Hack trackball to simulate mousewheel

trackball_hack.cpp

#include <Windows.h>
#include <iostream>
#include <chrono>

HHOOK mhook;
MSG msg;
bool forwardButtonHeld = false;
long mouseX = 0;
long mouseY = 0;

std::chrono::time_point<std::chrono::high_resolution_clock> forwardDownTime;

LRESULT WINAPI LLMouseProc(int nCode, WPARAM wParam, LPARAM lParam);

void InstallHook() {
	if (!(mhook = SetWindowsHookEx(WH_MOUSE_LL, LLMouseProc, NULL, 0))) {
		printf_s("Error: %x \n", GetLastError());
	}
}

void UninstallHook() {
	UnhookWindowsHookEx(mhook);
}

LRESULT WINAPI LLMouseProc(int nCode, WPARAM wParam, LPARAM lParam) {
	if (nCode >= 0) {
		MSLLHOOKSTRUCT* pMouseStruct = (MSLLHOOKSTRUCT*)lParam;
		switch (wParam) {
		case WM_MOUSEMOVE: {
			if (pMouseStruct != NULL) {
				long newX = pMouseStruct->pt.x;
				long newY = pMouseStruct->pt.y;

				if (mouseX == 0 && mouseY == 0) {
					mouseX = newX;
					mouseY = newY;
				}

				if (forwardButtonHeld) {
					UninstallHook();
					long diff = mouseY - newY;
					mouse_event(MOUSEEVENTF_WHEEL, 0, 0, diff, 0);
					diff = newX - mouseX;
					mouse_event(MOUSEEVENTF_HWHEEL, 0, 0, diff, 0);
					InstallHook();
					return -1;
				}
				else {
					mouseX = newX;
					mouseY = newY;
				}
			}
			break;
		}
		case WM_XBUTTONDOWN: {
			if (pMouseStruct != NULL) {
				if ((pMouseStruct->mouseData >> 16) == 0x2) {
					forwardButtonHeld = true;
					forwardDownTime = std::chrono::high_resolution_clock::now();
					return -1;
				}
			}
			break;
		}
		case WM_XBUTTONUP: {
			if (pMouseStruct != NULL) {
				if ((pMouseStruct->mouseData >> 16) == 0x2) {
					forwardButtonHeld = false;
					auto now = std::chrono::high_resolution_clock::now();
					if ((now - forwardDownTime).count() < std::chrono::nanoseconds(800000000).count()) {
						UninstallHook();
						mouse_event(MOUSEEVENTF_MIDDLEDOWN, 0, 0, 0, 0);
						mouse_event(MOUSEEVENTF_MIDDLEUP, 0, 0, 0, 0);
						InstallHook();
						return -1;
					}
				}
			}
			break;
		}
		}

	}

	return CallNextHookEx(mhook, nCode, wParam, lParam);
}

int main() {
	InstallHook();
	while (msg.message != WM_QUIT) {
		if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
	}

	UninstallHook();

	return (int)msg.wParam;
}