Dynamic loading of OpenXR Loader on Android

This change implements dynamic loading of the OpenXR Loader library
on Android. If an OpenXR Loader library is not found,
Godot will still function with OpenXR disabled.

Also, on every platform, the OpenXR symbols are resolved at runtime
using xrGetInstanceProcAddr.

On Windows and Linux the OpenXR loader is included in the main
engine binary.

On Android, the OpenXR Loader is not built with the engine. Separately
distributed Android plugins will be provided with the correct loader
library for each device.

Co-authored-by: Gábor Pál Korom <[email protected]>
Co-authored-by: Gábor Koncz <[email protected]>

modules/openxr/SCsub

@@ -18,38 +18,36 @@ env_openxr.Prepend(
         thirdparty_dir + "/src",
         thirdparty_dir + "/src/common",
         thirdparty_dir + "/src/external/jsoncpp/include",
-        thirdparty_dir + "/src/loader",
     ]
 )
 
-# may need to check and set:
-# - XR_USE_TIMESPEC
-
-env_thirdparty = env_openxr.Clone()
-env_thirdparty.disable_warnings()
-env_thirdparty.AppendUnique(CPPDEFINES=["DISABLE_STD_FILESYSTEM"])
-
 if env["platform"] == "android":
     # may need to set OPENXR_ANDROID_VERSION_SUFFIX
-    env_thirdparty.AppendUnique(CPPDEFINES=["XR_OS_ANDROID", "XR_USE_PLATFORM_ANDROID"])
+    env_openxr.AppendUnique(CPPDEFINES=["XR_OS_ANDROID", "XR_USE_PLATFORM_ANDROID"])
+    env_openxr.AppendUnique(CPPDEFINES=["JSON_USE_EXCEPTION=0"])
 
     # may need to include java parts of the openxr loader
 elif env["platform"] == "linuxbsd":
-    env_thirdparty.AppendUnique(CPPDEFINES=["XR_OS_LINUX"])
+    env_openxr.AppendUnique(CPPDEFINES=["XR_OS_LINUX"])
 
     if env["x11"]:
-        env_thirdparty.AppendUnique(CPPDEFINES=["XR_USE_PLATFORM_XLIB"])
+        env_openxr.AppendUnique(CPPDEFINES=["XR_USE_PLATFORM_XLIB"])
 
     # FIXME: Review what needs to be set for Android and macOS.
-    env_thirdparty.AppendUnique(CPPDEFINES=["HAVE_SECURE_GETENV"])
+    env_openxr.AppendUnique(CPPDEFINES=["HAVE_SECURE_GETENV"])
 elif env["platform"] == "windows":
-    env_thirdparty.AppendUnique(CPPDEFINES=["XR_OS_WINDOWS", "NOMINMAX", "XR_USE_PLATFORM_WIN32"])
+    env_openxr.AppendUnique(CPPDEFINES=["XR_OS_WINDOWS", "NOMINMAX", "XR_USE_PLATFORM_WIN32"])
 
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/xr_generated_dispatch_table.c")
+# may need to check and set:
+# - XR_USE_TIMESPEC
 
-# add in common files (hope these don't clash with us)
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/common/filesystem_utils.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/common/object_info.cpp")
+env_thirdparty = env_openxr.Clone()
+env_thirdparty.disable_warnings()
+env_thirdparty.AppendUnique(CPPDEFINES=["DISABLE_STD_FILESYSTEM"])
+
+if "-fno-exceptions" in env_thirdparty["CXXFLAGS"]:
+    env_thirdparty["CXXFLAGS"].remove("-fno-exceptions")
+env_thirdparty.Append(CPPPATH=[thirdparty_dir + "/src/loader"])
 
 # add in external jsoncpp dependency
 env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/external/jsoncpp/src/lib_json/json_reader.cpp")
@@ -57,17 +55,24 @@ env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/external/
 env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/external/jsoncpp/src/lib_json/json_writer.cpp")
 
 # add in load
-if env["platform"] == "android":
-    env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/android_utilities.cpp")
-
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/api_layer_interface.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/loader_core.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/loader_instance.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/loader_logger_recorders.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/loader_logger.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/manifest_file.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/runtime_interface.cpp")
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_dir + "/src/loader/xr_generated_loader.cpp")
+if env["platform"] != "android":
+    # On Android the openxr_loader is provided by separate plugins for each device
+    # Build the engine using object files
+    khrloader_obj = []
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/xr_generated_dispatch_table.c")
+
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/common/filesystem_utils.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/common/object_info.cpp")
+
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/api_layer_interface.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/loader_core.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/loader_instance.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/loader_logger_recorders.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/loader_logger.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/manifest_file.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/runtime_interface.cpp")
+    env_thirdparty.add_source_files(khrloader_obj, thirdparty_dir + "/src/loader/xr_generated_loader.cpp")
+    env.modules_sources += khrloader_obj
 
 env.modules_sources += thirdparty_obj
 

modules/openxr/config.py

@@ -1,7 +1,5 @@
 def can_build(env, platform):
-    if (
-        platform == "linuxbsd" or platform == "windows"
-    ):  # or platform == "android" -- temporarily disabled android support
+    if platform in ("linuxbsd", "windows", "android"):
         return env["openxr"]
     else:
         # not supported on these platforms

modules/openxr/extensions/openxr_android_extension.cpp

@@ -29,7 +29,12 @@
 /*************************************************************************/
 
 #include "openxr_android_extension.h"
+#include "java_godot_wrapper.h"
+#include "os_android.h"
+#include "thread_jandroid.h"
 
+#include <jni.h>
+#include <modules/openxr/openxr_api.h>
 #include <openxr/openxr.h>
 #include <openxr/openxr_platform.h>
 
