(markup) => markup.value.clone(),
+        })
+    } else {
+        None
+    };
+
+    contents.set_signature_doc(signature_doc);
+
+    let active_param_range = || -> Option<(usize, usize)> {
+        let param_idx = signature
+            .active_parameter
+            .or(response.active_parameter)
+            .unwrap_or(0) as usize;
+        let param = signature.parameters.as_ref()?.get(param_idx)?;
+        match &param.label {
+            lsp::ParameterLabel::Simple(string) => {
+                let start = signature.label.find(string.as_str())?;
+                Some((start, start + string.len()))
+            }
+            lsp::ParameterLabel::LabelOffsets([start, end]) => {
+                // LS sends offsets based on utf-16 based string representation
+                // but highlighting in helix is done using byte offset.
+                use helix_core::str_utils::char_to_byte_idx;
+                let from = char_to_byte_idx(&signature.label, *start as usize);
+                let to = char_to_byte_idx(&signature.label, *end as usize);
+                Some((from, to))
+            }
+        }
+    };
+    contents.set_active_param_range(active_param_range());
+
+    let old_popup = compositor.find_id::<Popup<SignatureHelp>>(SignatureHelp::ID);
+    let mut popup = Popup::new(SignatureHelp::ID, contents)
+        .position(old_popup.and_then(|p| p.get_position()))
+        .position_bias(Open::Above)
+        .ignore_escape_key(true);
+
+    // Don't create a popup if it intersects the auto-complete menu.
+    let size = compositor.size();
+    if compositor
+        .find::<ui::EditorView>()
+        .unwrap()
+        .completion
+        .as_mut()
+        .map(|completion| completion.area(size, editor))
+        .filter(|area| area.intersects(popup.area(size, editor)))
+        .is_some()
+    {
+        return;
+    }
+
+    compositor.replace_or_push(SignatureHelp::ID, popup);
+}
+
+fn signature_help_post_insert_char_hook(
+    tx: &Sender<SignatureHelpEvent>,
+    PostInsertChar { cx, .. }: &mut PostInsertChar<'_, '_>,
+) -> anyhow::Result<()> {
+    if !cx.editor.config().lsp.auto_signature_help {
+        return Ok(());
+    }
+    let (view, doc) = current!(cx.editor);
+    // TODO support multiple language servers (not just the first that is found), likely by merging UI somehow
+    let Some(language_server) = doc
+            .language_servers_with_feature(LanguageServerFeature::SignatureHelp)
+            .next()
+        else {
+            return Ok(());
+        };
+
+    let capabilities = language_server.capabilities();
+
+    if let lsp::ServerCapabilities {
+        signature_help_provider:
+            Some(lsp::SignatureHelpOptions {
+                trigger_characters: Some(triggers),
+                // TODO: retrigger_characters
+                ..
+            }),
+        ..
+    } = capabilities
+    {
+        let mut text = doc.text().slice(..);
+        let cursor = doc.selection(view.id).primary().cursor(text);
+        text = text.slice(..cursor);
+        if triggers.iter().any(|trigger| rope_ends_with(trigger, text)) {
+            send_blocking(tx, SignatureHelpEvent::Trigger)
+        }
+    }
+    Ok(())
+}
+
+pub(super) fn register_hooks(handlers: &Handlers) {
+    let tx = handlers.signature_hints.clone();
+    register_hook!(move |event: &mut OnModeSwitch<'_, '_>| {
+        match (event.old_mode, event.new_mode) {
+            (Mode::Insert, _) => {
+                send_blocking(&tx, SignatureHelpEvent::Cancel);
+                event.cx.callback.push(Box::new(|compositor, _| {
+                    compositor.remove(SignatureHelp::ID);
+                }));
+            }
+            (_, Mode::Insert) => {
+                if event.cx.editor.config().lsp.auto_signature_help {
+                    send_blocking(&tx, SignatureHelpEvent::Trigger);
+                }
+            }
+            _ => (),
+        }
+        Ok(())
+    });
+
+    let tx = handlers.signature_hints.clone();
+    register_hook!(
+        move |event: &mut PostInsertChar<'_, '_>| signature_help_post_insert_char_hook(&tx, event)
+    );
+
+    let tx = handlers.signature_hints.clone();
+    register_hook!(move |event: &mut DocumentDidChange<'_>| {
+        if event.doc.config.load().lsp.auto_signature_help {
+            send_blocking(&tx, SignatureHelpEvent::ReTrigger);
+        }
+        Ok(())
+    });
+
+    let tx = handlers.signature_hints.clone();
+    register_hook!(move |event: &mut SelectionDidChange<'_>| {
+        if event.doc.config.load().lsp.auto_signature_help {
+            send_blocking(&tx, SignatureHelpEvent::ReTrigger);
+        }
+        Ok(())
+    });
+}

