#include "Graphics.h"

#pragma comment(lib,"d3d11.lib")

Graphics::Graphics( HWND hWnd )
{
	// 交换链的参数定义
	DXGI_SWAP_CHAIN_DESC sd = {};
	sd.BufferDesc.Width = 0;
	sd.BufferDesc.Height = 0;
	sd.BufferDesc.Format = DXGI_FORMAT_B8G8R8A8_UNORM;
	sd.BufferDesc.RefreshRate.Numerator = 0;
	sd.BufferDesc.RefreshRate.Denominator = 0;
	sd.BufferDesc.Scaling = DXGI_MODE_SCALING_UNSPECIFIED;
	sd.BufferDesc.ScanlineOrdering = DXGI_MODE_SCANLINE_ORDER_UNSPECIFIED;
	sd.SampleDesc.Count = 1;
	sd.SampleDesc.Quality = 0;
	sd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
	sd.BufferCount = 1;
	sd.OutputWindow = hWnd;
	sd.Windowed = TRUE;
	sd.SwapEffect = DXGI_SWAP_EFFECT_DISCARD;
	sd.Flags = 0;

	// create device and front/back buffers, and swap chain and rendering context
	// 创建Device，SwapChain和Context
	D3D11CreateDeviceAndSwapChain(
		nullptr,
		D3D_DRIVER_TYPE_HARDWARE,
		nullptr,
		0,
		nullptr,
		0,
		D3D11_SDK_VERSION,
		&sd,
		&pSwap,
		&pDevice,
		nullptr,
		&pContext
	);
	// gain access to texture subresource in swap chain (back buffer)
	// 定义指向backBuffer的指针
	ID3D11Resource* pBackBuffer = nullptr;
	// 通过SwapChian，取得backBuffer
	pSwap->GetBuffer(0, __uuidof(ID3D11Resource), reinterpret_cast<void**>(&pBackBuffer));
	// 取得指向属于backBuffer的View的指针
	pDevice->CreateRenderTargetView(
		pBackBuffer,
		nullptr,
		&pTarget
	);
	pBackBuffer->Release();
}

Graphics::~Graphics()
{
	// 释放View, Context, SwapChain和Device
	if (pTarget != nullptr)
	{
		pTarget->Release();
	}
	if( pContext != nullptr )
	{
		pContext->Release();
	}
	if( pSwap != nullptr )
	{
		pSwap->Release();
	}
	if( pDevice != nullptr )
	{
		pDevice->Release();
	}
}

void Graphics::EndFrame()
{
	// flipping，使用SwapChain将back buffer的内容展现到屏幕
	pSwap->Present( 1u,0u );  // 同步频率1，代表屏幕每刷新一次，就进行图形刷新。
}

void Graphics::ClearBuffer(float red, float green, float blue) noexcept
{
	const float color[] = { red,green,blue,1.0f };
	pContext->ClearRenderTargetView(pTarget, color);
}