Added controls to QuickSettingsPanel to control second subtitles position and delay

[uiryuu]

• I have read CONTRIBUTING.md
• This implements/fixes issues:
  • Make the second subtitle position adjustable #4009
  • Separate control for secondary subtitle delay #4524

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Description:
mpv recently added secondary-sub-pos and secondary-sub-delay options, which enables user to control position and delay separately for primary subtitles and secondary subtitles. This PR implement these two new options by added a SegmentedControl in the QuickSettingsPanel to let user choose from primary or secondary subtitles when adjusting subtitle position and delay.

Note that the other options (e.g. sub-scale) apply to both primary subtitles and secondary subtitles, so they are outside of the NSBox.

Screen.Recording.2024-06-24.at.12.36.33.mov

The layout of the subtitle tab of the QuickSettingPanel also got changed to better illustrate the new feature (before -> after):

[low-batt]

I really like the segmented controls. They look great and should be easy for users to understand.

I pushed a commit to add the segmented control label names to QuickSettingViewController.strings. With that I think this can be merged as is. The next step is to add the corresponding OSD messages for secondary sub position and delay changing like we have for the primary sub.

Need to merge the simple PR #5019 that adds a couple of missing secondary options to watch-later-options.

"Secondary" is the proper term. We should consider changing the menu items that use the term "Second".

And of course subtitle preferences needs some enhancement in this area.

To test this I used the YouTube video 10 Minute Timer (count-up stopwatch) with these two subtitle files:
sub-1.srt.txt
sub-2.srt.txt

I checked RTL:

The messed up label at the end of the delay slider is issue #4895 / PR #4896. That PR is in draft mode because it needs a UI expert to take over from me and solve the last little issue shown in the screenshots in this comment.

[low-batt]

One more related topic. The secondary-sub-pos, like sub-pos has a range of 0% to 150%. IINA tries to limit it to 100%. I believe this is because unlike mpv IINA ties the window size to the video size. I know removing that restriction has been reported in multiple issues, for example #4712. @svobs has looked into this. Anyway, I said "tries" because if you keep pressing the T key you can go past 100%. Given how IINA does not provide a way to have a black border you could move subtitles into I think it makes sense to restrict the sliders to 100%. I only mention this as a reminder of another subtitle feature that could be improved.

[uiryuu]

I pushed a commit to add the segmented control label names to QuickSettingViewController.strings.

Sorry I forgot to do that, and thanks!

And of course subtitle preferences needs some enhancement in this area.

I was unsure of how to design the UI to add secondary subtitles in, so I didn't include that in this PR.

"Secondary" is the proper term. We should consider changing the menu items that use the term "Second".

Besides this, I remember I've heard that the word "subtitle" should always be in plural form, is that correct? Should we enforce that (in the future)?

[low-batt]

It usually is "subtitles" but not always "subtitles".

It is a "subtitle file" as can be seen in the mpv manual entry for the sub-file option:

--sub-files=<file-list>, --sub-file=<filename>
Add a subtitle file to the list of external subtitles.

It is a "subtitle stream" as can be seen in the mpv manual entry for the sid option:

--sid=<ID|auto|no>
Display the subtitle stream specified by <ID>. auto selects the default, no disables subtitles.

The IINA menu items are about selecting a "subtitle stream".

One label that should be changed is the Subtitle tab name in IINA's settings. that should be Subtitles, just like the Subtitles tab on the quick settings panel and the Subtitles menu.

[lhc70000]

Update the styling and also enabled the macOS 13+ NSColorWell.