helix-term/src/job.rs

@@ -1,15 +1,39 @@
+use helix_event::status::StatusMessage;
+use helix_event::{runtime_local, send_blocking};
 use helix_view::Editor;
+use once_cell::sync::OnceCell;
 
 use crate::compositor::Compositor;
 
-use futures_util::future::{BoxFuture, Future, FutureExt, LocalBoxFuture};
-use futures_util::stream::{FuturesOrdered, FuturesUnordered, StreamExt};
+use futures_util::future::LocalBoxFuture;
+use futures_util::future::{BoxFuture, Future, FutureExt};
+use futures_util::stream::{FuturesUnordered, StreamExt};
+use tokio::sync::mpsc::{channel, Receiver, Sender};
 
 pub type EditorCompositorCallback = Box<dyn FnOnce(&mut Editor, &mut Compositor) + Send>;
 pub type EditorCallback = Box<dyn FnOnce(&mut Editor) + Send>;
 
 pub type ThreadLocalEditorCompositorCallback =
     Box<dyn FnOnce(&mut Editor, &mut Compositor, &mut Jobs)>;
+runtime_local! {
+    static JOB_QUEUE: OnceCell<Sender<Callback>> = OnceCell::new();
+}
+
+pub async fn dispatch_callback(job: Callback) {
+    let _ = JOB_QUEUE.wait().send(job).await;
+}
+
+pub async fn dispatch(job: impl FnOnce(&mut Editor, &mut Compositor) + Send + 'static) {
+    let _ = JOB_QUEUE
+        .wait()
+        .send(Callback::EditorCompositor(Box::new(job)))
+        .await;
+}
+
+pub fn dispatch_blocking(job: impl FnOnce(&mut Editor, &mut Compositor) + Send + 'static) {
+    let jobs = JOB_QUEUE.wait();
+    send_blocking(jobs, Callback::EditorCompositor(Box::new(job)))
+}
 
 pub enum Callback {
     EditorCompositor(EditorCompositorCallback),
@@ -27,13 +51,13 @@ pub struct Job {
 pub type ThreadLocalJob =
     LocalBoxFuture<'static, anyhow::Result<Option<ThreadLocalEditorCompositorCallback>>>;
 
-#[derive(Default)]
 pub struct Jobs {
-    pub futures: FuturesUnordered<JobFuture>,
-    /// These are the ones that need to complete before we exit.
+    /// jobs the ones that need to complete before we exit.
     pub wait_futures: FuturesUnordered<JobFuture>,
 
     pub local_futures: FuturesUnordered<ThreadLocalJob>,
+    pub callbacks: Receiver<Callback>,
+    pub status_messages: Receiver<StatusMessage>,
 }
 
 impl Job {
@@ -60,8 +84,17 @@ impl Job {
 }
 
 impl Jobs {
+    #[allow(clippy::new_without_default)]
     pub fn new() -> Self {
-        Self::default()
+        let (tx, rx) = channel(1024);
+        let _ = JOB_QUEUE.set(tx);
+        let status_messages = helix_event::status::setup();
+        Self {
+            wait_futures: FuturesUnordered::new(),
+            local_futures: FuturesUnordered::new(),
+            callbacks: rx,
+            status_messages,
+        }
     }
 
     pub fn spawn<F: Future<Output = anyhow::Result<()>> + Send + 'static>(&mut self, f: F) {
@@ -118,18 +151,24 @@ impl Jobs {
         }
     }
 
