How to Hook Mouse Event in C++ Builder Application using Windows Mouse Hook API Function?

Question

I have a problem hooking mouse event in C++Builder, it's showing an error:

[bcc32 Error] MainUnit.cpp(24): E2034 Cannot convert 'long * (__stdcall * (_closure )(int,unsigned int,long))(int,unsigned int,long)' to 'long (__stdcall *)(int,unsigned int,long)'
  Full parser context
    MainUnit.cpp(22): parsing: void TInputHookMain::SetHook()`.

And:

[bcc32 Error] MainUnit.cpp(24): E2342 Type mismatch in parameter 'lpfn' (wanted 'long (__stdcall *)(int,unsigned int,long)', got 'void')
  Full parser context
    MainUnit.cpp(22): parsing: void TInputHookMain::SetHook()`.

Here is my code in my main unit:

HHOOK mouseHook;

void TInputHookMain::ReleaseHook()
{
    UnhookWindowsHookEx(mouseHook);
}

void TInputHookMain::SetHook()
{
    if ( !(mouseHook = SetWindowsHookExW(WH_MOUSE_LL, MouseInputHook, NULL, 0)) )
    {
        ShowMessage("Failed To Install Mouse Hook!");
    }
}

LRESULT __stdcall TInputHookMain::MouseInputHook(int nCode, WPARAM MsgID, LPARAM Data)
{
    if ( nCode >= 0 )
    {
        switch ( MsgID ) {
            case WM_LBUTTONDOWN: ShowMessage("Left Mouse Button Clicked!");
                break;
            case WM_RBUTTONDOWN: ShowMessage("Right Mouse Button Clicked!");
                break;
        }
    }

    return CallNextHookEx(mouseHook, nCode, MsgID, Data);
}

Sadly, I cannot find where the problem is coming from. I tried to follow a C++ Tutorial step-by-step, but no luck so far.

Answer 1

MouseInputHook() should be a global function, or a static class method. So, add the static keyword to the declaration of MouseInputHook() in your class header file.

The error message means: a _closure function doesn't match the required callback function prototype. _closure means "a pointer to a non-static class method" in the C++Builder compiler. A non-static class method has a hidden this parameter, which makes it incompatible with the function prototype that SetWindowsHookExW() requires.