BCGControlBar Pro for MFC
BOOL CBCGPEditCtrl::m_bReplaceTabsAndEOLOnCopy

Specifies whether to replace tab symbols and end of line symbols when the text is copied to the Clipboard.

If this member variable is TRUE all spaces are replaced with '\t' and all '\n' symbols are replaced with '\r\n' when the text is being copied into the Clipboard, otherwise the text is copied as is.

If you're working with large text buffers you may want to turn this option off to improve performance.