🐛 Fix casting to script types

Casting to script types requires [this PR](godotengine/godot#80040), which will make this extension require Godot 4.2 when it is merged.

README.md

@@ -8,6 +8,11 @@ And I want to use it in Godot.
 
 # Current State
 
+```
+⚠ NOTE -- Current master of this extension currently requires [this PR](https://github.com/godotengine/godot/pull/80040). Once that
+PR is merged, this extension will only be Godot 4.2 compatible
+```
+
 Here's a list of planned features and work still to be done ( ✅ - Seems to be
 working, 🟨 - Partially working, ❌ - Not working)
 
@@ -44,7 +49,7 @@ I have only tested this on Windows. I know for certain it will only work on 'flo
 
 * A clone of this repo.
 * Dart (2.19 Current Stable, not tested with 3.0)
-* Godot 4.1.x or a custom build compatible with 4.1.x
+* Godot 4.2.x - Note above the pending pull request.
 * A build of the [Dart Shared
   Library](https://github.com/fuzzybinary/dart_shared_libray). Windows x64 .dlls
   for Dart 2.19 are provided in `src/dart_dll/bin/win64`.

godot-headers/godot/gdextension_interface.h

@@ -2114,10 +2114,11 @@ typedef GDExtensionScriptInstancePtr (*GDExtensionInterfaceScriptInstanceCreate)
  * Get the script instance data attached to this object.
  * 
  * @param p_object A pointer to the Object
+ * @param p_language A pointer to the language expected for this script instance
  * 
  * @return A GDExtensionScriptInstanceDataPtr that was attached to this object as part of script_instance_create
  */
-typedef GDExtensionScriptInstanceDataPtr (*GDExtensionInterfaceObjectGetScriptInstance)(GDExtensionConstObjectPtr p_object);
+typedef GDExtensionScriptInstanceDataPtr (*GDExtensionInterfaceObjectGetScriptInstance)(GDExtensionConstObjectPtr p_object, GDExtensionObjectPtr p_language);
 
 /* INTERFACE: ClassDB */
 

src/cpp/dart_bindings.cpp

@@ -253,6 +253,9 @@ bool GodotDartBindings::initialize(const char *script_path, const char *package_
       };
       DART_CHECK_RET(result, Dart_Invoke(godot_dart_library, Dart_NewStringFromCString("_registerGodot"), 2, args),
                      false, "Error calling '_registerGodot'");
+
+      // Get the language pointer from the result:
+      _dart_language = get_object_address(result);
     }
 
     // And call the main function from the user supplied library
@@ -987,6 +990,18 @@ GDE_EXPORT void *create_script_instance(Dart_Handle type, Dart_Handle script, vo
   return godot_script_instance;
 }
 
+GDE_EXPORT Dart_Handle object_from_script_instance(DartScriptInstance *script_instance) {
+  if (!script_instance) {
+    return Dart_Null();
+  }
+
+  Dart_PersistentHandle persistent = script_instance->get_dart_object();
+  DART_CHECK_RET(dart_object, Dart_HandleFromPersistent(persistent), Dart_Null(),
+                 "Failed to get object from persistent handle");
+
+  return dart_object;
+}
+
 GDE_EXPORT void perform_frame_maintenance() {
   Dart_EnterScope();
 

src/cpp/dart_bindings.h

@@ -53,6 +53,10 @@ class GodotDartBindings {
   bool initialize(const char *script_path, const char *package_config);
   void shutdown();
 
+  GDExtensionScriptLanguagePtr get_language() {
+    return _dart_language;
+  }
+
   void bind_method(const TypeInfo &bind_type, const char *method_name, const TypeInfo &ret_type_info,
                    Dart_Handle args_list, MethodFlags method_flags);
   void add_property(const TypeInfo &bind_type, Dart_Handle dart_prop_info);
@@ -84,6 +88,7 @@ class GodotDartBindings {
   Dart_PersistentHandle _native_library;
 
   // Some things we need often
+  GDExtensionScriptLanguagePtr _dart_language;
   Dart_PersistentHandle _void_pointer_type;
   Dart_PersistentHandle _void_pointer_optional_type;
   Dart_PersistentHandle _void_pointer_pointer_type;

src/cpp/dart_script_instance.cpp

@@ -425,8 +425,7 @@ bool DartScriptInstance::get_fallback(const GDStringName &p_name, GDExtensionVar
 }
 
