refactor DocumentDidChange events

in the past DocumentDidChange and SelectionDidChange events were implemented in
a simplistic manner to get a simple prototype out. However, if you want to use
these events in more complex scenarios with interdependencies between the two
handlers the system fell short.

The `SelectionDidChange` event was dispatched before the DocumentDidChange (and
not at all if the selection wasn't manually set) so any handlers that wants to
track selection was not able to map their ranges yet.

The reason for this was actually the way that apply_impl was structured. The
function was slightly refactored to address these problems and enable moving
other range mappings to event handlers.

helix-term/src/handlers/signature_help.rs

@@ -354,7 +354,7 @@ pub(super) fn register_hooks(handlers: &Handlers) {
 
     let tx = handlers.signature_hints.clone();
     register_hook!(move |event: &mut DocumentDidChange<'_>| {
-        if event.doc.config.load().lsp.auto_signature_help {
+        if event.doc.config.load().lsp.auto_signature_help && !event.ghost_transaction {
             send_blocking(&tx, SignatureHelpEvent::ReTrigger);
         }
         Ok(())

helix-view/src/document.rs

@@ -1360,6 +1360,8 @@ impl Document {
             doc: self,
             view: view_id,
             old_text: &old_doc,
+            changes,
+            ghost_transaction: !emit_lsp_notification,
         });
 
         // if specified, the current selection should instead be replaced by transaction.selection

helix-view/src/events.rs

@@ -1,10 +1,16 @@
-use helix_core::Rope;
+use helix_core::{ChangeSet, Rope};
 use helix_event::events;
 
 use crate::{Document, DocumentId, Editor, ViewId};
 
 events! {
-    DocumentDidChange<'a> { doc: &'a mut Document, view: ViewId, old_text: &'a Rope  }
+    DocumentDidChange<'a> {
+        doc: &'a mut Document,
+        view: ViewId,
+        old_text: &'a Rope,
+        changes: &'a ChangeSet,
+        ghost_transaction: bool
+    }
     SelectionDidChange<'a> { doc: &'a mut Document, view: ViewId }
     DiagnosticsDidChange<'a> { editor: &'a mut Editor, doc: DocumentId }
 }