goldberg_emulator/overlay_experimental/OpenGL_Hook.cpp

#include "../dll/base.h"
#include "OpenGL_Hook.h"
#include "Hook_Manager.h"

#include <imgui.h>
#include <impls/imgui_impl_win32.h>
#include <impls/imgui_impl_opengl3.h>

#include <GL/glew.h>

#pragma comment(lib, "opengl32")
#pragma comment(lib, "glew32s")


// This is created by OpenGL_Hook::Create, and deleted by the Hook_Manager if not used
static OpenGL_Hook* hook;

void OpenGL_Hook::hook_ogl()
{
    if (!_hooked)
    {
        PRINT_DEBUG("Hooked OpenGL\n");
        _hooked = true;
        Hook_Manager::Inst().FoundHook(this);

        GLenum err = glewInit();
        if (GLEW_OK != err)
        {
            /* Problem: glewInit failed, something is seriously wrong. */
            PRINT_DEBUG("Error: %s\n", glewGetErrorString(err));
        }

        UnhookAll();
        BeginHook();
        HookFuncs(
            std::make_pair<void**, void*>(&(PVOID&)wglSwapBuffers, &OpenGL_Hook::MywglSwapBuffers)
        );
        EndHook();
    }
}

void OpenGL_Hook::resetRenderState()
{
    if (initialized)
    {
        ImGui_ImplOpenGL3_Shutdown();
        ImGui_ImplWin32_Shutdown();
        ImGui::DestroyContext();

        initialized = false;
    }
}

void OpenGL_Hook::prepareForOverlay(HDC hDC)
{
    HWND hWnd = WindowFromDC(hDC);
    RECT rect;

    GetClientRect(hWnd, &rect);

    if (!initialized)
    {
        ImGui::CreateContext();
        ImGuiIO& io = ImGui::GetIO();
        io.IniFilename = NULL;

        Hook_Manager::Inst().ChangeGameWindow(hWnd);

        ImGui_ImplWin32_Init(hWnd);
        ImGui_ImplOpenGL3_Init();

        initialized = true;
    }
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplWin32_NewFrame();

    ImGui::NewFrame();

    Hook_Manager::Inst().CallOverlayProc(rect.right, rect.bottom);

    ImGui::EndFrame();

    ImGui::Render();

    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
}

/////////////////////////////////////////////////////////////////////////////////////
// OpenGL Initialization functions
BOOL WINAPI OpenGL_Hook::MywglMakeCurrent(HDC hDC, HGLRC hGLRC)
{
    auto res = hook->wglMakeCurrent(hDC, hGLRC);
    hook->hook_ogl();
    return res;
}

/////////////////////////////////////////////////////////////////////////////////////
BOOL WINAPI OpenGL_Hook::MywglSwapBuffers(HDC hDC)
{
    hook->prepareForOverlay(hDC);
    return hook->wglSwapBuffers(hDC);
}

OpenGL_Hook::OpenGL_Hook():
    initialized(false),
    wglSwapBuffers(nullptr)
{
    _dll = GetModuleHandle(DLL_NAME);
    _hooked = false;
    // Hook to wglMakeCurrent so we know when it gets called.
    // If its called, then OpenGL will be used to render the overlay.
    wglMakeCurrent = (decltype(wglMakeCurrent))GetProcAddress(_dll, "wglMakeCurrent");
    wglSwapBuffers = (decltype(wglSwapBuffers))GetProcAddress(_dll, "wglSwapBuffers");

    BeginHook();
    HookFuncs(
        std::make_pair<void**, void*>(&(PVOID&)wglMakeCurrent, &OpenGL_Hook::MywglMakeCurrent)
    );
    EndHook();
}

OpenGL_Hook::~OpenGL_Hook()
{
    PRINT_DEBUG("OpenGL Hook removed\n");

    if (_hooked)
    {
        ImGui_ImplOpenGL3_Shutdown();
        ImGui_ImplWin32_Shutdown();
        ImGui::DestroyContext();
    }

    hook = nullptr;
}

void OpenGL_Hook::Create()
{
    if (hook == nullptr)
    {
        hook = new OpenGL_Hook;
        // Register the hook to the Hook Manager
        Hook_Manager::Inst().AddHook(hook);
    }
}