@@ -42,19 +47,16 @@ OpenXRAndroidExtension *OpenXRAndroidExtension::get_singleton() {
 OpenXRAndroidExtension::OpenXRAndroidExtension(OpenXRAPI *p_openxr_api) :
 		OpenXRExtensionWrapper(p_openxr_api) {
 	singleton = this;
-
 	request_extensions[XR_KHR_ANDROID_THREAD_SETTINGS_EXTENSION_NAME] = nullptr; // must be available
+}
 
-	// Initialize the loader
-	PFN_xrInitializeLoaderKHR xrInitializeLoaderKHR;
-	result = xrGetInstanceProcAddr(XR_NULL_HANDLE, "xrInitializeLoaderKHR", (PFN_xrVoidFunction *)(&xrInitializeLoaderKHR));
-	ERR_FAIL_COND_MSG(XR_FAILED(result), "Failed to retrieve pointer to xrInitializeLoaderKHR");
+void OpenXRAndroidExtension::on_before_instance_created() {
+	EXT_INIT_XR_FUNC(xrInitializeLoaderKHR);
 
-	// TODO fix this code, this is still code from GDNative!
-	JNIEnv *env = android_api->godot_android_get_env();
+	JNIEnv *env = get_jni_env();
 	JavaVM *vm;
 	env->GetJavaVM(&vm);
-	jobject activity_object = env->NewGlobalRef(android_api->godot_android_get_activity());
+	jobject activity_object = env->NewGlobalRef(static_cast<OS_Android *>(OS::get_singleton())->get_godot_java()->get_activity());
 
 	XrLoaderInitInfoAndroidKHR loader_init_info_android = {
 		.type = XR_TYPE_LOADER_INIT_INFO_ANDROID_KHR,
@@ -62,7 +64,7 @@ OpenXRAndroidExtension::OpenXRAndroidExtension(OpenXRAPI *p_openxr_api) :
 		.applicationVM = vm,
 		.applicationContext = activity_object
 	};
-	xrInitializeLoaderKHR((const XrLoaderInitInfoBaseHeaderKHR *)&loader_init_info_android);
+	XrResult result = xrInitializeLoaderKHR((const XrLoaderInitInfoBaseHeaderKHR *)&loader_init_info_android);
 	ERR_FAIL_COND_MSG(XR_FAILED(result), "Failed to call xrInitializeLoaderKHR");
 }
 

modules/openxr/extensions/openxr_android_extension.h

@@ -31,6 +31,7 @@
 #ifndef OPENXR_ANDROID_EXTENSION_H
 #define OPENXR_ANDROID_EXTENSION_H
 
+#include "../util.h"
 #include "openxr_extension_wrapper.h"
 
 class OpenXRAndroidExtension : public OpenXRExtensionWrapper {
@@ -38,10 +39,16 @@ public:
 	static OpenXRAndroidExtension *get_singleton();
 
 	OpenXRAndroidExtension(OpenXRAPI *p_openxr_api);
+
+	virtual void on_before_instance_created() override;
+
 	virtual ~OpenXRAndroidExtension() override;
 
 private:
 	static OpenXRAndroidExtension *singleton;
+
+	// Initialize the loader
+	EXT_PROTO_XRRESULT_FUNC1(xrInitializeLoaderKHR, (const XrLoaderInitInfoBaseHeaderKHR *), loaderInitInfo)
 };
 
 #endif // OPENXR_ANDROID_EXTENSION_H

modules/openxr/extensions/openxr_extension_wrapper.h

@@ -66,6 +66,7 @@ public:
 	virtual void *set_session_create_and_get_next_pointer(void *p_next_pointer) { return p_next_pointer; }
 	virtual void *set_swapchain_create_info_and_get_next_pointer(void *p_next_pointer) { return p_next_pointer; }
 
+	virtual void on_before_instance_created() {}
 	virtual void on_instance_created(const XrInstance p_instance) {}
 	virtual void on_instance_destroyed() {}
 	virtual void on_session_created(const XrSession p_instance) {}

modules/openxr/extensions/openxr_vulkan_extension.cpp

@@ -31,30 +31,12 @@
 #include "core/string/print_string.h"
 
 #include "../extensions/openxr_vulkan_extension.h"
-#include "../openxr_api.h"
 #include "../openxr_util.h"
 #include "servers/rendering/renderer_rd/effects/copy_effects.h"
 #include "servers/rendering/renderer_rd/storage_rd/texture_storage.h"
 #include "servers/rendering/rendering_server_globals.h"
 #include "servers/rendering_server.h"
 
-// need to include Vulkan so we know of type definitions
-#define XR_USE_GRAPHICS_API_VULKAN
-
-#ifdef WINDOWS_ENABLED
-// Including windows.h here is absolutely evil, we shouldn't be doing this outside of platform
-// however due to the way the openxr headers are put together, we have no choice.
-#include <windows.h>
-#endif
-
-// include platform dependent structs
-#include <openxr/openxr_platform.h>
-
-PFN_xrGetVulkanGraphicsRequirements2KHR xrGetVulkanGraphicsRequirements2KHR_ptr = nullptr;
-PFN_xrCreateVulkanInstanceKHR xrCreateVulkanInstanceKHR_ptr = nullptr;
-PFN_xrGetVulkanGraphicsDevice2KHR xrGetVulkanGraphicsDevice2KHR_ptr = nullptr;
-PFN_xrCreateVulkanDeviceKHR xrCreateVulkanDeviceKHR_ptr = nullptr;
-
 OpenXRVulkanExtension::OpenXRVulkanExtension(OpenXRAPI *p_openxr_api) :
 		OpenXRGraphicsExtensionWrapper(p_openxr_api) {
 	VulkanContext::set_vulkan_hooks(this);
@@ -69,36 +51,15 @@ OpenXRVulkanExtension::~OpenXRVulkanExtension() {
 }
 
 void OpenXRVulkanExtension::on_instance_created(const XrInstance p_instance) {
-	XrResult result;
-
 	ERR_FAIL_NULL(openxr_api);
 
