CoopAllTheThings/tools/mock_game/render_dx12.cpp

// DX12 backend for the mock game. Renders the same animated pattern as the DX11 backend
// (animated background + moving bar + top-left frame-counter block) so the capture tests
// can verify the DX12 capture path against an identical, frame-numbered source.
#include "render_backend.hpp"

#include <d3d12.h>
#include <dxgi1_4.h>
#include <wrl/client.h>

using Microsoft::WRL::ComPtr;

namespace coop::mock
{
namespace
{
constexpr UINT kBackBuffers = 3; // DX12 rotates these explicitly -- the case the capture must get right

class Dx12Backend : public RenderBackend
{
public:
	bool init(HWND hwnd, std::uint32_t width, std::uint32_t height) override
	{
		width_ = width;
		height_ = height;

		if (FAILED(D3D12CreateDevice(nullptr, D3D_FEATURE_LEVEL_11_0, IID_PPV_ARGS(device_.GetAddressOf()))))
		{
			return false;
		}

		D3D12_COMMAND_QUEUE_DESC qd = {};
		qd.Type = D3D12_COMMAND_LIST_TYPE_DIRECT;
		if (FAILED(device_->CreateCommandQueue(&qd, IID_PPV_ARGS(queue_.GetAddressOf()))))
		{
			return false;
		}

		ComPtr<IDXGIFactory4> factory;
		if (FAILED(CreateDXGIFactory1(IID_PPV_ARGS(factory.GetAddressOf()))))
		{
			return false;
		}
		DXGI_SWAP_CHAIN_DESC1 desc = {};
		desc.Width = width;
		desc.Height = height;
		desc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
		desc.SampleDesc.Count = 1;
		desc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
		desc.BufferCount = kBackBuffers;
		desc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_DISCARD;
		ComPtr<IDXGISwapChain1> sc1;
		if (FAILED(factory->CreateSwapChainForHwnd(queue_.Get(), hwnd, &desc, nullptr, nullptr,
		                                           sc1.GetAddressOf())) ||
		    FAILED(sc1.As(&swap_)))
		{
			return false;
		}
		factory->MakeWindowAssociation(hwnd, DXGI_MWA_NO_ALT_ENTER);

		D3D12_DESCRIPTOR_HEAP_DESC hd = {};
		hd.Type = D3D12_DESCRIPTOR_HEAP_TYPE_RTV;
		hd.NumDescriptors = kBackBuffers;
		if (FAILED(device_->CreateDescriptorHeap(&hd, IID_PPV_ARGS(rtv_heap_.GetAddressOf()))))
		{
			return false;
		}
		rtv_stride_ = device_->GetDescriptorHandleIncrementSize(D3D12_DESCRIPTOR_HEAP_TYPE_RTV);
		D3D12_CPU_DESCRIPTOR_HANDLE h = rtv_heap_->GetCPUDescriptorHandleForHeapStart();
		for (UINT i = 0; i < kBackBuffers; ++i)
		{
			if (FAILED(swap_->GetBuffer(i, IID_PPV_ARGS(targets_[i].GetAddressOf()))))
			{
				return false;
			}
			device_->CreateRenderTargetView(targets_[i].Get(), nullptr, h);
			rtv_handles_[i] = h;
			h.ptr += rtv_stride_;
			if (FAILED(device_->CreateCommandAllocator(D3D12_COMMAND_LIST_TYPE_DIRECT,
			                                           IID_PPV_ARGS(allocs_[i].GetAddressOf()))))
			{
				return false;
			}
		}
		if (FAILED(device_->CreateCommandList(0, D3D12_COMMAND_LIST_TYPE_DIRECT, allocs_[0].Get(), nullptr,
		                                      IID_PPV_ARGS(list_.GetAddressOf()))))
		{
			return false;
		}
		list_->Close();

		if (FAILED(device_->CreateFence(0, D3D12_FENCE_FLAG_NONE, IID_PPV_ARGS(fence_.GetAddressOf()))))
		{
			return false;
		}
		fence_event_ = CreateEventW(nullptr, FALSE, FALSE, nullptr);
		return fence_event_ != nullptr;
	}

	void render_and_present(std::uint32_t frame) override
	{
		const UINT idx = swap_->GetCurrentBackBufferIndex();
		allocs_[idx]->Reset();
		list_->Reset(allocs_[idx].Get(), nullptr);

		transition(targets_[idx].Get(), D3D12_RESOURCE_STATE_PRESENT, D3D12_RESOURCE_STATE_RENDER_TARGET);

