virtualx-engine/modules/openxr/extensions/openxr_extension_wrapper.h

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/*  openxr_extension_wrapper.h                                            */
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#ifndef OPENXR_EXTENSION_WRAPPER_H
#define OPENXR_EXTENSION_WRAPPER_H

#include "core/error/error_macros.h"
#include "core/math/projection.h"
#include "core/templates/hash_map.h"
#include "core/templates/rid.h"

#include <openxr/openxr.h>

class OpenXRAPI;
class OpenXRActionMap;

// `OpenXRExtensionWrapper` allows us to implement OpenXR extensions.
class OpenXRExtensionWrapper {
public:
	// `get_requested_extensions` should return a list of OpenXR extensions related to this extension.
	// If the bool * is a nullptr this extension is mandatory
	// If the bool * points to a boolean, the boolean will be updated
	// to true if the extension is enabled.
	virtual HashMap<String, bool *> get_requested_extensions() = 0;

	// These functions allow an extension to add entries to a struct chain.
	// `p_next_pointer` points to the last struct that was created for this chain
	// and should be used as the value for the `pNext` pointer in the first struct you add.
	// You should return the pointer to the last struct you define as your result.
	// If you are not adding any structs, just return `p_next_pointer`.
	// See existing extensions for examples of this implementation.
	virtual void *set_system_properties_and_get_next_pointer(void *p_next_pointer) { return p_next_pointer; } // Add additional data structures when we interogate OpenXRS system abilities.
	virtual void *set_instance_create_info_and_get_next_pointer(void *p_next_pointer) { return p_next_pointer; } // Add additional data structures when we create our OpenXR instance.
	virtual void *set_session_create_and_get_next_pointer(void *p_next_pointer) { return p_next_pointer; } // Add additional data structures when we create our OpenXR session.
	virtual void *set_swapchain_create_info_and_get_next_pointer(void *p_next_pointer) { return p_next_pointer; } // Add additional data structures when creating OpenXR swap chains.
	virtual void *set_hand_joint_locations_and_get_next_pointer(int p_hand_index, void *p_next_pointer) { return p_next_pointer; }

	// `on_register_metadata` allows extensions to register additional controller metadata.
	// This function is called even when OpenXRApi is not constructured as the metadata
	// needs to be available to the editor.
	// Also extensions should provide metadata regardless of whether they are supported
	// on the host system as the controller data is used to setup action maps for users
	// who may have access to the relevant hardware.
	virtual void on_register_metadata() {}

	virtual void on_before_instance_created() {} // `on_before_instance_created` is called before we create our OpenXR instance.
	virtual void on_instance_created(const XrInstance p_instance) {} // `on_instance_created` is called right after we've successfully created our OpenXR instance.
	virtual void on_instance_destroyed() {} // `on_instance_destroyed` is called right before we destroy our OpenXR instance.
	virtual void on_session_created(const XrSession p_instance) {} // `on_session_created` is called right after we've successfully created our OpenXR session.
	virtual void on_session_destroyed() {} // `on_session_destroyed` is called right before we destroy our OpenXR session.

	// `on_process` is called as part of our OpenXR process handling,
	// this happens right before physics process and normal processing is run.
	// This is when controller data is queried and made available to game logic.
	virtual void on_process() {}
	virtual void on_pre_render() {} // `on_pre_render` is called right before we start rendering our XR viewports.
	virtual void on_pre_draw_viewport(RID p_render_target) {} // `on_pre_draw_viewport` is called right before we start rendering this viewport
	virtual void on_post_draw_viewport(RID p_render_target) {} // `on_port_draw_viewport` is called right after we start rendering this viewport (note that on Vulkan draw commands may only be queued)

	virtual void on_state_idle() {} // `on_state_idle` is called when the OpenXR session state is changed to idle.
	virtual void on_state_ready() {} // `on_state_ready` is called when the OpenXR session state is changed to ready, this means OpenXR is ready to setup our session.
	virtual void on_state_synchronized() {} // `on_state_synchronized` is called when the OpenXR session state is changed to synchronized, note that OpenXR also returns to this state when our application looses focus.
	virtual void on_state_visible() {} // `on_state_visible` is called when the OpenXR session state is changed to visible, OpenXR is now ready to receive frames.
	virtual void on_state_focused() {} // `on_state_focused` is called when the OpenXR session state is changed to focused, this state is the active state when our game runs.
	virtual void on_state_stopping() {} // `on_state_stopping` is called when the OpenXR session state is changed to stopping.
	virtual void on_state_loss_pending() {} // `on_state_loss_pending` is called when the OpenXR session state is changed to loss pending.
	virtual void on_state_exiting() {} // `on_state_exiting` is called when the OpenXR session state is changed to exiting.

	// `on_event_polled` is called when there is an OpenXR event to process.
	// Should return true if the event was handled, false otherwise.
	virtual bool on_event_polled(const XrEventDataBuffer &event) {
		return false;
	}

	OpenXRExtensionWrapper() = default;
	virtual ~OpenXRExtensionWrapper() = default;
};

// `OpenXRGraphicsExtensionWrapper` implements specific logic for each supported graphics API.
class OpenXRGraphicsExtensionWrapper : public OpenXRExtensionWrapper {
public:
	virtual void get_usable_swapchain_formats(Vector<int64_t> &p_usable_swap_chains) = 0; // `get_usable_swapchain_formats` should return a list of usable color formats.
	virtual void get_usable_depth_formats(Vector<int64_t> &p_usable_swap_chains) = 0; // `get_usable_depth_formats` should return a list of usable depth formats.
	virtual String get_swapchain_format_name(int64_t p_swapchain_format) const = 0; // `get_swapchain_format_name` should return the constant name of a given format.
	virtual bool get_swapchain_image_data(XrSwapchain p_swapchain, int64_t p_swapchain_format, uint32_t p_width, uint32_t p_height, uint32_t p_sample_count, uint32_t p_array_size, void **r_swapchain_graphics_data) = 0; // `get_swapchain_image_data` extracts image IDs for the swapchain images and stores there in an implementation dependent data structure.
	virtual void cleanup_swapchain_graphics_data(void **p_swapchain_graphics_data) = 0; // `cleanup_swapchain_graphics_data` cleans up the data held in our implementation dependent data structure and should free up its memory.
	virtual bool create_projection_fov(const XrFovf p_fov, double p_z_near, double p_z_far, Projection &r_camera_matrix) = 0; // `create_projection_fov` creates a proper projection matrix based on asymmetric FOV data provided by OpenXR.
	virtual RID get_texture(void *p_swapchain_graphics_data, int p_image_index) = 0; // `get_texture` returns a Godot texture RID for the current active texture in our swapchain.
};

#endif // OPENXR_EXTENSION_WRAPPER_H