From 77fbb68a8058fa54561daa6a2b1579003a4422b0 Mon Sep 17 00:00:00 2001
From: Norman Dankert <norman.dankert@outlook.com>
Date: Fri, 7 Feb 2025 23:31:54 +0100
Subject: [PATCH] Fix handling of surrogate pairs in length calculation

---
 PSReadLine/Render.Helper.cs | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/PSReadLine/Render.Helper.cs b/PSReadLine/Render.Helper.cs
index 8fc56bea1..8fa9ca642 100644
--- a/PSReadLine/Render.Helper.cs
+++ b/PSReadLine/Render.Helper.cs
@@ -57,7 +57,13 @@ internal static int LengthInBufferCells(string str, int start, int end)
             for (var i = start; i < end; i++)
             {
                 var c = str[i];
-                if (c == 0x1b && (i+1) < end && str[i+1] == '[')
+                if (char.IsHighSurrogate(c) && (i + 1) < end && char.IsLowSurrogate(str[i + 1]))
+                {
+                    sum++;
+                    i++; // Skip the low surrogate
+                    continue;
+                }
+                else if (c == 0x1b && (i + 1) < end && str[i + 1] == '[')
                 {
                     // Simple escape sequence skipping
                     i += 2;
@@ -77,7 +83,13 @@ internal static int LengthInBufferCells(StringBuilder sb, int start, int end)
             for (var i = start; i < end; i++)
             {
                 var c = sb[i];
-                if (c == 0x1b && (i + 1) < end && sb[i + 1] == '[')
+                if (char.IsHighSurrogate(c) && (i + 1) < end && char.IsLowSurrogate(sb[i + 1]))
+                {
+                    sum++;
+                    i++; // Skip the low surrogate
+                    continue;
+                }
+                else if (c == 0x1b && (i + 1) < end && sb[i + 1] == '[')
                 {
                     // Simple escape sequence skipping
                     i += 2;