DWG Support

// optional DWG file loading via LibreDWG WASM

The @cadview/dwg package adds DWG file support by converting DWG to DXF using LibreDWG compiled to WebAssembly.

License: @cadview/dwg is licensed under GPL-3.0 due to its dependency on LibreDWG. If GPL is not compatible with your project, you can still use the rest of @cadview (MIT) for DXF-only support.

Installation

pnpm add @cadview/dwg

Basic Usage

Register the dwgConverter with your viewer:

import { CadViewer } from '@cadview/core';
import { dwgConverter } from '@cadview/dwg';

const viewer = new CadViewer(canvas, {
	formatConverters: [dwgConverter]
});

// Now loadFile() and loadBuffer() accept both .dxf and .dwg files
await viewer.loadFile(file);

For framework wrappers, pass it as a prop:

import { dwgConverter } from '@cadview/dwg';

<CadViewer file={file} formatConverters={[dwgConverter]} />;

How It Works

1. dwgConverter.detect(buffer) checks the file’s magic bytes for the "AC10" signature
2. If detected as DWG, dwgConverter.convert(buffer) is called
3. The WASM module is lazily loaded (~6 MB from jsDelivr CDN)
4. The DWG buffer is written to Emscripten’s virtual filesystem (MEMFS)
5. LibreDWG converts DWG to DXF
6. The DXF string is returned and parsed by @cadview/core

WASM Loading

By default, the WASM binary is loaded from jsDelivr CDN on first use. You can preload it or self-host it.

Preloading

Preload the WASM binary before the user opens a file to avoid the initial load delay:

import { initWasm } from '@cadview/dwg';

// Call early in your app initialization
await initWasm();

Self-hosting

Host the WASM binary on your own server:

import { initWasm } from '@cadview/dwg';

await initWasm({
	wasmUrl: '/assets/libredwg.wasm'
});

Or pass it through the converter options:

import { convertDwgToDxf } from '@cadview/dwg';

const dxfString = await convertDwgToDxf(buffer, {
	wasmUrl: '/assets/libredwg.wasm',
	timeout: 60000 // 60 seconds
});

Checking WASM Status

import { isWasmReady } from '@cadview/dwg';

if (isWasmReady()) {
	console.log('WASM module is loaded and ready');
}

Detection Utilities

Inspect DWG files without converting them:

import { isDwg, getDwgVersion, getDwgReleaseName } from '@cadview/dwg';

// Check if a buffer is a DWG file
isDwg(buffer); // true or false

// Get the version string
getDwgVersion(buffer); // "AC1032"

// Get the human-readable release name
getDwgReleaseName('AC1032'); // "R2018"

Supported Versions

Minimum supported version is AC1012 (R13).

ConvertOptions

interface ConvertOptions {
	wasmUrl?: string; // Custom URL for the WASM binary
	timeout?: number; // Timeout in ms (default: 30000, set 0 to disable)
}

Conversion API

For advanced use cases, call the conversion function directly:

import { convertDwgToDxf } from '@cadview/dwg';

const dxfString = await convertDwgToDxf(dwgBuffer, {
	timeout: 60000
});

// Parse the DXF string with the core parser
import { parseDxf } from '@cadview/core';
const doc = parseDxf(dxfString);

FormatConverter Interface

dwgConverter implements the FormatConverter interface from @cadview/core:

interface FormatConverter {
	detect(buffer: ArrayBuffer): boolean;
	convert(buffer: ArrayBuffer): Promise<string>;
}

You can create your own format converters following this interface to support additional file formats.

Troubleshooting

If the WASM module won’t load, it’s almost always a CSP issue. Make sure cdn.jsdelivr.net is in your script-src and that wasm-unsafe-eval is allowed. Self-hosting the binary sidesteps this entirely.

Large or complex DWG files can exceed the default 30-second timeout. Bump it with the timeout option — some files genuinely need a minute or more.

Anything older than AC1012 (AutoCAD R12 and earlier) isn’t supported. LibreDWG can’t read those formats.