Initial public release: DWG/DXF 2D viewer sample

Standalone Vite sample composing acadrust-dwg WASM, dxf-parser, and Viewer2D.

src/viewer2d/decodeDxf.ts

@@ -0,0 +1,35 @@
+/**
+ * Decode a DXF buffer to text.
+ *
+ * Modern CAD exports are UTF-8 but often keep a legacy $DWGCODEPAGE
+ * (e.g. ANSI_949) that no longer matches the bytes — so the header is
+ * unreliable. Strategy: try UTF-8 strictly (self-validating); on failure
+ * fall back to the header's single-byte codepage. The DXF group/value
+ * structure is ASCII regardless, so this only affects TEXT/MTEXT strings.
+ */
+export function decodeDxf(buf: ArrayBuffer): string {
+  try {
+    return new TextDecoder('utf-8', { fatal: true }).decode(buf);
+  } catch {
+    /* not valid UTF-8 → legacy single-byte codepage */
+  }
+  const head = new TextDecoder('latin1').decode(
+    new Uint8Array(buf, 0, Math.min(buf.byteLength, 4096)),
+  );
+  const cp = head
+    .match(/\$DWGCODEPAGE[\s\S]*?\n\s*3\s*\n\s*([^\r\n]+)/i)?.[1]
+    ?.trim()
+    .toLowerCase();
+  let label = 'windows-1252';
+  if (cp) {
+    if (/949/.test(cp)) label = 'euc-kr';
+    else if (/932/.test(cp)) label = 'shift_jis';
+    else if (/936/.test(cp)) label = 'gbk';
+    else if (/950/.test(cp)) label = 'big5';
+  }
+  try {
+    return new TextDecoder(label).decode(buf);
+  } catch {
+    return new TextDecoder('utf-8').decode(buf);
+  }
+}