How to handle mixed left-to-right and right-to-left text?

[slouken]

If you have a string with "some latin chars ... some arabic chars.. " you probably have to use multiple fonts, but also change left-to-right and right-to-left rendering.

Also, beside LTR/RTL, you may also want to change style (italic bold etc), size, breaking, hyphenation, or justification

interesting links:

Unicode Bidirectional Algorithm: https://www.unicode.org/reports/tr9/

What HarfBuzz doesn't do: https://harfbuzz.github.io/what-harfbuzz-doesnt-do.html

Originally posted by @1bsyl in #362

[slouken]

More information on using ICU to handle this:
https://unicode-org.github.io/icu-docs/apidoc/released/icu4c/ubidi_8h.html#details

[slouken]

So you can potentially implement this on top of the SDL_ttf 3.0 API, using text objects and TTF_SetTextPosition() to align them correctly.

[slouken]

I've updated SDL_ttf's right-to-left language support. It doesn't do the full BiDi algorithm, but if you've split your text into multiple single-direction runs it should handle them correctly. You can call TTF_SetTextDirection() to explicitly set the direction if you're using text objects, but if you've split them properly HarfBuzz should be able to detect the correct flow direction.