-    pub async fn next_job(&mut self) -> Option<anyhow::Result<Option<Callback>>> {
-        tokio::select! {
-            event = self.futures.next() => {  event }
-            event = self.wait_futures.next() => { event }
-        }
-    }
+    // pub async fn next_job(&mut self) -> Option<anyhow::Result<Option<Callback>>> {
+    //     tokio::select! {
+    //         event = self.futures.next() => {  event }
+    //         event = self.wait_futures.next() => { event }
+    //     }
+    // }
 
     pub fn add(&self, j: Job) {
         if j.wait {
             self.wait_futures.push(j.future);
         } else {
-            self.futures.push(j.future);
+            tokio::spawn(async move {
+                match j.future.await {
+                    Ok(Some(cb)) => dispatch_callback(cb).await,
+                    Ok(None) => (),
+                    Err(err) => helix_event::status::report(err).await,
+                }
+            });
         }
     }
 

helix-term/src/lib.rs

@@ -6,12 +6,16 @@ pub mod args;
 pub mod commands;
 pub mod compositor;
 pub mod config;
+pub mod events;
 pub mod health;
 pub mod job;
 pub mod keymap;
 pub mod ui;
+
 use std::path::Path;
 
+mod handlers;
+
 use ignore::DirEntry;
 pub use keymap::macros::*;
 

helix-term/src/ui/completion.rs

@@ -1,7 +1,11 @@
-use crate::compositor::{Component, Context, Event, EventResult};
+use crate::{
+    compositor::{Component, Context, Event, EventResult},
+    handlers::trigger_auto_completion,
+};
 use helix_view::{
     document::SavePoint,
     editor::CompleteAction,
+    handlers::lsp::SignatureHelpInvoked,
     theme::{Modifier, Style},
     ViewId,
 };
@@ -9,7 +13,7 @@ use tui::{buffer::Buffer as Surface, text::Span};
 
 use std::{borrow::Cow, sync::Arc};
 
-use helix_core::{Change, Transaction};
+use helix_core::{chars, Change, Transaction};
 use helix_view::{graphics::Rect, Document, Editor};
 
 use crate::commands;
@@ -94,10 +98,9 @@ pub struct CompletionItem {
 /// Wraps a Menu.
 pub struct Completion {
     popup: Popup<Menu<CompletionItem>>,
-    start_offset: usize,
     #[allow(dead_code)]
     trigger_offset: usize,
-    // TODO: maintain a completioncontext with trigger kind & trigger char
+    filter: String,
 }
 
 impl Completion {
@@ -107,7 +110,6 @@ impl Completion {
         editor: &Editor,
         savepoint: Arc<SavePoint>,
         mut items: Vec<CompletionItem>,
-        start_offset: usize,
         trigger_offset: usize,
     ) -> Self {
         let preview_completion_insert = editor.config().preview_completion_insert;
@@ -245,7 +247,7 @@ impl Completion {
                     // (also without sending the transaction to the LS) *before any further transaction is applied*.
                     // Otherwise incremental sync breaks (since the state of the LS doesn't match the state the transaction
                     // is applied to).
-                    if editor.last_completion.is_none() {
+                    if matches!(editor.last_completion, Some(CompleteAction::Triggered)) {
                         editor.last_completion = Some(CompleteAction::Selected {
                             savepoint: doc.savepoint(view),
                         })
@@ -323,20 +325,46 @@ impl Completion {
                             doc.apply(&transaction, view.id);
                         }
                     }
+                    // we could have just inserted a trigger char (like a `crate::` completion for rust
+                    // so we want to retrigger immedietly when accepting a completion.
+                    trigger_auto_completion(&editor.handlers.completions, editor, true);
                 }
             };
+
+            // In case the popup was deleted because of an intersection w/ the auto-complete menu.
+            if event != PromptEvent::Update {
+                editor
+                    .handlers
+                    .trigger_signature_help(SignatureHelpInvoked::Automatic, editor);
+            }
         });
         let popup = Popup::new(Self::ID, menu)
             .with_scrollbar(false)
             .ignore_escape_key(true);
+        let (view, doc) = current_ref!(editor);
+        let text = doc.text().slice(..);
+        let cursor = doc.selection(view.id).primary().cursor(text);
+        let offset = text
+            .chars_at(cursor)
+            .reversed()
+            .take_while(|ch| chars::char_is_word(*ch))
+            .count();
+        let start_offset = cursor.saturating_sub(offset);
+
+        let fragment = doc.text().slice(start_offset..cursor);
         let mut completion = Self {
             popup,
-            start_offset,
             trigger_offset,
+            // TODO: expand nucleo api to allow moving straight to a Utf32String here
+            // and avoid allocation during matching
+            filter: String::from(fragment),
         };
 
