Fix DX12 Capture transition state handling for MSAA (#532)

DDSTextureLoader/DDSTextureLoader11.cpp

@@ -18,6 +18,7 @@
 
 #include <algorithm>
 #include <cassert>
+#include <cstdint>
 #include <memory>
 #include <new>
 
@@ -53,6 +54,8 @@ using namespace DirectX;
 //
 // See DDS.h in the 'Texconv' sample and the 'DirectXTex' library
 //--------------------------------------------------------------------------------------
+namespace
+{
     #pragma pack(push,1)
 
     constexpr uint32_t DDS_MAGIC = 0x20534444; // "DDS "
@@ -126,9 +129,15 @@ struct DDS_HEADER_DXT10
 
     #pragma pack(pop)
 
+    static_assert(sizeof(DDS_PIXELFORMAT) == 32, "DDS pixel format size mismatch");
+    static_assert(sizeof(DDS_HEADER) == 124, "DDS Header size mismatch");
+    static_assert(sizeof(DDS_HEADER_DXT10) == 20, "DDS DX10 Extended Header size mismatch");
+
+    constexpr size_t DDS_MIN_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER);
+    constexpr size_t DDS_DX10_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10);
+    static_assert(DDS_DX10_HEADER_SIZE > DDS_MIN_HEADER_SIZE, "DDS DX10 Header should be larger than standard header");
+
     //--------------------------------------------------------------------------------------
-namespace
-{
     struct handle_closer { void operator()(HANDLE h) noexcept { if (h) CloseHandle(h); } };
 
     using ScopedHandle = std::unique_ptr<void, handle_closer>;
@@ -168,7 +177,7 @@ namespace
             return E_FAIL;
         }
 
-        if (ddsDataSize < (sizeof(uint32_t) + sizeof(DDS_HEADER)))
+        if (ddsDataSize < DDS_MIN_HEADER_SIZE)
         {
             return E_FAIL;
         }
@@ -195,7 +204,7 @@ namespace
             (MAKEFOURCC('D', 'X', '1', '0') == hdr->ddspf.fourCC))
         {
             // Must be long enough for both headers and magic value
-            if (ddsDataSize < (sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10)))
+            if (ddsDataSize < DDS_DX10_HEADER_SIZE)
             {
                 return E_FAIL;
             }
@@ -205,8 +214,7 @@ namespace
 
         // setup the pointers in the process request
         *header = hdr;
-        auto offset = sizeof(uint32_t)
+        auto offset = DDS_MIN_HEADER_SIZE
-            + sizeof(DDS_HEADER)
             + (bDXT10Header ? sizeof(DDS_HEADER_DXT10) : 0u);
         *bitData = ddsData + offset;
         *bitSize = ddsDataSize - offset;
@@ -264,7 +272,7 @@ namespace
         }
 
         // Need at least enough data to fill the header and magic number to be a valid DDS
-        if (fileInfo.EndOfFile.LowPart < (sizeof(uint32_t) + sizeof(DDS_HEADER)))
+        if (fileInfo.EndOfFile.LowPart < DDS_MIN_HEADER_SIZE)
         {
             return E_FAIL;
         }
@@ -319,7 +327,7 @@ namespace
             (MAKEFOURCC('D', 'X', '1', '0') == hdr->ddspf.fourCC))
         {
             // Must be long enough for both headers and magic value
-            if (fileInfo.EndOfFile.LowPart < (sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10)))
+            if (fileInfo.EndOfFile.LowPart < DDS_DX10_HEADER_SIZE)
             {
                 ddsData.reset();
                 return E_FAIL;
@@ -330,7 +338,7 @@ namespace
 
         // setup the pointers in the process request
         *header = hdr;
-        auto offset = sizeof(uint32_t) + sizeof(DDS_HEADER)
+        auto offset = DDS_MIN_HEADER_SIZE
             + (bDXT10Header ? sizeof(DDS_HEADER_DXT10) : 0u);
         *bitData = ddsData.get() + offset;
         *bitSize = fileInfo.EndOfFile.LowPart - offset;

DDSTextureLoader/DDSTextureLoader12.cpp

@@ -18,6 +18,7 @@
 
 #include <algorithm>
 #include <cassert>
+#include <cstdint>
 #include <memory>
 #include <new>
 
