Add an Android GDExtension plugin sample

This sample shows how to integrate gdextension capabilities with Android java/kotlin code by leveraging JNI.

8 files changed, 309 insertions, 0 deletions

diff --git a/plugins/hello_gdextension/src/main/cpp/gdexample.cpp b/plugins/hello_gdextension/src/main/cpp/gdexample.cpp
new file mode 100644
index 0000000..1652936
--- /dev/null
+++ b/plugins/hello_gdextension/src/main/cpp/gdexample.cpp
@@ -0,0 +1,22 @@
+#include "gdexample.h"
+#include <godot_cpp/core/class_db.hpp>
+
+using namespace godot;
+
+void GDExample::_bind_methods() {
+
+}
+
+GDExample::GDExample() {
+    time_passed = 0.0;
+}
+
+GDExample::~GDExample() {}
+
+void GDExample::_process(double delta) {
+    time_passed += delta;
+
+    Vector2 new_position = Vector2(10.0 + (10.0 * sin(time_passed * 2.0)), 10.0 + (10.0 * cos(time_passed * 1.5)));
+
+    set_position(new_position);
+}
diff --git a/plugins/hello_gdextension/src/main/cpp/gdexample.h b/plugins/hello_gdextension/src/main/cpp/gdexample.h
new file mode 100644
index 0000000..6add085
--- /dev/null
+++ b/plugins/hello_gdextension/src/main/cpp/gdexample.h
@@ -0,0 +1,25 @@
+#ifndef GDEXAMPLE_H
+#define GDEXAMPLE_H
+
+#include <godot_cpp/classes/sprite2d.hpp>
+
+namespace godot {
+
+class GDExample : public Sprite2D {
+    GDCLASS(GDExample, Sprite2D)
+
+private:
+    double time_passed;
+
+protected:
+    static void _bind_methods();
+
+public:
+    GDExample();
+    ~GDExample();
+
+    void _process(double delta) override;
+};
+}
+
+#endif // GDEXAMPLE_H
diff --git a/plugins/hello_gdextension/src/main/cpp/jni/plugin_jni.cpp b/plugins/hello_gdextension/src/main/cpp/jni/plugin_jni.cpp
new file mode 100644
index 0000000..36aa658
--- /dev/null
+++ b/plugins/hello_gdextension/src/main/cpp/jni/plugin_jni.cpp
@@ -0,0 +1,20 @@
+#include <jni.h>
+
+#include "plugin_manager.h"
+#include "utils.h"
+
+#undef JNI_PACKAGE_NAME
+#define JNI_PACKAGE_NAME fhuyakou_godot_plugin_android_hellogdextension
+
+#undef JNI_CLASS_NAME
+#define JNI_CLASS_NAME HelloGDExtensionPlugin
+
+extern "C" {
+    JNIEXPORT void JNICALL JNI_METHOD(nativeAddGDExampleNode)(JNIEnv *env, jobject, jstring p_parent_node_path) {
+        godot::PluginManager::get_singleton()->add_gdexample_node(jstring_to_string(env, p_parent_node_path));
+    }
+
+    JNIEXPORT void JNICALL JNI_METHOD(nativeToggleVisibility)(JNIEnv *env, jobject, jboolean p_visible) {
+        godot::PluginManager::get_singleton()->toggle_visibility(p_visible);
+    }
+};
diff --git a/plugins/hello_gdextension/src/main/cpp/jni/plugin_manager.cpp b/plugins/hello_gdextension/src/main/cpp/jni/plugin_manager.cpp
new file mode 100644
index 0000000..647dd3e
--- /dev/null
+++ b/plugins/hello_gdextension/src/main/cpp/jni/plugin_manager.cpp
@@ -0,0 +1,87 @@
+#include "plugin_manager.h"
+
+#include <godot_cpp/classes/engine.hpp>
+#include <godot_cpp/classes/main_loop.hpp>
+#include <godot_cpp/classes/resource.hpp>
+#include <godot_cpp/classes/resource_loader.hpp>
+#include <godot_cpp/classes/scene_tree.hpp>
+#include <godot_cpp/classes/window.hpp>
+
+#include "utils.h"
+
+namespace godot {
+
+PluginManager *PluginManager::singleton = nullptr;
+
+PluginManager::PluginManager() {
+    gdexample_node = memnew(GDExample);
+
+    Ref<Resource> resource_ref = ResourceLoader::get_singleton()->load("res://addons/hello_gdextension_plugin/interface/android_icon.svg");
+    gdexample_node->set_texture(resource_ref);
+}
+
+PluginManager::~PluginManager() {
+    memdelete(gdexample_node);
+}
+
+PluginManager *PluginManager::get_singleton() {
+    if (singleton == nullptr) {
+        singleton = new PluginManager();
+    }
+    return singleton;
+}
+
+void PluginManager::toggle_visibility(bool p_visible) {
+    ALOG_ASSERT(gdexample_node != nullptr, "Uninitialized gdexample node");
+
+    gdexample_node->set_visible(p_visible);
+}
+
+void PluginManager::add_gdexample_node(const String &p_parent_node_path) {
+    ALOG_ASSERT(gdexample_node != nullptr, "Uninitialized gdexample node");
+
+    if (p_parent_node_path.is_empty()) {
+        ALOGW("Empty parent node path, aborting...");
+        return;
+    }
+
+    // Retrieve the parent node.
