From 68201ae622eda51b0111e73d9227fd2744d84c60 Mon Sep 17 00:00:00 2001
From: Pascal Kuthe <pascalkuthe@pm.me>
Date: Sun, 3 Mar 2024 23:20:30 +0100
Subject: [PATCH] add DocumentFocusLost event

---
 helix-term/src/events.rs |  5 ++++-
 helix-view/src/editor.rs | 30 ++++++++++++++++++++++++------
 helix-view/src/events.rs |  2 ++
 3 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/helix-term/src/events.rs b/helix-term/src/events.rs
index 415213c22..15d811529 100644
--- a/helix-term/src/events.rs
+++ b/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>();
 }
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index ba7337f22..7b9c9aff8 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -3,6 +3,7 @@ use crate::{
     document::{
         DocumentOpenError, DocumentSavedEventFuture, DocumentSavedEventResult, Mode, SavePoint,
     },
+    events::DocumentFocusLost,
     graphics::{CursorKind, Rect},
     handlers::Handlers,
     info::Info,
@@ -13,6 +14,7 @@ use crate::{
     Document, DocumentId, View, ViewId,
 };
 use dap::StackFrame;
+use helix_event::dispatch;
 use helix_vcs::DiffProviderRegistry;
 
 use futures_util::stream::select_all::SelectAll;
@@ -1553,7 +1555,7 @@ impl Editor {
             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.
@@ -1603,6 +1605,10 @@ impl Editor {
 
                 self.replace_document_in_view(view_id, id);
 
+                dispatch(DocumentFocusLost {
+                    editor: self,
+                    doc: id,
+                });
                 return;
             }
             Action::Load => {
@@ -1613,6 +1619,7 @@ impl Editor {
                 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
@@ -1632,10 +1639,17 @@ impl Editor {
                 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.
@@ -1862,11 +1876,15 @@ impl Editor {
                 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,
+            });
         }
-
-        let view = view!(self, view_id);
-        let doc = doc_mut!(self, &view.doc);
-        doc.mark_as_focused();
     }
 
     pub fn focus_next(&mut self) {
diff --git a/helix-view/src/events.rs b/helix-view/src/events.rs
index 136d60c51..eb97268ce 100644
--- a/helix-view/src/events.rs
+++ b/helix-view/src/events.rs
@@ -13,4 +13,6 @@ events! {
     }
     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 }
 }