C++ GMod Anti Screenshot

#include <assert.h>
#include <Windows.h>
 
#include "cdll_int.h"
#include "materialsystem/imaterial.h"
 
#include "Hook/VTable.h"
#include "Hook/VMT.h"
#include "SigScan.h"
 
typedef void *(*FactoryFn)(const char *name, int ret);
typedef void (__thiscall *CMatRenderContext_ReadPixelsFn)(void *_this, int x, int y, int w, int h, unsigned char *buffer, void *format);
 
const int CMaterialSystem_GetRenderContext_Offset = 98;
const int CMatRenderContext_ReadPixels_Offset = 13;
 
Hook::VMT *CMatRenderContext_Hooks;
 
IVEngineClient *client;
 
void __fastcall CMatRenderContext_ReadPixels_Hook(IMatRenderContext *_this, void *, int x, int y, int w, int h, unsigned char *buffer, void *format) {
        _this->ClearColor3ub(255, 0, 255);
        _this->ClearBuffers(true, true);
 
        client->ClientCmd_Unrestricted("say Hey, don't take screenshots of me!\n");
 
        return CMatRenderContext_Hooks->GetOriginal<CMatRenderContext_ReadPixelsFn>(CMatRenderContext_ReadPixels_Offset)(_this, x, y, w, h, buffer, format);
}
 
DWORD WINAPI Load(LPVOID lpParameter) {
        HMODULE engine;
        HMODULE materialsystem;
       
        while (!(engine = GetModuleHandle("engine.dll")));
        while (!(materialsystem = GetModuleHandle("materialsystem.dll")));
       
        auto EngineFactory = (FactoryFn)GetProcAddress(engine, "CreateInterface");
        client = (IVEngineClient *)EngineFactory("VEngineClient013", 0);
 
        auto MaterialSystemFactory = (FactoryFn)GetProcAddress(materialsystem, "CreateInterface");
        auto *material = (IMaterialSystem *)MaterialSystemFactory(MATERIAL_SYSTEM_INTERFACE_VERSION, 0);
 
        auto RenderContext = material->GetRenderContext();
 
        CMatRenderContext_Hooks = new Hook::VMT(RenderContext);
        CMatRenderContext_Hooks->Hook(CMatRenderContext_ReadPixels_Offset, CMatRenderContext_ReadPixels_Hook);
 
        return 0;
}
 
bool APIENTRY DllMain(HMODULE hModule, DWORD dwReason, LPVOID lpReserved) {
        if (dwReason == DLL_PROCESS_ATTACH) {
                CreateThread(0, 0, Load, NULL, 0, NULL);
        }
 
        return true;
}