         // need to recompute immediately in case start_offset != trigger_offset
-        completion.recompute_filter(editor);
+        completion
+            .popup
+            .contents_mut()
+            .score(&completion.filter, false);
 
         completion
     }
@@ -356,39 +384,22 @@ impl Completion {
         }
     }
 
-    pub fn recompute_filter(&mut self, editor: &Editor) {
+    /// Appends (`c: Some(c)`) or removes (`c: None`) a character to/from the filter
+    /// this should be called whenever the user types or deltes a character in insert mode.
+    pub fn update_filter(&mut self, c: Option<char>) {
         // recompute menu based on matches
         let menu = self.popup.contents_mut();
-        let (view, doc) = current_ref!(editor);
-
-        // cx.hooks()
-        // cx.add_hook(enum type,  ||)
-        // cx.trigger_hook(enum type, &str, ...) <-- there has to be enough to identify doc/view
-        // callback with editor & compositor
-        //
-        // trigger_hook sends event into channel, that's consumed in the global loop and
-        // triggers all registered callbacks
-        // TODO: hooks should get processed immediately so maybe do it after select!(), before
-        // looping?
-
-        let cursor = doc
-            .selection(view.id)
-            .primary()
-            .cursor(doc.text().slice(..));
-        if self.trigger_offset <= cursor {
-            let fragment = doc.text().slice(self.start_offset..cursor);
-            let text = Cow::from(fragment);
-            // TODO: logic is same as ui/picker
-            menu.score(&text);
-        } else {
-            // we backspaced before the start offset, clear the menu
-            // this will cause the editor to remove the completion popup
+        match c {
+            Some(c) => self.filter.push(c),
+            None => {
+                self.filter.pop();
+                if self.filter.is_empty() {
                     menu.clear();
+                    return;
                 }
             }
-
-    pub fn update(&mut self, cx: &mut commands::Context) {
-        self.recompute_filter(cx.editor)
+        }
+        menu.score(&self.filter, c.is_some());
     }
 
     pub fn is_empty(&self) -> bool {

helix-term/src/ui/editor.rs

@@ -1,7 +1,7 @@
 use crate::{
     commands::{self, engine::ScriptingEngine, OnKeyCallback},
     compositor::{Component, Context, Event, EventResult},
-    job::{self, Callback},
+    events::{OnModeSwitch, PostCommand},
     key,
     keymap::{KeymapResult, Keymaps},
     ui::{
@@ -33,8 +33,8 @@ use std::{mem::take, num::NonZeroUsize, path::PathBuf, rc::Rc, sync::Arc};
 
 use tui::{buffer::Buffer as Surface, text::Span};
 
+use super::document::LineDecoration;
 use super::{completion::CompletionItem, statusline};
-use super::{document::LineDecoration, lsp::SignatureHelp};
 
 pub struct EditorView {
     pub keymaps: Keymaps,
@@ -813,35 +813,26 @@ impl EditorView {
 
         let mut execute_command = |command: &commands::MappableCommand| {
             command.execute(cxt);
+            helix_event::dispatch(PostCommand { command, cx: cxt });
+
             let current_mode = cxt.editor.mode();
-            match (last_mode, current_mode) {
-                (Mode::Normal, Mode::Insert) => {
+            if current_mode != last_mode {
+                helix_event::dispatch(OnModeSwitch {
+                    old_mode: last_mode,
+                    new_mode: current_mode,
+                    cx: cxt,
+                });
+
                 // HAXX: if we just entered insert mode from normal, clear key buf
                 // and record the command that got us into this mode.
-
+                if current_mode == Mode::Insert {
                     // how we entered insert mode is important, and we should track that so
                     // we can repeat the side effect.
                     self.last_insert.0 = command.clone();
                     self.last_insert.1.clear();
+                }
+            }
 
