From fcc7dfb89699faa3b09543fee9b2430863f31687 Mon Sep 17 00:00:00 2001
From: t8y2 <1156263951@qq.com>
Date: Mon, 7 Sep 2026 19:21:42 +0800
Subject: [PATCH] fix(editor): restore viewport on uncached tab activations

Closes #8374
---
 .../src/components/editor/QueryEditor.vue     |  6 +++
 .../editorTabSwitchViewportRestore.test.ts    | 38 +++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 packages/app-tests/editorTabSwitchViewportRestore.test.ts

diff --git a/apps/desktop/src/components/editor/QueryEditor.vue b/apps/desktop/src/components/editor/QueryEditor.vue
index cce624676f..ee6909c88d 100644
--- a/apps/desktop/src/components/editor/QueryEditor.vue
+++ b/apps/desktop/src/components/editor/QueryEditor.vue
@@ -6701,6 +6701,12 @@ function activateTabDocument(prevTabId: string | undefined, tabId: string | unde
   const cached = tabId === undefined ? undefined : tabStateCache.get(tabId);
   if (!cached) {
     swapEditorDocument(doc);
+    // First activation in this editor instance (or a cache-evicted tab, e.g.
+    // beyond MAX_CACHED_TAB_STATES): restore the tab's saved cursor and scroll
+    // position exactly like the cached-state branch, otherwise the swapped-in
+    // document keeps whatever scroll offset the dispatch left behind (#8374).
+    restoreEditorSelection();
+    restoreEditorViewport();
     return;
   }
   // setState swaps doc, selection, undo history and all fields at once, but it
diff --git a/packages/app-tests/editorTabSwitchViewportRestore.test.ts b/packages/app-tests/editorTabSwitchViewportRestore.test.ts
new file mode 100644
index 0000000000..1261e3c695
--- /dev/null
+++ b/packages/app-tests/editorTabSwitchViewportRestore.test.ts
@@ -0,0 +1,38 @@
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import path from "node:path";
+import { test } from "vitest";
+
+/**
+ * The shared editor swaps documents on tab switches (per-tab EditorState cache
+ * since the undo-isolation fix). Both branches of that swap — the cached
+ * `setState` path AND the uncached `swapEditorDocument` path (first activation
+ * in this editor instance, or a tab evicted from the state cache) — must
+ * restore the incoming tab's saved cursor and scroll position. Skipping the
+ * restore on the uncached branch is what made switching back to a tab land on
+ * line 1 instead of the previous viewport (#8374).
+ */
+function activateTabDocumentSource(): string {
+  const source = readFileSync(path.resolve("apps/desktop/src/components/editor/QueryEditor.vue"), "utf8");
+  const start = source.indexOf("function activateTabDocument");
+  assert.notEqual(start, -1, "expected activateTabDocument in QueryEditor.vue");
+  const end = source.indexOf("\n}", start);
+  assert.notEqual(end, -1, "expected activateTabDocument closing brace");
+  return source.slice(start, end);
+}
+
+test("uncached tab activation restores the saved cursor and scroll position", () => {
+  const source = activateTabDocumentSource();
+  assert.match(source, /if \(!cached\) \{[\s\S]*?swapEditorDocument\(doc\);[\s\S]*?restoreEditorSelection\(\);[\s\S]*?restoreEditorViewport\(\);[\s\S]*?return;/, "the swapEditorDocument branch must restore selection and viewport before returning");
+});
+
+test("cached tab activation keeps restoring selection and viewport", () => {
+  const source = activateTabDocumentSource();
+  assert.match(source, /currentView\.setState\(cached\);/);
+  assert.match(source, /currentView\.setState\(cached\);[\s\S]*?restoreEditorSelection\(\);\s*restoreEditorViewport\(\);/);
+});
+
+test("viewport restore prefers the per-tab saved viewport", () => {
+  const source = readFileSync(path.resolve("apps/desktop/src/components/editor/QueryEditor.vue"), "utf8");
+  assert.match(source, /function restoreEditorViewport\(\) \{[\s\S]*?const viewport = props\.initialViewport \?\? latestViewport;/);
+});