Implement working example

Implement a working example using the GDExtension C API.

src/main.c

@@ -19,6 +19,9 @@ int main()
 }
 */
 
+/* Boilerplate provided by examples. */
+/* Some lines are over 80 characters. */
+
 typedef struct {
     uint8_t godot_data_dont_touch_this[sizeof(void *)];
 } String;
@@ -31,55 +34,46 @@ typedef struct {
     uint8_t godot_data_dont_touch_this[24];
 } Variant;
 
-// GDExtension interface function pointers
 static GDExtensionInterfaceStringNewWithUtf8Chars string_new_with_utf8_chars;
 static GDExtensionInterfaceVariantGetPtrConstructor variant_get_ptr_constructor;
 static GDExtensionInterfaceVariantGetPtrDestructor variant_get_ptr_destructor;
 static GDExtensionInterfaceGetVariantFromTypeConstructor get_variant_from_type_constructor;
 static GDExtensionInterfaceVariantGetPtrUtilityFunction variant_get_ptr_utility_function;
 static GDExtensionInterfaceVariantDestroy variant_destroy;
-// Godot API function pointers
+
+/* GDExtension API Pointers */
 static GDExtensionPtrConstructor construct_StringName_from_String;
 static GDExtensionVariantFromTypeConstructorFunc construct_Variant_from_String;
 static GDExtensionPtrDestructor destroy_String;
 static GDExtensionPtrDestructor destroy_StringName;
 
-// here is our global "print" StringName
 static StringName print_StringName;
-// and here is our global "print" function
+
 static GDExtensionPtrUtilityFunction print_function;
 
 StringName construct_StringName_from_cstring(const char *text) {
-    // 1. Construct a String from the C string
     String string;
     string_new_with_utf8_chars(&string, text);
 
-    // 2. Construct a StringName from the String
     StringName string_name;
     GDExtensionConstTypePtr constructor_arguments[1] = { &string };
     construct_StringName_from_String(&string_name, constructor_arguments);
 
-    // 3. Destroy the String, since it's not needed anymore
     destroy_String(&string);
 
     return string_name;
 }
 
 void print(const char *text) {
-    // 1. Construct a String from the C string
     String string;
     string_new_with_utf8_chars(&string, text);
 
-    // 2. Construct a Variant from the String
     Variant arg1;
     construct_Variant_from_String(&arg1, &string);
 
-    // 3. Call the utility function
-    // Since it's a void function, use "NULL" for the return pointer
     GDExtensionConstVariantPtr args[1] = { &arg1 };
     print_function(NULL, args, 1);
 
-    // 4. Clean up resources that are no longer needed
     variant_destroy(&arg1);
     destroy_String(&string);
 }
@@ -89,19 +83,15 @@ void initialize(void *userdata, GDExtensionInitializationLevel p_level) {
         return;
     }
 
-    // StringName constructor at index 2 is the one that receives String
-    // You can find this information in `extension_api.json` file
     construct_StringName_from_String = variant_get_ptr_constructor(GDEXTENSION_VARIANT_TYPE_STRING_NAME, 2);
     construct_Variant_from_String = get_variant_from_type_constructor(GDEXTENSION_VARIANT_TYPE_STRING);
     destroy_String = variant_get_ptr_destructor(GDEXTENSION_VARIANT_TYPE_STRING);
     destroy_StringName = variant_get_ptr_destructor(GDEXTENSION_VARIANT_TYPE_STRING_NAME);
 
-    // Initialize "print" StringName
     print_StringName = construct_StringName_from_cstring("print");
-    // then fetch the "print" function pointer
     print_function = variant_get_ptr_utility_function(&print_StringName, 2648703342);
 
-    print("Hello GDExtension from C!");
+    print("Starting...");
 }
 
 void deinitialize(void *userdata, GDExtensionInitializationLevel p_level) {
@@ -109,20 +99,20 @@ void deinitialize(void *userdata, GDExtensionInitializationLevel p_level) {
         return;
     }
 
-    print("Goodbye GDExtension from C!");
+    print("Exited.");
 
-    // Destroy "print" StringName
     destroy_StringName(&print_StringName);
 }
 
-GDExtensionBool hello_extension_entry(
+/* librtr object; called by Godot when it reads the librtr.gdextension file that
+ * provides a configuration using this name. */
+GDExtensionBool librtr_extension_init(
     GDExtensionInterfaceGetProcAddress p_get_proc_address,
     GDExtensionClassLibraryPtr p_library,
     GDExtensionInitialization *r_initialization
 ) {
     r_initialization->initialize = &initialize;
     r_initialization->deinitialize = &deinitialize;
-    // save the GDExtension API function pointers globally
     string_new_with_utf8_chars = (GDExtensionInterfaceStringNewWithUtf8Chars) p_get_proc_address("string_new_with_utf8_chars");
     variant_get_ptr_constructor = (GDExtensionInterfaceVariantGetPtrConstructor) p_get_proc_address("variant_get_ptr_constructor");
     variant_get_ptr_destructor = (GDExtensionInterfaceVariantGetPtrDestructor) p_get_proc_address("variant_get_ptr_destructor");