+    Node *parent_node = get_node(p_parent_node_path);
+    if (!parent_node) {
+        ALOGE("Unable to retrieve parent node with path %s", p_parent_node_path.utf8().get_data());
+        return;
+    }
+
+    if (gdexample_node->get_parent() != nullptr) {
+        gdexample_node->get_parent()->remove_child(gdexample_node);
+    }
+
+    parent_node->add_child(gdexample_node);
+    gdexample_node->set_owner(parent_node);
+    gdexample_node->set_centered(false);
+}
+
+Node *PluginManager::get_node(const String &p_node_path) {
+    if (p_node_path.is_empty()) {
+        ALOGW("Empty node path argument.");
+        return nullptr;
+    }
+
+    MainLoop *main_loop = Engine::get_singleton()->get_main_loop();
+    auto *scene_tree = Object::cast_to<SceneTree>(main_loop);
+    if (!scene_tree) {
+        ALOGW("Unable to retrieve the scene tree.");
+        return nullptr;
+    }
+
+    const Window *window = scene_tree->get_root();
+    NodePath node_path(p_node_path);
+    Node *node = window->get_node_or_null(node_path);
+    if (!node) {
+        // Try again by treating the parameter as the node's name
+        node = window->find_child(p_node_path, true, false);
+    }
+
+    return node;
+}
+}
diff --git a/plugins/hello_gdextension/src/main/cpp/jni/plugin_manager.h b/plugins/hello_gdextension/src/main/cpp/jni/plugin_manager.h
new file mode 100644
index 0000000..473a7e6
--- /dev/null
+++ b/plugins/hello_gdextension/src/main/cpp/jni/plugin_manager.h
@@ -0,0 +1,32 @@
+#ifndef PLUGIN_MANAGER_H
+#define PLUGIN_MANAGER_H
+
+#include <godot_cpp/variant/string.hpp>
+
+#include "../gdexample.h"
+
+namespace godot {
+
+class PluginManager {
+public:
+    static PluginManager *get_singleton();
+
+    void add_gdexample_node(const String &p_parent_node_path);
+
+    void toggle_visibility(bool p_visible);
+
+private:
+    PluginManager();
+
+    ~PluginManager();
+
+    static Node *get_node(const String &p_node_path);
+
+    static PluginManager *singleton;
+
+    GDExample *gdexample_node = nullptr;
+};
+
+}
+
+#endif // PLUGIN_MANAGER_H
diff --git a/plugins/hello_gdextension/src/main/cpp/jni/utils.h b/plugins/hello_gdextension/src/main/cpp/jni/utils.h
new file mode 100644
index 0000000..e55cb6b
--- /dev/null
+++ b/plugins/hello_gdextension/src/main/cpp/jni/utils.h
@@ -0,0 +1,75 @@
+#ifndef UTILS_H
+#define UTILS_H
+
+#include <android/log.h>
+#include <godot_cpp/variant/string.hpp>
+#include <jni.h>
+
+#define LOG_TAG "HelloGDExtension"
+
+#define ALOG_ASSERT(_cond, ...) \
+    if (!(_cond)) __android_log_assert("conditional", LOG_TAG, __VA_ARGS__)
+#define ALOGE(...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
+#define ALOGW(...) __android_log_print(ANDROID_LOG_WARN, LOG_TAG, __VA_ARGS__)
+#define ALOGV(...) __android_log_print(ANDROID_LOG_VERBOSE, LOG_TAG, __VA_ARGS__)
+
+/** Auxiliary macros */
+#define __JNI_METHOD_BUILD(package, class_name, method) \
+    Java_ ## package ## _ ## class_name ## _ ## method
+#define __JNI_METHOD_EVAL(package, class_name, method) \
+    __JNI_METHOD_BUILD(package, class_name, method)
+
+/**
+ * Expands the JNI signature for a JNI method.
