Subtitles are moved off screen when using pan&scan feature

Mpv will move subtitles off screen (partially) if pan&scan feature is used (obviously, with not burned-in subtitles such as DVD subtitles).

This is annoying for example with DVDs, played on an ultrawide monitor.

Important Information

• mpv 0.35.1-dirty Copyright © 2000-2023 mpv/MPlayer/mplayer2 projects
• Arch Linux - mpv from extra
• mpv binary from [extra] in official Arch repositories

Reproduction steps

Play a video with not-burned-in subtitles (such as DVD subtitles), encoded with black bars (letterboxed). Use Pan&scan.

Expected behavior

Subtitles should always stay on screen. Pan&Scan should not affect their position on screen, but their position should be handled separately.

Actual behavior

Subtitles are always shown in relation to the original video dimensions. They will move off screen (partially), if video is zoomed.

Log file

When playing a DVD backup, selecting English audio, Finnish subtitles, and then fast forwarding to a part with subtitles to, I get:

Log: https://0x0.st/HqOA.txt
Screenshot: https://0x0.st/HqOm.png

Possibly related:

Issue #11705

This issue could affect all platforms.

Workaround:

Press 'r'. Or 'SHIFT+r' if subtitles are too high up.

I didn't find that out before I had typed out this bug report!

Other notes:

Most content in wider than 16:9 aspect ratios, such as 2.35:1, are (sadly) encoded letterboxed. When played back on ultrawide displays they will display black areas all around. It is much desired to zoom into the picture so that there are no black bars all around.

However, the last points are irrelevant - the subtitles should not "move" in relation to screen borders when zooming in, even if zooming on a display matching the expectations of the letterboxing.

IIRC this issue has been reported and was fixed a long, long time ago, it may have even been in mplayer before mpv was a thing. If so, this could be a regression.

Start by reproducing the issue with DVD subtitles on a letterboxed video, then apply pan&scan and compare subtitle placement with the screen borders. Use the linked log and screenshot for context; done means subtitles remain fully on screen and their placement is not shifted by pan&scan.