Make a event for a mouse button even if application is minimized

Question

I want to make an application that responds to a mouse button so I done this:

case WM_LBUTTONDOWN:
        MessageBox(
            NULL,
            (LPCWSTR)L"HALLOOOO",
            (LPCWSTR)L"Worked",
            MB_ICONASTERISK | MB_OK | MB_DEFBUTTON2
        );
        break;

but the problem is that this only works if the user clicks on the window and I want it to work even with the window minimized this work even if the application is minimized

GetKeyState(VK_LBUTTON);

but if I put this in a loop if I press it once it will detect 1 million times because it will just check if the key is down and if I add delay using Sleep(250) it may work but sometimes it will not detect anything even if the user pressed the key I want my app to be able to detect if a key is pressed even if it's minimized how can I do this?

Answer 1

Since you already have a window, call SetWindowsHookEx with WH_MOUSE_LL.

The API is documented here and the parameters are explained.

HHOOK SetWindowsHookExW(
  [in] int       idHook,
  [in] HOOKPROC  lpfn,
  [in] HINSTANCE hmod,
  [in] DWORD     dwThreadId
);

The lpfn hook procedure can be defined as follows:

HWND hmain_window;
HHOOK hhook;
LRESULT CALLBACK mouse_proc(int code, WPARAM wparam, LPARAM lparam)
{
    if (code == HC_ACTION && lparam) 
    {
        if (wparam == WM_LBUTTONDOWN)
        {
            //MOUSEHOOKSTRUCT* mstruct = (MOUSEHOOKSTRUCT*)lparam;
            static int i = 0;
            std::wstring str = L"mouse down " + std::to_wstring(i++);
            SetWindowText(hmain_window, str.c_str());
        }
    }
    return CallNextHookEx(hhook, code, wparam, lparam);
}

int APIENTRY wWinMain(HINSTANCE hinst, HINSTANCE, LPWSTR, int)
{
    ...
    RegisterClassEx(...);
    hmain_window = CreateWindow(...);
    hhook = SetWindowsHookEx(WH_MOUSE_LL, mouse_proc, hinst, 0);
    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0) > 0) 
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    UnhookWindowsHookEx(hhook);
    return 0;
}