Introduce AsyncAppContext and simplify spawning

Now when you call spawn in various context, you pass an FnOnce that is called with an AsyncAppContext and returns a static future. This allows you to write async code similar to how our tests work, borrowing the guts of the AsyncAppContext when needed to interact, but using normal async await semantics instead of callbacks.

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

zed/src/editor/buffer_view.rs

@@ -4,11 +4,10 @@ use super::{
 };
 use crate::{settings::Settings, util::post_inc, workspace, worktree::FileHandle};
 use anyhow::Result;
-use futures_core::future::LocalBoxFuture;
 use gpui::{
     fonts::Properties as FontProperties, geometry::vector::Vector2F, keymap::Binding, text_layout,
     AppContext, ClipboardItem, Element, ElementBox, Entity, FontCache, ModelHandle,
-    MutableAppContext, TextLayoutCache, View, ViewContext, WeakViewHandle,
+    MutableAppContext, Task, TextLayoutCache, View, ViewContext, WeakViewHandle,
 };
 use parking_lot::Mutex;
 use postage::watch;
@@ -2348,13 +2347,13 @@ impl BufferView {
         ctx.notify();
 
         let epoch = self.next_blink_epoch();
-        ctx.spawn(
-            async move {
-                Timer::after(CURSOR_BLINK_INTERVAL).await;
-                epoch
-            },
-            Self::resume_cursor_blinking,
-        )
+        let handle = ctx.handle();
+        ctx.spawn(|mut ctx| async move {
+            Timer::after(CURSOR_BLINK_INTERVAL).await;
+            handle.update(&mut ctx, |this, ctx| {
+                this.resume_cursor_blinking(epoch, ctx);
+            })
+        })
         .detach();
     }
 
@@ -2371,13 +2370,11 @@ impl BufferView {
             ctx.notify();
 
             let epoch = self.next_blink_epoch();
-            ctx.spawn(
-                async move {
-                    Timer::after(CURSOR_BLINK_INTERVAL).await;
-                    epoch
-                },
-                Self::blink_cursors,
-            )
+            let handle = ctx.handle();
+            ctx.spawn(|mut ctx| async move {
+                Timer::after(CURSOR_BLINK_INTERVAL).await;
+                handle.update(&mut ctx, |this, ctx| this.blink_cursors(epoch, ctx));
+            })
             .detach();
         }
     }
@@ -2498,7 +2495,7 @@ impl workspace::ItemView for BufferView {
         &mut self,
         new_file: Option<FileHandle>,
         ctx: &mut ViewContext<Self>,
-    ) -> LocalBoxFuture<'static, Result<()>> {
+    ) -> Task<Result<()>> {
         self.buffer.update(ctx, |b, ctx| b.save(new_file, ctx))
     }