From f3f4dcaf9fa295a4b3807391bf9336d741c8557e Mon Sep 17 00:00:00 2001
From: Daniel Imms <2193314+Tyriar@users.noreply.github.com>
Date: Wed, 3 Jun 2026 07:05:19 -0700
Subject: [PATCH] fix(CharacterJoiner): bound join ranges to trimmed line
 length (#5990)

Character joiner scanning already iterated cells with
getTrimmedLength(), but trailing attribute runs and
_stringRangesToCellRanges used buffer cols. On short lines that
could run joiners on a single trailing cell and extend open ranges
through empty tail columns, affecting ligature/join rendering.

Use trimmed length consistently for trailing-run detection, the
cell-range walk, and the final range end column.

Co-authored-by: Cursor <cursoragent@cursor.com>
---
 src/browser/services/CharacterJoinerService.ts | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/browser/services/CharacterJoinerService.ts b/src/browser/services/CharacterJoinerService.ts
index e1da0bd28..2cf3bd506 100644
--- a/src/browser/services/CharacterJoinerService.ts
+++ b/src/browser/services/CharacterJoinerService.ts
@@ -100,6 +100,7 @@ export class CharacterJoinerService implements ICharacterJoinerService {
 
     const ranges: [number, number][] = [];
     const lineStr = line.translateToString(true);
+    const trimmedLength = line.getTrimmedLength();
 
     // Because some cells can be represented by multiple javascript characters,
     // we track the cell and the string indexes separately. This allows us to
@@ -111,7 +112,7 @@ export class CharacterJoinerService implements ICharacterJoinerService {
     let rangeAttrFG = line.getFg(0);
     let rangeAttrBG = line.getBg(0);
 
-    for (let x = 0; x < line.getTrimmedLength(); x++) {
+    for (let x = 0; x < trimmedLength; x++) {
       line.loadCell(x, this._workCell);
 
       if (this._workCell.getWidth() === 0) {
@@ -147,7 +148,7 @@ export class CharacterJoinerService implements ICharacterJoinerService {
     }
 
     // Process any trailing ranges.
-    if (this._bufferService.cols - rangeStartColumn > 1) {
+    if (trimmedLength - rangeStartColumn > 1) {
       const joinedRanges = this._getJoinedRanges(
         lineStr,
         rangeStartStringIndex,
@@ -216,7 +217,8 @@ export class CharacterJoinerService implements ICharacterJoinerService {
       return;
     }
 
-    for (let x = startCol; x < this._bufferService.cols; x++) {
+    const trimmedLength = line.getTrimmedLength();
+    for (let x = startCol; x < trimmedLength; x++) {
       const width = line.getWidth(x);
       const length = line.getString(x).length || WHITESPACE_CELL_CHAR.length;
 
@@ -264,7 +266,7 @@ export class CharacterJoinerService implements ICharacterJoinerService {
     // If there is still a range left at the end, it must extend all the way to
     // the end of the line.
     if (currentRange) {
-      currentRange[1] = this._bufferService.cols;
+      currentRange[1] = trimmedLength;
     }
   }