 	// Obtain pointers to functions we're accessing here, they are (not yet) part of core.
-	result = xrGetInstanceProcAddr(p_instance, "xrGetVulkanGraphicsRequirements2KHR", (PFN_xrVoidFunction *)&xrGetVulkanGraphicsRequirements2KHR_ptr);
-	if (XR_FAILED(result)) {
-		print_line("OpenXR: Failed to xrGetVulkanGraphicsRequirements2KHR entry point [", openxr_api->get_error_string(result), "]");
-	}
 
-	result = xrGetInstanceProcAddr(p_instance, "xrCreateVulkanInstanceKHR", (PFN_xrVoidFunction *)&xrCreateVulkanInstanceKHR_ptr);
-	if (XR_FAILED(result)) {
-		print_line("OpenXR: Failed to xrCreateVulkanInstanceKHR entry point [", openxr_api->get_error_string(result), "]");
-	}
-
-	result = xrGetInstanceProcAddr(p_instance, "xrGetVulkanGraphicsDevice2KHR", (PFN_xrVoidFunction *)&xrGetVulkanGraphicsDevice2KHR_ptr);
-	if (XR_FAILED(result)) {
-		print_line("OpenXR: Failed to xrGetVulkanGraphicsDevice2KHR entry point [", openxr_api->get_error_string(result), "]");
-	}
-
-	result = xrGetInstanceProcAddr(p_instance, "xrCreateVulkanDeviceKHR", (PFN_xrVoidFunction *)&xrCreateVulkanDeviceKHR_ptr);
-	if (XR_FAILED(result)) {
-		print_line("OpenXR: Failed to xrCreateVulkanDeviceKHR entry point [", openxr_api->get_error_string(result), "]");
-	}
-}
-
-XrResult OpenXRVulkanExtension::xrGetVulkanGraphicsRequirements2KHR(XrInstance p_instance, XrSystemId p_system_id, XrGraphicsRequirementsVulkanKHR *p_graphics_requirements) {
-	ERR_FAIL_NULL_V(xrGetVulkanGraphicsRequirements2KHR_ptr, XR_ERROR_HANDLE_INVALID);
-
-	return (*xrGetVulkanGraphicsRequirements2KHR_ptr)(p_instance, p_system_id, p_graphics_requirements);
+	EXT_INIT_XR_FUNC(xrGetVulkanGraphicsRequirements2KHR);
+	EXT_INIT_XR_FUNC(xrCreateVulkanInstanceKHR);
+	EXT_INIT_XR_FUNC(xrGetVulkanGraphicsDevice2KHR);
+	EXT_INIT_XR_FUNC(xrCreateVulkanDeviceKHR);
+	EXT_INIT_XR_FUNC(xrEnumerateSwapchainImages);
 }
 
 bool OpenXRVulkanExtension::check_graphics_api_support(XrVersion p_desired_version) {
@@ -141,12 +102,6 @@ bool OpenXRVulkanExtension::check_graphics_api_support(XrVersion p_desired_versi
 	return true;
 }
 
-XrResult OpenXRVulkanExtension::xrCreateVulkanInstanceKHR(XrInstance p_instance, const XrVulkanInstanceCreateInfoKHR *p_create_info, VkInstance *r_vulkan_instance, VkResult *r_vulkan_result) {
-	ERR_FAIL_NULL_V(xrCreateVulkanInstanceKHR_ptr, XR_ERROR_HANDLE_INVALID);
-
-	return (*xrCreateVulkanInstanceKHR_ptr)(p_instance, p_create_info, r_vulkan_instance, r_vulkan_result);
-}
-
 bool OpenXRVulkanExtension::create_vulkan_instance(const VkInstanceCreateInfo *p_vulkan_create_info, VkInstance *r_instance) {
 	// get the vulkan version we are creating
 	uint32_t vulkan_version = p_vulkan_create_info->pApplicationInfo->apiVersion;
@@ -195,12 +150,6 @@ bool OpenXRVulkanExtension::create_vulkan_instance(const VkInstanceCreateInfo *p
 	return true;
 }
 
-XrResult OpenXRVulkanExtension::xrGetVulkanGraphicsDevice2KHR(XrInstance p_instance, const XrVulkanGraphicsDeviceGetInfoKHR *p_get_info, VkPhysicalDevice *r_vulkan_physical_device) {
-	ERR_FAIL_NULL_V(xrGetVulkanGraphicsDevice2KHR_ptr, XR_ERROR_HANDLE_INVALID);
-
-	return (*xrGetVulkanGraphicsDevice2KHR_ptr)(p_instance, p_get_info, r_vulkan_physical_device);
-}
-
 bool OpenXRVulkanExtension::get_physical_device(VkPhysicalDevice *r_device) {
 	ERR_FAIL_NULL_V(openxr_api, false);
 
@@ -222,12 +171,6 @@ bool OpenXRVulkanExtension::get_physical_device(VkPhysicalDevice *r_device) {
 	return true;
 }
 
