Zooming In on a Selection: Step 2

L_BOOL FirstDraw; /* The state for the first WM_MOUSEMOVE event when cropping */
int StartGDIX; /* Starting X position in screen pixels */
int StartGDIY; /* Starting Y position in screen pixels */
int EndGDIX; /* Ending X position in screen pixels */
int EndGDIY; /* Ending Y position in screen pixels */
int StartPixelX; /* Starting X position in bitmap pixels */
int StartPixelY; /* Starting Y position in bitmap pixels */
int EndPixelX; /* Ending X position in bitmap pixels */
int EndPixelY; /* Ending Y position in bitmap pixels */
HPEN SavedPen;
HBRUSH SavedBrush;
RECT rLeadDest;
RECT rLeadSource;
RECT rClientSize;
L_INT DisplayMode;
L_INT DisplayLeft, DisplayTop;
L_INT DisplayWidth, DisplayHeight;