feat: implement OLE2Frame embedded image parsing and exact coordinate rendering

src/viewer2d/fixDwgKoreanText.ts

@@ -0,0 +1,106 @@
+/**
+ * Repair Korean text that acadrust emits as Latin-1 mojibake of CP949/EUC-KR.
+ *
+ * Older Korean DWGs store strings in code page 949. When those bytes are
+ * decoded as ISO-8859-1/Windows-1252, Hangul becomes garbled Latin
+ * (e.g. "½Ã°ø½Ã" instead of "시공시"). Unicode-correct drawings
+ * (already containing Hangul syllables) are left unchanged.
+ *
+ * Apply after parse_dwg, before Viewer2D.load().
+ */
+
+const HANGUL_SYLLABLE = /[\uAC00-\uD7A3]/;
+const HANGUL_JAMO = /[\u1100-\u11FF\u3130-\u318F]/;
+
+/** Labels tried in order; first supported decoder wins. */
+const KOREAN_LABELS = ['cp949', 'windows-949', 'euc-kr'] as const;
+
+let koreanDecoder: TextDecoder | null | undefined;
+
+function getKoreanDecoder(): TextDecoder | null {
+  if (koreanDecoder !== undefined) return koreanDecoder;
+  for (const label of KOREAN_LABELS) {
+    try {
+      koreanDecoder = new TextDecoder(label);
+      return koreanDecoder;
+    } catch {
+      /* label not available in this runtime */
+    }
+  }
+  koreanDecoder = null;
+  return null;
+}
+
+/**
+ * If `s` looks like CP949 bytes misread as Latin-1, return the Hangul
+ * form; otherwise return `s` unchanged.
+ */
+export function fixCp949Mojibake(s: string): string {
+  if (!s) return s;
+  // Already real Hangul → leave alone (e.g. BasicSample.dwg).
+  if (HANGUL_SYLLABLE.test(s) || HANGUL_JAMO.test(s)) return s;
+
+  let hasHigh = false;
+  const bytes = new Uint8Array(s.length);
+  for (let i = 0; i < s.length; i++) {
+    const code = s.charCodeAt(i);
+    if (code > 255) return s; // true Unicode beyond Latin-1
+    if (code > 127) hasHigh = true;
+    bytes[i] = code;
+  }
+  if (!hasHigh) return s; // pure ASCII
+
+  const decoder = getKoreanDecoder();
+  if (!decoder) return s;
+
+  let fixed: string;
+  try {
+    fixed = decoder.decode(bytes);
+  } catch {
+    return s;
+  }
+
+  // Accept only when we gain Hangul and the decode is clean.
+  if (
+    (HANGUL_SYLLABLE.test(fixed) || HANGUL_JAMO.test(fixed)) &&
+    !fixed.includes('\uFFFD')
+  ) {
+    return fixed;
+  }
+  return s;
+}
+
+/**
+ * Deep-walk a CadParseResult (or any JSON-like tree) and fix string fields
+ * in place. Returns the same object for chaining.
+ */
+export function fixDwgKoreanText<T>(root: T): T {
+  if (root == null || typeof root !== 'object') return root;
+  const seen = new WeakSet<object>();
+
+  const walk = (value: unknown): void => {
+    if (value == null || typeof value !== 'object') return;
+    if (seen.has(value as object)) return;
+    seen.add(value as object);
+
+    if (Array.isArray(value)) {
+      for (let i = 0; i < value.length; i++) {
+        const item = value[i];
+        if (typeof item === 'string') value[i] = fixCp949Mojibake(item);
+        else walk(item);
+      }
+      return;
+    }
+
+    const obj = value as Record<string, unknown>;
+    for (const key of Object.keys(obj)) {
+      if (key === 'imageDataUrl') continue;
+      const item = obj[key];
+      if (typeof item === 'string') obj[key] = fixCp949Mojibake(item);
+      else walk(item);
+    }
+  };
+
+  walk(root);
+  return root;
+}