C / C++ / MFC

LRESULT CALLBACK DlgProc(HWND hwnd, UINT Msg, WPARAM wParam, LPARAM lParam) {
    switch (Msg) {
        case WM_INITDIALOG:
            break; //You can do whatever here

        case WM_COMMAND:
            switch (LOWORD(wParam)) {
                case IDC_MYBUTTON:
                    return 0; //something happened to MYBUTTON
            }
            break; //We havn't handled it, use default handler

        case WM_CLOSE:
            //cleanup
            return 0;
    }
    return pOriginalProcedure(hwnd, Msg, wParam, lParam); //This is set as GetWindowLong(GWL_MSGPROC) before changing the procedure.
}

case WM_PAINT: // custom control window paint handler
{
// some checks for need of repainting
Gdiplus::Graphics graphics(hdc);
Gdiplus::Bitmap *bmp = new Gdiplus::Bitmap(CtrlRect.right, CtrlRect.bottom);
Gdiplus::Graphics *temp = Gdiplus::Graphics::FromImage(bmp);
temp->SetSmoothingMode(Gdiplus::SmoothingMode::SmoothingModeAntiAlias);
// .. drawing goes here
// .. paint "ball" with new mouse coords
Gdiplus::CachedBitmap *cbmp = new Gdiplus::CachedBitmap(bmp, &graphics);
delete bmp;
delete temp;
graphics.DrawCachedBitmap(cbmp, 0, 0);
// done
}

*(BOOL*)&m_bool = FALSE;

class CBaseClass
{
 public:
  CBaseClass(){}
  virtual ~CBaseClass(){}

//members...
};

class CClass : public CBaseClass
{
 public:
  CClass(){}
  virtual ~CClass(){}

//members...
};