Question

I am creating a keyboard hook, wherein KeyboardProc is a static member of a class CWidget.

class CWidget {    static LRESULT CALLBACK KeyboardProc(int code, WPARAM wParam, LPARAM lParam );  }; 

I want to call the non-static members of CWidget inside the CWidget::KeyboardProc.

What is the best way to do it?

KeyboardProc does not have any 32 bit DWORD where I can pass the ‘this’ pointer.

Answer 1

Given that you probably only want one keyboard hook installed at a time, just add a static pThis member to your class:

// Widget.h class CWidget {     static HHOOK m_hHook;     static CWidget *m_pThis;  public:     /* NOT static */     bool SetKeyboardHook()     {         m_pThis = this;         m_hHook = ::SetWindowsHookEx(WH_KEYBOARD, StaticKeyboardProc, /* etc */);     }      // Trampoline     static LRESULT CALLBACK StaticKeyboardProc(int code, WPARAM wParam, LPARAM lParam)     {         ASSERT(m_pThis != NULL);         m_pThis->KeyboardProc(code, wParam, lParam);     }      LRESULT KeyboardProc(int code, WPARAM wParam, LPARAM lParam);      /* etc. */ }; 

You need to define the static member:

// Widget.cpp CWidget *CWidget::m_pThis = NULL;