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fix(web): file tabs keep their scroll position when you switch back - #37361
All file tabs in a workspace share one FilePreviewPanel, but the code view (EditableFileSurface, keyed by relativePath, or ReadOnlySourcePreview, whose Virtualizer is keyed by name) is rebuilt for each file, and nothing remembered its scroll offset, so a tab you return to always started at scrollTop 0. The fix lives in useFileLineReveal, which already keeps state per path and is the onPostRender for both code views. On the File's 'unmount' post-render it saves the .file-preview-virtualizer scrollTop; the container is still connected at that point and holds the real offset (4200 in the test). On the first post-render inside a new container it restores the saved offset. It waits for animation frames, up to REVEAL_MAX_ATTEMPTS, until scrollHeight - clientHeight can fit the offset, so the value isn't clipped. It skips the restore if the user has already scrolled (scrollTop != 0) or a line reveal for that path is still pending, which keeps the jump-to-line behaviour unchanged. A first version recorded the offset from scroll events and still failed the test, because scroll events fire on the next frame, after the tab switch has removed the view; saving on unmount fixes that. Nothing else changes visibly. No new regex or parser.
Commit b732621 (origin/main). Fresh worktree, vp i, T3CODE_DEV_SEED=0 vp run dev, paired the preview browser at the dev web URL. The auto-created project was apps/server. Opened right panel > Files, searched src/ws.ts and opened it (its own tab; .file-preview-virtualizer scrollHeight 78,436). Scrolled the code view with a real wheel scroll to scrollTop 4200. Opened serverSettings.test.ts from the explorer, which got a second tab ('Close ws.ts', 'Close serverSettings.test.ts'); only one virtualizer stays mounted. Clicked the ws.ts tab: breadcrumb showed server/src/ws.ts, and scrollTop was 0 at 100 ms, 600 ms and 2 s. Failing test on branch factory/repro-37348 (dd551b7): a new case in apps/web/src/components/files/FilePreviewPanel.browser.test.tsx renders a 2,000-line a.ts, sets scrollTop 4200, rerenders with b.ts (scrollTop 0), rerenders with a.ts, and expects 4200. It fails on main with 'expected +0 to be 4200'.
Evidence
Being captured: before and after in the real app. This section is filled in before the pull request can merge.
Tests
vp test run apps/web/src/components/files/FilePreviewPanel.browser.test.tsx: 10/10 passed, including the repro case 'returns a file tab to where it was scrolled after another file was shown'. A scroll-listener variant of the fix still failed it with 'expected +0 to be 4200', the same failure as main. vp run check:changed: format, lint, knip, typecheck (2 packages), tests (2 files) and react compiler all pass. Not checked by hand in the running dev app; the browser test covers the same remount sequence.
Not in this change
Saved offsets live only as long as the FilePreviewPanel, so they are lost when the right panel closes or the workspace changes; making them last longer was left out.
Every file tab in a workspace shares one FilePreviewPanel, and the code
view remounts per file, so returning to a tab showed it at the top.
Record the code view's offset when a file's view unmounts and restore it
on the next mount, unless a line reveal is pending for that file.
Fixes#37348
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Macroscope's review found this PR approvable — File previews now remember their scroll position when switching tabs, while explicit line navigation takes precedence. The change is limited to transient UI state and introduces no material data or operational exposure.
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No actionable comments were generated in the recent review.
Walkthrough
Code file previews now save each file’s scroll position when its view unmounts and restore it when the view returns. A browser test checks that the original file returns to its saved position and that a newly shown file starts at the top.
Changes: Code file scroll restoration
Layer / File(s)
Summary
Save per-file scroll state apps/web/src/components/files/FilePreviewPanel.tsx
Per-path state tracks the scroll offset and container. The unmount callback saves the offset and cancels pending restoration work.
Restore scroll position apps/web/src/components/files/FilePreviewPanel.tsx, apps/web/src/components/files/FilePreviewPanel.browser.test.tsx
When a file view returns, restoration retries until the saved offset fits or the attempt limit is reached. It stops if the container disconnects or has already scrolled. The test checks that switching files preserves the original file’s position and starts the other file at 0.
