a throwaway C++ program that uses WinAPI calls to fix a very specific scrollbar issue caused by ActiveX controls on a specific intranet website on a specific version of Windows 10

scrollbar_fix.cpp

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
//detect if the scrollbar is one of the ones affected by the bug
bool IsBrokenScrollbar(HWND hw) {
	char clsname[256];
	GetClassName(hw, clsname, 256);
	if (strcmp(clsname, "ScrollBar")) return false;
	GetClassName(GetParent(hw), clsname, 256);
	if (strcmp(clsname, "DataTable5")) return false;
	return true;
}
//replace the broken scrollbar's weird VB6 WndProc with a proper Win32 scrollbar WndProc
LRESULT CALLBACK CallWndProc(int code, WPARAM wp, LPARAM lp) {
	CWPSTRUCT* cwp = (CWPSTRUCT*)lp;
	if (code < 0) return CallNextHookEx(0, code, wp, lp);
	if (cwp->message == WM_CREATE && IsBrokenScrollbar(cwp->hwnd)) {
		HWND win32_scrollbar = CreateWindow("SCROLLBAR", "", 0, 0, 0, 0, 0, cwp->hwnd, 0, GetModuleHandle(0), 0);
		WNDPROC win32_proc = (WNDPROC)GetWindowLong(win32_scrollbar, GWL_WNDPROC);
		DestroyWindow(win32_scrollbar);
		SetWindowLong(cwp->hwnd, GWL_WNDPROC, (LONG)win32_proc);
	}
	return CallNextHookEx(0,code,wp,lp);
}
//rundll32 entry point for hook
extern "C" LRESULT _declspec(dllexport) WINAPI Activate(HINSTANCE hi, HINSTANCE hp, char* cmd, int sc) {
	HHOOK hook = SetWindowsHookEx(WH_CALLWNDPROC, (HOOKPROC)CallWndProc, (HINSTANCE)GetModuleHandle("scrollbar_fix.dll"), 0);
	WaitForSingleObject(GetCurrentProcess(), INFINITE);
	return 0;
}
//TO RUN: compile this DLL and run 'rundll32.exe c:\path\to\scrollbar_fix.dll,_Activate@16' after login.
//TO CLOSE: close the rundll32.exe processes associated with this process and the hook will uninstall.