@@ -81,6 +82,8 @@ using namespace DirectX;
 //
 // See DDS.h in the 'Texconv' sample and the 'DirectXTex' library
 //--------------------------------------------------------------------------------------
+namespace
+{
     #pragma pack(push,1)
 
     constexpr uint32_t DDS_MAGIC = 0x20534444; // "DDS "
@@ -154,9 +157,15 @@ struct DDS_HEADER_DXT10
 
     #pragma pack(pop)
 
+    static_assert(sizeof(DDS_PIXELFORMAT) == 32, "DDS pixel format size mismatch");
+    static_assert(sizeof(DDS_HEADER) == 124, "DDS Header size mismatch");
+    static_assert(sizeof(DDS_HEADER_DXT10) == 20, "DDS DX10 Extended Header size mismatch");
+
+    constexpr size_t DDS_MIN_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER);
+    constexpr size_t DDS_DX10_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10);
+    static_assert(DDS_DX10_HEADER_SIZE > DDS_MIN_HEADER_SIZE, "DDS DX10 Header should be larger than standard header");
+
     //--------------------------------------------------------------------------------------
-namespace
-{
 #ifdef _WIN32
     struct handle_closer { void operator()(HANDLE h) noexcept { if (h) CloseHandle(h); } };
 
@@ -214,7 +223,7 @@ namespace
             return E_FAIL;
         }
 
-        if (ddsDataSize < (sizeof(uint32_t) + sizeof(DDS_HEADER)))
+        if (ddsDataSize < DDS_MIN_HEADER_SIZE)
         {
             return E_FAIL;
         }
@@ -241,7 +250,7 @@ namespace
             (MAKEFOURCC('D', 'X', '1', '0') == hdr->ddspf.fourCC))
         {
             // Must be long enough for both headers and magic value
-            if (ddsDataSize < (sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10)))
+            if (ddsDataSize < DDS_DX10_HEADER_SIZE)
             {
                 return E_FAIL;
             }
@@ -251,8 +260,7 @@ namespace
 
         // setup the pointers in the process request
         *header = hdr;
-        auto offset = sizeof(uint32_t)
+        auto offset = DDS_MIN_HEADER_SIZE
-            + sizeof(DDS_HEADER)
             + (bDXT10Header ? sizeof(DDS_HEADER_DXT10) : 0u);
         *bitData = ddsData + offset;
         *bitSize = ddsDataSize - offset;
@@ -302,7 +310,7 @@ namespace
         }
 
         // Need at least enough data to fill the header and magic number to be a valid DDS
-        if (fileInfo.EndOfFile.LowPart < (sizeof(uint32_t) + sizeof(DDS_HEADER)))
+        if (fileInfo.EndOfFile.LowPart < DDS_MIN_HEADER_SIZE)
         {
             return E_FAIL;
         }
@@ -345,7 +353,7 @@ namespace
             return E_FAIL;
 
         // Need at least enough data to fill the header and magic number to be a valid DDS
-        if (fileLen < (sizeof(uint32_t) + sizeof(DDS_HEADER)))
+        if (fileLen < DDS_MIN_HEADER_SIZE)
             return E_FAIL;
 
         ddsData.reset(new (std::nothrow) uint8_t[size_t(fileLen)]);
@@ -395,7 +403,7 @@ namespace
             (MAKEFOURCC('D', 'X', '1', '0') == hdr->ddspf.fourCC))
         {
             // Must be long enough for both headers and magic value
-            if (len < (sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10)))
+            if (len < DDS_DX10_HEADER_SIZE)
             {
                 ddsData.reset();
                 return E_FAIL;
@@ -406,7 +414,7 @@ namespace
 
         // setup the pointers in the process request
         *header = hdr;
-        auto offset = sizeof(uint32_t) + sizeof(DDS_HEADER)
+        auto offset = DDS_MIN_HEADER_SIZE
             + (bDXT10Header ? sizeof(DDS_HEADER_DXT10) : 0u);
         *bitData = ddsData.get() + offset;
         *bitSize = len - offset;

DDSTextureLoader/DDSTextureLoader9.cpp

@@ -20,6 +20,7 @@
 
 #include <algorithm>
 #include <cassert>
+#include <cstdint>
 #include <cstring>
 #include <memory>
 #include <new>
@@ -57,6 +58,8 @@ using Microsoft::WRL::ComPtr;
 //
 // See DDS.h in the 'Texconv' sample and the 'DirectXTex' library
 //--------------------------------------------------------------------------------------
+namespace
+{
     #pragma pack(push,1)
 
     constexpr uint32_t DDS_MAGIC = 0x20534444; // "DDS "
@@ -115,9 +118,12 @@ struct DDS_HEADER
 
