Add MultiBufferItemHandle

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

crates/diagnostics/src/diagnostics.rs

@@ -538,10 +538,8 @@ impl workspace::Item for ProjectDiagnostics {
 }
 
 impl workspace::ItemView for ProjectDiagnosticsEditor {
-    type ItemHandle = ModelHandle<ProjectDiagnostics>;
-
-    fn item_handle(&self, _: &AppContext) -> Self::ItemHandle {
-        self.model.clone()
+    fn item_id(&self, _: &AppContext) -> usize {
+        self.model.id()
     }
 
     fn tab_content(&self, style: &theme::Tab, _: &AppContext) -> ElementBox {

crates/editor/src/editor.rs

@@ -27,7 +27,7 @@ use gpui::{
     text_layout, AppContext, ClipboardItem, Element, ElementBox, Entity, ModelHandle,
     MutableAppContext, RenderContext, Task, View, ViewContext, WeakModelHandle, WeakViewHandle,
 };
-use items::BufferItemHandle;
+use items::{BufferItemHandle, MultiBufferItemHandle};
 use itertools::Itertools as _;
 use language::{
     AnchorRangeExt as _, BracketPair, Buffer, CodeAction, Completion, CompletionLabel, Diagnostic,

crates/editor/src/items.rs

@@ -25,6 +25,12 @@ pub struct BufferItemHandle(pub ModelHandle<Buffer>);
 #[derive(Clone)]
 struct WeakBufferItemHandle(WeakModelHandle<Buffer>);
 
+#[derive(Clone)]
+pub struct MultiBufferItemHandle(pub ModelHandle<MultiBuffer>);
+
+#[derive(Clone)]
+struct WeakMultiBufferItemHandle(WeakModelHandle<MultiBuffer>);
+
 impl PathOpener for BufferOpener {
     fn open(
         &self,
@@ -87,6 +93,48 @@ impl ItemHandle for BufferItemHandle {
     }
 }
 
+impl ItemHandle for MultiBufferItemHandle {
+    fn add_view(
+        &self,
+        window_id: usize,
+        workspace: &Workspace,
+        nav_history: Rc<RefCell<NavHistory>>,
+        cx: &mut MutableAppContext,
+    ) -> Box<dyn ItemViewHandle> {
+        let weak_buffer = self.0.downgrade();
+        Box::new(cx.add_view(window_id, |cx| {
+            let mut editor = Editor::for_buffer(
+                self.0.clone(),
+                crate::settings_builder(weak_buffer, workspace.settings()),
+                Some(workspace.project().clone()),
+                cx,
+            );
+            editor.nav_history = Some(ItemNavHistory::new(nav_history, &cx.handle()));
+            editor
+        }))
+    }
+
+    fn boxed_clone(&self) -> Box<dyn ItemHandle> {
+        Box::new(self.clone())
+    }
+
+    fn to_any(&self) -> gpui::AnyModelHandle {
+        self.0.clone().into()
+    }
+
+    fn downgrade(&self) -> Box<dyn WeakItemHandle> {
+        Box::new(WeakMultiBufferItemHandle(self.0.downgrade()))
+    }
+
+    fn project_path(&self, _: &AppContext) -> Option<ProjectPath> {
+        None
+    }
+
+    fn id(&self) -> usize {
+        self.0.id()
+    }
+}
+
 impl WeakItemHandle for WeakBufferItemHandle {
     fn upgrade(&self, cx: &AppContext) -> Option<Box<dyn ItemHandle>> {
         self.0
@@ -99,11 +147,25 @@ impl WeakItemHandle for WeakBufferItemHandle {
     }
 }
 
-impl ItemView for Editor {
-    type ItemHandle = BufferItemHandle;
+impl WeakItemHandle for WeakMultiBufferItemHandle {
+    fn upgrade(&self, cx: &AppContext) -> Option<Box<dyn ItemHandle>> {
+        self.0
+            .upgrade(cx)
+            .map(|buffer| Box::new(MultiBufferItemHandle(buffer)) as Box<dyn ItemHandle>)
+    }
 
-    fn item_handle(&self, cx: &AppContext) -> Self::ItemHandle {
-        BufferItemHandle(self.buffer.read(cx).as_singleton().unwrap())
+    fn id(&self) -> usize {
+        self.0.id()
+    }
+}
+
+impl ItemView for Editor {
+    fn item_id(&self, cx: &AppContext) -> usize {
+        if let Some(buffer) = self.buffer.read(cx).as_singleton() {
+            buffer.id()
+        } else {
+            self.buffer.id()
+        }
     }
 
     fn navigate(&mut self, data: Box<dyn std::any::Any>, cx: &mut ViewContext<Self>) {

crates/workspace/src/pane.rs

@@ -279,7 +279,7 @@ impl Pane {
         item_view.added_to_pane(cx);
         let item_idx = cmp::min(self.active_item_index + 1, self.item_views.len());
         self.item_views
-            .insert(item_idx, (item_view.item_handle(cx).id(), item_view));
+            .insert(item_idx, (item_view.item_id(cx), item_view));
         self.activate_item(item_idx, cx);
         cx.notify();
     }

crates/workspace/src/workspace.rs

@@ -150,11 +150,9 @@ pub trait Item: Entity + Sized {
 }
 
 pub trait ItemView: View {
-    type ItemHandle: ItemHandle;
-
     fn deactivated(&mut self, _: &mut ViewContext<Self>) {}
     fn navigate(&mut self, _: Box<dyn Any>, _: &mut ViewContext<Self>) {}
-    fn item_handle(&self, cx: &AppContext) -> Self::ItemHandle;
+    fn item_id(&self, cx: &AppContext) -> usize;
     fn tab_content(&self, style: &theme::Tab, cx: &AppContext) -> ElementBox;
     fn project_path(&self, cx: &AppContext) -> Option<ProjectPath>;
     fn clone_on_split(&self, _: &mut ViewContext<Self>) -> Option<Self>
@@ -222,7 +220,7 @@ pub trait WeakItemHandle {
 }
 
 pub trait ItemViewHandle: 'static {
-    fn item_handle(&self, cx: &AppContext) -> Box<dyn ItemHandle>;
+    fn item_id(&self, cx: &AppContext) -> usize;
     fn tab_content(&self, style: &theme::Tab, cx: &AppContext) -> ElementBox;
     fn project_path(&self, cx: &AppContext) -> Option<ProjectPath>;
     fn boxed_clone(&self) -> Box<dyn ItemViewHandle>;
@@ -354,8 +352,8 @@ impl dyn ItemViewHandle {
 }
 
 impl<T: ItemView> ItemViewHandle for ViewHandle<T> {
-    fn item_handle(&self, cx: &AppContext) -> Box<dyn ItemHandle> {
-        Box::new(self.read(cx).item_handle(cx))
+    fn item_id(&self, cx: &AppContext) -> usize {
+        self.read(cx).item_id(cx)
     }
 
     fn tab_content(&self, style: &theme::Tab, cx: &AppContext) -> ElementBox {