2

我正在试验 Windows 10、Direct3D 11 和 IDXGISwapChain::Present() 函数。当我在全屏模式下调用 Present 函数时，它会将命令排入队列并且直到大约第 4 次调用才会阻塞，这是预期的行为。

但是，当我在窗口模式下调用相同的函数时，它会在第一次调用和每个后续调用时阻塞。

我还尝试将 IDXGIDevice1::SetMaximumFrameLatency 函数设置为不同的值，但在窗口模式下，该函数似乎被忽略了。在全屏模式下，该功能可以正常工作。

我想知道是否有办法绕过 Present 函数在每次调用时阻塞，同时保持窗口模式。

这是我用来对上述问题进行单元测试的 C++ 代码：

#include <windows.h>
#include <windowsx.h>
#include <d3d11_1.h>
#include <wrl.h>
#include <dxgi1_2.h>

#include <iostream>
#include <chrono>
#include <stdio.h>
#include <list>

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

#define SCREEN_WIDTH  2560
#define SCREEN_HEIGHT 1440

using namespace std;
using chrono::milliseconds;
using chrono::high_resolution_clock;
using chrono::duration_cast;
using chrono::duration;
using Microsoft::WRL::ComPtr;

ComPtr<IDXGISwapChain> swapchain;
ComPtr<ID3D11Device> dev;
ComPtr<ID3D11DeviceContext> devcon;
ID3D11RenderTargetView* backbuffer;

list<milliseconds> times;

void initConsole()
{
    AllocConsole();

    FILE* pstdin, * pstdout, * pstderr;

    freopen_s(&pstdin, "CONIN$", "r", stdin);
    freopen_s(&pstdout, "CONOUT$", "w", stdout);
    freopen_s(&pstderr, "CONOUT$", "w", stderr);
}

LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_DESTROY:
    {
        PostQuitMessage(0);
        return 0;
    } break;
    }

    return DefWindowProc(hWnd, message, wParam, lParam);
}

void InitD3D(HWND hWnd)
{
    DXGI_SWAP_CHAIN_DESC scd = {};
    scd.BufferCount = 2;
    scd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    scd.BufferDesc.Width = SCREEN_WIDTH;
    scd.BufferDesc.Height = SCREEN_HEIGHT;
    scd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
    scd.OutputWindow = hWnd;
    scd.SampleDesc.Count = 1;
    scd.Windowed = true;
    scd.Flags = DXGI_SWAP_CHAIN_FLAG_ALLOW_MODE_SWITCH;
    D3D11CreateDeviceAndSwapChain(nullptr, D3D_DRIVER_TYPE_HARDWARE, nullptr, 0, nullptr, 0, D3D11_SDK_VERSION, &scd, &swapchain, &dev, nullptr, &devcon);

    //swapchain->SetFullscreenState(true, nullptr);

    ComPtr<ID3D11Texture2D> pBackBuffer;
    swapchain->GetBuffer(0, IID_PPV_ARGS(&pBackBuffer));

    dev->CreateRenderTargetView(pBackBuffer.Get(), nullptr, &backbuffer);

    devcon->OMSetRenderTargets(1, &backbuffer, nullptr);

    D3D11_VIEWPORT viewport = {};
    viewport.Width = SCREEN_WIDTH;
    viewport.Height = SCREEN_HEIGHT;
    devcon->RSSetViewports(1, &viewport);
}

void RenderFrame(void)
{
    float color[] = { 0.0f, 0.2f, 0.4f, 1.0f };
    devcon->ClearRenderTargetView(backbuffer, color);

    auto t1 = high_resolution_clock::now();

    swapchain->Present(1, 0);

    auto t2 = high_resolution_clock::now();
    auto time = duration_cast<milliseconds>(t2 - t1);
    times.push_back(time);
}

void CleanD3D(void)
{
    swapchain->SetFullscreenState(false, nullptr);
    backbuffer->Release();
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    initConsole();

    WNDCLASSEX wc = {};
    wc.cbSize = sizeof(WNDCLASSEX);
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WindowProc;
    wc.hInstance = hInstance;
    wc.hCursor = LoadCursor(nullptr, IDC_ARROW);
    wc.lpszClassName = L"WindowClass";

    RegisterClassEx(&wc);

    RECT wr = { 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT };
    AdjustWindowRect(&wr, WS_OVERLAPPEDWINDOW, FALSE);

    auto hWnd = CreateWindowEx(NULL, L"WindowClass", L"Our First Direct3D Program", WS_OVERLAPPEDWINDOW, 0, 0, wr.right - wr.left, wr.bottom - wr.top, nullptr, nullptr, hInstance, nullptr);

    ShowWindow(hWnd, nCmdShow);

    InitD3D(hWnd);

    MSG msg;

    for (int i = 0; i < 20; ++i)
    {
        if (PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);

            if (msg.message == WM_QUIT) {
                break;
            }
        }

        RenderFrame();
    }

    CleanD3D();

    for (auto time : times)
    {
        cout << time << " ";
    }
    cin.ignore();

    return 0;
}

如果你运行上面的代码，它会输出：

4ms 8ms 15ms 16ms 14ms 16ms 14ms 16ms 15ms 16ms 16ms 16ms 16ms 16ms 16ms 16ms 16ms 15ms 16ms 16ms

但是，如果您取消注释 SetFullscreenState 行，则会输出：

1ms 0ms 0ms 13ms 16ms 49ms 33ms 50ms 16ms 16ms 16ms 16ms 16ms 16ms 16ms 16ms 16ms 15ms 16ms 16ms

在窗口化的情况下，它会从第一次调用开始阻塞。在全屏情况下，它会从第四次调用开始阻塞。

编辑：添加了示例代码。

4

0 回答 0