mirror of
https://github.com/arsvendg/Stirling-PDF.git
synced 2026-07-14 18:44:05 +02:00
62 lines
2.6 KiB
Markdown
62 lines
2.6 KiB
Markdown
# Windows PDF Thumbnail Handler
|
||
|
||
A lightweight COM DLL that provides PDF page-preview thumbnails in Windows Explorer when Stirling-PDF is the default PDF application.
|
||
|
||
## Why this exists
|
||
|
||
When Stirling-PDF registers as the default PDF handler, Windows associates `.pdf` files with Stirling's ProgID. Without a thumbnail handler on that ProgID, Explorer falls back to showing the application icon (the big S logo) instead of a page preview. This DLL restores thumbnail previews by implementing the Windows Shell `IThumbnailProvider` COM interface.
|
||
|
||
## How it works
|
||
|
||
1. **Explorer requests a thumbnail** — when a folder with PDFs is opened in Medium/Large icon view, Explorer loads the DLL via the registered COM CLSID.
|
||
2. **Shell calls `IInitializeWithStream`** — passes the PDF file content as an `IStream`.
|
||
3. **Shell calls `IThumbnailProvider::GetThumbnail(cx)`** — requests a bitmap of size `cx × cx`.
|
||
4. **The DLL renders page 1** using the built-in `Windows.Data.Pdf` WinRT API (the same engine Edge uses), preserving aspect ratio.
|
||
5. **WIC decodes the rendered PNG** into BGRA pixels, which are copied into an `HBITMAP` via `CreateDIBSection`.
|
||
6. **Explorer displays the bitmap** as the file's thumbnail.
|
||
|
||
All COM methods are wrapped in `catch_unwind` so a malformed PDF cannot crash Explorer.
|
||
|
||
## Technical details
|
||
|
||
| | |
|
||
|---|---|
|
||
| **Language** | Rust (cdylib) |
|
||
| **DLL size** | ~156 KB |
|
||
| **External deps** | None — uses only Windows built-in APIs |
|
||
| **PDF renderer** | `Windows.Data.Pdf` (WinRT, Windows 10+) |
|
||
| **Image decode** | WIC (`IWICImagingFactory`) with BGRA32 format conversion |
|
||
| **COM CLSID** | `{2D2FBE3A-9A88-4308-A52E-7EF63CA7CF48}` |
|
||
| **Threading model** | Apartment (STA — standard for shell extensions) |
|
||
| **Min Windows** | Windows 10 |
|
||
|
||
## Registry entries (managed by MSI)
|
||
|
||
The WiX installer (`provisioning.wxs`) registers:
|
||
|
||
- **CLSID** at `HKLM\SOFTWARE\Classes\CLSID\{2D2FBE3A-...}\InprocServer32` pointing to the DLL
|
||
- **Shellex** at `HKLM\SOFTWARE\Classes\.pdf\shellex\{E357FCCD-...}` linking `.pdf` thumbnails to our CLSID
|
||
|
||
Both are automatically removed on uninstall.
|
||
|
||
## Building
|
||
|
||
The DLL is built automatically as part of the Tauri build pipeline via `build-provisioner.mjs`:
|
||
|
||
```bash
|
||
cd frontend
|
||
npm run tauri-build
|
||
```
|
||
|
||
To build the DLL standalone:
|
||
|
||
```bash
|
||
cd frontend/src-tauri/thumbnail-handler
|
||
cargo build --release
|
||
# Output: target/release/stirling_thumbnail_handler.dll
|
||
```
|
||
|
||
## Linux / macOS
|
||
|
||
This DLL is Windows-only. Linux and macOS don't need it — their thumbnail systems (thumbnailers on Linux, Quick Look on macOS) are decoupled from the default app association and continue working regardless of which app is set as default.
|