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, 23 insertions, 13 deletions

diff --git a/modules/openxr/extensions/openxr_vulkan_extension.h b/modules/openxr/extensions/openxr_vulkan_extension.h
index 5dddc4b9c9..d6e9917900 100644
--- a/modules/openxr/extensions/openxr_vulkan_extension.h
+++ b/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