-XrResult OpenXRVulkanExtension::xrCreateVulkanDeviceKHR(XrInstance p_instance, const XrVulkanDeviceCreateInfoKHR *p_create_info, VkDevice *r_device, VkResult *r_result) {
-	ERR_FAIL_NULL_V(xrCreateVulkanDeviceKHR_ptr, XR_ERROR_HANDLE_INVALID);
-
-	return (*xrCreateVulkanDeviceKHR_ptr)(p_instance, p_create_info, r_device, r_result);
-}
-
 bool OpenXRVulkanExtension::create_vulkan_device(const VkDeviceCreateInfo *p_device_create_info, VkDevice *r_device) {
 	ERR_FAIL_NULL_V(openxr_api, false);
 

modules/openxr/extensions/openxr_vulkan_extension.h

@@ -36,16 +36,25 @@
 
 #include "drivers/vulkan/vulkan_context.h"
 
-// Forward declare these so we don't need OpenXR headers where-ever this is included
-// Including OpenXR at this point gives loads and loads of compile issues especially
-// on Windows because windows.h is EVIL and really shouldn't be included outside of platform
-// but we really don't have a choice in the matter
+#include "../openxr_api.h"
+#include "../util.h"
 
-struct XrGraphicsRequirementsVulkanKHR;
-struct XrVulkanInstanceCreateInfoKHR;
-struct XrVulkanGraphicsDeviceGetInfoKHR;
-struct XrVulkanDeviceCreateInfoKHR;
-struct XrGraphicsBindingVulkanKHR;
+// need to include Vulkan so we know of type definitions
+#define XR_USE_GRAPHICS_API_VULKAN
+
+#ifdef WINDOWS_ENABLED
+// Including windows.h here is absolutely evil, we shouldn't be doing this outside of platform
+// however due to the way the openxr headers are put together, we have no choice.
+#include <windows.h>
+#endif
+
+#ifdef ANDROID_ENABLED
+// The jobject type from jni.h is used by openxr_platform.h on Android.
+#include <jni.h>
+#endif
+
+// include platform dependent structs
+#include <openxr/openxr_platform.h>
 
 class OpenXRVulkanExtension : public OpenXRGraphicsExtensionWrapper, VulkanHooks {
 public:
@@ -84,10 +93,11 @@ private:
 	uint32_t vulkan_queue_family_index = 0;
 	uint32_t vulkan_queue_index = 0;
 
-	XrResult xrGetVulkanGraphicsRequirements2KHR(XrInstance p_instance, XrSystemId p_system_id, XrGraphicsRequirementsVulkanKHR *p_graphics_requirements);
-	XrResult xrCreateVulkanInstanceKHR(XrInstance p_instance, const XrVulkanInstanceCreateInfoKHR *p_create_info, VkInstance *r_vulkan_instance, VkResult *r_vulkan_result);
-	XrResult xrGetVulkanGraphicsDevice2KHR(XrInstance p_instance, const XrVulkanGraphicsDeviceGetInfoKHR *p_get_info, VkPhysicalDevice *r_vulkan_physical_device);
-	XrResult xrCreateVulkanDeviceKHR(XrInstance p_instance, const XrVulkanDeviceCreateInfoKHR *p_create_info, VkDevice *r_device, VkResult *r_result);
+	EXT_PROTO_XRRESULT_FUNC3(xrGetVulkanGraphicsRequirements2KHR, (XrInstance), p_instance, (XrSystemId), p_system_id, (XrGraphicsRequirementsVulkanKHR *), p_graphics_requirements)
+	EXT_PROTO_XRRESULT_FUNC4(xrCreateVulkanInstanceKHR, (XrInstance), p_instance, (const XrVulkanInstanceCreateInfoKHR *), p_create_info, (VkInstance *), r_vulkan_instance, (VkResult *), r_vulkan_result)
+	EXT_PROTO_XRRESULT_FUNC3(xrGetVulkanGraphicsDevice2KHR, (XrInstance), p_instance, (const XrVulkanGraphicsDeviceGetInfoKHR *), p_get_info, (VkPhysicalDevice *), r_vulkan_physical_device)
+	EXT_PROTO_XRRESULT_FUNC4(xrCreateVulkanDeviceKHR, (XrInstance), p_instance, (const XrVulkanDeviceCreateInfoKHR *), p_create_info, (VkDevice *), r_device, (VkResult *), r_result)
+	EXT_PROTO_XRRESULT_FUNC4(xrEnumerateSwapchainImages, (XrSwapchain), p_swapchain, (uint32_t), p_image_capacity_input, (uint32_t *), p_image_count_output, (XrSwapchainImageBaseHeader *), p_images)
 };
 
 #endif // OPENXR_VULKAN_EXTENSION_H

modules/openxr/openxr_api.cpp

@@ -41,6 +41,7 @@
 #endif
 
 #ifdef ANDROID_ENABLED
+#define OPENXR_LOADER_NAME "libopenxr_loader.so"
 #include "extensions/openxr_android_extension.h"
 #endif
 
@@ -284,6 +285,9 @@ bool OpenXRAPI::create_instance() {
 		0, // runtimeVersion, from here will be set by our get call
 		"" // runtimeName
 	};
+
+	OPENXR_API_INIT_XR_FUNC_V(xrGetInstanceProperties);
+
 	result = xrGetInstanceProperties(instance, &instanceProps);
 	if (XR_FAILED(result)) {
 		// not fatal probably
@@ -992,9 +996,94 @@ bool OpenXRAPI::is_running() {
 	return running;
 }
 
