Swiper Pagination Dynamic Bullets work incorrectly when loop is enabled

[electrodrel]

Check that this is really a bug

• I confirm

Reproduction link

https://codepen.io/electrodrel/pen/VwEaKGE

Bug description

Pagination bullets are shifting to the left when looped if dynamicBullets option is enabled. It happens even if the number of slides are smaller than the value of dynamicMainBullets parameter (see the demo). The shifted dots on the left are 'converted' to the dynamic (smaller dots) making the whole pagination look off.

From my quick investigation, something is incorrect in the offset calculation once the slides are looped over and thus rearranged. Here is the place where I suspect something is off:

swiper/src/modules/pagination/pagination.js

Lines 201 to 209 in f146726

	if (params.dynamicBullets) {
	const dynamicBulletsLength = Math.min(bullets.length, params.dynamicMainBullets + 4);
	const bulletsOffset =
	(bulletSize * dynamicBulletsLength - bulletSize) / 2 - midIndex * bulletSize;
	const offsetProp = rtl ? 'right' : 'left';
	bullets.forEach((bullet) => {
	bullet.style[swiper.isHorizontal() ? offsetProp : 'top'] = `${bulletsOffset}px`;
	});
	}

Possibly, the midIndex is incorrectly calculated in the loop mode.

Expected Behavior

When looped over the pagination bullets they should not shift to any side and stay centred, just like when dynamicBullets is off:

Screen.Recording.2023-04-14.at.4.39.32.PM.mov

Actual Behavior

After the first loop is done, the dots shift to the left side, and the shifted dots are rendered as the 'dynamic' ones even though the number of slides is less than the dynamicMainPoints

Screen.Recording.2023-04-14.at.4.41.48.PM.mov

Swiper version

9

Platform/Target and Browser Versions

macOS, Chrome, Firefox

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