[Bug]: File list partially missing after opening a file in viewer until scroll

[kesselb]

Bug description

File list partially missing after opening a file in viewer until scroll. Some folders that were previously visible become invisible. The file list appears truncated or partially blank.

Steps to reproduce

1. Have viewer and files_pdfviewer
2. Go to the Files app
3. Create a new folder named "Documents" and open it
4. Upload one or more files (PDF or text) that can be opened in the viewer
5. Create several subfolders such as "Dossier A", "Dossier B", "Dossier C", ... , "Dossier P" (the documents, to be opened, must not be visible when opening the folder).
6. Click on the folder name in the breadcrumbs (make sure you see the folder’s ID in the URL)
7. Scroll down to the uploaded file
8. Click the file to open it in the viewer

Screencast.From.2025-11-02.20-45-17.mp4

Expected behavior

No blank list.

Nextcloud Server version

32 / 31 / 30

Additional info

• Scrolling (with the mouse or keyboard) makes the missing folders reappear.
• After opening the file once, the file ID in the URL is replaced. If the page is reloaded at this point, the list loads correctly and no truncation occurs.
• Debug output shows that in the broken case the startIndex is 17, while in the working case it is 4.

[kesselb]

Hi,

I’m not so familiar with VirtuaList and its expected behavior, but in my tests I was able to resolve the blank state by using:

this.index = Math.min(index, clampedIndex)

just like we do for calculating scrollTop.

server/apps/files/src/components/VirtualList.vue

Lines 350 to 358 in 143d486

	// We can not scroll further as the last page of rows
	// For the grid view we also need to account for all columns in that row (columnCount - 1)
	const clampedIndex = (this.totalRowCount - this.visibleRows) * this.columnCount + (this.columnCount - 1)
	// The scroll position
	let scrollTop = this.indexToScrollPos(Math.min(index, clampedIndex))
	// First we need to update the internal index for rendering.
	// This will cause the <tbody> element to be resized allowing us to set the correct scroll position.
	this.index = index