CODEWITHSUNDEEP
c++windowshookmousemovemouse-hook
motsu35
motsu35

Reputation: 21

Confusion about mouse hooks in c++

I am trying to get global mouse position. I have a hook working that can get the mouse position, however it only has access to it inside the hook code. Trying to access the data inside main doesn't work.

The best way to explain this is with code:

LRESULT CALLBACK mouseHookProc(int nCode, WPARAM wParam, LPARAM lParam)
{
     PMSLLHOOKSTRUCT p = (PMSLLHOOKSTRUCT) lParam;
     position.x = p->pt.x;
     position.y = p->pt.y;
     std::cout<<position.x<<std::endl;
     return CallNextHookEx(NULL, nCode, wParam, lParam);
}

int WINAPI WinMain (HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpszArgument,int nCmdShow)
{
     HHOOK mouseHook = SetWindowsHookEx(WH_MOUSE_LL,mouseHookProc,hInstance,NULL);

     MessageBox(NULL, "Press OK to close.", "", MB_OK);
     return 0;
}

With the above code, moving the mouse will show the new position in the console window. However, if I put the std::cout<<position.x<<std::endl; inside of main, it will just say 0. position is a global variable.

Code when the output is inside of main:

LRESULT CALLBACK mouseHookProc(int nCode, WPARAM wParam, LPARAM lParam)
{
     PMSLLHOOKSTRUCT p = (PMSLLHOOKSTRUCT) lParam;
     position.x = p->pt.x;
     position.y = p->pt.y;

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

int WINAPI WinMain (HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpszArgument,int nCmdShow)
{
     HHOOK mouseHook = SetWindowsHookEx(WH_MOUSE_LL,mouseHookProc,hInstance,NULL);
     for(;;)
     {
         std::cout<<position.x<<std::endl;
     }
     MessageBox(NULL, "Press OK to close.", "", MB_OK);
     return 0;
}

The first chunk of code works fine, it detects the mouse position, I just don't know how to get the x,y data into my main.

Upvotes: 0

Views: 5185

Answers (2)

Cheers and hth. - Alf
Cheers and hth. - Alf

Reputation: 145239

re this posted code:

LRESULT CALLBACK mouseHookProc(int nCode, WPARAM wParam, LPARAM lParam)
{
     PMSLLHOOKSTRUCT p = (PMSLLHOOKSTRUCT) lParam;
     position.x = p->pt.x;
     position.y = p->pt.y;

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

int WINAPI WinMain (HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpszArgument,int nCmdShow)
{
     HHOOK mouseHook = SetWindowsHookEx(WH_MOUSE_LL,mouseHookProc,hInstance,NULL);
     std::cout<<position.x<<std::endl;
     MessageBox(NULL, "Press OK to close.", "", MB_OK);
     return 0;
}

Here's what the main function specifies should happen:

  • First, a call to SetWindowsHookEx (this happens once).
  • Then, outputting position (this happens once).
  • Then, displaying a MessageBox (this happens once).

That's all.

During the call to MessageBox the hook procedure is called (whenever you move your mouse), but it doesn't do anything visible, just an internal update.

Why did you expect more?

How to fix:

  • Instead of relying on the internal message loop in MessageBox, which doesn't do any output, code up your own.
  • Not to do with functionality, but just because the current code is like very dirty clothing that does serve its purpose but feels ungood to wear: replace Microsoft's WinMain monstrosity with a standard C and C++ main.

Upvotes: 2

Abhijit-K
Abhijit-K

Reputation: 3669

For global hook the hook procedure mouseHookProc should be in a DLL so that it can be injected into processes. Check this: http://www.codeproject.com/Articles/1037/Hooks-and-DLLs

Upvotes: 1

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