From 915e616ff593bd788239895cb4ed062fe4cd12c4 Mon Sep 17 00:00:00 2001
From: nsrCodes <navdeepsinghrathore2000@gmail.com>
Date: Fri, 27 Jun 2025 09:13:36 +0530
Subject: [PATCH] fix: avoid random updates to view while the user is typing

---
 core/src/timeoutLatch.ts  | 98 +++++++++++++++++++++++++++++++++++++++
 core/src/useCodeMirror.ts | 42 +++++++++++++++--
 2 files changed, 136 insertions(+), 4 deletions(-)
 create mode 100644 core/src/timeoutLatch.ts

diff --git a/core/src/timeoutLatch.ts b/core/src/timeoutLatch.ts
new file mode 100644
index 000000000..528355646
--- /dev/null
+++ b/core/src/timeoutLatch.ts
@@ -0,0 +1,98 @@
+// Setting / Unsetting timeouts for every keystroke was a significant overhead
+// Inspired from https://github.com/iostreamer-X/timeout-latch
+
+export class TimeoutLatch {
+  private timeLeftMS: number;
+  private timeoutMS: number;
+  private isCancelled = false;
+  private isTimeExhausted = false;
+  private callbacks: Function[] = [];
+
+  constructor(callback: Function, timeoutMS: number) {
+    this.timeLeftMS = timeoutMS;
+    this.timeoutMS = timeoutMS;
+    this.callbacks.push(callback);
+  }
+
+  tick(): void {
+    if (!this.isCancelled && !this.isTimeExhausted) {
+      this.timeLeftMS--;
+      if (this.timeLeftMS <= 0) {
+        this.isTimeExhausted = true;
+        const callbacks = this.callbacks.slice();
+        this.callbacks.length = 0;
+        callbacks.forEach((callback) => {
+          try {
+            callback();
+          } catch (error) {
+            console.error('TimeoutLatch callback error:', error);
+          }
+        });
+      }
+    }
+  }
+
+  cancel(): void {
+    this.isCancelled = true;
+    this.callbacks.length = 0;
+  }
+
+  reset(): void {
+    this.timeLeftMS = this.timeoutMS;
+    this.isCancelled = false;
+    this.isTimeExhausted = false;
+  }
+
+  get isDone(): boolean {
+    return this.isCancelled || this.isTimeExhausted;
+  }
+}
+
+class Scheduler {
+  private interval: NodeJS.Timeout | null = null;
+  private latches = new Set<TimeoutLatch>();
+
+  add(latch: TimeoutLatch): void {
+    this.latches.add(latch);
+    this.start();
+  }
+
+  remove(latch: TimeoutLatch): void {
+    this.latches.delete(latch);
+    if (this.latches.size === 0) {
+      this.stop();
+    }
+  }
+
+  private start(): void {
+    if (this.interval === null) {
+      this.interval = setInterval(() => {
+        this.latches.forEach((latch) => {
+          latch.tick();
+          if (latch.isDone) {
+            this.remove(latch);
+          }
+        });
+      }, 1);
+    }
+  }
+
+  private stop(): void {
+    if (this.interval !== null) {
+      clearInterval(this.interval);
+      this.interval = null;
+    }
+  }
+}
+
+let globalScheduler: Scheduler | null = null;
+
+export const getScheduler = (): Scheduler => {
+  if (typeof window === 'undefined') {
+    return new Scheduler();
+  }
+  if (!globalScheduler) {
+    globalScheduler = new Scheduler();
+  }
+  return globalScheduler;
+};
diff --git a/core/src/useCodeMirror.ts b/core/src/useCodeMirror.ts
index a24caf7de..7e0abd02e 100644
--- a/core/src/useCodeMirror.ts
+++ b/core/src/useCodeMirror.ts
@@ -4,8 +4,10 @@ import { EditorView, type ViewUpdate } from '@codemirror/view';
 import { getDefaultExtensions } from './getDefaultExtensions';
 import { getStatistics } from './utils';
 import { type ReactCodeMirrorProps } from '.';
+import { TimeoutLatch, getScheduler } from './timeoutLatch';
 
 const External = Annotation.define<boolean>();
+const TYPING_TIMOUT = 200; // ms
 
 export interface UseCodeMirror extends ReactCodeMirrorProps {
   container?: HTMLDivElement | null;
@@ -41,6 +43,8 @@ export function useCodeMirror(props: UseCodeMirror) {
   const [container, setContainer] = useState<HTMLDivElement | null>();
   const [view, setView] = useState<EditorView>();
   const [state, setState] = useState<EditorState>();
+  const typingLatch = useState<{ current: TimeoutLatch | null }>(() => ({ current: null }))[0];
+  const pendingUpdate = useState<{ current: (() => void) | null }>(() => ({ current: null }))[0];
   const defaultThemeOption = EditorView.theme({
     '&': {
       height,
@@ -62,6 +66,20 @@ export function useCodeMirror(props: UseCodeMirror) {
       // If transaction is market as remote we don't have to call `onChange` handler again
       !vu.transactions.some((tr) => tr.annotation(External))
     ) {
+      if (typingLatch.current) {
+        typingLatch.current.reset();
+      } else {
+        typingLatch.current = new TimeoutLatch(() => {
+          if (pendingUpdate.current) {
+            const forceUpdate = pendingUpdate.current;
+            pendingUpdate.current = null;
+            forceUpdate();
+          }
+          typingLatch.current = null;
+        }, TYPING_TIMOUT);
+        getScheduler().add(typingLatch.current);
+      }
+
       const doc = vu.state.doc;
       const value = doc.toString();
       onChange(value, vu);
@@ -126,6 +144,10 @@ export function useCodeMirror(props: UseCodeMirror) {
         view.destroy();
         setView(undefined);
       }
+      if (typingLatch.current) {
+        typingLatch.current.cancel();
+        typingLatch.current = null;
+      }
     },
     [view],
   );
@@ -165,10 +187,22 @@ export function useCodeMirror(props: UseCodeMirror) {
     }
     const currentValue = view ? view.state.doc.toString() : '';
     if (view && value !== currentValue) {
-      view.dispatch({
-        changes: { from: 0, to: currentValue.length, insert: value || '' },
-        annotations: [External.of(true)],
-      });
+      const isTyping = typingLatch.current && !typingLatch.current.isDone;
+
+      const forceUpdate = () => {
+        if (view && value !== view.state.doc.toString()) {
+          view.dispatch({
+            changes: { from: 0, to: view.state.doc.toString().length, insert: value || '' },
+            annotations: [External.of(true)],
+          });
+        }
+      };
+
+      if (!isTyping) {
+        forceUpdate();
+      } else {
+        pendingUpdate.current = forceUpdate;
+      }
     }
   }, [value, view]);