-                    commands::signature_help_impl(cxt, commands::SignatureHelpInvoked::Automatic);
-                }
-                (Mode::Insert, Mode::Normal) => {
-                    // if exiting insert mode, remove completion
-                    self.clear_completion(cxt.editor);
-                    cxt.editor.completion_request_handle = None;
-
-                    // TODO: Use an on_mode_change hook to remove signature help
-                    cxt.jobs.callback(async {
-                        let call: job::Callback =
-                            Callback::EditorCompositor(Box::new(|_editor, compositor| {
-                                compositor.remove(SignatureHelp::ID);
-                            }));
-                        Ok(call)
-                    });
-                }
-                _ => (),
-            }
             last_mode = current_mode;
         };
 
@@ -969,12 +960,10 @@ impl EditorView {
         editor: &mut Editor,
         savepoint: Arc<SavePoint>,
         items: Vec<CompletionItem>,
-        start_offset: usize,
         trigger_offset: usize,
         size: Rect,
     ) -> Option<Rect> {
-        let mut completion =
-            Completion::new(editor, savepoint, items, start_offset, trigger_offset);
+        let mut completion = Completion::new(editor, savepoint, items, trigger_offset);
 
         if completion.is_empty() {
             // skip if we got no completion results
@@ -982,7 +971,7 @@ impl EditorView {
         }
 
         let area = completion.area(size, editor);
-        editor.last_completion = None;
+        editor.last_completion = Some(CompleteAction::Triggered);
         self.last_insert.1.push(InsertEvent::TriggerCompletion);
 
         // TODO : propagate required size on resize to completion too
@@ -995,6 +984,7 @@ impl EditorView {
         self.completion = None;
         if let Some(last_completion) = editor.last_completion.take() {
             match last_completion {
+                CompleteAction::Triggered => (),
                 CompleteAction::Applied {
                     trigger_offset,
                     changes,
@@ -1008,9 +998,6 @@ impl EditorView {
                 }
             }
         }
-
-        // Clear any savepoints
-        editor.clear_idle_timer(); // don't retrigger
     }
 
     pub fn handle_idle_timeout(&mut self, cx: &mut commands::Context) -> EventResult {
@@ -1024,13 +1011,7 @@ impl EditorView {
             };
         }
 
-        if cx.editor.mode != Mode::Insert || !cx.editor.config().auto_completion {
-            return EventResult::Ignored(None);
-        }
-
-        crate::commands::insert::idle_completion(cx);
-
-        EventResult::Consumed(None)
+        EventResult::Ignored(None)
     }
 }
 
@@ -1243,7 +1224,7 @@ impl Component for EditorView {
             editor: context.editor,
             count: None,
             register: None,
-            callback: None,
+            callback: Vec::new(),
             on_next_key_callback: None,
             jobs: context.jobs,
         };
@@ -1318,12 +1299,6 @@ impl Component for EditorView {
                                     if callback.is_some() {
                                         // assume close_fn
                                         self.clear_completion(cx.editor);
-
-                                        // In case the popup was deleted because of an intersection w/ the auto-complete menu.
-                                        commands::signature_help_impl(
-                                            &mut cx,
-                                            commands::SignatureHelpInvoked::Automatic,
-                                        );
                                     }
                                 }
                             }
@@ -1334,14 +1309,6 @@ impl Component for EditorView {
 
                                 // record last_insert key
                                 self.last_insert.1.push(InsertEvent::Key(key));
-
-                                // lastly we recalculate completion
-                                if let Some(completion) = &mut self.completion {
-                                    completion.update(&mut cx);
-                                    if completion.is_empty() {
-                                        self.clear_completion(cx.editor);
-                                    }
-                                }
                             }
                         }
                         mode => self.command_mode(mode, &mut cx, key),
@@ -1355,7 +1322,7 @@ impl Component for EditorView {
                 }
 
