Implement IShader and ISwapChain interfaces for D3D12 backend

- D3D12Shader now implements IShader interface with GetBytecode, GetBytecodeSize, GetType, GetInputLayout
- D3D12SwapChain now implements ISwapChain interface with GetBackBuffer returning IResource*
- Added D3D12Texture back buffer storage to SwapChain
- Fixed ISwapChain const correctness (GetCurrentBackBufferIndex, GetBackBuffer)
- main.cpp: use GetD3D12Bytecode() instead of GetBytecode() for PSO creation

engine/src/RHI/D3D12/D3D12SwapChain.cpp

@@ -56,6 +56,13 @@ bool D3D12SwapChain::Initialize(IDXGISwapChain* swapChain, uint32_t width, uint3
     m_width = width;
     m_height = height;
 
+    m_backBuffers.resize(m_bufferCount);
+    for (uint32_t i = 0; i < m_bufferCount; ++i) {
+        ID3D12Resource* resource = nullptr;
+        m_swapChain->GetBuffer(i, IID_PPV_ARGS(&resource));
+        m_backBuffers[i].InitializeFromExisting(resource);
+    }
+
     return true;
 }
 
@@ -67,10 +74,11 @@ uint32_t D3D12SwapChain::GetCurrentBackBufferIndex() const {
     return m_swapChain->GetCurrentBackBufferIndex();
 }
 
-ID3D12Resource* D3D12SwapChain::GetBackBuffer(uint32_t index) const {
-    ID3D12Resource* resource = nullptr;
-    m_swapChain->GetBuffer(index, IID_PPV_ARGS(&resource));
-    return resource;
+IResource* D3D12SwapChain::GetBackBuffer(uint32_t index) const {
+    if (index < m_backBuffers.size()) {
+        return const_cast<D3D12Texture*>(&m_backBuffers[index]);
+    }
+    return nullptr;
 }
 
 void D3D12SwapChain::Present(uint32_t syncInterval, uint32_t flags) {
@@ -83,5 +91,19 @@ void D3D12SwapChain::Resize(uint32_t width, uint32_t height) {
     m_height = height;
 }
 
+void D3D12SwapChain::SetFullscreen(bool fullscreen) {
+    m_swapChain->SetFullscreenState(fullscreen, nullptr);
+}
+
+bool D3D12SwapChain::IsFullscreen() const {
+    BOOL fullscreen = FALSE;
+    m_swapChain->GetFullscreenState(&fullscreen, nullptr);
+    return fullscreen != FALSE;
+}
+
+void* D3D12SwapChain::GetNativeHandle() const {
+    return reinterpret_cast<void*>(m_swapChain.Get());
+}
+
 } // namespace RHI
 } // namespace XCEngine