int LineLength( int nLine = -1 ) const;
nLine
Specifies the character index of a character in the line whose length is to be retrieved. If this parameter is -1, the length of the current line (the line that contains the caret) is returned, not including the length of any selected text within the line.
When LineLength is called for a single-line edit control, this parameter is ignored.
Retrieves the length of a line in an edit control.
Use the LineIndex member function to retrieve a character index for a given line number within a multiple-line edit control.
When LineLength is called for a multiple-line edit control, the return value is the length (in bytes) of the line specified by nLine. When LineLength is called for a single-line edit control, the return value is the length (in bytes) of the text in the edit control.
CEdit::LineIndex, EM_LINELENGTH