Rust OpenXR绑定库openxr-sys使用指南

概述

openxr-sys是Rust语言对OpenXR API的低级绑定库，允许开发者直接与OpenXR运行时交互，实现跨平台的VR/AR应用程序开发。它提供了与C API几乎1:1对应的绑定，适合需要高性能和精细控制的XR应用开发。

安装方法

在Cargo.toml中添加依赖：

[dependencies]
openxr-sys = "0.20"

基本使用方法

1. 初始化OpenXR实例

use openxr_sys as xr;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // 初始化实例
    let mut instance = std::ptr::null_mut();
    let app_info = xr::ApplicationInfo {
        application_name: "Rust XR App".as_ptr() as *const i8,
        application_version: 1,
        engine_name: "Rust Engine".as_ptr() as *const i8,
        engine_version: 1,
        api_version: xr::CURRENT_API_VERSION,
    };
    
    let create_info = xr::InstanceCreateInfo {
        ty: xr::StructureType::INSTANCE_CREATE_INFO,
        next: std::ptr::null(),
        create_flags: 0,
        application_info: app_info,
        enabled_api_layer_count: 0,
        enabled_api_layer_names: std::ptr::null(),
        enabled extension_count: 0,
        enabled_extension_names: std::ptr::null(),
    };
    
    unsafe {
        let result = xr::create_instance(&create_info, &mut instance);
        if result != xr::Result::SUCCESS {
            return Err(format!("Failed to create OpenXR instance: {:?}", result).into());
        }
    }
    
    // 使用instance进行后续操作...
    
    // 清理
    unsafe {
        xr::destroy_instance(instance);
    }
    
    Ok(())
}

2. 查询系统信息

unsafe fn query_system_info(instance: xr::Instance) -> Result<(), String> {
    let mut system_id = xr::SystemId::default();
    let system_get_info = xr::SystemGetInfo {
        ty: xr::StructureType::SYSTEM_GET_INFO,
        next: std::ptr::null(),
        form_factor: xr::FormFactor::HEAD_MOUNTED_DISPLAY,
    };
    
    let result = xr::get_system(instance, &system_get_info, &mut system_id);
    if result != xr::Result::SUCCESS {
        return Err(format!("Failed to get system: {:?}", result));
    }
    
    let mut system_properties = xr::SystemProperties {
        ty: xr::StructureType::SYSTEM_PROPERTIES,
        next: std::ptr::null_mut(),
        ..Default::default()
    };
    
    let result = xr::get_system_properties(instance, system_id, &mut system_properties);
    if result != xr::Result::SUCCESS {
        return Err(format!("Failed to get system properties: {:?}", result));
    }
    
    println!("System properties:");
    println!("  Vendor ID: {}", system_properties.vendor_id);
    println!("  System Name: {:?}", std::ffi::CStr::from_ptr(system_properties.system_name.as_ptr()));
    println!("  Graphics Properties:");
    println!("    Max swapchain width: {}", system_properties.graphics_properties.max_swapchain_image_width);
    println!("    Max swapchain height: {}", system_properties.graphics_properties.max_swapchain_image_height);
    
    Ok(())
}

3. 创建会话和交换链

unsafe fn create_session(
    instance: xr::Instance,
    system_id: xr::SystemId,
) -> Result<xr::Session, String> {
    // 这里需要根据你的图形API(Vulkan/OpenGL等)创建绑定
    // 以Vulkan为例:
    
    let mut graphics_binding = xr::GraphicsBindingVulkanKHR {
        ty: xr::StructureType::GRAPHICS_BINDING_VULKAN_KHR,
        next: std::ptr::null(),
        instance: std::ptr::null_mut(),
        physical_device: std::ptr::null_mut(),
        device: std::ptr::null_mut(),
        queue_family_index: 0,
        queue_index: 0,
    };
    
    // 实际应用中需要填充真实的Vulkan设备信息
    // ...
    
    let mut session = std::ptr::null_mut();
    let create_info = xr::SessionCreateInfo {
        ty: xr::StructureType::SESSION_CREATE_INFO,
        next: &graphics_binding as *const _ as *const _,
        create_flags: 0,
        system_id,
    };
    
    let result = xr::create_session(instance, &create_info, &mut session);
    if result != xr::Result::SUCCESS {
        return Err(format!("Failed to create session: {:?}", result));
    }
    
    Ok(session)
}

高级功能

事件循环处理

unsafe fn poll_events(instance: xr::Instance) -> Result<bool, String> {
    let mut event = xr::EventDataBuffer {
        ty: xr::StructureType::EVENT_DATA_BUFFER,
        next: std::ptr::null_mut(),
        ..Default::default()
    };
    
    let result = xr::poll_event(instance, &mut event);
    match result {
        xr::Result::SUCCESS => {
            match event.ty {
                xr::StructureType::EVENT_DATA_INSTANCE_LOSS_PING => {
                    println!("Instance loss pending!");
                    return Ok(false);
                }
                xr::StructureType::EVENT_DATA_SESSION_STATE_CHANGED => {
                    let event = &*(&event as *const _ as *const xr::EventDataSessionStateChanged);
                    println!("Session state changed to {:?}", event.state);
                }
                _ => {
                    println!("Received unhandled event type: {:?}", event.ty);
                }
            }
            Ok(true)
        }
        xr::Result::EVENT_UNAVAILABLE => Ok(true), // 没有更多事件
        _ => Err(format!("Failed to poll events: {:?}", result)),
    }
}

