Hook WH_GETMESSAGE message - c++

Question

I'm trying to hook WH_GETMESSAGE from my class to determine the moment when specific window is resizing. However, looks like the hook isn't set.
Class from where I try to hook:
class WindowDisplayHelper : // public ...
{
public:
// some other public methods here
void SetMsgHook();
protected:
LRESULT CALLBACK GetMsgProcHook(int code, WPARAM wParam, LPARAM lParam);
static LRESULT CALLBACK MsgPoc(int code, WPARAM wParam, LPARAM lParam);
private:
// some other private members there
HWND m_windowHandle;
bool m_isWindowResizing = false;
static HHOOK m_msgHook;
static WindowsDisplayHelperMasterWindow* m_pThis;
};
.cpp file:
WindowDisplayHelper* WindowDisplayHelper ::m_pThis = nullptr;
HHOOK WindowDisplayHelper ::m_msgHook = NULL;
void WindowDisplayHelper ::SetMsgHook()
{
m_pThis = this;
m_msgHook = SetWindowsHookEx(WH_GETMESSAGE, MsgPoc, NULL, 0);
}
LRESULT CALLBACK WindowDisplayHelper::MsgPoc(int code, WPARAM wParam, LPARAM lParam)
{
if (m_pThis != nullptr)
{
return m_pThis->GetMsgProcHook(code, wParam, lParam);
}
return CallNextHookEx(0, code, wParam, lParam);
}
LRESULT CALLBACK WindowDisplayHelper::GetMsgProcHook(int code, WPARAM wParam, LPARAM lParam)
{
DUMPER_INFO("Hooked");
if (code < 0)
{
return CallNextHookEx(0, code, wParam, lParam);
}
MSG* lpmsg = (MSG*)lParam;
DUMPER_INFO("Hooked for HWND: %p. Current window %p", lpmsg->hwnd, m_windowHandle);
if (lpmsg->hwnd != m_windowHandle)
{
return CallNextHookEx(0, code, wParam, lParam);
}
if (lpmsg->message == WM_ENTERSIZEMOVE && !m_isWindowResizing)
{
DUMPER_INFO("Start window resizing");
m_isWindowResizing = true;
}
else if (lpmsg->message == WM_EXITSIZEMOVE && m_isWindowResizing)
{
DUMPER_INFO("Stop window resizing");
m_isWindowResizing = false;
}
return CallNextHookEx(0, code, wParam, lParam);
}
Here is how I create WindowDisplayHelper object:
bool DisplayManager::CreateWindowDisplay(TDisplayId displayId, void * windowHandle)
{
auto helper = boost::make_shared<WindowDisplayHelper>(windowHandle);
helper->SetMsgHook();
AddDisplayHelper(displayId, helper);
return true;
}
Though I call SetMsgHook() after the object is created, looks like hook isn't set, because I don't see any debug outputs in my log file and m_isWindowResizing variable always == false. So the question is why my hook doesn't work?
Thanks.

Answer 1

m_msgHook = SetWindowsHookEx(WH_GETMESSAGE, MsgPoc, NULL, 0);
This line produce a ERROR_HOOK_NEEDS_HMOD (1428) system error. It means that Cannot set nonlocal hook without a module handle. If you set dwThreadId parameter to zero, the hook procedure is associated with all existing threads running in the same desktop as the calling thread. It is a nonload hook you need specified a valid hmod parameter. You need put the hook code in a DLL as #Remy Lebeau pointed out.
Or set a valid dwThreadId parameter using GetCurrentThreadId() as #rudolfninja pointed out.
I test based on a Windows Desktop Application Template with the following code. It works. You can have a try.
int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPWSTR lpCmdLine,
_In_ int nCmdShow)
{
// ...
HHOOK m_msgHook = SetWindowsHookEx(WH_GETMESSAGE, MsgPoc, NULL, GetCurrentThreadId());
DWORD errCode = GetLastError();
MSG msg;
// Main message loop:
while (GetMessage(&msg, nullptr, 0, 0))
{
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
return (int) msg.wParam;
}
LRESULT CALLBACK MsgPoc(int code, WPARAM wParam, LPARAM lParam)
{
OutputDebugString(L"Hooked");
if (code < 0)
{
return CallNextHookEx(0, code, wParam, lParam);
}
MSG* lpmsg = (MSG*)lParam;
//OutputDebugString("Hooked for HWND: %p. Current window %p", lpmsg->hwnd, m_windowHandle);
if (lpmsg->hwnd != m_windowHandle)
{
return CallNextHookEx(0, code, wParam, lParam);
}
if (lpmsg->message == WM_ENTERSIZEMOVE && !m_isWindowResizing)
{
OutputDebugString(L"Start window resizing");
m_isWindowResizing = true;
}
else if (lpmsg->message == WM_EXITSIZEMOVE && m_isWindowResizing)
{
OutputDebugString(L"Stop window resizing");
m_isWindowResizing = false;
}
return CallNextHookEx(0, code, wParam, lParam);
}