TexThumbnailProvider

Windows Explorer thumbnail handler for League of Legends .tex textures.

Once installed, Explorer renders real thumbnails for .tex files — in the file list, the preview pane, and "extra large icons" view — instead of a blank/generic icon. It decodes the texture directly, so no app needs to be open.

Supported formats

.tex code	Format	Notes
0x0A	DXT1 / BC1
0x0C	DXT5 / BC3
0x0D	BC7	full 8-mode software decode
0x0E	BC5	two-channel; blue reconstructed as normal-map Z
0x14	BGRA8	uncompressed

Mipmapped textures are handled (the largest mip is decoded for the thumbnail).

Install

Run in PowerShell (admin not required — registration is per-user):

iwr -useb https://raw.githubusercontent.com/RitoShark/TexThumbnailProvider/master/scripts/install-thumbnail-handler.ps1 | iex

This downloads TexThumbnailProvider.dll from the latest release, installs it to %LOCALAPPDATA%\RitoShark\TexThumbnailProvider, and registers it.

Pin a specific version:

& ([scriptblock]::Create((iwr -useb https://raw.githubusercontent.com/RitoShark/TexThumbnailProvider/master/scripts/install-thumbnail-handler.ps1))) -Version v1.1.0

Uninstall

iwr -useb https://raw.githubusercontent.com/RitoShark/TexThumbnailProvider/master/scripts/uninstall-thumbnail-handler.ps1 | iex

Already-cached thumbnails not updating? Windows caches thumbnails per file. After installing, existing .tex thumbnails repaint only once the file's modified-time changes or the cache is cleared (Disk Cleanup → Thumbnails).

Priority over Photoshop

If you also have the RitoTex Photoshop plugin installed, Photoshop registers itself as the .tex thumbnail handler and would normally win. Windows resolves the handler by precedence:

ProgID(.tex)  >  SystemFileAssociations\.tex  >  .tex\ShellEx

Photoshop owns the .tex ProgID's handler (in HKLM), so a plain .tex\ShellEx registration never gets picked. The installer therefore also writes this handler's CLSID under the current .tex ProgID and under SystemFileAssociations\.tex in HKCU — which overrides HKLM in the merged HKEY_CLASSES_ROOT view — so these thumbnails win. Only the thumbnail subkey is touched; double-clicking a .tex still opens whatever app you have associated.

Build from source

Requires Visual Studio 2022 (v143 toolset) with the Desktop development with C++ workload.

msbuild TexThumbnailProvider.sln /p:Configuration=Release /p:Platform=x64

Output: x64\Release\TexThumbnailProvider.dll. Build and install a local copy for testing (same install location as the public installer, re-runnable after each rebuild) with:

scripts\install-local.bat build

CI builds every push (Build workflow); tagging v* builds and attaches the DLL to a GitHub Release (Release workflow).

How it works

File	Responsibility
Dll.cpp	COM class factory + DllRegisterServer/DllUnregisterServer (incl. priority registration).
TexThumbnailProvider.cpp	IThumbnailProvider / IInitializeWithStream: parses the .tex header, decodes, builds the HBITMAP.
s3tc.cpp / s3tc.h	Self-contained block decoders: DXT1, DXT5, BC5, BC7. No external deps.

The decoders are deliberately standalone (no DirectXTex) to keep the shell extension small and fast to load inside DllHost.exe. The BC7 tables and decode flow match the BC7 specification.

Debugging

Explorer hosts thumbnail providers in an isolated DllHost.exe process, and thumbnails are cached per file, which makes debugging awkward. The easiest loop is to test the handler in a standalone test app (e.g. the Microsoft UsingThumbnailProviders sample) before testing inside Explorer. To clear the cache between runs, change the file's modified-time or run Disk Cleanup → Thumbnails.

License

See LICENSE.txt. Originally derived from the Microsoft Windows classic samples thumbnail-provider recipe.