     #pragma pack(pop)
 
+    static_assert(sizeof(DDS_PIXELFORMAT) == 32, "DDS pixel format size mismatch");
+    static_assert(sizeof(DDS_HEADER) == 124, "DDS Header size mismatch");
+
+    constexpr size_t DDS_DX9_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER);
+
     //--------------------------------------------------------------------------------------
-namespace
-{
     struct handle_closer { void operator()(HANDLE h) noexcept { if (h) CloseHandle(h); } };
 
     using ScopedHandle = std::unique_ptr<void, handle_closer>;
@@ -144,7 +150,7 @@ namespace
             return E_FAIL;
         }
 
-        if (ddsDataSize < (sizeof(uint32_t) + sizeof(DDS_HEADER)))
+        if (ddsDataSize < DDS_DX9_HEADER_SIZE)
         {
             return E_FAIL;
         }
@@ -175,9 +181,8 @@ namespace
 
         // setup the pointers in the process request
         *header = hdr;
-        auto offset = sizeof(uint32_t) + sizeof(DDS_HEADER);
+        *bitData = ddsData + DDS_DX9_HEADER_SIZE;
-        *bitData = ddsData + offset;
+        *bitSize = ddsDataSize - DDS_DX9_HEADER_SIZE;
-        *bitSize = ddsDataSize - offset;
 
         return S_OK;
     }
@@ -234,7 +239,7 @@ namespace
         }
 
         // Need at least enough data to fill the header and magic number to be a valid DDS
-        if (fileInfo.EndOfFile.LowPart < (sizeof(uint32_t) + sizeof(DDS_HEADER)))
+        if (fileInfo.EndOfFile.LowPart < DDS_DX9_HEADER_SIZE)
         {
             return E_FAIL;
         }
@@ -294,9 +299,8 @@ namespace
 
         // setup the pointers in the process request
         *header = hdr;
-        auto offset = sizeof(uint32_t) + sizeof(DDS_HEADER);
+        *bitData = ddsData.get() + DDS_DX9_HEADER_SIZE;
-        *bitData = ddsData.get() + offset;
+        *bitSize = fileInfo.EndOfFile.LowPart - DDS_DX9_HEADER_SIZE;
-        *bitSize = fileInfo.EndOfFile.LowPart - offset;
 
         return S_OK;
     }

DirectXTex/DirectXTexD3D12.cpp

@@ -217,8 +217,11 @@ namespace
         bufferDesc.SampleDesc.Count = 1;
 
         ComPtr<ID3D12Resource> copySource(pSource);
+        D3D12_RESOURCE_STATES beforeStateSource = beforeState;
         if (desc.SampleDesc.Count > 1)
         {
+            TransitionResource(commandList.Get(), pSource, beforeState, D3D12_RESOURCE_STATE_RESOLVE_SOURCE);
+
             // MSAA content must be resolved before being copied to a staging texture
             auto descCopy = desc;
             descCopy.SampleDesc.Count = 1;
@@ -230,7 +233,7 @@ namespace
                 &defaultHeapProperties,
                 D3D12_HEAP_FLAG_NONE,
                 &descCopy,
-                D3D12_RESOURCE_STATE_COPY_DEST,
+                D3D12_RESOURCE_STATE_RESOLVE_DEST,
                 nullptr,
                 IID_GRAPHICS_PPV_ARGS(pTemp.GetAddressOf()));
             if (FAILED(hr))
@@ -267,6 +270,11 @@ namespace
             }
 
             copySource = pTemp;
+            beforeState = D3D12_RESOURCE_STATE_RESOLVE_DEST;
+        }
+        else
+        {
+            beforeStateSource = D3D12_RESOURCE_STATE_COPY_SOURCE;
         }
 
         // Create a staging texture
@@ -283,7 +291,7 @@ namespace
         assert(*pStaging);
 
         // Transition the resource if necessary
-        TransitionResource(commandList.Get(), pSource, beforeState, D3D12_RESOURCE_STATE_COPY_SOURCE);
+        TransitionResource(commandList.Get(), copySource.Get(), beforeState, D3D12_RESOURCE_STATE_COPY_SOURCE);
 