+ *
+ * Requires to redefine the macros JNI_PACKAGE_NAME and JNI_CLASS_NAME.
+ * Not doing so will raise preprocessor errors during build.
+ *
+ * JNI_PACKAGE_NAME must be the JNI representation Java class package name.
+ * JNI_CLASS_NAME must be the JNI representation of the Java class name.
+ *
+ * For example, for the class com.example.package.SomeClass:
+ * JNI_PACKAGE_NAME: com_example_package
+ * JNI_CLASS_NAME: SomeClass
+ *
+ * Note that underscores in Java package and class names are replaced with "_1"
+ * in their JNI representations.
+ */
+#define JNI_METHOD(method) \
+    __JNI_METHOD_EVAL(JNI_PACKAGE_NAME, JNI_CLASS_NAME, method)
+
+/**
+ * Expands a Java class name using slashes as package separators into its
+ * JNI type string representation.
+ *
+ * For example, to get the JNI type representation of a Java String:
+ * JAVA_TYPE("java/lang/String")
+ */
+#define JAVA_TYPE(class_name) "L" class_name ";"
+
+/**
+ * Default definitions for the macros required in JNI_METHOD.
+ * Used to raise build errors if JNI_METHOD is used without redefining them.
+ */
+#define JNI_CLASS_NAME "Error: JNI_CLASS_NAME not redefined"
+#define JNI_PACKAGE_NAME "Error: JNI_PACKAGE_NAME not redefined"
+
+/**
+* Converts JNI jstring to Godot String.
+* @param source Source JNI string. If null an empty string is returned.
+* @param env JNI environment instance.
+* @return Godot string instance.
+*/
+static inline godot::String jstring_to_string(JNIEnv *env, jstring source) {
+    if (env && source) {
+        const char *const source_utf8 = env->GetStringUTFChars(source, NULL);
+        if (source_utf8) {
+            godot::String result(source_utf8);
+            env->ReleaseStringUTFChars(source, source_utf8);
+            return result;
+        }
+    }
+    return godot::String();
+}
+
+#endif // UTILS_H
diff --git a/plugins/hello_gdextension/src/main/cpp/register_types.cpp b/plugins/hello_gdextension/src/main/cpp/register_types.cpp
new file mode 100644
index 0000000..e6be489
--- /dev/null
+++ b/plugins/hello_gdextension/src/main/cpp/register_types.cpp
@@ -0,0 +1,41 @@
+#include "register_types.h"
+
+#include "gdexample.h"
+
+#include <gdextension_interface.h>
+#include <godot_cpp/core/defs.hpp>
+#include <godot_cpp/core/class_db.hpp>
+#include <godot_cpp/godot.hpp>
+
+using namespace godot;
+
+void initialize_example_module(ModuleInitializationLevel p_level) {
+    if (p_level!=godot::MODULE_INITIALIZATION_LEVEL_SCENE) {
+        return;
+    }
+
+    ClassDB::register_class<GDExample>();
+}
+
+void uninitialize_example_module(ModuleInitializationLevel p_level) {
+    if (p_level!=godot::MODULE_INITIALIZATION_LEVEL_SCENE) {
+        return;
+    }
+}
+
+extern "C" {
+// Initialization
+GDExtensionBool GDE_EXPORT example_library_init(GDExtensionInterfaceGetProcAddress
+                                                p_get_proc_address,
+                                                const GDExtensionClassLibraryPtr p_library,
+                                                GDExtensionInitialization
+                                                *r_initialization) {
+    godot::GDExtensionBinding::InitObject init_obj(p_get_proc_address, p_library, r_initialization);
+
+    init_obj.register_initializer(initialize_example_module);
+    init_obj.register_terminator(uninitialize_example_module);
+    init_obj.set_minimum_library_initialization_level(godot::MODULE_INITIALIZATION_LEVEL_SCENE);
+
+    return init_obj.init();
+}
+}
diff --git a/plugins/hello_gdextension/src/main/cpp/register_types.h b/plugins/hello_gdextension/src/main/cpp/register_types.h
new file mode 100644
index 0000000..d01d663
--- /dev/null
+++ b/plugins/hello_gdextension/src/main/cpp/register_types.h
@@ -0,0 +1,7 @@
+#ifndef REGISTER_TYPES_H
+#define REGISTER_TYPES_H
+
+void initialize_example_module();
+void uninitialize_example_module();
+
+#endif // REGISTER_TYPES_H