Zooming In on a Selection: Step 6

/* Set the source and destination rectangles for painting */
SetRect(&rLeadSource, 0, 0, LeadBitmap.GetWidth(), LeadBitmap.GetHeight());
SetRect(&rLeadDest, 0, 0, LeadBitmap.GetWidth(), LeadBitmap.GetHeight());
/* Update the global variables for keeping track of the display */
DisplayLeft = 0;
DisplayTop = 0;
DisplayWidth = LeadBitmap.GetWidth();
DisplayHeight = LeadBitmap.GetHeight();
/* Repaint the whole client area */
::InvalidateRect(this->m_hWnd,NULL,FALSE);