Retrieves a sequence of characters. The characters that are retrieved
are those characters at positions from @start_pos up to, but not
including @end_pos. If @end_pos is negative, then the characters
retrieved are those characters from @start_pos to the end of the text.
Note that positions are specified in characters, not bytes.
Return: a pointer to the contents of the widget as a
string. This string is allocated by the #GtkEditable
implementation and should be freed by the caller.
Retrieves a sequence of characters. The characters that are retrieved are those characters at positions from @start_pos up to, but not including @end_pos. If @end_pos is negative, then the characters retrieved are those characters from @start_pos to the end of the text.
Note that positions are specified in characters, not bytes.