Code file tabs now keep their vertical scroll position when you switch back. The change is limited to code previews and appears low risk, with no outstanding issues found.
Pre-merge checks: 3 · 1
Failed checks: 1 inconclusive
Check name
Status
Explanation
Resolution
Description check
The description follows the template. It covers the problem (scroll reset on tab return), the change (save on unmount, restore on remount, skip rules), scope (links issue #37348, Markdown excluded via…
Complete the Evidence section with before/after screenshots (or a short recording) of the real app showing a code tab keeping its scroll position after switching back. The template requires these for UI changes. Remove the statement that th…
Passed checks: 3 passed
Check name
Status
Explanation
Title check
The title names the fix (file tabs restoring scroll position on switch back), the web scope, and the conventional commit format. It matches the changeset, which saves and restores the code-view scroll…
Linked Issues check
Directly linked issue #37348 requires code files to keep their vertical scroll offset when their right-panel tab is hidden and shown again. The whole-PR diff against merge base b732621 changes useF…
Out of Scope Changes check
The whole-PR diff changes FilePreviewPanel.tsx and FilePreviewPanel.browser.test.tsx. The FilePreviewPanel.tsx changes add scroll-offset fields to FileRevealState, save the offset on unmount, add a gu…
Full details: Title check
Explanation
The title names the fix (file tabs restoring scroll position on switch back), the web scope, and the conventional commit format. It matches the changeset, which saves and restores the code-view scroll offset in useFileLineReveal. It does not mention that the scope is limited to code previews, which is a minor omission.
Full details: Linked Issues check
Explanation
Directly linked issue #37348 requires code files to keep their vertical scroll offset when their right-panel tab is hidden and shown again. The whole-PR diff against merge base b732621 changes useFileLineReveal in FilePreviewPanel.tsx. On the 'unmount' phase, the hook stores the .file-preview-virtualizer scrollTop in per-path state. On the first post-render in a new container, it restores the saved offset in animation frames, up to REVEAL_MAX_ATTEMPTS, until scrollHeight - clientHeight can hold the offset. The restore is skipped when the container is disconnected, scrollTop is not 0, or a line reveal for the path is pending. The head adds a restorePending guard. It keeps the saved offset when a restore is still pending during a StrictMode mount-unmount-remount sequence. The browser test 'returns a file tab to where it was scrolled after another file was shown' covers the reported sequence (a.ts at 4200, switch to b.ts, return to a.ts, expect 4200). The PR reports 10/10 passing. The incremental diff from the previous reviewed head could not be read, so this verdict relies on the whole-PR diff. The Evidence section is pending. Manual verification in the running app is not established. The automated test covers the requirement.
Full details: Out of Scope Changes check
Explanation
The whole-PR diff changes FilePreviewPanel.tsx and FilePreviewPanel.browser.test.tsx. The FilePreviewPanel.tsx changes add scroll-offset fields to FileRevealState, save the offset on unmount, add a guarded restore loop, and cancel the restore frame in the existing cleanup. Each change serves the scroll-restoration objective of #37348. The test file adds a regression test for the same objective, including a StrictMode variant. The PR description states that Markdown, table, large-text, and other non-code previews, persistence after panel close, and scrollLeft are not changed. No changed code path in the reviewed diff touches those previews. No unrelated change was found.
Full details: Description check
Explanation
The description follows the template. It covers the problem (scroll reset on tab return), the change (save on unmount, restore on remount, skip rules), scope (links issue #37348, Markdown excluded via #23503), and verification (test run and check results). The Evidence section is explicitly still pending, and the template asks for before/after screenshots for UI changes. The template's requirement for a model/harness attribution is met. The description notes the manual check was not performed in the running app.
Resolution
Complete the Evidence section with before/after screenshots (or a short recording) of the real app showing a code tab keeping its scroll position after switching back. The template requires these for UI changes. Remove the statement that the section 'is filled in before the pull request can merge' once the evidence is attached. Optionally state the manual check result in the Verification section, since the author reports it was not checked by hand in the running dev app.
