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

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/*  openxr_fb_foveation_extension.h                                       */
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#ifndef OPENXR_FB_FOVEATION_EXTENSION_H
#define OPENXR_FB_FOVEATION_EXTENSION_H

// This extension implements the FB Foveation extension.
// This is an extension Meta added due to VRS being unavailable on Android.
// Other Android based devices are implementing this as well, see:
// https://github.khronos.org/OpenXR-Inventory/extension_support.html#XR_FB_foveation

// Note: Currently we only support this for OpenGL.
// This extension works on enabling foveated rendering on the swapchain.
// Vulkan does not render 3D content directly to the swapchain image
// hence this extension can't be used.

#include "../openxr_api.h"
#include "../util.h"
#include "openxr_extension_wrapper.h"
#include "openxr_fb_update_swapchain_extension.h"

class OpenXRFBFoveationExtension : public OpenXRExtensionWrapper {
public:
	static OpenXRFBFoveationExtension *get_singleton();

	OpenXRFBFoveationExtension(const String &p_rendering_driver);
	virtual ~OpenXRFBFoveationExtension() override;

	virtual HashMap<String, bool *> get_requested_extensions() override;

	virtual void on_instance_created(const XrInstance p_instance) override;
	virtual void on_instance_destroyed() override;

	virtual void *set_swapchain_create_info_and_get_next_pointer(void *p_next_pointer) override;

	virtual void on_main_swapchains_created() override;

	bool is_enabled() const;

	XrFoveationLevelFB get_foveation_level() const;
	void set_foveation_level(XrFoveationLevelFB p_foveation_level);

	XrFoveationDynamicFB get_foveation_dynamic() const;
	void set_foveation_dynamic(XrFoveationDynamicFB p_foveation_dynamic);

private:
	static OpenXRFBFoveationExtension *singleton;

	// Setup
	String rendering_driver;
	bool fb_foveation_ext = false;
	bool fb_foveation_configuration_ext = false;

	// Configuration
	XrFoveationLevelFB foveation_level = XR_FOVEATION_LEVEL_NONE_FB;
	XrFoveationDynamicFB foveation_dynamic = XR_FOVEATION_DYNAMIC_DISABLED_FB;

	static void _update_profile();

	void update_profile() {
		// If we're rendering on a separate thread, we may still be processing the last frame, don't communicate this till we're ready...
		RenderingServer *rendering_server = RenderingServer::get_singleton();
		ERR_FAIL_NULL(rendering_server);

		rendering_server->call_on_render_thread(callable_mp_static(&OpenXRFBFoveationExtension::_update_profile));
	}

	// Enable foveation on this swapchain
	XrSwapchainCreateInfoFoveationFB swapchain_create_info_foveation_fb;
	OpenXRFBUpdateSwapchainExtension *swapchain_update_state_ext = nullptr;

	// OpenXR API call wrappers
	EXT_PROTO_XRRESULT_FUNC3(xrCreateFoveationProfileFB, (XrSession), session, (const XrFoveationProfileCreateInfoFB *), create_info, (XrFoveationProfileFB *), profile);
	EXT_PROTO_XRRESULT_FUNC1(xrDestroyFoveationProfileFB, (XrFoveationProfileFB), profile);
};

#endif // OPENXR_FB_FOVEATION_EXTENSION_H