WinAPI - Hook Mouse Move not working

Question

I am trying to hook all mouse move events but I never reciever any message. This is whole code:

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

LRESULT CALLBACK MouseHookProc(int nCode, WPARAM wParam, LPARAM lParam)
{
    if (wParam != WM_MOUSEMOVE)
    {
        return CallNextHookEx(NULL, nCode, wParam, lParam);
    }

    std::cout << GET_X_LPARAM(lParam) << std::endl;
    return 0;
}

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;

    case WM_MOUSEMOVE:
        int xPos = GET_X_LPARAM(lParam);
        int yPos = GET_Y_LPARAM(lParam);
        std::cout << xPos << " - " << yPos << std::endl;
        return 0;
    }

    return DefWindowProc(hwnd, uMsg, wParam, lParam);
}

int __stdcall WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR lpCmdLine, INT nCmdShow)
{
    AllocConsole();

    HHOOK mouseHook = SetWindowsHookEx(WH_MOUSE_LL, MouseHookProc, hInstance, NULL);

    MSG msg;

    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return 0;
}

For a global hook, your hook procedure must be in a loadable module (DLL). Your MouseHookProc should always call CallNextHookEx unless you wish to filter out the message altogether. In the latter case your hook procedure should return a nonzero value. Failing to meet the requirements will break other hooks in the system. Make sure to read LowLevelMouseProc thoroughly. Everything I just said is spelled out there. — IInspectable
– IInspectable, Commented Jun 7, 2014 at 18:12
@David Good point. For a low level hook the hook procedure is not required to reside in a DLL. The remaining requirements still hold, and the MouseHookProc needs to be fixed. — IInspectable
– IInspectable, Commented Jun 8, 2014 at 10:44

Hans Passant · Accepted Answer · 2014-06-07 18:31:16Z

   std::cout << GET_X_LPARAM(lParam) << std::endl;

The hook works fine, you are just overrating the ability of the CRT to initialize stdout correctly when you build a program that does not have a console. The hook callback code is in general not correct. You'll light it up like this:

LRESULT CALLBACK MouseHookProc(int nCode, WPARAM wParam, LPARAM lParam) {
    if (nCode >= 0 && wParam == WM_MOUSEMOVE) {
        MSLLHOOKSTRUCT* mh = (MSLLHOOKSTRUCT*)lParam;
        std::stringstream ss;
        ss << mh->pt.x << ", " << mh->pt.y << std::endl;
        OutputDebugStringA(ss.str().c_str());
    }
    return CallNextHookEx(NULL, nCode, wParam, lParam);
}

You'll see text appear in the debugger, for Visual Studio it will show up in the Output window.

Another way to do this is to simply build a console mode app so you get the console right away and stdout will work. Change WinMain() to main().

Or by re-opening stdout, probably what you prefer. Like this:

  AllocConsole();
  freopen("CONOUT$", "wb", stdout);

Bob Moore · Accepted Answer · 2014-06-07 17:58:20Z

1

If you're trying to capture mouse events for ALL processes (your NULL last parameter implies that), you need a system wide hook in a DLL.

I have an example on my website here.

answered Jun 7, 2014 at 17:58

Bob Moore

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2 Comments

Hans Passant Over a year ago

That's not correct, the low-level mouse hook never uses a DLL.

Bob Moore Over a year ago

Ahh, didn't spot it was a low level one.

Waras · Accepted Answer · 2014-06-08 00:03:59Z

yes like @HansPassant mentioned std::cout is not efficient way to display things unless u make your console refresh each time it's updated.

I have remade the whole program, because I needed too, using code:blocks default win32 template and replaced MouseHookProc :)

#include <windows.h>
#include <windowsx.h>
#include <iostream>
#include <sstream>

LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK MouseHookProc(int nCode, WPARAM wParam, LPARAM lParam);

char szClassName[ ] = "CodeBlocksWindowsApp";
HWND Label1, Label2; //adding 2 static controls to display things

int WINAPI WinMain (HINSTANCE hThisInstance,
                 HINSTANCE hPrevInstance,
                 LPSTR lpszArgument,
                 int nCmdShow)
{
// adding hook
HHOOK mouseHook = SetWindowsHookEx(WH_MOUSE_LL, MouseHookProc, hThisInstance, NULL);

HWND hwnd;
MSG messages;
WNDCLASSEX wincl;
wincl.hInstance = hThisInstance;
wincl.lpszClassName = szClassName;
wincl.lpfnWndProc = WindowProcedure;
wincl.style = CS_DBLCLKS;
wincl.cbSize = sizeof (WNDCLASSEX);
wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
wincl.lpszMenuName = NULL;
wincl.cbClsExtra = 0;
wincl.cbWndExtra = 0;
wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

if (!RegisterClassEx (&wincl))
    return 0;

hwnd = CreateWindowEx (0, szClassName, "Code::Blocks Template Windows App", 
       WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 544, 375, 
       HWND_DESKTOP, NULL, hThisInstance, NULL);

ShowWindow (hwnd, nCmdShow);

while (GetMessage (&messages, NULL, 0, 0))
{
    TranslateMessage(&messages);
    DispatchMessage(&messages);
}

return messages.wParam;
}


LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
    case WM_CREATE:
        //creating those 2 static controls
        Label1 = CreateWindow("STATIC", "Label1", WS_VISIBLE | WS_CHILD, 10,10,60,18, hwnd, NULL, NULL, NULL);
        Label2 = CreateWindow("STATIC", "Label2", WS_VISIBLE | WS_CHILD, 70,10,60,18, hwnd, NULL, NULL, NULL);
    break;
    //adding mousemove event
    case WM_MOUSEMOVE: {
        int xPos = GET_X_LPARAM(lParam);
        int yPos = GET_Y_LPARAM(lParam);
        //std::cout << xPos << " - " << yPos << std::endl;
        TCHAR Coords[20];
        wsprintf(Coords, "%i, %i", xPos, yPos);
        SetWindowText(Label1, Coords);
    return 0; }

    case WM_DESTROY:
        PostQuitMessage (0);
        break;
    default:
        return DefWindowProc (hwnd, message, wParam, lParam);
}
return 0;
}

//replacing MouseHookProc
LRESULT CALLBACK MouseHookProc(int nCode, WPARAM wParam, LPARAM lParam) {
    if (nCode >= 0 && wParam == WM_MOUSEMOVE) {
        MSLLHOOKSTRUCT* mh = (MSLLHOOKSTRUCT*)lParam;
        std::stringstream ss;
        ss << mh->pt.x << ", " << mh->pt.y << std::endl;
        //OutputDebugStringA(ss.str().c_str());
        SetWindowText(Label2, ss.str().c_str());
    }
    return CallNextHookEx(NULL, nCode, wParam, lParam);
}

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