From abcc5342eee8e7e2fc22b3b35bc0afeaf9e8192c Mon Sep 17 00:00:00 2001
From: "neovim-backports[bot]"
 <175700243+neovim-backports[bot]@users.noreply.github.com>
Date: Mon, 13 Apr 2026 18:31:24 -0400
Subject: [PATCH] fix(terminal): do not reflow altscreen on resize #39024

Problem: reflow can break tui display
Solution: disable reflow on altscreen
(cherry picked from commit 7bb8231577d11b31cbc85b563c6bc299b64957d4)

Co-authored-by: phanium <91544758+phanen@users.noreply.github.com>
---
 src/nvim/vterm/screen.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/nvim/vterm/screen.c b/src/nvim/vterm/screen.c
index 1206373241..99c8e61748 100644
--- a/src/nvim/vterm/screen.c
+++ b/src/nvim/vterm/screen.c
@@ -498,17 +498,19 @@ static void resize_buffer(VTermScreen *screen, int bufidx, int new_rows, int new
   // scrolling into
   int final_blank_row = new_rows;
 
+  bool do_reflow = screen->reflow && (bufidx == BUFIDX_PRIMARY);
+
   while (old_row >= 0) {
     int old_row_end = old_row;
     // TODO(vterm): Stop if dwl or dhl
-    while (screen->reflow && old_lineinfo && old_row > 0 && old_lineinfo[old_row].continuation) {
+    while (do_reflow && old_lineinfo && old_row > 0 && old_lineinfo[old_row].continuation) {
       old_row--;
     }
     int old_row_start = old_row;
 
     int width = 0;
     for (int row = old_row_start; row <= old_row_end; row++) {
-      if (screen->reflow && row < (old_rows - 1) && old_lineinfo[row + 1].continuation) {
+      if (do_reflow && row < (old_rows - 1) && old_lineinfo[row + 1].continuation) {
         width += old_cols;
       } else {
         width += line_popcount(old_buffer, row, old_rows, old_cols);
@@ -519,7 +521,7 @@ static void resize_buffer(VTermScreen *screen, int bufidx, int new_rows, int new
       final_blank_row = new_row;
     }
 
-    int new_height = screen->reflow
+    int new_height = do_reflow
                      ? width ? (width + new_cols - 1) / new_cols : 1
                      : 1;
 
@@ -595,7 +597,7 @@ static void resize_buffer(VTermScreen *screen, int bufidx, int new_rows, int new
         if (old_col == old_cols) {
           old_row++;
 
-          if (!screen->reflow) {
+          if (!do_reflow) {
             new_col++;
             break;
           }