Respect singleton handles in codegen

Add a singleton_has_handle flag to MappedClass and initialize it when mapping classes. Compute is_singleton in TypeMapper and avoid requiring an instance handle for methods of true singletons by adjusting needs_instance_handle logic. In generator, compute has_handle_classes (any class that is not a singleton or a singleton that has a handle) and expose it in the file context as has_handle_classes. These changes make handle/FFI generation aware of singleton classes that do not require instance handles.

Author: lijy91

tools/bindgen/codegen/context.py

@@ -181,6 +181,7 @@ class MappedClass:
     destroy_symbol: str = ""
     is_singleton: bool = False
     singleton_symbol: str = ""
+    singleton_has_handle: bool = False
     qualified_name: Optional[str] = None
     raw: Optional[IRClass] = None
 
@@ -692,6 +693,7 @@ def map_method(self, ir_method: IRMethod, ir_class: IRClass) -> MappedMethod:
         class_key = ir_class.qualified_name or ir_class.name
         method_key = f"{class_key}::{ir_method.name}"
         force_instance = method_key in self.force_instance_methods
+        is_singleton = self.namer.class_name(ir_class.name) in self.singleton_classes
 
         call_args: List[str] = []
         pre_call_lines: List[str] = []
@@ -751,7 +753,7 @@ def map_method(self, ir_method: IRMethod, ir_class: IRClass) -> MappedMethod:
             property_name=property_name,
             method_kind=ir_method.kind,
             static=ir_method.static and not force_instance,
-            needs_instance_handle=(not ir_method.static) or force_instance,
+            needs_instance_handle=((not ir_method.static) or force_instance) and not is_singleton,
             const=ir_method.const,
             access=ir_method.access,
             variadic=ir_method.variadic,
@@ -774,6 +776,7 @@ def map_class(self, ir_class: IRClass) -> MappedClass:
             destroy_symbol=self._symbol_for_class_destroy(ir_class),
             is_singleton=is_singleton,
             singleton_symbol=singleton_symbol,
+            singleton_has_handle=False,
             qualified_name=ir_class.qualified_name,
             raw=ir_class,
         )

tools/bindgen/codegen/generator.py

@@ -143,6 +143,7 @@ def _iter_callable_bridges():
         callable_item.return_bridge in {"offset", "size", "rect"}
         for callable_item in callables
     )
+    has_handle_classes = any(not cls.is_singleton or cls.singleton_has_handle for cls in mapped_file.classes)
     uses_ffi = any(
         callable_item.return_bridge in {"string", "struct"}
         or callable_item.pre_call_lines
@@ -191,6 +192,7 @@ def _iter_callable_bridges():
         "has_enums": bool(mapped_file.enums),
         "has_functions": bool(mapped_file.functions),
         "has_classes": bool(mapped_file.classes),
+        "has_handle_classes": has_handle_classes,
         "has_constants": bool(mapped_file.constants),
         "has_aliases": bool(mapped_file.aliases),
         "uses_ffi": uses_ffi,