如何在帶有DX11繪圖介面的軟體上畫imgui介面

前言

處於某些研究目的，我們經常需要在dx11繪製的介面上繪製我們自己的操作選單，以方便進行一些視覺化操作；這裡面imgui庫因為其優越的可用性，健壯性和美觀性，得到了很多人的青睞。那麼我們應該如何在一個帶有dx的軟體介面上利用imgui繪製我們自己的介面呢？下面的程式碼就是為了解決這個問題的（採用dx11版本舉例）。

程式碼樣例

#include <windows.h>
#include <memory>
#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <thread>
#include <d3d11.h>
#include "Imgui/imgui.h"
#include "Imgui/imgui_impl_win32.h"
#include "Imgui/imgui_impl_dx11.h"

#ifdef _DEBUG
#define LOG(_text, ...) printf(_text "\n", __VA_ARGS__)
#else
#define LOG(_text, ...)
#endif

namespace
{
    /*
     * 0 ProcessAttach NoCall
     * 1 ProcessAttach Called
     */
    LONG volatile g_iDllMainProcessAttachFlag = 0;
    LONG volatile g_iDX11NeedInit = TRUE;

    BOOL g_bInitSuccess = FALSE;

    HWND g_GameHwnd = NULL;

    IDXGISwapChain* g_pHookedSwapChain = nullptr;
    IDXGISwapChain* g_pSwapChain = nullptr;

    ID3D11Device* g_pd3dDevice = nullptr;
    ID3D11DeviceContext* g_pd3dDeviceContext = nullptr;
    ID3D11RenderTargetView* g_mainRenderTargetView = nullptr;
}

void CleanupRenderTarget()
{
    if (g_mainRenderTargetView) { g_mainRenderTargetView->Release(); g_mainRenderTargetView = nullptr; }
}

void CleanupDeviceD3D()
{
    CleanupRenderTarget();
    if (g_pHookedSwapChain) { g_pHookedSwapChain->Release(); g_pHookedSwapChain = nullptr; }
    if (g_pSwapChain) { g_pSwapChain->Release(); g_pSwapChain = nullptr; }
    if (g_pd3dDeviceContext) { g_pd3dDeviceContext->Release(); g_pd3dDeviceContext = nullptr; }
    if (g_pd3dDevice) { g_pd3dDevice->Release(); g_pd3dDevice = nullptr; }
}

void CreateRenderTarget()
{
    ID3D11Texture2D* pBackBuffer = nullptr;
    g_pSwapChain->GetBuffer(0, IID_PPV_ARGS(&pBackBuffer));
    g_pd3dDevice->CreateRenderTargetView(pBackBuffer, nullptr, &g_mainRenderTargetView);
    pBackBuffer->Release();
}

LRESULT CreateDeviceD3D(HWND hWnd)
{
    // Setup swap chain
    DXGI_SWAP_CHAIN_DESC sd;
    ZeroMemory(&sd, sizeof(sd));
    sd.BufferCount = 2;
    sd.BufferDesc.Width = 0;
    sd.BufferDesc.Height = 0;
    sd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    sd.BufferDesc.RefreshRate.Numerator = 60;
    sd.BufferDesc.RefreshRate.Denominator = 1;
    sd.Flags = DXGI_SWAP_CHAIN_FLAG_ALLOW_MODE_SWITCH;
    sd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
    sd.OutputWindow = hWnd;
    sd.SampleDesc.Count = 1;
    sd.SampleDesc.Quality = 0;
    sd.Windowed = TRUE;
    sd.SwapEffect = DXGI_SWAP_EFFECT_DISCARD;

    UINT createDeviceFlags = 0;
    //createDeviceFlags |= D3D11_CREATE_DEVICE_DEBUG;
    D3D_FEATURE_LEVEL featureLevel;