+bool OpenXRAPI::openxr_loader_init() {
+#ifdef ANDROID_ENABLED
+	ERR_FAIL_COND_V_MSG(openxr_loader_library_handle != nullptr, false, "OpenXR Loader library is already loaded.");
+
+	{
+		Error error_code = OS::get_singleton()->open_dynamic_library(OPENXR_LOADER_NAME, openxr_loader_library_handle);
+		ERR_FAIL_COND_V_MSG(error_code != OK, false, "OpenXR loader not found.");
+	}
+
+	{
+		Error error_code = OS::get_singleton()->get_dynamic_library_symbol_handle(openxr_loader_library_handle, "xrGetInstanceProcAddr", (void *&)xrGetInstanceProcAddr);
+		ERR_FAIL_COND_V_MSG(error_code != OK, false, "Symbol xrGetInstanceProcAddr not found in OpenXR Loader library.");
+	}
+#endif
+
+	// Resolve the symbols that don't require an instance
+	OPENXR_API_INIT_XR_FUNC_V(xrCreateInstance);
+	OPENXR_API_INIT_XR_FUNC_V(xrEnumerateApiLayerProperties);
+	OPENXR_API_INIT_XR_FUNC_V(xrEnumerateInstanceExtensionProperties);
+
+	return true;
+}
+
+bool OpenXRAPI::resolve_instance_openxr_symbols() {
+	ERR_FAIL_COND_V(instance == XR_NULL_HANDLE, false);
+
+	OPENXR_API_INIT_XR_FUNC_V(xrAcquireSwapchainImage);
+	OPENXR_API_INIT_XR_FUNC_V(xrApplyHapticFeedback);
+	OPENXR_API_INIT_XR_FUNC_V(xrAttachSessionActionSets);
+	OPENXR_API_INIT_XR_FUNC_V(xrBeginFrame);
+	OPENXR_API_INIT_XR_FUNC_V(xrBeginSession);
+	OPENXR_API_INIT_XR_FUNC_V(xrCreateAction);
+	OPENXR_API_INIT_XR_FUNC_V(xrCreateActionSet);
+	OPENXR_API_INIT_XR_FUNC_V(xrCreateActionSpace);
+	OPENXR_API_INIT_XR_FUNC_V(xrCreateReferenceSpace);
+	OPENXR_API_INIT_XR_FUNC_V(xrCreateSession);
+	OPENXR_API_INIT_XR_FUNC_V(xrCreateSwapchain);
+	OPENXR_API_INIT_XR_FUNC_V(xrDestroyAction);
+	OPENXR_API_INIT_XR_FUNC_V(xrDestroyActionSet);
+	OPENXR_API_INIT_XR_FUNC_V(xrDestroyInstance);
+	OPENXR_API_INIT_XR_FUNC_V(xrDestroySession);
+	OPENXR_API_INIT_XR_FUNC_V(xrDestroySpace);
+	OPENXR_API_INIT_XR_FUNC_V(xrDestroySwapchain);
+	OPENXR_API_INIT_XR_FUNC_V(xrEndFrame);
+	OPENXR_API_INIT_XR_FUNC_V(xrEndSession);
+	OPENXR_API_INIT_XR_FUNC_V(xrEnumerateReferenceSpaces);
+	OPENXR_API_INIT_XR_FUNC_V(xrEnumerateSwapchainFormats);
+	OPENXR_API_INIT_XR_FUNC_V(xrEnumerateViewConfigurations);
+	OPENXR_API_INIT_XR_FUNC_V(xrEnumerateViewConfigurationViews);
+	OPENXR_API_INIT_XR_FUNC_V(xrGetActionStateBoolean);
+	OPENXR_API_INIT_XR_FUNC_V(xrGetActionStateFloat);
+	OPENXR_API_INIT_XR_FUNC_V(xrGetActionStateVector2f);
+	OPENXR_API_INIT_XR_FUNC_V(xrGetCurrentInteractionProfile);
+	OPENXR_API_INIT_XR_FUNC_V(xrGetSystem);
+	OPENXR_API_INIT_XR_FUNC_V(xrGetSystemProperties);
+	OPENXR_API_INIT_XR_FUNC_V(xrLocateViews);
+	OPENXR_API_INIT_XR_FUNC_V(xrLocateSpace);
+	OPENXR_API_INIT_XR_FUNC_V(xrPathToString);
+	OPENXR_API_INIT_XR_FUNC_V(xrPollEvent);
+	OPENXR_API_INIT_XR_FUNC_V(xrReleaseSwapchainImage);
+	OPENXR_API_INIT_XR_FUNC_V(xrResultToString);
+	OPENXR_API_INIT_XR_FUNC_V(xrStringToPath);
+	OPENXR_API_INIT_XR_FUNC_V(xrSuggestInteractionProfileBindings);
+	OPENXR_API_INIT_XR_FUNC_V(xrSyncActions);
+	OPENXR_API_INIT_XR_FUNC_V(xrWaitFrame);
+	OPENXR_API_INIT_XR_FUNC_V(xrWaitSwapchainImage);
+
+	return true;
+}
+
+XrResult OpenXRAPI::get_instance_proc_addr(const char *p_name, PFN_xrVoidFunction *p_addr) {
+	XrResult result = xrGetInstanceProcAddr(instance, p_name, p_addr);
+
+	if (result != XR_SUCCESS) {
+		String error_message = String("Symbol ") + p_name + " not found in OpenXR instance.";
+		ERR_FAIL_COND_V_MSG(true, result, error_message.utf8().get_data());
+	}
+
+	return result;
+}
+
 bool OpenXRAPI::initialize(const String &p_rendering_driver) {
 	ERR_FAIL_COND_V_MSG(instance != XR_NULL_HANDLE, false, "OpenXR instance was already created");
 
+	if (!openxr_loader_init()) {
+		return false;
+	}
+
 	if (p_rendering_driver == "vulkan") {
 #ifdef VULKAN_ENABLED
 		graphics_extension = memnew(OpenXRVulkanExtension(this));
@@ -1017,6 +1106,10 @@ bool OpenXRAPI::initialize(const String &p_rendering_driver) {
 	}
 
