GPU: D3D12 stencil plane transition (#15519)

src/gpu/d3d12/SDL_gpu_d3d12.c

@@ -1838,6 +1838,16 @@ static inline Uint32 D3D12_INTERNAL_CalcSubresource(
     return mipLevel + (layer * numLevels);
 }
 
+static inline Uint32 D3D12_INTERNAL_CalcSubresourceWithPlane(
+    Uint32 mipLevel,
+    Uint32 layer,
+    Uint32 planeSlice,
+    Uint32 numLevels,
+    Uint32 arraySize)
+{
+    return mipLevel + (layer * numLevels) + (planeSlice * numLevels * arraySize);
+}
+
 static void D3D12_INTERNAL_ResourceBarrier(
     D3D12CommandBuffer *commandBuffer,
     D3D12_RESOURCE_STATES sourceState,
@@ -1894,6 +1904,27 @@ static void D3D12_INTERNAL_TextureSubresourceBarrier(
         textureSubresource->parent->resource,
         textureSubresource->index,
         needsUAVBarrier);
+
+    // D3D12 stores planar values on a separate subresource.
+    // Since depth-stencil is our only supported planar format,
+    // just force an extra transition if we're using a stencil format.
+    if (IsStencilFormat(textureSubresource->parent->container->header.info.format)) {
+        Uint32 planeSubresourceIndex = D3D12_INTERNAL_CalcSubresourceWithPlane(
+            textureSubresource->level,
+            textureSubresource->layer,
+            1,
+            textureSubresource->parent->container->header.info.num_levels,
+            textureSubresource->parent->container->header.info.layer_count_or_depth
+        );
+
+        D3D12_INTERNAL_ResourceBarrier(
+            commandBuffer,
+            sourceState,
+            destinationState,
+            textureSubresource->parent->resource,
+            planeSubresourceIndex,
+            needsUAVBarrier);
+    }
 }
 
 static D3D12_RESOURCE_STATES D3D12_INTERNAL_DefaultTextureResourceState(