                 // appease borrowck
-                let callback = cx.callback.take();
+                let callbacks = take(&mut cx.callback);
 
                 // if the command consumed the last view, skip the render.
                 // on the next loop cycle the Application will then terminate.
@@ -1378,6 +1345,16 @@ impl Component for EditorView {
                         doc.append_changes_to_history(view);
                     }
                 }
+                let callback = if callbacks.is_empty() {
+                    None
+                } else {
+                    let callback: crate::compositor::Callback = Box::new(move |compositor, cx| {
+                        for callback in callbacks {
+                            callback(compositor, cx)
+                        }
+                    });
+                    Some(callback)
+                };
 
                 EventResult::Consumed(callback)
             }

helix-term/src/ui/menu.rs

@@ -89,13 +89,26 @@ impl<T: Item> Menu<T> {
         }
     }
 
-    pub fn score(&mut self, pattern: &str) {
-        // reuse the matches allocation
-        self.matches.clear();
+    pub fn score(&mut self, pattern: &str, incremental: bool) {
         let mut matcher = MATCHER.lock();
         matcher.config = Config::DEFAULT;
         let pattern = Atom::new(pattern, CaseMatching::Ignore, AtomKind::Fuzzy, false);
         let mut buf = Vec::new();
+        if incremental {
+            self.matches.retain_mut(|(index, score)| {
+                let option = &self.options[*index as usize];
+                let text = option.filter_text(&self.editor_data);
+                let new_score = pattern.score(Utf32Str::new(&text, &mut buf), &mut matcher);
+                match new_score {
+                    Some(new_score) => {
+                        *score = new_score as u32;
+                        true
+                    }
+                    None => false,
+                }
+            })
+        } else {
+            self.matches.clear();
             let matches = self.options.iter().enumerate().filter_map(|(i, option)| {
                 let text = option.filter_text(&self.editor_data);
                 pattern
@@ -103,6 +116,7 @@ impl<T: Item> Menu<T> {
                     .map(|score| (i as u32, score as u32))
             });
             self.matches.extend(matches);
+        }
         self.matches
             .sort_unstable_by_key(|&(i, score)| (Reverse(score), i));
 

helix-view/src/document.rs

@@ -34,6 +34,7 @@ use helix_core::{
 };
 
 use crate::editor::Config;
+use crate::events::{DocumentDidChange, SelectionDidChange};
 use crate::{DocumentId, Editor, Theme, View, ViewId};
 
 /// 8kB of buffer space for encoding and decoding `Rope`s.
@@ -112,19 +113,6 @@ pub struct SavePoint {
     /// The view this savepoint is associated with
     pub view: ViewId,
     revert: Mutex<Transaction>,
-    pub text: Rope,
-}
-
-impl SavePoint {
-    pub fn cursor(&self) -> usize {
-        // we always create transactions with selections
-        self.revert
-            .lock()
-            .selection()
-            .unwrap()
-            .primary()
-            .cursor(self.text.slice(..))
-    }
 }
 
 pub struct Document {
@@ -1105,6 +1093,10 @@ impl Document {
         // TODO: use a transaction?
         self.selections
             .insert(view_id, selection.ensure_invariants(self.text().slice(..)));
+        helix_event::dispatch(SelectionDidChange {
+            doc: self,
+            view: view_id,
+        })
     }
 
     /// Find the origin selection of the text in a document, i.e. where
@@ -1158,6 +1150,14 @@ impl Document {
         let success = transaction.changes().apply(&mut self.text);
 
         if success {
+            if emit_lsp_notification {
+                helix_event::dispatch(DocumentDidChange {
+                    doc: self,
+                    view: view_id,
+                    old_text: &old_doc,
+                });
+            }
+
             for selection in self.selections.values_mut() {
                 *selection = selection
                     .clone()
@@ -1173,6 +1173,10 @@ impl Document {
                     view_id,
                     selection.clone().ensure_invariants(self.text.slice(..)),
                 );
+                helix_event::dispatch(SelectionDidChange {
+                    doc: self,
+                    view: view_id,
+                });
             }
 
