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 <gabor.p.korom@migeran.com>
Co-authored-by: Gábor Koncz <gabor.koncz@migeran.com>

1 files changed, 105 insertions, 0 deletions

diff --git a/modules/openxr/openxr_api.cpp b/modules/openxr/openxr_api.cpp
index 92d074cb75..f2b1c3da14 100644
--- a/modules/openxr/openxr_api.cpp
+++ b/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;
 }