From 0867b10cf24ea6bdb66c28b55a789b913267b71f Mon Sep 17 00:00:00 2001
From: James Holderness <j4_james@hotmail.com>
Date: Thu, 5 May 2022 00:57:02 +0100
Subject: [PATCH] Don't change the viewport position when in the alt buffer.

---
 src/cascadia/TerminalCore/TerminalApi.cpp | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/cascadia/TerminalCore/TerminalApi.cpp b/src/cascadia/TerminalCore/TerminalApi.cpp
index c8af8f07b2b..f888cfa67f9 100644
--- a/src/cascadia/TerminalCore/TerminalApi.cpp
+++ b/src/cascadia/TerminalCore/TerminalApi.cpp
@@ -41,9 +41,13 @@ til::rect Terminal::GetViewport() const
 
 void Terminal::SetViewportPosition(const til::point position)
 {
-    const auto dimensions = _GetMutableViewport().Dimensions();
-    _mutableViewport = Viewport::FromDimensions(position.to_win32_coord(), dimensions);
-    Terminal::_NotifyScrollEvent();
+    // The viewport is fixed at 0,0 for the alt buffer, so this is a no-op.
+    if (!_inAltBuffer())
+    {
+        const auto dimensions = _GetMutableViewport().Dimensions();
+        _mutableViewport = Viewport::FromDimensions(position.to_win32_coord(), dimensions);
+        Terminal::_NotifyScrollEvent();
+    }
 }
 
 void Terminal::SetTextAttributes(const TextAttribute& attrs)