             self.modified_since_accessed = true;
@@ -1263,6 +1267,7 @@ impl Document {
             }
 
             if emit_lsp_notification {
+                // TODO: move to hook
                 // emit lsp notification
                 for language_server in self.language_servers() {
                     let notify = language_server.text_document_did_change(
@@ -1373,7 +1378,6 @@ impl Document {
         let savepoint = Arc::new(SavePoint {
             view: view.id,
             revert: Mutex::new(revert),
-            text: self.text.clone(),
         });
         self.savepoints.push(Arc::downgrade(&savepoint));
         savepoint

helix-view/src/editor.rs

@@ -2,6 +2,7 @@ use crate::{
     align_view,
     document::{DocumentSavedEventFuture, DocumentSavedEventResult, Mode, SavePoint},
     graphics::{CursorKind, Rect},
+    handlers::Handlers,
     info::Info,
     input::KeyEvent,
     register::Registers,
@@ -30,10 +31,7 @@ use std::{
 };
 
 use tokio::{
-    sync::{
-        mpsc::{unbounded_channel, UnboundedReceiver, UnboundedSender},
-        oneshot,
-    },
+    sync::mpsc::{unbounded_channel, UnboundedReceiver, UnboundedSender},
     time::{sleep, Duration, Instant, Sleep},
 };
 
@@ -244,12 +242,19 @@ pub struct Config {
     /// Set a global text_width
     pub text_width: usize,
     /// Time in milliseconds since last keypress before idle timers trigger.
-    /// Used for autocompletion, set to 0 for instant. Defaults to 250ms.
+    /// Used for various UI timeouts. Defaults to 250ms.
     #[serde(
         serialize_with = "serialize_duration_millis",
         deserialize_with = "deserialize_duration_millis"
     )]
     pub idle_timeout: Duration,
+    /// Time in milliseconds after typing a word character before auto completions
+    /// are shown, set to 5 for instant. Defaults to 250ms.
+    #[serde(
+        serialize_with = "serialize_duration_millis",
+        deserialize_with = "deserialize_duration_millis"
+    )]
+    pub completion_timeout: Duration,
     /// Whether to insert the completion suggestion on hover. Defaults to true.
     pub preview_completion_insert: bool,
     pub completion_trigger_len: u8,
@@ -823,6 +828,7 @@ impl Default for Config {
             auto_format: true,
             auto_save: false,
             idle_timeout: Duration::from_millis(250),
+            completion_timeout: Duration::from_millis(250),
             preview_completion_insert: true,
             completion_trigger_len: 2,
             auto_info: true,
@@ -946,14 +952,7 @@ pub struct Editor {
     /// avoid calculating the cursor position multiple
     /// times during rendering and should not be set by other functions.
     pub cursor_cache: Cell<Option<Option<Position>>>,
-    /// When a new completion request is sent to the server old
-    /// unfinished request must be dropped. Each completion
-    /// request is associated with a channel that cancels
-    /// when the channel is dropped. That channel is stored
-    /// here. When a new completion request is sent this
-    /// field is set and any old requests are automatically
-    /// canceled as a result
-    pub completion_request_handle: Option<oneshot::Sender<()>>,
+    pub handlers: Handlers,
 }
 
 pub type Motion = Box<dyn Fn(&mut Editor)>;
@@ -981,13 +980,16 @@ enum ThemeAction {
 
 #[derive(Debug, Clone)]
 pub enum CompleteAction {
+    Triggered,
+    /// A savepoint of the currently selected completion. The savepoint
+    /// MUST be restored before sending any event to the LSP
+    Selected {
+        savepoint: Arc<SavePoint>,
+    },
     Applied {
         trigger_offset: usize,
         changes: Vec<Change>,
     },
-    /// A savepoint of the currently selected completion. The savepoint
-    /// MUST be restored before sending any event to the LSP
-    Selected { savepoint: Arc<SavePoint> },
 }
 
