openvr_compositor.hpp

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// Copyright 2026, Beyley Cardellio
// SPDX-License-Identifier: BSL-1.0
/*!
 * @file
 * @brief Implementation of compositor-related functionality for OpenVR.
 *
 * @author Beyley Cardellio <ep1cm1n10n123@gmail.com>
 * @ingroup openvr
 */
 
#pragma once
 
#include "xrt/xrt_compositor.h"
#include "xrt/xrt_config_build.h"
#include "xrt/xrt_device.h"
#include "xrt/xrt_system.h"
#include "xrt/xrt_gfx_vk.h"
 
#include "util/u_time.h"
 
#include "common/openvr_logger.hpp"
 
#include "openvr_interfaces_unified.h"
 
#include "openvr_events.hpp"
 
#include <array>
#include <optional>
#include <memory>
 
 
namespace xrt::state_trackers::openvr {
 
struct EyeTexture
{
        //! The swapchain in use
        xrt_swapchain *xsc{nullptr};
        //! The index into the eye's swapchain for the currently held texture.
        uint32_t swapchain_index;
 
        //! The format of the currently held texture.
        uint32_t format;
        //! The width of the currently held texture.
        uint32_t width;
        //! The height of the currently held texture.
        uint32_t height;
        //! The sample count of the currently held texture.
        uint32_t sample_count;
 
        //! The bounds of the submitted texture.
        xrt_rect bounds;
 
        ~EyeTexture()
        {
                if (this->xsc != nullptr) {
                        xrt_swapchain_release_image(this->xsc, this->swapchain_index);
                }
 
                xrt_swapchain_reference(&this->xsc, nullptr);
        }
};
 
struct EyeState
{
        EyeTexture texture;
};
 
struct FrameState
{
        int64_t frame_id{-1};
        timepoint_ns predicted_display_time{0};
        time_duration_ns predicted_display_period{0};
};
 
/*!
 * Since eye textures are created by the clients, and not the runtime, we have to do a copy into a runtime-owned
 * swapchain, this structure cached created swapchains to avoid creating a new one every frame.
 */
struct SwapchainCache
{
public: // Fields
        xrt_swapchain *xsc{nullptr};
 
        uint32_t width{0};
        uint32_t height{0};
        uint32_t format{0};
        uint32_t sample_count{0};
 
public: // Methods
        //! Ensures that there is a swapchain in the cache with the given properties, creating one if necessary.
        xrt_result_t
        EnsureSwapchain(xrt_compositor *xc, uint32_t format, uint32_t width, uint32_t height, uint32_t sample_count);
 
        ~SwapchainCache();
};
 
struct RenderStateCache
{
        std::array<xrt_fov, 2> fovs;
        std::array<xrt_pose, 2> T_head_eyes;
 
        xrt_pose head_relation;
};
 
struct Compositor
{
private: // Fields
        //! The state for the current active frame
        std::optional<FrameState> active_frame{std::nullopt};
        //! The state for each submit eye.
        std::array<std::optional<EyeState>, 2> frame_eye_states{std::nullopt, std::nullopt};
        //! Caches of swapchains for each eye, keyed by the format/size/sample count of the submitted texture.
        std::array<SwapchainCache, 2> swapchain_caches{};
 
        //! The active system devices
        xrt_system_devices *xsysd{nullptr};
 
        //! The current native compositor
        xrt_compositor_native *xcn{nullptr};
 
        xrt_system_compositor *xsysc{nullptr};
 
        //! The currently active compositor, implicitly also has an active session.
        xrt_compositor *active_compositor{nullptr};
 
#ifdef XRT_HAVE_VULKAN
        struct xrt_compositor_vk *xc_vk{nullptr};
#endif
 
        std::optional<RenderStateCache> render_state_cache{std::nullopt};
 
        std::shared_ptr<Events> events{};
 
public: // Fields
        std::optional<timepoint_ns> last_predicted_display_time{std::nullopt};
        std::optional<time_duration_ns> last_predicted_display_period{std::nullopt};
 
        std::array<vr::TrackedDevicePose_t, vr::k_unMaxTrackedDeviceCount> last_render_poses{};
        std::array<vr::TrackedDevicePose_t, vr::k_unMaxTrackedDeviceCount> last_game_poses{};
 
        vr::ETrackingUniverseOrigin current_tracking_universe{vr::ETrackingUniverseOrigin::TrackingUniverseSeated};
 
private: // Methods
#ifdef XRT_HAVE_VULKAN
         //! Sets up the Vulkan compositor as the active compositor, and begins the session.
        xrt_result_t
        SetupVulkanCompositor(openvr_logger &logger, vr::VRVulkanTextureData_t &vulkan_data);
 
        xrt_result_t
        BlitAppImageToSwapchainImage(openvr_logger &logger,
                                     xrt_swapchain *xsc,
                                     uint32_t dst_index,
                                     vr::VRVulkanTextureData_t &texture_data,
                                     vr::EColorSpace color_space,
                                     const xrt_rect &rect);
 
        //! Handles submission of a Vulkan texture, which involves copying it into a runtime-owned swapchain image.
        vr::EVRCompositorError
        SubmitVulkan(openvr_logger &logger,
                     vr::EVREye eye,
                     vr::VRVulkanTextureData_t &texture_data,
                     vr::EColorSpace color_space,
                     const vr::VRTextureBounds_t &bounds);
 
        void
        GetVulkanOutputDevice(openvr_logger &logger, uint64_t *out_device, VkInstance pInstance);
#endif
 
        //! Gets the projection layer data from the passed eye state
        xrt_layer_projection_view_data
        GetProjectionLayerDataForEye(vr::EVREye eye, const EyeState &eye_state);
 
        //! Completes a frame and submits textures to the runtime.
        vr::EVRCompositorError
        CompleteFrame(openvr_logger &logger);
 
public: // Methods
        Compositor(xrt_system_devices *xsysd,
                   xrt_compositor_native *xcn,
                   xrt_system_compositor *xsysc,
                   std::shared_ptr<Events> &events);
 
        ~Compositor();
 
        /*!
         * Waits for the next frame and begins it, cancelling/releasing any previously active frame and it's resources,
         * if it exists.
         */
        vr::EVRCompositorError
        WaitBeginFrame(openvr_logger &logger);
 
        //! Submits a texture for an eye, completing the frame if both eyes have been submit.
        vr::EVRCompositorError
        Submit(openvr_logger &logger,
               vr::EVREye eye,
               const vr::Texture_t &texture,
               const vr::VRTextureBounds_t &bounds,
               vr::EVRSubmitFlags nSubmitFlags);
 
        void
        GetOutputDevice(openvr_logger &logger,
                        uint64_t *out_device,
                        vr::ETextureType texture_type,
                        VkInstance pInstance);
 
        timepoint_ns
        GetTimeForPredictions();
 
        time_duration_ns
        GetFramePeriod();
 
        xrt_result_t
        GetFrameRenderState(std::array<xrt_fov, 2> &fovs,
                            std::array<xrt_pose, 2> &T_head_eyes,
                            xrt_pose &head_relation);
};
 
}; // namespace xrt::state_trackers::openvr