Fix RTL punctuation marks issues with mixed BiDi subtitles

[orenskl]

This PR fixes the punctuation marks issues with subtitles text containing a mix of RTL and LTR languages.

https://github.com/google/ExoPlayer/issues/11214 https://github.com/jellyfin/jellyfin-androidtv/issues/4296

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[orenskl]

Hi, thanks for the comments.

This is a standard SRT file that can be used to reproduce this issue (just rename to srt if needed):

subtitles.txt

Here are some examples:

These lines are displayed as:

should be displayed as:

These lines are displayed as:

Should be displayed as:

You can notice that the punctuation marks are displayed to the right of the sentences and should be displayed to the left (as in all RTL languages). Hope you are good with Hebrew :-)

[icbaker]

Thank you for the test file and screenshots, that's really helpful.

I took your SRT file and adapted it to WebVTT so I could add some styling (borrowed from one of our test files), and confirmed that this PR currently strips styling info.

Using this file (just rename to .vtt suffix): vtt-2553.txt

Compare before your change (styling visible, punctuation in the wrong place):

With after (styling lost, punctuation in the correct place):

---

Please take a look and see if you can tweak this PR so it puts the punctuation in the correct place while preserving (or restoring) the span styling.

[orenskl]

I was able to reproduce the styling issues with the VTT file on my side, I think the best option here will be to manipulate the cues and then restore the original spans with the indices fixed. I am working on this.

[orenskl]

Hi, is there anything I can do to help you merge this PR ?

[icbaker]

Thanks for pinging, I was waiting for the tests and didn't realise they'd already been added (I think just 'resolving' a conversation on GitHub maybe doesn't trigger an email - so I didn't know to look back here) - I'll take another look.

[icbaker]

I'm going to send this for internal review now. You may see some more commits being added as I make changes in response to review feedback. Please refrain from pushing any more substantive changes as it will complicate the internal review - thanks!