feat(RHI): 实现 RHIFence 抽象基类

- 新增 RHIFence 抽象基类
- D3D12Fence 继承 RHIFence
- OpenGLFence 继承 RHIFence
- 文档更新 RHIFence 差异处理策略

docs/RHI抽象层设计与实现.md

@@ -539,7 +539,57 @@ public:
    - OpenGL：GLuint
    - 解决：GetNativeHandle() 返回 void*
 
-### 5.9 根签名 vs OpenGL 资源绑定
+### 5.9 同步栅栏（RHIFence）抽象设计
+
+#### 5.9.1 设计理念对应
+
+| 差异点 | 设计理念 | 处理方案 |
+|--------|---------|---------|
+| 初始化参数差异 | 求同存异 | 后端各自实现初始化 |
+| 句柄类型差异 | 底层逃逸 | 统一返回 void* |
+| 状态查询 | 求同存异 | 统一 IsSignaled/GetCompletedValue 接口 |
+
+#### 5.9.2 现有实现对比
+
+| 功能 | D3D12Fence | OpenGLFence |
+|------|-------------|-------------|
+| 初始化 | Initialize(device, value) | Initialize(signaled) |
+| Signal | Signal(value) | Signal()/Signal(value) |
+| Wait | Wait(value) | Wait(timeoutNs) |
+| 状态 | GetCompletedValue() | IsSignaled()/GetStatus() |
+| 句柄 | ID3D12Fence* | GLsync |
+
+#### 5.9.3 抽象接口定义
+
+```cpp
+class RHIFence {
+public:
+    virtual ~RHIFence() = default;
+
+    virtual void Shutdown() = 0;
+
+    virtual void Signal(uint64_t value) = 0;
+    virtual void Wait(uint64_t value) = 0;
+    virtual uint64_t GetCompletedValue() = 0;
+    virtual bool IsSignaled() const = 0;
+
+    virtual void* GetNativeHandle() = 0;
+};
+```
+
+#### 5.9.4 差异处理策略
+
+1. **初始化参数差异（求同存异）**
+   - D3D12：需要 device 参数
+   - OpenGL：不需要 device
+   - 解决：后端各自实现 Initialize()
+
+2. **句柄类型差异（底层逃逸）**
+   - D3D12：ID3D12Fence*
+   - OpenGL：GLsync
+   - 解决：GetNativeHandle() 返回 void*
+
+### 5.10 根签名 vs OpenGL 资源绑定
 - **D3D12**：显式 `RootSignature` 定义资源绑定规则
 - **OpenGL**：隐式通过 `glUniformLocation`、`glBindTextureUnit` 绑定
 - **解决方案**：

engine/include/XCEngine/RHI/D3D12/D3D12Fence.h

@@ -3,26 +3,28 @@
 #include <d3d12.h>
 #include <wrl/client.h>
 
-#include <cstdint>
+#include "../RHIFence.h"
 
 using Microsoft::WRL::ComPtr;
 
 namespace XCEngine {
 namespace RHI {
 
-class D3D12Fence {
+class D3D12Fence : public RHIFence {
 public:
     D3D12Fence();
-    ~D3D12Fence();
+    ~D3D12Fence() override;
 
     bool Initialize(ID3D12Device* device, uint64_t initialValue = 0);
-    void Shutdown();
+    void Shutdown() override;
 
-    void Signal(uint64_t value);
-    void Wait(uint64_t value);
-    uint64_t GetCompletedValue();
+    void Signal(uint64_t value) override;
+    void Wait(uint64_t value) override;
+    uint64_t GetCompletedValue() const override;
+    bool IsSignaled() const override { return GetCompletedValue() > 0; }
     void* GetEventHandle() { return m_eventHandle; }
 
+    void* GetNativeHandle() override { return m_fence.Get(); }
     ID3D12Fence* GetFence() const { return m_fence.Get(); }
 
 private:

engine/include/XCEngine/RHI/OpenGL/OpenGLFence.h

@@ -3,6 +3,8 @@
 #include <GLFW/glfw3.h>
 #include <cstdint>
 
+#include "../RHIFence.h"
+
 namespace XCEngine {
 namespace RHI {
 
@@ -12,24 +14,26 @@ enum class FenceStatus {
     Error
 };
 
-class OpenGLFence {
+class OpenGLFence : public RHIFence {
 public:
     OpenGLFence();
-    ~OpenGLFence();
+    ~OpenGLFence() override;
 
     bool Initialize(bool signaled = false);
-    void Shutdown();
+    void Shutdown() override;
 
-    void Signal();
-    void Signal(uint64_t value);
-    void Wait(uint64_t timeoutNs = UINT64_MAX);
+    void Signal() override;
+    void Signal(uint64_t value) override;
+    void Wait(uint64_t value) override;
     void Reset();
 
-    bool IsSignaled() const;
+    bool IsSignaled() const override;
     FenceStatus GetStatus() const;
-    uint64_t GetCompletedValue() const;
+    uint64_t GetCompletedValue() const override;
     uint64_t GetCurrentValue() const { return m_fenceValue; }
 
+    void* GetNativeHandle() override { return m_sync; }
+
 private:
     void* m_sync;
     uint64_t m_fenceValue;

engine/include/XCEngine/RHI/RHIFence.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include "RHITypes.h"
+
+namespace XCEngine {
+namespace RHI {
+
+class RHIFence {
+public:
+    virtual ~RHIFence() = default;
+
+    virtual void Shutdown() = 0;
+
+    virtual void Signal() = 0;
+    virtual void Signal(uint64_t value) = 0;
+    virtual void Wait(uint64_t value) = 0;
+    virtual uint64_t GetCompletedValue() const = 0;
+    virtual bool IsSignaled() const = 0;
+
+    virtual void* GetNativeHandle() = 0;
+};
+
+} // namespace RHI
+} // namespace XCEngine

engine/src/RHI/D3D12/D3D12Fence.cpp

@@ -44,7 +44,7 @@ void D3D12Fence::Wait(uint64_t value) {
     }
 }
 
-uint64_t D3D12Fence::GetCompletedValue() {
+uint64_t D3D12Fence::GetCompletedValue() const {
     return m_fence->GetCompletedValue();
 }