		// Animated background (full RT clear).
		const float bg[4] = {static_cast<float>((frame * 2) % 256) / 255.0f,
		                     static_cast<float>((frame * 3) % 256) / 255.0f,
		                     static_cast<float>((frame * 5) % 256) / 255.0f, 1.0f};
		list_->ClearRenderTargetView(rtv_handles_[idx], bg, 0, nullptr);

		// Moving vertical bar.
		const float white[4] = {1.0f, 1.0f, 1.0f, 1.0f};
		const LONG span = width_ > 24 ? static_cast<LONG>(width_ - 24) : 1;
		const LONG bx = static_cast<LONG>((frame * 4) % static_cast<std::uint32_t>(span));
		const D3D12_RECT bar = {bx, 0, bx + 24, static_cast<LONG>(height_)};
		list_->ClearRenderTargetView(rtv_handles_[idx], white, 1, &bar);

		// Frame-counter block (top-left).
		std::uint8_t r = 0, g = 0, b = 0;
		frame_to_rgb(frame, r, g, b);
		const float code[4] = {r / 255.0f, g / 255.0f, b / 255.0f, 1.0f};
		const D3D12_RECT block = {0, 0, static_cast<LONG>(kFrameBlock), static_cast<LONG>(kFrameBlock)};
		list_->ClearRenderTargetView(rtv_handles_[idx], code, 1, &block);

		transition(targets_[idx].Get(), D3D12_RESOURCE_STATE_RENDER_TARGET, D3D12_RESOURCE_STATE_PRESENT);
		list_->Close();
		ID3D12CommandList* lists[] = {list_.Get()};
		queue_->ExecuteCommandLists(1, lists);

		swap_->Present(1, 0);
		wait_for_gpu(); // simple per-frame sync (mock game: correctness over throughput)
	}

	[[nodiscard]] const char* name() const override
	{
		return "dx12";
	}

	~Dx12Backend() override
	{
		if (fence_ != nullptr)
		{
			wait_for_gpu();
		}
		if (fence_event_ != nullptr)
		{
			CloseHandle(fence_event_);
		}
	}

private:
	void transition(ID3D12Resource* res, D3D12_RESOURCE_STATES from, D3D12_RESOURCE_STATES to)
	{
		D3D12_RESOURCE_BARRIER b = {};
		b.Type = D3D12_RESOURCE_BARRIER_TYPE_TRANSITION;
		b.Transition.pResource = res;
		b.Transition.StateBefore = from;
		b.Transition.StateAfter = to;
		b.Transition.Subresource = D3D12_RESOURCE_BARRIER_ALL_SUBRESOURCES;
		list_->ResourceBarrier(1, &b);
	}

	void wait_for_gpu()
	{
		const UINT64 v = ++fence_value_;
		queue_->Signal(fence_.Get(), v);
		if (fence_->GetCompletedValue() < v)
		{
			fence_->SetEventOnCompletion(v, fence_event_);
			WaitForSingleObject(fence_event_, INFINITE);
		}
	}

	std::uint32_t width_ = 0;
	std::uint32_t height_ = 0;
	ComPtr<ID3D12Device> device_;
	ComPtr<ID3D12CommandQueue> queue_;
	ComPtr<IDXGISwapChain3> swap_;
	ComPtr<ID3D12DescriptorHeap> rtv_heap_;
	UINT rtv_stride_ = 0;
	ComPtr<ID3D12Resource> targets_[kBackBuffers];
	D3D12_CPU_DESCRIPTOR_HANDLE rtv_handles_[kBackBuffers] = {};
	ComPtr<ID3D12CommandAllocator> allocs_[kBackBuffers];
	ComPtr<ID3D12GraphicsCommandList> list_;
	ComPtr<ID3D12Fence> fence_;
	UINT64 fence_value_ = 0;
	HANDLE fence_event_ = nullptr;
};
} // namespace

std::unique_ptr<RenderBackend> create_dx12_backend()
{
	return std::make_unique<Dx12Backend>();
}

} // namespace coop::mock