Finishing Touches
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Actionable comments posted: 1
Fix comments: Fix CodeRabbit comments on this PR
Prompt to fix all issues
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Inline comments:
Review comments at @apps/web/src/components/files/FilePreviewPanel.tsx:
- Line 550: Update the scroll-position save logic around state.scrollTop so
switching away during a pending restoration does not overwrite the saved offset
with the container’s temporary position. Preserve the offset until restoration
completes or user input establishes a new position, and extend the existing
browser case to verify that an interrupted restoration retains the saved offset.
---
Failed pre-merge checks:
- Description check:
Add the before/after screenshots for the UI change to the Evidence section.
Upload them to GitHub and embed or link them. Replace the placeholder text
'Being captured' with the final evidence. Otherwise the description is complete.
The Problem, Change, Scope, Verification, and attribution sections are present
and specific.
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…ed offset
The app renders under StrictMode, so a file view returning to its tab
mounts, unmounts before its restore frame runs, and mounts again. That
unmount recorded scrollTop 0 over the saved offset. Keep the saved offset
when a view unmounts with its restore still pending, and render the
scroll test under StrictMode so it covers this path.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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All file tabs in a workspace share one FilePreviewPanel, but the code view (EditableFileSurface, keyed by relativePath, or ReadOnlySourcePreview, whose Virtualizer is keyed by name) is rebuilt for each file, and nothing remembered its scroll offset, so a tab you return to always started at scrollTop 0. The fix lives in useFileLineReveal, which already keeps state per path and is the onPostRender for both code views. On the File's 'unmount' post-render it saves the .file-preview-virtualizer scrollTop; the container is still connected at that point and holds the real offset (4200 in the test). On the first post-render inside a new container it restores the saved offset. It waits for animation frames, up to REVEAL_MAX_ATTEMPTS, until scrollHeight - clientHeight can fit the offset, so the value isn't clipped. It skips the restore if the user has already scrolled (scrollTop != 0) or a line reveal for that path is still pending, which keeps the jump-to-line behaviour unchanged. A first version recorded the offset from scroll events and still failed the test, because scroll events fire on the next frame, after the tab switch has removed the view; saving on unmount fixes that. Nothing else changes visibly. No new regex or parser.
Fixes #37348
Reproduction on main
Commit b732621 (origin/main). Fresh worktree,
vp i,T3CODE_DEV_SEED=0 vp run dev, paired the preview browser at the dev web URL. The auto-created project was apps/server. Opened right panel > Files, searchedsrc/ws.tsand opened it (its own tab; .file-preview-virtualizer scrollHeight 78,436). Scrolled the code view with a real wheel scroll to scrollTop 4200. Opened serverSettings.test.ts from the explorer, which got a second tab ('Close ws.ts', 'Close serverSettings.test.ts'); only one virtualizer stays mounted. Clicked the ws.ts tab: breadcrumb showed server/src/ws.ts, and scrollTop was 0 at 100 ms, 600 ms and 2 s. Failing test on branch factory/repro-37348 (dd551b7): a new case in apps/web/src/components/files/FilePreviewPanel.browser.test.tsx renders a 2,000-line a.ts, sets scrollTop 4200, rerenders with b.ts (scrollTop 0), rerenders with a.ts, and expects 4200. It fails on main with 'expected +0 to be 4200'.Evidence
Being captured: before and after in the real app. This section is filled in before the pull request can merge.
Tests
vp test run apps/web/src/components/files/FilePreviewPanel.browser.test.tsx: 10/10 passed, including the repro case 'returns a file tab to where it was scrolled after another file was shown'. A scroll-listener variant of the fix still failed it with 'expected +0 to be 4200', the same failure as main. vp run check:changed: format, lint, knip, typecheck (2 packages), tests (2 files) and react compiler all pass. Not checked by hand in the running dev app; the browser test covers the same remount sequence.
Not in this change
Who did the work
Run by the t3code factory in T3 Code.