Quicklook Thumbnailing not working in iOS 16 betas

Our app has a custom file format and implements a Quicklook Thumbnailing extension. In iOS 16 (through to the latest beta 8 release) thumbnails are not generated in the Files app. And also are not returned for calls to QLThumbnailGenerator.

Apple's sample app for this shows the same problem:

https://developer.apple.com/documentation/uikit/view_controllers/building_a_document_browser_app_for_custom_file_formats

I rolled back to iOS 15 to be sure and both our app and Apple's sample work there but fail in iOS 16.

The console shows:

error	13:34:59.136343-0700	LocalStorageFileProvider	[ERROR] Creating internal error for "startFetchThumbnailOperationOverall", original error was: NSError: Cocoa 3328 "<private>"
error	13:34:59.136801-0700	LocalStorageFileProvider	[ERROR] Creating internal error for "startFetchThumbnailOperationOverall", original error was: NSError: Cocoa 3328 "<private>"
error	13:34:59.137602-0700	com.apple.quicklook.ThumbnailsAgent	Failing <private>, which did not get a per-thumbnail download completion block
error	13:34:59.137767-0700	com.apple.quicklook.ThumbnailsAgent	Failing <private>, which did not get a per-thumbnail download completion block
error	13:34:59.137841-0700	com.apple.quicklook.ThumbnailsAgent	Failing <private>, which did not get a per-thumbnail download completion block
error	13:34:59.137948-0700	com.apple.quicklook.ThumbnailsAgent	Failing <private>, which did not get a per-thumbnail download completion block
error	13:34:59.138159-0700	com.apple.quicklook.ThumbnailsAgent	Failing <private>, which did not get a per-thumbnail download completion block
error	13:34:59.138283-0700	com.apple.quicklook.ThumbnailsAgent	Failing <private>, which did not get a per-thumbnail download completion block
error	13:34:59.620873-0700	LocalStorageFileProvider	[ERROR] Creating internal error for "startFetchThumbnailOperationOverall", original error was: NSError: Cocoa 3328 "<private>"
error	13:34:59.621362-0700	LocalStorageFileProvider	[ERROR] Creating internal error for "startFetchThumbnailOperationOverall", original error was: NSError: Cocoa 3328 "<private>"
error	13:34:59.622256-0700	com.apple.quicklook.ThumbnailsAgent	Failing <private>, which did not get a per-thumbnail download completion block

I filed feedback at the start of August (FB11066418) but have had no response. Is anyone else seeing this issue?

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combinatorial
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This is fixed in iPadOS 16 beta 11 and iOS 16.1 beta 4

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combinatorial
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  • I can confirm it works in iOS 16.1 beta 4, however it still does not work on my other devices run iOS 14 and iOS 15. Btw, do you know how to create a thumbnail with transparent part? My file thumbnails always have a white background, if I don't draw the image on the whole context. I tried context.flush, context.clearRect() without success. My file thumbnails looks not so great in light mode and even worse in dark mode

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    quochuywdm
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I am seeing the same problem with iOS 16, including with the release candidate. I am getting a slightly different error message, probably because we are trying to get the thumbnails from within our own app.

For files stored in iCloud (ubiquitous container) I am seeing this error:

Error Domain=QLThumbnailErrorDomain Code=3 "No thumbnail in the cloud for file:///private/var/mobile/Library/Mobile%20Documents/iCloud~com~pixite~Zinnia/Documents/Journals/Untitled%2011.zinnia/pages/0B10F371-94FB-4658-9333-04C9C9D81163.zinniapage" UserInfo={NSErrorFailingURLKey=file:///private/var/mobile/Library/Mobile%20Documents/iCloud~com~pixite~Zinnia/Documents/Journals/Untitled%2011.zinnia/pages/0B10F371-94FB-4658-9333-04C9C9D81163.zinniapage}

For files in local storage, I see this error:

Error Domain=QLThumbnailErrorDomain Code=0 "Could not generate a thumbnail"

I also filed a bug at the beginning of August (FB11011263) but have received no response. Before that I opened a DTS ticket about it, and they eventually just told me to file a bug. So apparently they know it is a bug on their end.

