refactor completion and signature help using hooks

2 files changed, 800 insertions, 0 deletions

diff --git a/helix-term/src/handlers/completion.rs b/helix-term/src/handlers/completion.rs
new file mode 100644
index 00000000..d71fd24f
--- /dev/null
+++ b/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_stdx::rope::RopeSliceExt;
+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::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 people 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,
+                });
+            }
+            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 immediately 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 cancel = self.request.take().map_or(false, |req| !req.is_closed());
+            let timeout = if trigger.kind == TriggerKind::Auto && !cancel {
+                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| trigger_text.ends_with(trigger))
+                        });
+                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 {
+        return;
+    }
+    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| text.ends_with(trigger)))
+        });
+    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,
+                    }
+                }
+                // hacks: some commands are handeled elsewhere and we don't want to
+                // cancel in that case
+                MappableCommand::Static {
+                    name: "completion" | "insert_mode" | "append_mode",
+                    ..
+                } => 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(())
+    });
+}
diff --git a/helix-term/src/handlers/signature_help.rs b/helix-term/src/handlers/signature_help.rs
new file mode 100644
index 00000000..3c746548
--- /dev/null
+++ b/helix-term/src/handlers/signature_help.rs
@@ -0,0 +1,335 @@
+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_stdx::rope::RopeSliceExt;
+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::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 it's 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| text.ends_with(trigger)) {
+            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(())
+    });
+}