Usually in text processing context RTL means “right-to-left language”, i.e. Arabic, Farsi, Hebrew, … RTL is an intrinsic property provided:
- text is correctly flagged (with a language attribute in Writer)
- or an adequate Unicode font is used and characters are taken from the appropriate script blocks (which excludes converted legacy fonts where “exotic” glyphs are stored in the Private Use Area)
This also excludes .txt files using ISO-8859-x encoding because these encodings are ambiguous unless some hints are also explicitly given.
Please, edit your question to give more information about your intent. As usual, don’t forget to mention OS name and LO version.