 GDExtensionScriptLanguagePtr DartScriptInstance::get_language() {
-
-  return nullptr;
+  return GodotDartBindings::instance()->get_language();
 }
 
 // * Static Callback Functions for Godot */

src/cpp/dart_script_instance.h

@@ -44,6 +44,10 @@ class DartScriptInstance {
 
   GDExtensionScriptLanguagePtr get_language();
 
+  Dart_PersistentHandle get_dart_object() {
+    return _dart_object;
+  }
+
   static const GDExtensionScriptInstanceInfo* get_script_instance_info();
 
 private:

src/cpp/gde_c_interface.cpp

@@ -350,6 +350,15 @@ GDExtensionScriptInstancePtr gde_script_instance_create(const GDExtensionScriptI
   return nullptr;
 }
 
+static GDExtensionInterfaceObjectGetScriptInstance _object_get_script_instance_func = nullptr;
+GDExtensionScriptInstanceDataPtr gde_object_get_script_instance(GDExtensionConstObjectPtr p_object,
+                                                                GDExtensionObjectPtr p_language) {
+  if (_object_get_script_instance_func) {
+    return _object_get_script_instance_func(p_object, p_language);
+  }
+  return nullptr;
+}
+
 #define LOAD_METHOD(method, type) _##method##_func = (type)get_proc_address(#method)
 
 void gde_init_c_interface(GDExtensionInterfaceGetProcAddress get_proc_address) {
@@ -395,6 +404,7 @@ void gde_init_c_interface(GDExtensionInterfaceGetProcAddress get_proc_address) {
   LOAD_METHOD(ref_get_object, GDExtensionInterfaceRefGetObject);
   LOAD_METHOD(ref_set_object, GDExtensionInterfaceRefSetObject);
   LOAD_METHOD(script_instance_create, GDExtensionInterfaceScriptInstanceCreate);
+  LOAD_METHOD(object_get_script_instance, GDExtensionInterfaceObjectGetScriptInstance);
 }
 
 }

src/cpp/gde_c_interface.h

@@ -108,6 +108,8 @@ GDE_EXPORT void gde_ref_set_object(GDExtensionRefPtr p_ref, GDExtensionObjectPtr
 
 GDE_EXPORT GDExtensionScriptInstancePtr gde_script_instance_create(const GDExtensionScriptInstanceInfo *p_info,
                                                                    GDExtensionScriptInstanceDataPtr p_instance_data);
+GDE_EXPORT GDExtensionScriptInstanceDataPtr gde_object_get_script_instance(GDExtensionConstObjectPtr p_object,
+                                                                           GDExtensionObjectPtr p_language);
 
 #ifdef __cplusplus
 }

src/cpp/gde_dart_converters.cpp

@@ -6,6 +6,23 @@
 #include "gde_wrapper.h"
 #include "godot_string_wrappers.h"
 
+void *get_object_address(Dart_Handle engine_handle) {
+  Dart_Handle native_ptr = Dart_GetField(engine_handle, Dart_NewStringFromCString("nativePtr"));
+  if (Dart_IsError(native_ptr)) {
+    GD_PRINT_ERROR(Dart_GetError(native_ptr));
+    return nullptr;
+  }
+  Dart_Handle address = Dart_GetField(native_ptr, Dart_NewStringFromCString("address"));
+  if (Dart_IsError(address)) {
+    GD_PRINT_ERROR(Dart_GetError(address));
+    return nullptr;
+  }
+  uint64_t object_ptr = 0;
+  Dart_IntegerToUint64(address, &object_ptr);
+
+  return reinterpret_cast<void *>(object_ptr);
+}
+
 void *get_opaque_address(Dart_Handle variant_handle) {
   // TODO: Look for a better way convert the variant.
   Dart_Handle opaque = Dart_GetField(variant_handle, Dart_NewStringFromCString("_opaque"));

src/cpp/gde_dart_converters.h

@@ -17,6 +17,7 @@ struct TypeInfo {
 // Actually defined in dart_bindings.cpp
 void type_info_from_dart(TypeInfo *type_info, Dart_Handle dart_type_info);
 