    ID3D11Device* pd3dDevice = nullptr;
    ID3D11DeviceContext* pd3dDeviceContext = nullptr;

    const D3D_FEATURE_LEVEL featureLevelArray[2] = { D3D_FEATURE_LEVEL_11_0, D3D_FEATURE_LEVEL_10_0, };
    HRESULT res = D3D11CreateDeviceAndSwapChain(nullptr, D3D_DRIVER_TYPE_HARDWARE, nullptr, createDeviceFlags, featureLevelArray, 2, D3D11_SDK_VERSION, &sd, &g_pHookedSwapChain, &pd3dDevice, &featureLevel, &pd3dDeviceContext);
    if (res == DXGI_ERROR_UNSUPPORTED) // Try high-performance WARP software driver if hardware is not available.
        res = D3D11CreateDeviceAndSwapChain(nullptr, D3D_DRIVER_TYPE_WARP, nullptr, createDeviceFlags, featureLevelArray, 2, D3D11_SDK_VERSION, &sd, &g_pHookedSwapChain, &pd3dDevice, &featureLevel, &pd3dDeviceContext);

    // We just need SwapChain, to get its virtual table and hook It!!
    if (pd3dDeviceContext) { pd3dDeviceContext->Release(); pd3dDeviceContext = nullptr; }
    if (pd3dDevice) { pd3dDevice->Release(); pd3dDevice = nullptr; }

    return res;
}

// Forward declare message handler from imgui_impl_win32.cpp
typedef LRESULT(WINAPI* typedef_WndProc)(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

typedef HRESULT(STDMETHODCALLTYPE* typedef_Present)(
    /* [in] */ IDXGISwapChain* This,
    /* [in] */ UINT SyncInterval,
    /* [in] */ UINT Flags);

typedef HRESULT(STDMETHODCALLTYPE* typedef_ResizeBuffers)(
    /* [in] */ IDXGISwapChain* This,
    /* [in] */ UINT BufferCount,
    /* [in] */ UINT Width,
    /* [in] */ UINT Height,
    /* [in] */ DXGI_FORMAT NewFormat,
    /* [in] */ UINT SwapChainFlags);

extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

static typedef_WndProc Real_WndProc = nullptr;
static constexpr typedef_WndProc Mine_WndProc = [](HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) -> LRESULT
    {
        LOG("Mine_WndProc Hooked!!");

        if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
            return S_FALSE;

        return Real_WndProc ? CallWindowProcW(Real_WndProc, hWnd, msg, wParam, lParam) : S_OK;
    };

static typedef_Present Real_Present = nullptr;
static constexpr typedef_Present Mine_Present =
[](IDXGISwapChain* This, UINT SyncInterval, UINT Flags) -> HRESULT {
    LOG("Mine_Present Hooked!!");

    if (InterlockedCompareExchange(&g_iDX11NeedInit, 0, 1)) {
        g_pSwapChain = This;
        g_pSwapChain->GetDevice(__uuidof(g_pd3dDevice), (void**)&g_pd3dDevice);
        g_pd3dDevice->GetImmediateContext(&g_pd3dDeviceContext);

        CreateRenderTarget();
        ImGui_ImplWin32_Init(g_GameHwnd);
        ImGui_ImplDX11_Init(g_pd3dDevice, g_pd3dDeviceContext);
    }

    // Start the Dear ImGui frame
    ImGui_ImplDX11_NewFrame();
    ImGui_ImplWin32_NewFrame();
    ImGui::NewFrame();

    ImGui::Begin("AHA");
    ImGui::Text("Gugu!!");
    ImGui::End();

    ImGui::Render();
    g_pd3dDeviceContext->OMSetRenderTargets(1, &g_mainRenderTargetView, nullptr);
    ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());

    return Real_Present(This, SyncInterval, Flags);
    };

static typedef_ResizeBuffers Real_ResizeBuffers = nullptr;
static constexpr typedef_ResizeBuffers Mine_ResizeBuffers =
[](IDXGISwapChain* This,
    UINT BufferCount,
    UINT Width,
    UINT Height,
    DXGI_FORMAT NewFormat,
    UINT SwapChainFlags) -> HRESULT {
        LOG("Mine_ResizeBuffers Hooked!!");

        ImGui_ImplDX11_Shutdown();
        ImGui_ImplWin32_Shutdown();
        CleanupDeviceD3D();
        InterlockedCompareExchange(&g_iDX11NeedInit, 1, 0);

        return Real_ResizeBuffers(This, BufferCount, Width, Height, NewFormat, SwapChainFlags);
    };

BOOL SetupHook() {
    Real_WndProc = reinterpret_cast<decltype(Real_WndProc)>(SetWindowLongPtrW(g_GameHwnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(Mine_WndProc)));

