From 0187ac8fde245d6e6d4d8af7c9b706531e5346c8 Mon Sep 17 00:00:00 2001
From: Nathan Sobo <nathan@zed.dev>
Date: Tue, 24 Aug 2021 18:16:13 -0600
Subject: [PATCH] Share a single pool of LineWrappers across all threads

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>
---
 zed/src/editor/display_map/line_wrapper.rs | 39 +++++++++++-----------
 zed/src/editor/display_map/wrap_map.rs     |  6 ++--
 2 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/zed/src/editor/display_map/line_wrapper.rs b/zed/src/editor/display_map/line_wrapper.rs
index 97ac2769e72b231e85d9f55c3fc5e763e674b36c..106e55a55facba66f786ef87f5ba2e070c956d33 100644
--- a/zed/src/editor/display_map/line_wrapper.rs
+++ b/zed/src/editor/display_map/line_wrapper.rs
@@ -1,15 +1,16 @@
 use crate::Settings;
 use gpui::{fonts::FontId, FontCache, FontSystem};
+use lazy_static::lazy_static;
+use parking_lot::Mutex;
 use std::{
-    cell::RefCell,
     collections::HashMap,
     iter,
     ops::{Deref, DerefMut},
     sync::Arc,
 };
 
-thread_local! {
-    static WRAPPERS: RefCell<Vec<LineWrapper>> = Default::default();
+lazy_static! {
+    static ref POOL: Mutex<Vec<LineWrapper>> = Default::default();
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -35,25 +36,24 @@ pub struct LineWrapper {
 impl LineWrapper {
     pub const MAX_INDENT: u32 = 256;
 
-    pub fn thread_local(
+    pub fn acquire(
         font_system: Arc<dyn FontSystem>,
         font_cache: &FontCache,
         settings: Settings,
     ) -> LineWrapperHandle {
-        let wrapper =
-            if let Some(mut wrapper) = WRAPPERS.with(|wrappers| wrappers.borrow_mut().pop()) {
-                let font_id = font_cache
-                    .select_font(settings.buffer_font_family, &Default::default())
-                    .unwrap();
-                let font_size = settings.buffer_font_size;
-                if wrapper.font_id != font_id || wrapper.font_size != font_size {
-                    wrapper.cached_ascii_char_widths = [f32::NAN; 128];
-                    wrapper.cached_other_char_widths.clear();
-                }
-                wrapper
-            } else {
-                LineWrapper::new(font_system, font_cache, settings)
-            };
+        let wrapper = if let Some(mut wrapper) = POOL.lock().pop() {
+            let font_id = font_cache
+                .select_font(settings.buffer_font_family, &Default::default())
+                .unwrap();
+            let font_size = settings.buffer_font_size;
+            if wrapper.font_id != font_id || wrapper.font_size != font_size {
+                wrapper.cached_ascii_char_widths = [f32::NAN; 128];
+                wrapper.cached_other_char_widths.clear();
+            }
+            wrapper
+        } else {
+            LineWrapper::new(font_system, font_cache, settings)
+        };
         LineWrapperHandle(Some(wrapper))
     }
 
@@ -163,6 +163,7 @@ impl LineWrapper {
     }
 
     fn compute_width_for_char(&self, c: char) -> f32 {
+        log::info!("cache miss {}", c);
         self.font_system
             .layout_line(
                 &c.to_string(),
@@ -178,7 +179,7 @@ pub struct LineWrapperHandle(Option<LineWrapper>);
 impl Drop for LineWrapperHandle {
     fn drop(&mut self) {
         let wrapper = self.0.take().unwrap();
-        WRAPPERS.with(|wrappers| wrappers.borrow_mut().push(wrapper))
+        POOL.lock().push(wrapper)
     }
 }
 
diff --git a/zed/src/editor/display_map/wrap_map.rs b/zed/src/editor/display_map/wrap_map.rs
index e831d800429ceab9d584626fd5827eddefae6070..1d5359eabff854d7d2e9a106b7e890f56d8b1f41 100644
--- a/zed/src/editor/display_map/wrap_map.rs
+++ b/zed/src/editor/display_map/wrap_map.rs
@@ -119,8 +119,7 @@ impl WrapMap {
             let font_cache = cx.font_cache().clone();
             let settings = self.settings.clone();
             let task = cx.background().spawn(async move {
-                let mut line_wrapper =
-                    LineWrapper::thread_local(font_system, &font_cache, settings);
+                let mut line_wrapper = LineWrapper::acquire(font_system, &font_cache, settings);
                 let tab_snapshot = new_snapshot.tab_snapshot.clone();
                 let range = TabPoint::zero()..tab_snapshot.max_point();
                 new_snapshot
@@ -194,8 +193,7 @@ impl WrapMap {
                 let font_cache = cx.font_cache().clone();
                 let settings = self.settings.clone();
                 let update_task = cx.background().spawn(async move {
-                    let mut line_wrapper =
-                        LineWrapper::thread_local(font_system, &font_cache, settings);
+                    let mut line_wrapper = LineWrapper::acquire(font_system, &font_cache, settings);
                     for (tab_snapshot, edits) in pending_edits {
                         snapshot
                             .update(tab_snapshot, &edits, wrap_width, &mut line_wrapper)