From 2368a66a8fb68df3eab52bd63b12ede335f0cdc7 Mon Sep 17 00:00:00 2001
From: liuweitao <tao@sadais.com>
Date: Fri, 10 Apr 2026 00:49:27 +0800
Subject: [PATCH] =?UTF-8?q?fix(terminal):=20=E9=94=81=E5=AE=9A=E7=94=A8?=
 =?UTF-8?q?=E6=88=B7=E6=BB=9A=E5=8A=A8=E4=BD=8D=E7=BD=AE=E9=98=B2=E6=AD=A2?=
 =?UTF-8?q?=20AI=20=E8=BE=93=E5=87=BA=E6=97=B6=E5=86=85=E5=AE=B9=E8=B7=B3?=
 =?UTF-8?q?=E5=8A=A8?=
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当用户向上滚动查看历史内容时，AI 持续输出的 TUI 控制序列
（如清屏 \x1b[2J、清滚动缓冲区 \x1b[3J）会改变 viewport 位置，
导致正在阅读的文字跳动或重叠。

修复方案：在 terminal.write() 前后锁定用户距离底部的滚动偏移量，
写入完成后用 scrollLines() 恢复 viewport 位置。
---
 src/renderer/hooks/useXterm.ts | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/renderer/hooks/useXterm.ts b/src/renderer/hooks/useXterm.ts
index 75e367ef..df8761f2 100644
--- a/src/renderer/hooks/useXterm.ts
+++ b/src/renderer/hooks/useXterm.ts
@@ -614,7 +614,27 @@ export function useXterm({
             setTimeout(() => {
               if (writeBufferRef.current.length > 0) {
                 const bufferedData = writeBufferRef.current;
+
+                // If user has scrolled up to view history, lock their viewport position.
+                // TUI control sequences (CSI 2J, CSI 3J, alternate buffer switch)
+                // can reset or scroll the viewport regardless of isUserScrolling.
+                // We preserve the user's scroll offset from the bottom.
+                const buffer = terminal.buffer.active;
+                const offsetFromBottom = buffer.baseY - buffer.viewportY;
+                const shouldLockViewport = offsetFromBottom > 0;
+                const savedOffsetFromBottom = shouldLockViewport ? offsetFromBottom : 0;
+
                 terminal.write(bufferedData);
+
+                // Restore viewport if it was moved by the write
+                if (shouldLockViewport) {
+                  const targetViewportY = terminal.buffer.active.baseY - savedOffsetFromBottom;
+                  const currentViewportY = terminal.buffer.active.viewportY;
+                  if (targetViewportY !== currentViewportY) {
+                    terminal.scrollLines(targetViewportY - currentViewportY);
+                  }
+                }
+
                 // Call onData after write to avoid React re-render storm
                 onDataRef.current?.(bufferedData);
                 writeBufferRef.current = '';