add DocumentFocusLost event

helix-term/src/events.rs

@@ -1,6 +1,8 @@
 use helix_event::{events, register_event};
 use helix_view::document::Mode;
-use helix_view::events::{DiagnosticsDidChange, DocumentDidChange, SelectionDidChange};
+use helix_view::events::{
+    DiagnosticsDidChange, DocumentDidChange, DocumentFocusLost, SelectionDidChange,
+};
 
 use crate::commands;
 use crate::keymap::MappableCommand;
@@ -16,6 +18,7 @@ pub fn register() {
     register_event::<PostInsertChar>();
     register_event::<PostCommand>();
     register_event::<DocumentDidChange>();
+    register_event::<DocumentFocusLost>();
     register_event::<SelectionDidChange>();
     register_event::<DiagnosticsDidChange>();
 }

helix-view/src/editor.rs

@@ -4,6 +4,7 @@
     document::{
         DocumentOpenError, DocumentSavedEventFuture, DocumentSavedEventResult, Mode, SavePoint,
     },
+    events::DocumentFocusLost,
     graphics::{CursorKind, Rect},
     handlers::Handlers,
     info::Info,
@@ -14,6 +15,7 @@
     Document, DocumentId, View, ViewId,
 };
 use dap::StackFrame;
+use helix_event::dispatch;
 use helix_vcs::DiffProviderRegistry;
 
 use futures_util::stream::select_all::SelectAll;
@@ -1590,7 +1592,7 @@ pub fn switch(&mut self, id: DocumentId, action: Action) {
             self.enter_normal_mode();
         }
 
-        match action {
+        let focust_lost = match action {
             Action::Replace => {
                 let (view, doc) = current_ref!(self);
                 // If the current view is an empty scratch buffer and is not displayed in any other views, delete it.
@@ -1640,6 +1642,10 @@ pub fn switch(&mut self, id: DocumentId, action: Action) {
 
                 self.replace_document_in_view(view_id, id);
 
+                dispatch(DocumentFocusLost {
+                    editor: self,
+                    doc: id,
+                });
                 return;
             }
             Action::Load => {
@@ -1650,6 +1656,7 @@ pub fn switch(&mut self, id: DocumentId, action: Action) {
                 return;
             }
             Action::HorizontalSplit | Action::VerticalSplit => {
+                let focus_lost = self.tree.try_get(self.tree.focus).map(|view| view.doc);
                 // copy the current view, unless there is no view yet
                 let view = self
                     .tree
@@ -1669,10 +1676,17 @@ pub fn switch(&mut self, id: DocumentId, action: Action) {
                 let doc = doc_mut!(self, &id);
                 doc.ensure_view_init(view_id);
                 doc.mark_as_focused();
+                focus_lost
             }
-        }
+        };
 
         self._refresh();
+        if let Some(focus_lost) = focust_lost {
+            dispatch(DocumentFocusLost {
+                editor: self,
+                doc: focus_lost,
+            });
+        }
     }
 
     /// Generate an id for a new document and register it.
@@ -1903,11 +1917,15 @@ pub fn focus(&mut self, view_id: ViewId) {
                 let doc = doc_mut!(self, &view.doc);
                 view.sync_changes(doc);
             }
-        }
-
             let view = view!(self, view_id);
             let doc = doc_mut!(self, &view.doc);
             doc.mark_as_focused();
+            let focus_lost = self.tree.get(prev_id).doc;
+            dispatch(DocumentFocusLost {
+                editor: self,
+                doc: focus_lost,
+            });
+        }
     }
 
     pub fn focus_next(&mut self) {

helix-view/src/events.rs

@@ -13,4 +13,6 @@
     }
     SelectionDidChange<'a> { doc: &'a mut Document, view: ViewId }
     DiagnosticsDidChange<'a> { editor: &'a mut Editor, doc: DocumentId }
+    // called **after** a document loses focus (but not when its closed)
+    DocumentFocusLost<'a> { editor: &'a mut Editor, doc: DocumentId }
 }