Returns the text in the range [start,end). Excludes undisplayed text (text marked with tags that set the invisibility attribute) if include_hidden_chars is FALSE. The returned string includes a 0xFFFC character whenever the buffer contains embedded images, so byte and character indexes into the returned string do correspond to byte and character indexes into the buffer. Contrast with TextBuffer.getText. Note that 0xFFFC can occur in normal text as well, so it is not a reliable indicator that a pixbuf or widget is in the buffer.