feat: Align local video/subtitle split by source aspect ratio on drop and theater toggle

[khajiitvaper2017]

This PR improves local playback layout when dropping a video + subtitle file.

On drop, the app reads source video metadata and initializes the split so the video pane matches the video aspect ratio as closely as possible, maximizing visible video area and reducing black side bars.

The same one-time recalculation also runs when Toggle Theater Mode changes layout (app bar hidden/shown), so split initialization stays correct after theater mode transitions.

After initialization, manual subtitle panel resizing remains user-controlled.

2026-03-01.23-09-06.mp4

[killergerbah]

Thanks for doing this but it's not really obvious to me that this behavior would benefit everyone. I think some users would like the subtitle list to be a certain size and for the app to remember that. I'm open to alternate solutions if you can think of any.

[khajiitvaper2017]

Thanks for doing this but it's not really obvious to me that this behavior would benefit everyone. I think some users would like the subtitle list to be a certain size and for the app to remember that. I'm open to alternate solutions if you can think of any.

Add setting like "Video-Subtitle Split Behavior" with options: "Remember my split position" or "Auto-maximize video"?

[killergerbah]

Add setting like "Video-Subtitle Split Behavior" with options: "Remember my split position" or "Auto-maximize video"?

I see, yeah a setting feels like the natural way to do this. My preference would be to default to "Remember my split position".

Only other alternative I can think of is to add a new button to the video player or subtitle list but I don't know if there's a suitable icon for the button and where it makes sense to put it.

[khajiitvaper2017]

Add setting like "Video-Subtitle Split Behavior" with options: "Remember my split position" or "Auto-maximize video"?

I see, yeah a setting feels like the natural way to do this. My preference would be to default to "Remember my split position".

Added the setting.

[khajiitvaper2017]

fixed scrollbars appearing on video player when toggling theater mode

[killergerbah]

Why was this added to subtitles.css?

[khajiitvaper2017]

When theater mode was toggled back on, the iframe document was ending up a bit taller than the viewport, so the browser showed a scrollbar. This problem is also present on live app, This fixes it.

[khajiitvaper2017]

Though it's mostly visible when using yarn run start, when using preview, it's rare

[khajiitvaper2017]

I kept only one overflow: hidden;, should be enough to fix this.

[killergerbah]

Can this be addressed in a separate change then? It doesn't seem critical to fix, if it is only dev-facing. Also, I'm not completely convinced it's the right fix, if it's really the iframe that's taller then setting overflow to hidden would just hide the part of the iframe that's overflowing.

[khajiitvaper2017]

Sure, feel free to remove it, just didn't seem to be worthy of separate pull request. In my first post's video you can see scrollbars appearing for a split second when toggling theater mode, that's what I am addressing. On live version this problem also exists but layout changes faster than scrollbar can appear and it jerks a little instead.

2026-03-23.20-42-49.mp4

I tried to log it and for some reason, htmlScrollHeight is taller than viewport:
bodyClientHeight = 847
bodyScrollHeight = 847
htmlClientHeight = 847
htmlScrollHeight = 865
If you can find anything better than just slapping overflow: hidden;, that would be great.