帧循环示例

unsafe fn frame_loop(
    instance: xr::Instance,
    session: xr::Session,
    space: xr::Space,
) -> Result<(), String> {
    let mut view_state = xr::ViewState {
        ty: xr::StructureType::VIEW_STATE,
        next: std::ptr::null_mut(),
        ..Default::default()
    };
    
    let mut frame_state = xr::FrameState {
        ty: xr::StructureType::FRAME_STATE,
        next: std::ptr::null_mut(),
        ..Default::default()
    };
    
    loop {
        let result = xr::wait_frame(session, std::ptr::null(), &mut frame_state);
        if result != xr::Result::SUCCESS {
            return Err(format!("Failed to wait frame: {:?}", result));
        }
        
        let result = xr::begin_frame(session, std::ptr::null());
        if result == xr::Result::SESSION_LOSS_PENDING {
            return Ok(());
        } else if result != xr::Result::SUCCESS {
            return Err(format!("Failed to begin frame: {:?}", result));
        }
        
        // 渲染代码...
        
        let layer = xr::CompositionLayerProjection {
            ty: xr::StructureType::COMPOSITION_LAYER_PROJECTION,
            next: std::ptr::null(),
            layer_flags: 0,
            space,
            view_count: 0,
            views: std::ptr::null(),
        };
        
        let frame_end_info = xr::FrameEndInfo {
            ty: xr::StructureType::FRAME_END_INFO,
            next: std::ptr::null(),
            display_time: frame_state.predicted_display_time,
            environment_blend_mode: xr::EnvironmentBlendMode::OPAQUE,
            layer_count: 1,
            layers: &layer as *const _ as *const *const _,
        };
        
        let result = xr::end_frame(session, &frame_end_info);
        if result == xr::Result::SESSION_LOSS_PENDING {
            return Ok(());
        } else if result != xr::Result::SUCCESS {
            return Err(format!("Failed to end frame: {:?}", result));
        }
    }
}

完整示例demo

use openxr_sys as xr;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // 1. 初始化OpenXR实例
    let mut instance = std::ptr::null_mut();
    let app_info = xr::ApplicationInfo {
        application_name: "Rust XR Demo".as_ptr() as *const i8,
        application_version: 1,
        engine_name: "Rust XR Engine".as_ptr() as *const i8,
        engine_version: 1,
        api_version: xr::CURRENT_API_VERSION,
    };
    
    let create_info = xr::InstanceCreateInfo {
        ty: xr::StructureType::INSTANCE_CREATE_INFO,
        next: std::ptr::null(),
        create_flags: 0,
        application_info: app_info,
        enabled_api_layer_count: 0,
        enabled_api_layer_names: std::ptr::null(),
        enabled_extension_count: 0,
        enabled_extension_names: std::ptr::null(),
    };
    
    unsafe {
        let result = xr::create_instance(&create_info, &mut instance);
        if result != xr::Result::SUCCESS {
            return Err(format!("Failed to create OpenXR instance: {:?}", result).into());
        }
    }
    
    // 2. 查询系统信息
    unsafe {
        let mut system_id = xr::SystemId::default();
        let system_get_info = xr::SystemGetInfo {
            ty: xr::StructureType::SYSTEM_GET_INFO,
            next: std::ptr::null(),
            form_factor: xr::FormFactor::HEAD_MOUNTED_DISPLAY,
        };
        
        let result = xr::get_system(instance, &system_get_info, &mut system_id);
        if result != xr::Result::SUCCESS {
            unsafe { xr::destroy_instance(instance); }
            return Err(format!("Failed to get system: {:?}", result).into());
        }
        
        let mut system_properties = xr::SystemProperties {
            ty: xr::StructureType::SYSTEM_PROPERTIES,
            next: std::ptr::null_mut(),
            ..Default::default()
        };
        
        let result = xr::get_system_properties(instance, system_id, &mut system_properties);
        if result != xr::Result::SUCCESS {
            unsafe { xr::destroy_instance(instance); }
            return Err(format!("Failed to get system properties: {:?}", result).into());
        }
        
        println!("Detected XR system:");
        println!("  System Name: {:?}", std::ffi::CStr::from_ptr(system_properties.system_name.as_ptr()));
    }
    
    // 3. 创建会话(简化版，实际需要图形API绑定)
    let session = unsafe {
        let mut session = std::ptr::null_mut();
        let create_info = xr::SessionCreateInfo {
            ty: xr::StructureType::SESSION_CREATE_INFO,
            next: std::ptr::null(),
            create_flags: 0,
            system_id: xr::SystemId::default(),
        };
        
        let result = xr::create_session(instance, &create_info, &mut session);
        if result != xr::Result::SUCCESS {
            unsafe { xr::destroy_instance(instance); }
            return Err(format!("Failed to create session: {:?}", result).into());
        }
        session
    };
    
    // 4. 简单的事件循环
    unsafe {
        let mut running = true;
        while running {
            running = poll_events(instance)?;
            // 这里可以添加简单的帧处理逻辑
        }
    }
    
    // 清理资源
    unsafe {
        xr::destroy_session(session);
        xr::destroy_instance(instance);
    }
    
    Ok(())
}

// 事件处理函数(同上)
unsafe fn poll_events(instance: xr::Instance) -> Result<bool, String> {
    // ... 同前面提供的事件循环代码 ...
}

注意事项

1. openxr-sys是unsafe-heavy的库，使用时需要格外注意内存安全和线程安全
2. 大多数OpenXR函数都需要在unsafe块中调用
3. 需要根据目标平台和图形API选择正确的扩展
4. 建议结合更高级的封装库(如openxrs)使用，除非你需要直接控制底层API