This function saves the current state of the specified device context by copying data describing selected objects and graphic modes (such as the bitmap, brush, palette, font, pen, region, and drawing mode) to a context stack.
If the function succeeds, the return value identifies the saved device context.
If the function fails, the return value is zero.
To get extended error information, call GetLastError.
The SaveDC function can be used any number of times to save any number of instances of the device context's state.
A saved state can later be restored by using the RestoreDC function.