From 44388e5e6c206c272c9d2370b85235dee6a729bf Mon Sep 17 00:00:00 2001
From: Daniel Imms <2193314+Tyriar@users.noreply.github.com>
Date: Wed, 28 Sep 2022 08:55:29 -0700
Subject: [PATCH 1/2] Use microtask to flush the write buffer after input

Fixes #4158
---
 src/common/CoreTerminal.ts      |  1 +
 src/common/input/WriteBuffer.ts | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/common/CoreTerminal.ts b/src/common/CoreTerminal.ts
index d7cb0f7e..02a94392 100644
--- a/src/common/CoreTerminal.ts
+++ b/src/common/CoreTerminal.ts
@@ -132,6 +132,7 @@ export abstract class CoreTerminal extends Disposable implements ICoreTerminal {
     this.register(forwardEvent(this._bufferService.onResize, this._onResize));
     this.register(forwardEvent(this.coreService.onData, this._onData));
     this.register(forwardEvent(this.coreService.onBinary, this._onBinary));
+    this.register(this.coreService.onUserInput(() =>  this._writeBuffer.handleUserInput()));
     this.register(this.optionsService.onOptionChange(key => this._updateOptions(key)));
     this.register(this._bufferService.onScroll(event => {
       this._onScroll.fire({ position: this._bufferService.buffer.ydisp, source: ScrollSource.TERMINAL });
diff --git a/src/common/input/WriteBuffer.ts b/src/common/input/WriteBuffer.ts
index 2cdf4e3c..1ac98b51 100644
--- a/src/common/input/WriteBuffer.ts
+++ b/src/common/input/WriteBuffer.ts
@@ -40,11 +40,16 @@ export class WriteBuffer {
   private _bufferOffset = 0;
   private _isSyncWriting = false;
   private _syncCalls = 0;
+  private _didUserInput = false;
   public get onWriteParsed(): IEvent<void> { return this._onWriteParsed.event; }
   private _onWriteParsed = new EventEmitter<void>();
 
   constructor(private _action: (data: string | Uint8Array, promiseResult?: boolean) => void | Promise<boolean>) { }
 
+  public handleUserInput(): void {
+    this._didUserInput = true;
+  }
+
   /**
    * @deprecated Unreliable, to be removed soon.
    */
@@ -99,7 +104,15 @@ export class WriteBuffer {
     // schedule chunk processing for next event loop run
     if (!this._writeBuffer.length) {
       this._bufferOffset = 0;
-      queueMicrotask(() => this._innerWrite());
+      // If this is the first write call after the user has done some input,
+      // parse it immediately in an upcoming microtask to minimize reduce input,
+      // otherwise schedule for the next event
+      if (this._didUserInput) {
+        this._didUserInput = false;
+        queueMicrotask(() => this._innerWrite());
+      } else {
+        setTimeout(() => this._innerWrite());
+      }
     }
 
     this._pendingData += data.length;

From 34df17e36dc309171880bd996b8b37f412bbb4de Mon Sep 17 00:00:00 2001
From: Daniel Imms <2193314+Tyriar@users.noreply.github.com>
Date: Wed, 28 Sep 2022 09:51:28 -0700
Subject: [PATCH 2/2] Call innerWrite immediately over a microtask

---
 src/common/input/WriteBuffer.ts | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/common/input/WriteBuffer.ts b/src/common/input/WriteBuffer.ts
index 1ac98b51..4f316f24 100644
--- a/src/common/input/WriteBuffer.ts
+++ b/src/common/input/WriteBuffer.ts
@@ -104,15 +104,20 @@ export class WriteBuffer {
     // schedule chunk processing for next event loop run
     if (!this._writeBuffer.length) {
       this._bufferOffset = 0;
+
       // If this is the first write call after the user has done some input,
       // parse it immediately in an upcoming microtask to minimize reduce input,
       // otherwise schedule for the next event
       if (this._didUserInput) {
         this._didUserInput = false;
-        queueMicrotask(() => this._innerWrite());
-      } else {
-        setTimeout(() => this._innerWrite());
+        this._pendingData += data.length;
+        this._writeBuffer.push(data);
+        this._callbacks.push(callback);
+        this._innerWrite();
+        return;
       }
+
+      setTimeout(() => this._innerWrite());
     }
 
     this._pendingData += data.length;