 	// initialize
+	for (OpenXRExtensionWrapper *wrapper : registered_extension_wrappers) {
+		wrapper->on_before_instance_created();
+	}
+
 	if (!load_layer_properties()) {
 		destroy_instance();
 		return false;
@@ -1032,6 +1125,11 @@ bool OpenXRAPI::initialize(const String &p_rendering_driver) {
 		return false;
 	}
 
+	if (!resolve_instance_openxr_symbols()) {
+		destroy_instance();
+		return false;
+	}
+
 	if (!get_system_info()) {
 		destroy_instance();
 		return false;
@@ -1669,6 +1767,13 @@ OpenXRAPI::~OpenXRAPI() {
 		layer_properties = nullptr;
 	}
 
+#ifdef ANDROID_ENABLED
+	if (openxr_loader_library_handle) {
+		OS::get_singleton()->close_dynamic_library(openxr_loader_library_handle);
+		openxr_loader_library_handle = nullptr;
+	}
+#endif
+
 	singleton = nullptr;
 }
 

modules/openxr/openxr_api.h

@@ -50,6 +50,8 @@
 #include "extensions/openxr_composition_layer_provider.h"
 #include "extensions/openxr_extension_wrapper.h"
 
+#include "util.h"
+
 // Note, OpenXR code that we wrote for our plugin makes use of C++20 notation for initialising structs which ensures zeroing out unspecified members.
 // Godot is currently restricted to C++17 which doesn't allow this notation. Make sure critical fields are set.
 
@@ -134,6 +136,61 @@ private:
 	bool load_supported_extensions();
 	bool is_extension_supported(const String &p_extension) const;
 