+void *get_object_address(Dart_Handle variant_handle);
 void *get_opaque_address(Dart_Handle variant_handle);
 
 void gde_method_info_from_dart(Dart_Handle dart_method_info, GDExtensionMethodInfo *method_info);

src/dart/godot_dart/lib/godot_dart.dart

@@ -26,7 +26,7 @@ late GodotDart _globalExtension;
 DartScriptLanguage? _dartScriptLanguage;
 
 @pragma('vm:entry-point')
-void _registerGodot(int libraryAddress, int bindingCallbacks) {
+DartScriptLanguage _registerGodot(int libraryAddress, int bindingCallbacks) {
   final godotDart = GodotDartNativeBindings.openLibrary('godot_dart');
   final ffiInterface = GDExtensionFFI(godotDart);
 
@@ -57,6 +57,8 @@ void _registerGodot(int libraryAddress, int bindingCallbacks) {
       .addResourceFormatSaver(Ref(DartResourceFormatSaver()), false);
 
   print('Everything loaded a-ok!');
+
+  return _dartScriptLanguage!;
 }
 
 @pragma('vm:entry-point')

src/dart/godot_dart/lib/src/core/gdextension.dart

@@ -257,19 +257,28 @@ class GodotDart {
       if (casted == nullptr) {
         return null;
       }
-    } else {
-      casted = from.nativePtr;
-    }
 
-    if (typeInfo.bindingToken != null) {
-      final persistent = gde.ffiBindings.gde_object_get_instance_binding(
-        casted,
-        typeInfo.bindingToken!,
-        gde.engineBindingCallbacks,
-      );
-      final dartObject = dartBindings.fromPersistentHandle(persistent);
+      if (typeInfo.bindingToken != null) {
+        final persistent = gde.ffiBindings.gde_object_get_instance_binding(
+          casted,
+          typeInfo.bindingToken!,
+          gde.engineBindingCallbacks,
+        );
+        final dartObject = dartBindings.fromPersistentHandle(persistent);
 
-      return dartObject as T;
+        return dartObject as T;
+      }
+      // TODO: What case is there where there is a class tag but no binding token?
+    } else {
+      // Try getting the script instance, and casting from that
+      final scriptInstance = gde.ffiBindings.gde_object_get_script_instance(
+          from.nativePtr, DartScriptLanguage.singleton.nativePtr);
+      if (scriptInstance != nullptr) {
+        final o = gde.dartBindings.objectFromScriptInstance(scriptInstance);
+        if (o is T) {
+          return o;
+        }
+      }
     }
 
     return null;

src/dart/godot_dart/lib/src/core/gdextension_ffi_bindings.dart

@@ -1071,6 +1071,25 @@ class GDExtensionFFI {
           GDExtensionScriptInstancePtr Function(
               ffi.Pointer<GDExtensionScriptInstanceInfo>,
               GDExtensionScriptInstanceDataPtr)>();
+
+  GDExtensionScriptInstanceDataPtr gde_object_get_script_instance(
+    GDExtensionConstObjectPtr p_object,
+    GDExtensionObjectPtr p_language,
+  ) {
+    return _gde_object_get_script_instance(
+      p_object,
+      p_language,
+    );
+  }
+
+  late final _gde_object_get_script_instancePtr = _lookup<
+      ffi.NativeFunction<
+          GDExtensionScriptInstanceDataPtr Function(GDExtensionConstObjectPtr,
+              GDExtensionObjectPtr)>>('gde_object_get_script_instance');
+  late final _gde_object_get_script_instance =
+      _gde_object_get_script_instancePtr.asFunction<
+          GDExtensionScriptInstanceDataPtr Function(
+              GDExtensionConstObjectPtr, GDExtensionObjectPtr)>();
 }
 
 typedef va_list = ffi.Pointer<ffi.Char>;

src/dart/godot_dart/lib/src/core/godot_dart_native_bindings.dart

@@ -41,6 +41,11 @@ class GodotDartNativeBindings {
                   Bool)>>('create_script_instance')
       .asFunction<
           Pointer<Void> Function(Type, DartScript, Pointer<Void>, bool)>();
+  late final objectFromScriptInstance = godotDartDylib
+      .lookup<NativeFunction<Handle Function(Pointer<Void>)>>(
+          'object_from_script_instance')
+      .asFunction<Object? Function(Pointer<Void>)>();
+
   late final _safeNewPersistentHandle = godotDartDylib
       .lookup<NativeFunction<Pointer<Void> Function(Handle)>>(
           'safe_new_persistent_handle')