This is actually completely crippling our app on iOS 16, because the users can't tell which of their documents are which without working thumbnails.

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NateP
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And I should note that when using iCloud (ubiquitous container), we get a different thumbnail error when we initially create the document:

Error Domain=NSCocoaErrorDomain Code=4101 "Provider returned unsupported error" UserInfo={NSDebugDescription=Provider returned unsupported error, NSUnderlyingError=0x2811fd920 {Error Domain=CKErrorDomain Code=11 "<CKError 0x102f0d760: "Unknown Item" (11/2003); server message = "Record not found"; op = B21EB1404E50EF3F; uuid = 46519FDB-FB10-48FF-B736-93650812BA45; container ID = "com.apple.clouddocs">" UserInfo={ContainerID=com.apple.clouddocs, NSDebugDescription=<CKError 0x102f0d760: "Unknown Item" (11/2003); server message = "Record not found"; op = B21EB1404E50EF3F; uuid = 46519FDB-FB10-48FF-B736-93650812BA45; container ID = "com.apple.clouddocs">, OperationID=B21EB1404E50EF3F, RequestUUID=46519FDB-FB10-48FF-B736-93650812BA45, errorKey=ckvneous, ServerErrorDescription=Record not found, CKErrorDescription=Error fetching record <CKRecordID: 0x101231ae0; recordName=documentContent/73A97D26-23B8-46CD-B326-51DCC94477EC, zoneID=iCloud.com.pixite.Zinnia:__defaultOwner__> from server: Record not found, NSLocalizedDescription=Error fetching record <CKRecordID: 0x101231ae0; recordName=documentContent/73A97D26-23B8-46CD-B326-51DCC94477EC, zoneID=iCloud.com.pixite.Zinnia:__defaultOwner__> from server: Record not found, NSUnderlyingError=0x2811ff360 {Error Domain=CKInternalErrorDomain Code=2003 "<CKError 0x102f31be0: "Unknown Item" (2003); server message = "Record not found"; op = B21EB1404E50EF3F; uuid = 46519FDB-FB10-48FF-B736-93650812BA45; container ID = "com.apple.clouddocs">" UserInfo={ContainerID=com.apple.clouddocs, OperationID=B21EB1404E50EF3F, NSDebugDescription=<CKError 0x102f31be0: "Unknown Item" (2003); server message = "Record not found"; op = B21EB1404E50EF3F; uuid = 46519FDB-FB10-48FF-B736-93650812BA45; container ID = "com.apple.clouddocs">, RequestUUID=46519FDB-FB10-48FF-B736-93650812BA45, errorKey=ckvneous, ServerErrorDescription=Record not found, CKErrorDescription=Error fetching record <CKRecordID: 0x101231ae0; recordName=documentContent/73A97D26-23B8-46CD-B326-51DCC94477EC, zoneID=iCloud.com.pixite.Zinnia:__defaultOwner__> from server: Record not found, NSLocalizedDescription=Error fetching record <CKRecordID: 0x101231ae0; recordName=documentContent/73A97D26-23B8-46CD-B326-51DCC94477EC, zoneID=iCloud.com.pixite.Zinnia:__defaultOwner__> from server: Record not found}}}}}
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NateP
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  • I have received a promising status update on my feedback... "Resolution: Potential fix identified - For a future OS update"

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    combinatorial
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This is fixed in iPadOS 16 beta 11 and iOS 16.1 beta 4

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combinatorial
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Post marked as solved

  • I can confirm it works in iOS 16.1 beta 4, however it still does not work on my other devices run iOS 14 and iOS 15. Btw, do you know how to create a thumbnail with transparent part? My file thumbnails always have a white background, if I don't draw the image on the whole context. I tried context.flush, context.clearRect() without success. My file thumbnails looks not so great in light mode and even worse in dark mode

    —
    quochuywdm
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