What does the WTS_E_EXTRACTIONPENDING HRESULT returned by IThumbnailCache::GetThumbnail mean?

jl-syno 0

Attemting to call IThumbnailCache::GetThumbnail on an dehydrated placeholder (i.e. from OneDrive or other sync programs that utilize Cloud Filter) which its thumbnail doesn't exist in the Windows Thumbnail Cache results in "WTS_E_EXTRACTIONPENDING".

If I wait for some time then call IThumbnailCache::GetThumbnail then it'll succeed, so I assume "WTS_E_EXTRACTIONPENDING" means "You triggered the OS to extract and save the thumbnail into the cache, but you must wait"? If so, then how would I know when? Other than calling IThumbnailCache::GetThumbnail with WTS_INCACHEONLY every 100 milliseconds or so?

Other interfaces for extracting thumbnails also return this HRESULT code, like IThumbnailProvider or IShellItemImageFactory. This HRESULT code "WTS_E_EXTRACTIONPENDING" does not show on ony of the documents. I presume this is a new thing introduced along the Cloud Filter API?

Xiaopo Yang - MSFT 11,496 Reputation points Microsoft Vendor

2024-03-28T08:49:46.99+00:00

Cannot reproduce with CloudMirror. It depends on the Windows Shell ThumbnailProviderHandler for cloud based placeholder files of application, desktop3:ThumbnailProviderHandler.

jl-syno 0

Thanks for the quick reply.

Here I got a minimal repro: (My Windows version is Windows 10 Pro 22H2 19045.2006)

#include <array>
#include <filesystem>
#include <format>
#include <iostream>
#include <string>
#include <string_view>

#include <Windows.h>
#include <atlimage.h>
#include <fcntl.h>
#include <io.h>
#include <objbase.h>
#include <thumbcache.h>
#include <winrt/base.h>

namespace {
struct CoInitializeWrapper {
	[[nodiscard]] CoInitializeWrapper()
	{
		winrt::init_apartment(winrt::apartment_type::single_threaded);
	}

	~CoInitializeWrapper() noexcept
	{
		winrt::uninit_apartment();
	}
};

void GenerateThumbnail(const std::wstring& path, const std::wstring& output_path, const unsigned int xy)
{
	std::array<wchar_t, 4096> full_path;
	winrt::check_hresult(::GetFullPathNameW(path.c_str(), full_path.size(), full_path.data(), nullptr));

	winrt::com_ptr<IShellItem> psi;
	psi.capture(::SHCreateItemFromParsingName, full_path.data(), nullptr);

	winrt::com_ptr<IThumbnailCache> ptc;
	ptc.capture(::CoCreateInstance, CLSID_LocalThumbnailCache, nullptr, CLSCTX_INPROC_SERVER);

	winrt::com_ptr<ISharedBitmap> pbm;
	winrt::check_hresult(ptc->GetThumbnail(psi.get(), xy, WTS_EXTRACT | WTS_SCALETOREQUESTEDSIZE, pbm.put(), nullptr, nullptr));

	ATL::CImage img;
	{
		HBITMAP temp = nullptr;
		winrt::check_hresult(pbm->Detach(&temp));
		img.Attach(temp);
	}

	winrt::check_hresult(img.Save(output_path.c_str()));
}
}  // namespace

int wmain(int argc, wchar_t* argv[])
{
	setmode(fileno(stdout), _O_U16TEXT);
	setmode(fileno(stderr), _O_U16TEXT);
	try {
		if (argc < 4) {
			std::wcout << std::format(L"Usage: {} <input> <output> <xy>", std::filesystem::path{std::wstring_view{argv[0]}}.filename().wstring()) << std::endl;
			return 1;
		}

		CoInitializeWrapper coinit_;

		const std::wstring& input = argv[1];
		const std::wstring& output = argv[2];
		const unsigned int xy = std::stoul(argv[3]);
		GenerateThumbnail(input, output, xy);
	} catch (const winrt::hresult_error& he) {
		std::wcout << std::format(L"({}): {}", he.code().operator int(), he.message().operator std::wstring_view()) << std::endl;
		return 1;
	}
	return 0;
}

Compile this (using C++20)
Then launch OneDrive App for PC to login and sync (My version: 24.045.0303.0003 (x64))
Upload an image to OneDrive with your browser
Now you shall see the notification that the image file is synced to your PC in the OneDrive Tray
Make sure you don't browse that image in Explorer or otherwise the thumbnail would be extracted and saved in cache
Now, use the program from step 1 to extract the thumbnail of that image, and it should throw WTS_E_EXTRACTIONPENDING
(optional) Run step 6 again. This time it would succeed.

BTW this HRESULT exists in "thumbcache.h" so I don't think it entirely depends on the implementation. Sure maybe it's OneDrive who decided to return this code, but this code is predifined in the API already. (There are 4 more HRESULTs defined in thumbcache.h which are not listed in IThumbnailCache::GetThumbnail's document: WTS_E_DATAFILEUNAVAILABLE, WTS_E_EXTRACTIONPENDING, WTS_E_EXTRACTIONBLOCKED, WTS_E_NOSTORAGEPROVIDERTHUMBNAILHANDLER. It would be great if you guys could also elaborate what those HRESULTs mean.

Xiaopo Yang - MSFT 11,496 Reputation points Microsoft Vendor

2024-03-29T05:59:43.86+00:00

It's just an error code and such even more error codes would be defined. Such error codes are meaningless until we encounter them. Why they are defined could also be related to Onedrive as we know Onedrive is a Microsoft product.

And as I said, the error code is returned by the ThumbnailProviderHandler of package applications.

7.(optional) Run step 6 again. This time it would succeed.

It should be a right way to handle the error code.
jl-syno 0 Reputation points

2024-03-29T06:11:10.88+00:00

But your saying as if OneDrive is developed by another company. Microsoft developed it, and it gets first class support (being able to directly add new HRESULTs to WINAPI; if I were to designate a new HRESULT code for my own product no one would honor it, and could be overridden by Microsoft at any time). Clearly the team responsible for shell APIs knows about (and approves) this code, instead of OneDrive team just adding it to the WINAPI codebase.

7.(optional) Run step 6 again. This time it would succeed.

Sure, but how long before retrying? How would I know extraction completed? As I said, you need to wait for some time, an immediate retry would still fail, and I really don't feel like writing a loop and retrying every 100 or so milliseconds.

I apologize if I'm asking in the wrong place; perhaps requests for clarification of the WINAPI documentation is a charged service and should be forwarded to "Submit an incident"?
Xiaopo Yang - MSFT 11,496 Reputation points Microsoft Vendor

2024-03-29T06:30:22.5966667+00:00

Clearly the team responsible for shell APIs knows about (and approves) this code, ...

From my viewpoint, it just delivers the return code to the caller(you).

You can also send document feedback at the IThumbnailCache::GetThumbnail's document page.