Fix race condition: serialize Pango/Cairo calls for thread safety

manimpango/__init__.py

@@ -1,19 +1,58 @@
 # -*- coding: utf-8 -*-
 import os
 import sys
+import threading
+from functools import wraps
 
-from ._version import __version__  # noqa: F403,F401
+from ._version import __version__  # noqa: F401
 
 if os.name == "nt":  # pragma: no cover
     os.environ["PATH"] = (
         f"{os.path.abspath(os.path.dirname(__file__))}"
         f"{os.pathsep}"
         f"{os.environ['PATH']}"
     )
+
+# Module-level lock for thread safety. Pango/Cairo access global state (the default
+# PangoCairoFontMap, Fontconfig config, etc.) and the `registered_fonts` set is shared
+# mutable state read during rendering and written during font registration. This lock
+# serializes all access to these shared resources.
+_pango_lock = threading.Lock()
+
+
+def _synchronized(func):
+    @wraps(func)
+    def wrapper(*args, **kwargs):
+        with _pango_lock:
+            return func(*args, **kwargs)
+    return wrapper
+
+
 try:
-    from .register_font import *  # isort:skip # noqa: F403,F401
-    from .cmanimpango import *  # noqa: F403,F401
-    from .enums import *  # noqa: F403,F401
+    from .register_font import (  # noqa: F401
+        registered_fonts,
+        RegisteredFont,
+    )
+    from .cmanimpango import (  # noqa: F401
+        TextSetting,
+        MarkupUtils,
+        pango_version,
+        cairo_version,
+    )
+    from .cmanimpango import text2svg as _text2svg_impl
+    from .register_font import (
+        register_font as _register_font_impl,
+        unregister_font as _unregister_font_impl,
+        fc_register_font as _fc_register_font_impl,
+        fc_unregister_font as _fc_unregister_font_impl,
+        list_fonts as _list_fonts_impl,
+    )
+    from .enums import (  # noqa: F401
+        Style,
+        Weight,
+        Variant,
+        Alignment,
+    )
 except ImportError as ie:  # pragma: no cover
     py_ver = ".".join(map(str, sys.version_info[:3]))
     msg = f"""
@@ -33,3 +72,11 @@
 Original error: {ie}
 """
     raise ImportError(msg)
+
+text2svg = _synchronized(_text2svg_impl)
+register_font = _synchronized(_register_font_impl)
+unregister_font = _synchronized(_unregister_font_impl)
+fc_register_font = _synchronized(_fc_register_font_impl)
+fc_unregister_font = _synchronized(_fc_unregister_font_impl)
+list_fonts = _synchronized(_list_fonts_impl)
+MarkupUtils.text2svg = staticmethod(_synchronized(MarkupUtils.text2svg))