int SaveDC() const;
Saves the current state of the device context by copying state information (such as clipping region, selected objects, and mapping mode) to a context stack maintained by Windows. The saved device context can later be restored by using RestoreDC.
SaveDC can be used any number of times to save any number of device-context states.
Specifies the saved device context. It is 0 if an error occurs. This return value is used on a subsequent call to RestoreDC to restore the device context state.
CDC::RestoreDC, ::SaveDC