From 91c08ed48e66722352f623a2029ac5c007cba621 Mon Sep 17 00:00:00 2001
From: Daniel Imms <2193314+Tyriar@users.noreply.github.com>
Date: Wed, 2 Aug 2023 11:30:43 -0700
Subject: [PATCH] Fix clear leaving viewport in a bad state

Fixes #4603
---
 src/browser/Terminal.ts | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/browser/Terminal.ts b/src/browser/Terminal.ts
index c4f8f26e..f0ce4694 100644
--- a/src/browser/Terminal.ts
+++ b/src/browser/Terminal.ts
@@ -1230,8 +1230,11 @@ export class Terminal extends CoreTerminal implements ITerminal {
     for (let i = 1; i < this.rows; i++) {
       this.buffer.lines.push(this.buffer.getBlankLine(DEFAULT_ATTR_DATA));
     }
-    this.refresh(0, this.rows - 1);
+    // IMPORTANT: Fire scroll event before viewport is reset. This ensures embedders get the clear
+    // scroll event and that the viewport's state will be valid for immediate writes.
     this._onScroll.fire({ position: this.buffer.ydisp, source: ScrollSource.TERMINAL });
+    this.viewport?.reset();
+    this.refresh(0, this.rows - 1);
   }
 
   /**