         // Get the copy target location
         for (UINT j = 0; j < numberOfResources; ++j)
@@ -293,8 +301,8 @@ namespace
             commandList->CopyTextureRegion(&copyDest, 0, 0, 0, &copySrc, nullptr);
         }
 
-        // Transition the resource to the next state
+        // Transition the source resource to the next state
-        TransitionResource(commandList.Get(), pSource, D3D12_RESOURCE_STATE_COPY_SOURCE, afterState);
+        TransitionResource(commandList.Get(), pSource, beforeStateSource, afterState);
 
         hr = commandList->Close();
         if (FAILED(hr))

ScreenGrab/ScreenGrab11.cpp

@@ -26,6 +26,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
+#include <cstdint>
 #include <cstring>
 #include <memory>
 #include <new>
@@ -71,7 +72,7 @@ namespace
 {
     #pragma pack(push,1)
 
-#define DDS_MAGIC 0x20534444 // "DDS "
+    constexpr uint32_t DDS_MAGIC = 0x20534444; // "DDS "
 
     struct DDS_PIXELFORMAT
     {
@@ -129,6 +130,14 @@ namespace
 
     #pragma pack(pop)
 
+    static_assert(sizeof(DDS_PIXELFORMAT) == 32, "DDS pixel format size mismatch");
+    static_assert(sizeof(DDS_HEADER) == 124, "DDS Header size mismatch");
+    static_assert(sizeof(DDS_HEADER_DXT10) == 20, "DDS DX10 Extended Header size mismatch");
+
+    constexpr size_t DDS_MIN_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER);
+    constexpr size_t DDS_DX10_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10);
+    static_assert(DDS_DX10_HEADER_SIZE > DDS_MIN_HEADER_SIZE, "DDS DX10 Header should be larger than standard header");
+
     const DDS_PIXELFORMAT DDSPF_DXT1 =
     { sizeof(DDS_PIXELFORMAT), DDS_FOURCC, MAKEFOURCC('D','X','T','1'), 0, 0, 0, 0, 0 };
 
@@ -816,13 +825,12 @@ HRESULT DirectX::SaveDDSTextureToFile(
     auto_delete_file delonfail(hFile.get());
 
     // Setup header
-    constexpr size_t MAX_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10);
+    uint8_t fileHeader[DDS_DX10_HEADER_SIZE] = {};
-    uint8_t fileHeader[MAX_HEADER_SIZE] = {};
 
     *reinterpret_cast<uint32_t*>(&fileHeader[0]) = DDS_MAGIC;
 
     auto header = reinterpret_cast<DDS_HEADER*>(&fileHeader[0] + sizeof(uint32_t));
-    size_t headerSize = sizeof(uint32_t) + sizeof(DDS_HEADER);
+    size_t headerSize = DDS_MIN_HEADER_SIZE;
     header->size = sizeof(DDS_HEADER);
     header->flags = DDS_HEADER_FLAGS_TEXTURE | DDS_HEADER_FLAGS_MIPMAP;
     header->height = desc.Height;
@@ -879,7 +887,7 @@ HRESULT DirectX::SaveDDSTextureToFile(
         memcpy_s(&header->ddspf, sizeof(header->ddspf), &DDSPF_DX10, sizeof(DDS_PIXELFORMAT));
 
         headerSize += sizeof(DDS_HEADER_DXT10);
-        extHeader = reinterpret_cast<DDS_HEADER_DXT10*>(fileHeader + sizeof(uint32_t) + sizeof(DDS_HEADER));
+        extHeader = reinterpret_cast<DDS_HEADER_DXT10*>(fileHeader + DDS_MIN_HEADER_SIZE);
         extHeader->dxgiFormat = desc.Format;
         extHeader->resourceDimension = D3D11_RESOURCE_DIMENSION_TEXTURE2D;
         extHeader->arraySize = 1;

ScreenGrab/ScreenGrab12.cpp

@@ -26,6 +26,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
+#include <cstdint>
 #include <cstring>
 #include <memory>
 #include <new>
@@ -93,7 +94,7 @@ namespace
 {
 #pragma pack(push,1)
 
-#define DDS_MAGIC 0x20534444 // "DDS "
+    constexpr uint32_t DDS_MAGIC = 0x20534444; // "DDS "
 
     struct DDS_PIXELFORMAT
     {
@@ -149,8 +150,16 @@ namespace
         uint32_t        reserved;
     };
 
