80 lines
3 KiB
Markdown
80 lines
3 KiB
Markdown
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# DWG thumbnails for OS file managers
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`dwg_thumbnailer::extract` reads **only** the embedded preview from a DWG (file
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header → preview seeker → parse — never the whole drawing) and returns it as an
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`image::RgbaImage`. It's the shared core behind every platform's thumbnail
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integration.
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```
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crates/
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dwg-thumbnailer/ this crate — shared core + macOS extension sources
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dwg-thumbnailer-win/ Windows IThumbnailProvider COM DLL (depends on the core)
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```
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---
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## Linux (COSMIC, GNOME, Nautilus, Nemo, …) — handled by OpenCADStudio itself
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No separate binary. OpenCADStudio embeds this core and, on startup, installs a
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freedesktop `.thumbnailer` pointing at its own hidden `--dwg-thumbnail` mode
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(see `src/io/file_association.rs::install_thumbnailer`). Launch OCS once and file
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managers render DWG thumbnails; clear stale "no thumbnail" cache if needed:
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```sh
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rm -f ~/.cache/thumbnails/fail/*/*.png
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```
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---
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## Windows (Explorer) — authored, build & test on Windows
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A COM in-proc server implementing `IThumbnailProvider`. **Not compiled/tested on
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the Linux dev host** — build and verify on Windows.
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```bat
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cd crates\dwg-thumbnailer-win && cargo build --release
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regsvr32 target\release\dwg_thumbnailer_win.dll :: register (elevated)
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regsvr32 /u target\release\dwg_thumbnailer_win.dll :: unregister
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ie4uinit.exe -show :: refresh thumbnails
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```
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If `regsvr32`'s self-registration needs adjusting, the equivalent registry keys
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are (replace the path):
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```reg
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Windows Registry Editor Version 5.00
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[HKEY_CLASSES_ROOT\CLSID\{8F2A9C41-3B6E-4E2D-9C7A-1E0B5D6F42AA}]
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@="OpenCADStudio DWG Thumbnail Provider"
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[HKEY_CLASSES_ROOT\CLSID\{8F2A9C41-3B6E-4E2D-9C7A-1E0B5D6F42AA}\InprocServer32]
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@="C:\\path\\to\\dwg_thumbnailer_win.dll"
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"ThreadingModel"="Apartment"
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[HKEY_CLASSES_ROOT\.dwg\ShellEx\{e357fccd-a995-4576-b01f-234630154e96}]
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@="{8F2A9C41-3B6E-4E2D-9C7A-1E0B5D6F42AA}"
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```
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---
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## macOS (Finder) — sources provided, build in Xcode
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A QuickLook **Thumbnail Extension** (`macos/ThumbnailProvider.swift`) calls the
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Rust core's C ABI, linked as a static library. Requires Xcode + a host app.
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1. Build the core as a static lib for your arch(s):
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```sh
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cargo build -p dwg-thumbnailer --release --target aarch64-apple-darwin
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# → target/aarch64-apple-darwin/release/libdwg_thumbnailer.a
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```
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2. In Xcode, add a **Thumbnail Extension** target to a host app.
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- Use `macos/Info.plist` (lists the `com.autodesk.dwg` UTI).
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- Add `macos/ThumbnailProvider.swift`.
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- Add a bridging header that `#include`s `macos/dwg_thumbnailer.h`.
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- Link `libdwg_thumbnailer.a` (+ system frameworks it needs).
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3. Sign, install the host app, and Finder picks up the extension.
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C ABI (see `dwg_thumbnailer.h`):
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`dwg_thumbnail_png(path, max_dim, &ptr, &len)` / `dwg_thumbnail_free(ptr, len)`.
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---
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Formats: DWG BMP-DIB and PNG embedded previews decode. WMF previews and files
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without a preview (or DXF) produce no thumbnail — the file manager falls back.
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