    DWORD dwOldProt = PAGE_EXECUTE_READ;
    if (!VirtualProtect(*reinterpret_cast<uintptr_t**>(g_pHookedSwapChain), 1, PAGE_EXECUTE_READWRITE, &dwOldProt)) {
        return FALSE;
    }

    Real_Present = static_cast<decltype(Real_Present)>(InterlockedExchangePointer(reinterpret_cast<volatile PVOID*>(*reinterpret_cast<uintptr_t**>(g_pHookedSwapChain) + 8), Mine_Present));
    Real_ResizeBuffers = static_cast<decltype(Real_ResizeBuffers)>(InterlockedExchangePointer(reinterpret_cast<volatile PVOID*>(*reinterpret_cast<uintptr_t**>(g_pHookedSwapChain) + 13), Mine_ResizeBuffers));
    VirtualProtect(*reinterpret_cast<uintptr_t**>(g_pHookedSwapChain), 1, dwOldProt, &dwOldProt);

    return TRUE;
}

void RemoveHook() {
    DWORD dwOldProt = PAGE_EXECUTE_READ;

    if (!VirtualProtect(*reinterpret_cast<uintptr_t**>(g_pHookedSwapChain), 1, PAGE_EXECUTE_READWRITE, &dwOldProt)) {
        return;
    }

    InterlockedCompareExchangePointer(reinterpret_cast<volatile PVOID*>(*reinterpret_cast<uintptr_t**>(g_pHookedSwapChain) + 8), Real_Present, Mine_Present);
    InterlockedCompareExchangePointer(reinterpret_cast<volatile PVOID*>(*reinterpret_cast<uintptr_t**>(g_pHookedSwapChain) + 13), Real_ResizeBuffers, Mine_ResizeBuffers);
    VirtualProtect(*reinterpret_cast<uintptr_t**>(g_pHookedSwapChain), 1, dwOldProt, &dwOldProt);

    if (Real_WndProc) {
        SetWindowLongPtrW(g_GameHwnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(Real_WndProc));
    }
}

void LibraryHandler_ProcAttach(HANDLE hModule) {
    LOG("Attach Begin!!");

    // 這裡要修改為你需要繪製的父視窗的類名，可透過spy++獲取
    g_GameHwnd = FindWindowW(L"ImGui Example", NULL);

    LRESULT res = CreateDeviceD3D(g_GameHwnd);
    if (res != S_OK) {
        LOG("CreateDeviceD3D Failed, res=0x%X", static_cast<unsigned int>(res));
        CleanupDeviceD3D();
        return;
    }

    // Setup Dear ImGui context
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();

    //// Setup Dear ImGui style
    ImGui::StyleColorsDark();
    //ImGui::StyleColorsLight();

    // Setup Platform/Renderer Backends
    if (!SetupHook()) {
        LOG("Setup Hook Failed");
    }

    LOG("Attach Init Success");
    g_bInitSuccess = TRUE;
}

void LibraryHandler_ProcDetach(HANDLE hModule) {
    LOG("Detach Begin!!");

    if (!g_bInitSuccess) {
        return;
    }

    RemoveHook();

    ImGui_ImplDX11_Shutdown();
    ImGui_ImplWin32_Shutdown();
    ImGui::DestroyContext();

    CleanupDeviceD3D();
}

BOOL WINAPI DllMain(HANDLE hModule, DWORD dwReason, LPVOID lpvReserved) {
    static FILE* g_stream = nullptr;

    switch (dwReason) {
    case DLL_PROCESS_ATTACH: {
        if (0 == InterlockedCompareExchange(&g_iDllMainProcessAttachFlag, 1, 0)) {
#ifdef _DEBUG
            AllocConsole();
            freopen_s(&g_stream, "CONOUT$", "w+", stdout);
#endif
            auto threadObj = std::thread([hModule]() -> void { LibraryHandler_ProcAttach(hModule); });
            threadObj.detach();
        }
        break;
    }
    case DLL_PROCESS_DETACH: {
        LibraryHandler_ProcDetach(hModule);
#ifdef _DEBUG
        fflush(stdout);
        fclose(g_stream);
#endif
        break;
    }
    case DLL_THREAD_ATTACH:
        break;
    case DLL_THREAD_DETACH:
        break;
    }

    return TRUE;
}