+    static_assert(sizeof(DDS_PIXELFORMAT) == 32, "DDS pixel format size mismatch");
+    static_assert(sizeof(DDS_HEADER) == 124, "DDS Header size mismatch");
+    static_assert(sizeof(DDS_HEADER_DXT10) == 20, "DDS DX10 Extended Header size mismatch");
+
     #pragma pack(pop)
 
+    constexpr size_t DDS_MIN_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER);
+    constexpr size_t DDS_DX10_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10);
+    static_assert(DDS_DX10_HEADER_SIZE > DDS_MIN_HEADER_SIZE, "DDS DX10 Header should be larger than standard header");
+
     const DDS_PIXELFORMAT DDSPF_DXT1 =
     { sizeof(DDS_PIXELFORMAT), DDS_FOURCC, MAKEFOURCC('D','X','T','1'), 0, 0, 0, 0, 0 };
 
@@ -755,8 +764,11 @@ namespace
         bufferDesc.SampleDesc.Count = 1;
 
         ComPtr<ID3D12Resource> copySource(pSource);
+        D3D12_RESOURCE_STATES beforeStateSource = beforeState;
         if (desc.SampleDesc.Count > 1)
         {
+            TransitionResource(commandList.Get(), pSource, beforeState, D3D12_RESOURCE_STATE_RESOLVE_SOURCE);
+
             // MSAA content must be resolved before being copied to a staging texture
             auto descCopy = desc;
             descCopy.SampleDesc.Count = 1;
@@ -768,7 +780,7 @@ namespace
                 &defaultHeapProperties,
                 D3D12_HEAP_FLAG_NONE,
                 &descCopy,
-                D3D12_RESOURCE_STATE_COPY_DEST,
+                D3D12_RESOURCE_STATE_RESOLVE_DEST,
                 nullptr,
                 IID_ID3D12Resource,
                 reinterpret_cast<void**>(pTemp.GetAddressOf()));
@@ -797,6 +809,11 @@ namespace
             }
 
             copySource = pTemp;
+            beforeState = D3D12_RESOURCE_STATE_RESOLVE_DEST;
+        }
+        else
+        {
+            beforeStateSource = D3D12_RESOURCE_STATE_COPY_SOURCE;
         }
 
         // Create a staging texture
@@ -815,7 +832,7 @@ namespace
         assert(*pStaging);
 
         // Transition the resource if necessary
-        TransitionResource(commandList.Get(), pSource, beforeState, D3D12_RESOURCE_STATE_COPY_SOURCE);
+        TransitionResource(commandList.Get(), copySource.Get(), beforeState, D3D12_RESOURCE_STATE_COPY_SOURCE);
 
         // Get the copy target location
         D3D12_PLACED_SUBRESOURCE_FOOTPRINT bufferFootprint = {};
@@ -831,8 +848,8 @@ namespace
         // Copy the texture
         commandList->CopyTextureRegion(&copyDest, 0, 0, 0, &copySrc, nullptr);
 
-        // Transition the resource to the next state
+        // Transition the source resource to the next state
-        TransitionResource(commandList.Get(), pSource, D3D12_RESOURCE_STATE_COPY_SOURCE, afterState);
+        TransitionResource(commandList.Get(), pSource, beforeStateSource, afterState);
 
         hr = commandList->Close();
         if (FAILED(hr))
@@ -954,13 +971,12 @@ HRESULT DirectX::SaveDDSTextureToFile(
 #endif
 
     // Setup header
-    constexpr size_t MAX_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER) + sizeof(DDS_HEADER_DXT10);
+    uint8_t fileHeader[DDS_DX10_HEADER_SIZE] = {};
-    uint8_t fileHeader[MAX_HEADER_SIZE] = {};
 