+	bool openxr_loader_init();
+	bool resolve_instance_openxr_symbols();
+
+	void *openxr_loader_library_handle = nullptr;
+
+	// function pointers
+#ifdef ANDROID_ENABLED
+	// On non-Android platforms we use the OpenXR symbol linked into the engine binary.
+	PFN_xrGetInstanceProcAddr xrGetInstanceProcAddr = nullptr;
+#endif
+	EXT_PROTO_XRRESULT_FUNC3(xrAcquireSwapchainImage, (XrSwapchain), swapchain, (const XrSwapchainImageAcquireInfo *), acquireInfo, (uint32_t *), index)
+	EXT_PROTO_XRRESULT_FUNC3(xrApplyHapticFeedback, (XrSession), session, (const XrHapticActionInfo *), hapticActionInfo, (const XrHapticBaseHeader *), hapticFeedback)
+	EXT_PROTO_XRRESULT_FUNC2(xrAttachSessionActionSets, (XrSession), session, (const XrSessionActionSetsAttachInfo *), attachInfo)
+	EXT_PROTO_XRRESULT_FUNC2(xrBeginFrame, (XrSession), session, (const XrFrameBeginInfo *), frameBeginInfo)
+	EXT_PROTO_XRRESULT_FUNC2(xrBeginSession, (XrSession), session, (const XrSessionBeginInfo *), beginInfo)
+	EXT_PROTO_XRRESULT_FUNC3(xrCreateAction, (XrActionSet), actionSet, (const XrActionCreateInfo *), createInfo, (XrAction *), action)
+	EXT_PROTO_XRRESULT_FUNC3(xrCreateActionSet, (XrInstance), instance, (const XrActionSetCreateInfo *), createInfo, (XrActionSet *), actionSet)
+	EXT_PROTO_XRRESULT_FUNC3(xrCreateActionSpace, (XrSession), session, (const XrActionSpaceCreateInfo *), createInfo, (XrSpace *), space)
+	EXT_PROTO_XRRESULT_FUNC2(xrCreateInstance, (const XrInstanceCreateInfo *), createInfo, (XrInstance *), instance)
+	EXT_PROTO_XRRESULT_FUNC3(xrCreateReferenceSpace, (XrSession), session, (const XrReferenceSpaceCreateInfo *), createInfo, (XrSpace *), space)
+	EXT_PROTO_XRRESULT_FUNC3(xrCreateSession, (XrInstance), instance, (const XrSessionCreateInfo *), createInfo, (XrSession *), session)
+	EXT_PROTO_XRRESULT_FUNC3(xrCreateSwapchain, (XrSession), session, (const XrSwapchainCreateInfo *), createInfo, (XrSwapchain *), swapchain)
+	EXT_PROTO_XRRESULT_FUNC1(xrDestroyAction, (XrAction), action)
+	EXT_PROTO_XRRESULT_FUNC1(xrDestroyActionSet, (XrActionSet), actionSet)
+	EXT_PROTO_XRRESULT_FUNC1(xrDestroyInstance, (XrInstance), instance)
+	EXT_PROTO_XRRESULT_FUNC1(xrDestroySession, (XrSession), session)
+	EXT_PROTO_XRRESULT_FUNC1(xrDestroySpace, (XrSpace), space)
+	EXT_PROTO_XRRESULT_FUNC1(xrDestroySwapchain, (XrSwapchain), swapchain)
+	EXT_PROTO_XRRESULT_FUNC2(xrEndFrame, (XrSession), session, (const XrFrameEndInfo *), frameEndInfo)
+	EXT_PROTO_XRRESULT_FUNC1(xrEndSession, (XrSession), session)
+	EXT_PROTO_XRRESULT_FUNC3(xrEnumerateApiLayerProperties, (uint32_t), propertyCapacityInput, (uint32_t *), propertyCountOutput, (XrApiLayerProperties *), properties)
+	EXT_PROTO_XRRESULT_FUNC4(xrEnumerateInstanceExtensionProperties, (const char *), layerName, (uint32_t), propertyCapacityInput, (uint32_t *), propertyCountOutput, (XrExtensionProperties *), properties)
+	EXT_PROTO_XRRESULT_FUNC4(xrEnumerateReferenceSpaces, (XrSession), session, (uint32_t), spaceCapacityInput, (uint32_t *), spaceCountOutput, (XrReferenceSpaceType *), spaces)
+	EXT_PROTO_XRRESULT_FUNC4(xrEnumerateSwapchainFormats, (XrSession), session, (uint32_t), formatCapacityInput, (uint32_t *), formatCountOutput, (int64_t *), formats)
+	EXT_PROTO_XRRESULT_FUNC5(xrEnumerateViewConfigurations, (XrInstance), instance, (XrSystemId), systemId, (uint32_t), viewConfigurationTypeCapacityInput, (uint32_t *), viewConfigurationTypeCountOutput, (XrViewConfigurationType *), viewConfigurationTypes)
+	EXT_PROTO_XRRESULT_FUNC6(xrEnumerateViewConfigurationViews, (XrInstance), instance, (XrSystemId), systemId, (XrViewConfigurationType), viewConfigurationType, (uint32_t), viewCapacityInput, (uint32_t *), viewCountOutput, (XrViewConfigurationView *), views)
+	EXT_PROTO_XRRESULT_FUNC3(xrGetActionStateBoolean, (XrSession), session, (const XrActionStateGetInfo *), getInfo, (XrActionStateBoolean *), state)
+	EXT_PROTO_XRRESULT_FUNC3(xrGetActionStateFloat, (XrSession), session, (const XrActionStateGetInfo *), getInfo, (XrActionStateFloat *), state)
+	EXT_PROTO_XRRESULT_FUNC3(xrGetActionStateVector2f, (XrSession), session, (const XrActionStateGetInfo *), getInfo, (XrActionStateVector2f *), state)
+	EXT_PROTO_XRRESULT_FUNC3(xrGetCurrentInteractionProfile, (XrSession), session, (XrPath), topLevelUserPath, (XrInteractionProfileState *), interactionProfile)
+	EXT_PROTO_XRRESULT_FUNC2(xrGetInstanceProperties, (XrInstance), instance, (XrInstanceProperties *), instanceProperties)
+	EXT_PROTO_XRRESULT_FUNC3(xrGetSystem, (XrInstance), instance, (const XrSystemGetInfo *), getInfo, (XrSystemId *), systemId)
+	EXT_PROTO_XRRESULT_FUNC3(xrGetSystemProperties, (XrInstance), instance, (XrSystemId), systemId, (XrSystemProperties *), properties)
+	EXT_PROTO_XRRESULT_FUNC4(xrLocateSpace, (XrSpace), space, (XrSpace), baseSpace, (XrTime), time, (XrSpaceLocation *), location)
+	EXT_PROTO_XRRESULT_FUNC6(xrLocateViews, (XrSession), session, (const XrViewLocateInfo *), viewLocateInfo, (XrViewState *), viewState, (uint32_t), viewCapacityInput, (uint32_t *), viewCountOutput, (XrView *), views)
+	EXT_PROTO_XRRESULT_FUNC5(xrPathToString, (XrInstance), instance, (XrPath), path, (uint32_t), bufferCapacityInput, (uint32_t *), bufferCountOutput, (char *), buffer)
+	EXT_PROTO_XRRESULT_FUNC2(xrPollEvent, (XrInstance), instance, (XrEventDataBuffer *), eventData)
+	EXT_PROTO_XRRESULT_FUNC2(xrReleaseSwapchainImage, (XrSwapchain), swapchain, (const XrSwapchainImageReleaseInfo *), releaseInfo)
+	EXT_PROTO_XRRESULT_FUNC3(xrResultToString, (XrInstance), instance, (XrResult), value, (char *), buffer)
+	EXT_PROTO_XRRESULT_FUNC3(xrStringToPath, (XrInstance), instance, (const char *), pathString, (XrPath *), path)
+	EXT_PROTO_XRRESULT_FUNC2(xrSuggestInteractionProfileBindings, (XrInstance), instance, (const XrInteractionProfileSuggestedBinding *), suggestedBindings)
+	EXT_PROTO_XRRESULT_FUNC2(xrSyncActions, (XrSession), session, (const XrActionsSyncInfo *), syncInfo)
+	EXT_PROTO_XRRESULT_FUNC3(xrWaitFrame, (XrSession), session, (const XrFrameWaitInfo *), frameWaitInfo, (XrFrameState *), frameState)
+	EXT_PROTO_XRRESULT_FUNC2(xrWaitSwapchainImage, (XrSwapchain), swapchain, (const XrSwapchainImageWaitInfo *), waitInfo)
+
 	// instance
 	bool create_instance();
 	bool get_system_info();
@@ -231,6 +288,7 @@ public:
 	static bool openxr_is_enabled(bool p_check_run_in_editor = true);
 	static OpenXRAPI *get_singleton();
 
