SelectionRectDrawn Example VC++

In this example, when the SelectionRectDrawn event fires, its parameters are evaluated.  A state variable is then set to True or False to indicate whether a selection rectangle has been drawn by the user.

void CImgEdit1Dlg::OnSelectionRectDrawn(long Left, long Top, long Width, long Height) 
{
    // If the parameters returned by this event are all 0, the user
    // has clicked on the image and removed a previously drawn rectangle
    // If parameters have values, a rectangle has been drawn
    // IsRectangle would need to be set to false if another image
    // is opened/created or another page is displayed.
    // This technique could also be used for enabling disable cut copy
    // paste menu picks.

    if (Width + Height == 0)
      blnIsRectangle = FALSE;
    else
      blnIsRectangle = TRUE;
}