     *reinterpret_cast<uint32_t*>(&fileHeader[0]) = DDS_MAGIC;
 
     auto header = reinterpret_cast<DDS_HEADER*>(&fileHeader[0] + sizeof(uint32_t));
-    size_t headerSize = sizeof(uint32_t) + sizeof(DDS_HEADER);
+    size_t headerSize = DDS_MIN_HEADER_SIZE;
     header->size = sizeof(DDS_HEADER);
     header->flags = DDS_HEADER_FLAGS_TEXTURE | DDS_HEADER_FLAGS_MIPMAP;
     header->height = desc.Height;
@@ -1017,7 +1033,7 @@ HRESULT DirectX::SaveDDSTextureToFile(
         memcpy(&header->ddspf, &DDSPF_DX10, sizeof(DDS_PIXELFORMAT));
 
         headerSize += sizeof(DDS_HEADER_DXT10);
-        extHeader = reinterpret_cast<DDS_HEADER_DXT10*>(fileHeader + sizeof(uint32_t) + sizeof(DDS_HEADER));
+        extHeader = reinterpret_cast<DDS_HEADER_DXT10*>(fileHeader + DDS_MIN_HEADER_SIZE);
         extHeader->dxgiFormat = desc.Format;
         extHeader->resourceDimension = D3D12_RESOURCE_DIMENSION_TEXTURE2D;
         extHeader->arraySize = 1;
@@ -1422,7 +1438,9 @@ HRESULT DirectX::SaveWICTextureToFile(
     else
     {
         // No conversion required
-        hr = frame->WritePixels(desc.Height, static_cast<UINT>(dstRowPitch), static_cast<UINT>(imageSize), static_cast<BYTE*>(pMappedMemory));
+        hr = frame->WritePixels(desc.Height,
+            static_cast<UINT>(dstRowPitch), static_cast<UINT>(imageSize),
+            static_cast<BYTE*>(pMappedMemory));
     }
 
     pStaging->Unmap(0, &writeRange);

ScreenGrab/ScreenGrab9.cpp

@@ -20,6 +20,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
+#include <cstdint>
 #include <cstring>
 #include <memory>
 #include <new>
@@ -65,7 +66,7 @@ namespace
 {
     #pragma pack(push,1)
 
-#define DDS_MAGIC 0x20534444 // "DDS "
+    constexpr uint32_t DDS_MAGIC = 0x20534444; // "DDS "
 
     struct DDS_PIXELFORMAT
     {
@@ -116,6 +117,11 @@ namespace
 
     #pragma pack(pop)
 
+    static_assert(sizeof(DDS_PIXELFORMAT) == 32, "DDS pixel format size mismatch");
+    static_assert(sizeof(DDS_HEADER) == 124, "DDS Header size mismatch");
+
+    constexpr size_t DDS_DX9_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER);
+
     const DDS_PIXELFORMAT DDSPF_DXT1 =
     { sizeof(DDS_PIXELFORMAT), DDS_FOURCC, MAKEFOURCC('D','X','T','1'), 0, 0, 0, 0, 0 };
 
@@ -606,13 +612,11 @@ HRESULT DirectX::SaveDDSTextureToFile(
     auto_delete_file delonfail(hFile.get());
 
     // Setup header
-    constexpr size_t MAX_HEADER_SIZE = sizeof(uint32_t) + sizeof(DDS_HEADER);
+    uint8_t fileHeader[DDS_DX9_HEADER_SIZE] = {};
-    uint8_t fileHeader[MAX_HEADER_SIZE] = {};
 
     *reinterpret_cast<uint32_t*>(&fileHeader[0]) = DDS_MAGIC;
 
     auto header = reinterpret_cast<DDS_HEADER*>(&fileHeader[0] + sizeof(uint32_t));
-    constexpr size_t headerSize = sizeof(uint32_t) + sizeof(DDS_HEADER);
     header->size = sizeof(DDS_HEADER);
     header->flags = DDS_HEADER_FLAGS_TEXTURE | DDS_HEADER_FLAGS_MIPMAP;
     header->height = desc.Height;
@@ -726,10 +730,10 @@ HRESULT DirectX::SaveDDSTextureToFile(
 
     // Write header & pixels
     DWORD bytesWritten;
-    if (!WriteFile(hFile.get(), fileHeader, static_cast<DWORD>(headerSize), &bytesWritten, nullptr))
+    if (!WriteFile(hFile.get(), fileHeader, static_cast<DWORD>(DDS_DX9_HEADER_SIZE), &bytesWritten, nullptr))
         return HRESULT_FROM_WIN32(GetLastError());
 
-    if (bytesWritten != headerSize)
+    if (bytesWritten != DDS_DX9_HEADER_SIZE)
         return E_FAIL;
 
     if (!WriteFile(hFile.get(), pixels.get(), static_cast<DWORD>(slicePitch), &bytesWritten, nullptr))