+	XrResult get_instance_proc_addr(const char *p_name, PFN_xrVoidFunction *p_addr);
 	String get_error_string(XrResult result);
 	String get_swapchain_format_name(int64_t p_swapchain_format) const;
 

modules/openxr/util.h

@@ -0,0 +1,110 @@
+/*************************************************************************/
+/*  util.h                                                               */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef UTIL_H
+#define UTIL_H
+
+#define UNPACK(...) __VA_ARGS__
+
+#define INIT_XR_FUNC_V(openxr_api, name)                                                                              \
+	do {                                                                                                              \
+		XrResult get_instance_proc_addr_result;                                                                       \
+		get_instance_proc_addr_result = openxr_api->get_instance_proc_addr(#name, (PFN_xrVoidFunction *)&name##_ptr); \
+		ERR_FAIL_COND_V(XR_FAILED(get_instance_proc_addr_result), false);                                             \
+	} while (0)
+
+#define EXT_INIT_XR_FUNC_V(name) INIT_XR_FUNC_V(openxr_api, name)
+#define OPENXR_API_INIT_XR_FUNC_V(name) INIT_XR_FUNC_V(this, name)
+
+#define INIT_XR_FUNC(openxr_api, name)                                                                                \
+	do {                                                                                                              \
+		XrResult get_instance_proc_addr_result;                                                                       \
+		get_instance_proc_addr_result = openxr_api->get_instance_proc_addr(#name, (PFN_xrVoidFunction *)&name##_ptr); \
+		ERR_FAIL_COND(XR_FAILED(get_instance_proc_addr_result));                                                      \
+	} while (0)
+
+#define EXT_INIT_XR_FUNC(name) INIT_XR_FUNC(openxr_api, name)
+#define OPENXR_API_INIT_XR_FUNC(name) INIT_XR_FUNC(this, name)
+
+#define EXT_PROTO_XRRESULT_FUNC1(func_name, arg1_type, arg1)                \
+	PFN_##func_name func_name##_ptr = nullptr;                              \
+	XRAPI_ATTR XrResult XRAPI_CALL func_name(UNPACK arg1_type arg1) const { \
+		if (!func_name##_ptr) {                                             \
+			return XR_ERROR_HANDLE_INVALID;                                 \
+		}                                                                   \
+		return (*func_name##_ptr)(arg1);                                    \
+	}
+
+#define EXT_PROTO_XRRESULT_FUNC2(func_name, arg1_type, arg1, arg2_type, arg2)                      \
+	PFN_##func_name func_name##_ptr = nullptr;                                                     \
+	XRAPI_ATTR XrResult XRAPI_CALL func_name(UNPACK arg1_type arg1, UNPACK arg2_type arg2) const { \
+		if (!func_name##_ptr) {                                                                    \
+			return XR_ERROR_HANDLE_INVALID;                                                        \
+		}                                                                                          \
+		return (*func_name##_ptr)(arg1, arg2);                                                     \
+	}
+
+#define EXT_PROTO_XRRESULT_FUNC3(func_name, arg1_type, arg1, arg2_type, arg2, arg3_type, arg3)                            \
+	PFN_##func_name func_name##_ptr = nullptr;                                                                            \
+	XRAPI_ATTR XrResult XRAPI_CALL func_name(UNPACK arg1_type arg1, UNPACK arg2_type arg2, UNPACK arg3_type arg3) const { \
+		if (!func_name##_ptr) {                                                                                           \
+			return XR_ERROR_HANDLE_INVALID;                                                                               \
+		}                                                                                                                 \
+		return (*func_name##_ptr)(arg1, arg2, arg3);                                                                      \
+	}
+
+#define EXT_PROTO_XRRESULT_FUNC4(func_name, arg1_type, arg1, arg2_type, arg2, arg3_type, arg3, arg4_type, arg4)                                  \
+	PFN_##func_name func_name##_ptr = nullptr;                                                                                                   \
+	XRAPI_ATTR XrResult XRAPI_CALL func_name(UNPACK arg1_type arg1, UNPACK arg2_type arg2, UNPACK arg3_type arg3, UNPACK arg4_type arg4) const { \
+		if (!func_name##_ptr) {                                                                                                                  \
+			return XR_ERROR_HANDLE_INVALID;                                                                                                      \
+		}                                                                                                                                        \
+		return (*func_name##_ptr)(arg1, arg2, arg3, arg4);                                                                                       \
+	}
+
+#define EXT_PROTO_XRRESULT_FUNC5(func_name, arg1_type, arg1, arg2_type, arg2, arg3_type, arg3, arg4_type, arg4, arg5_type, arg5)                                        \
+	PFN_##func_name func_name##_ptr = nullptr;                                                                                                                          \
+	XRAPI_ATTR XrResult XRAPI_CALL func_name(UNPACK arg1_type arg1, UNPACK arg2_type arg2, UNPACK arg3_type arg3, UNPACK arg4_type arg4, UNPACK arg5_type arg5) const { \
+		if (!func_name##_ptr) {                                                                                                                                         \
+			return XR_ERROR_HANDLE_INVALID;                                                                                                                             \
+		}                                                                                                                                                               \
+		return (*func_name##_ptr)(arg1, arg2, arg3, arg4, arg5);                                                                                                        \
+	}
+
+#define EXT_PROTO_XRRESULT_FUNC6(func_name, arg1_type, arg1, arg2_type, arg2, arg3_type, arg3, arg4_type, arg4, arg5_type, arg5, arg6_type, arg6)                                              \
+	PFN_##func_name func_name##_ptr = nullptr;                                                                                                                                                 \
+	XRAPI_ATTR XrResult XRAPI_CALL func_name(UNPACK arg1_type arg1, UNPACK arg2_type arg2, UNPACK arg3_type arg3, UNPACK arg4_type arg4, UNPACK arg5_type arg5, UNPACK arg6_type arg6) const { \
+		if (!func_name##_ptr) {                                                                                                                                                                \
+			return XR_ERROR_HANDLE_INVALID;                                                                                                                                                    \
+		}                                                                                                                                                                                      \
+		return (*func_name##_ptr)(arg1, arg2, arg3, arg4, arg5, arg6);                                                                                                                         \
+	}
+
+#endif // UTIL_H