twbs / bootstrap / 28537402743

94%

main: 96%

Build Type

push

github

Committed by web-flow

Commit Message

ScrollSpy: deterministic active-section detection (#42557)

* ScrollSpy: deterministic active-section detection

Replace the scroll-direction + sequential-offsetTop heuristic (which
depended on IntersectionObserver entry order and mis-highlighted when
several sections shared the viewport) with a deterministic geometric
model: the active section is the deepest one whose top has scrolled to
or above an activation line near the top of the scroll root, read fresh
from getBoundingClientRect on each (rAF-throttled) scroll. At the bottom
the last section wins; above the first nothing is active.

Also: settle on scrollend (with a scroll-idle fallback) to restore the
URL hash via replaceState and move focus to the target after a
smooth-scroll navigation; escape section ids via parseSelector so dotted
/special-character ids no longer throw; add a topMargin option for the
activation line.

Supersedes #41016. Fixes #37858, #39198, #39248, #36387, #40526.

* docs wip

* rewrite more, add debugger to docs to illustrate

* missing test file

* ScrollSpy: fix CI — cspell, bundlewatch, branch coverage

- Add 'Fpath' to the cspell dictionary (from the #%2Fpath encoded-id example)
- Bump the four JS bundlewatch thresholds for the rewritten ScrollSpy
- Add option-derived activation-line tests (topMargin %/px, derived rootMargin
  with/without a scroll root, non-numeric topMargin, explicit rootMargin,
  overflow state, observer rebuild no-op, resize listener add/remove) to lift
  branch coverage from 88.63% back over the 89% threshold (now 89.21%)

* Skill: add ScrollSpy migration section to match the guide

Mirror the migration.mdx ScrollSpy changelog in the migration skill:
IntersectionObserver rewrite / activation line, removed offset+method
options, new topMargin, rootMargin default null, threshold default [0],
smoothScroll hash+focus restore, and getElementById id resolution.
Keeps the skill and guide consistent as this PR lands ScrollSpy.

Coverage Stats

1075 of 1205 branches covered (89.21%)

Branch coverage included in aggregate %.

162 of 168 new or added lines in 1 file covered. (96.43%)

1 existing line in 1 file now uncovered.

3018 of 3142 relevant lines covered (96.05%)

257.13 hits per line