 #[derive(Debug, Copy, Clone)]
@@ -1021,6 +1023,7 @@ impl Editor {
         theme_loader: Arc<theme::Loader>,
         syn_loader: Arc<syntax::Loader>,
         config: Arc<dyn DynAccess<Config>>,
+        handlers: Handlers,
     ) -> Self {
         let language_servers = helix_lsp::Registry::new(syn_loader.clone());
         let conf = config.load();
@@ -1065,7 +1068,7 @@ impl Editor {
             config_events: unbounded_channel(),
             needs_redraw: false,
             cursor_cache: Cell::new(None),
-            completion_request_handle: None,
+            handlers,
         }
     }
 

helix-view/src/events.rs

@@ -0,0 +1,9 @@
+use helix_core::Rope;
+use helix_event::events;
+
+use crate::{Document, ViewId};
+
+events! {
+    DocumentDidChange<'a> { doc: &'a mut Document, view: ViewId, old_text: &'a Rope  }
+    SelectionDidChange<'a> { doc: &'a mut Document, view: ViewId }
+}

helix-view/src/handlers.rs

@@ -0,0 +1,41 @@
+use helix_event::send_blocking;
+use tokio::sync::mpsc::Sender;
+
+use crate::handlers::lsp::SignatureHelpInvoked;
+use crate::{DocumentId, Editor, ViewId};
+
+pub mod dap;
+pub mod lsp;
+
+pub struct Handlers {
+    // only public because most of the actual implementation is in helix-term right now :/
+    pub completions: Sender<lsp::CompletionEvent>,
+    pub signature_hints: Sender<lsp::SignatureHelpEvent>,
+}
+
+impl Handlers {
+    /// Manually trigger completion (c-x)
+    pub fn trigger_completions(&self, trigger_pos: usize, doc: DocumentId, view: ViewId) {
+        send_blocking(
+            &self.completions,
+            lsp::CompletionEvent::ManualTrigger {
+                cursor: trigger_pos,
+                doc,
+                view,
+            },
+        );
+    }
+
+    pub fn trigger_signature_help(&self, invocation: SignatureHelpInvoked, editor: &Editor) {
+        let event = match invocation {
+            SignatureHelpInvoked::Automatic => {
+                if !editor.config().lsp.auto_signature_help {
+                    return;
+                }
+                lsp::SignatureHelpEvent::Trigger
+            }
+            SignatureHelpInvoked::Manual => lsp::SignatureHelpEvent::Invoked,
+        };
+        send_blocking(&self.signature_hints, event)
+    }
+}

helix-view/src/handlers/lsp.rs

@@ -1 +1,41 @@
+use crate::{DocumentId, ViewId};
 
+pub enum CompletionEvent {
+    /// Auto completion was triggered by typing a word char
+    AutoTrigger {
+        cursor: usize,
+        doc: DocumentId,
+        view: ViewId,
+    },
+    /// Auto completion was triggered by typing a trigger char
+    /// specified by the LSP
+    TriggerChar {
+        cursor: usize,
+        doc: DocumentId,
+        view: ViewId,
+    },
+    /// A completion was manually requested (c-x)
+    ManualTrigger {
+        cursor: usize,
+        doc: DocumentId,
+        view: ViewId,
+    },
+    /// Some text was deleted and the cursor is now at `pos`
+    DeleteText { cursor: usize },
+    /// Invalidate the current auto completion trigger
+    Cancel,
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum SignatureHelpInvoked {
+    Automatic,
+    Manual,
+}
+
+pub enum SignatureHelpEvent {
+    Invoked,
+    Trigger,
+    ReTrigger,
+    Cancel,
+    RequestComplete { open: bool },
+}

helix-view/src/lib.rs

@@ -1,17 +1,15 @@
 #[macro_use]
 pub mod macros;
 
+pub mod base64;
 pub mod clipboard;
 pub mod document;
 pub mod editor;
 pub mod env;
+pub mod events;
 pub mod graphics;
 pub mod gutter;
-pub mod handlers {
-    pub mod dap;
-    pub mod lsp;
-}
-pub mod base64;
+pub mod handlers;
 pub mod info;
 pub mod input;
 pub mod keyboard;