Freemode repeatedly re-adds classes to slides when scrolling/moving, causing an unnecessary performance penalty

[WesselKroos]

Check that this is really a bug

• I confirm

Reproduction link

https://codesandbox.io/p/sandbox/swiper-default-forked-gx2lnh?file=%2Findex.html%3A63%2C48

Bug description

When freeMode is enabled every scroll(move) event re-adds the active, previous and next classes. This causes a performance penalty because it triggers unnecessary style recalculations on the active, previous and next slides.

Expected Behavior

The active, previous and next classes are only removed or added when necessary:

After.mp4

Actual Behavior

The active, previous and next classes are continuously re-added in every scroll(move) event:

Before.mp4

Swiper version

11.0.7

Platform/Target and Browser Versions

All platforms/targets

Validations

• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.
• Make sure this is a Swiper issue and not a framework-specific issue

Would you like to open a PR for this bug?

• I'm willing to open a PR