<rdar://problem/146993999>

Tim notices that 292089@main doesn't fix the failures in LayoutTests/imported/w3c/web-platform-tests/css/css-anchor-position/position-try-order-position-area.html LayoutTests/imported/w3c/web-platform-tests/css/css-anchor-position/position-try-order-basic.html Then the test got changed (https://github.com/web-platform-tests/wpt/commit/08aa9091e58d0c9c7b3f653c795cd80f8718bfdc) so now they pass in WebKit. But the test change removed some cases that quite possibly, removed cases that WebKit failed. So needs more investigation here.

Analysis of WPT Failures Part 1! https://wpt.fyi/results/css/css-anchor-position?label=experimental&label=master&aligned anchor-animation-dynamic-name - Passes on trunk. anchor-center-fallback-transition-behavior - Seems to be an incorrect test? anchor-function-pseudo-element-basic - Passes on trunk. anchor-function-pseudo-element-implicit-anchor - Passes on trunk. anchor-getComputedStyle-002 - Fragmentation (multicol, inline) bug. (A,B) anchor-ident-function - Testing ident() function. Also other stuff that should be split out. anchor-name-inline-002 - Passes on trunk. anchor-name-multicol-* - Multicol bug. (A) anchor-position-borders-002 - Scrollbar gutter calculation bug. (C) anchor-position-flip-sibling-index - Testing sibling-index() function. anchor-position-grid-001 - Multicol bug. (A) anchor-position-inline-00[123] - Passes on trunk. anchor-position-inline-004 - Multicol bug. (A) anchor-position-multicol-* - Multicol bug. (A) anchor-position-sibling-index - Testing sibling-index() function. anchor-position-top-layer-* - Top layer bug. (D) anchor-scope-scroll - Off-by-one anchor-scope bug. (E) anchor-scope-shadow-names - ::part() names not scoped correctly. (F) anchor-scroll-003 - Multicol bug. (A) anchor-scroll-004 - Inline abspos containing blocks break stuff. (G) anchor-scroll-006 - No scroll adjustment for fixedpos anchored boxes. (H) anchor-scroll-007 - No scroll adjustment for fixedpos multi-anchored boxes. (H) anchor-scroll-chained - No scroll adjustment when anchored to scroll-adjusted anchored box. (I) anchor-scroll-fixedpos - No scroll adjustment for fixedpos anchored boxes. (H) anchor-scroll-js-expose - Element.offset*, IntersectionObserver not updated for scroll. Missing features unrelated to anchor positioning that cause us to fail tests in this directory: - ident() - sibling-index() Bugs related to anchor positioning that cause us to fail tests in this directory: A. Multicol fragmentation is not handled correctly. B. Inline fragmentation is not handled correctly? C. Non-overlay scrollbars unaccounted for in anchor() calculations. D. Anchoring relationships across top-level layers not handled correctly. E. Off-by-one error for anchor-scope: same element can name and scope to descendants. F. Names declared on ::part() not scoped to match light DOM slotted elements. G. Inline abspos containing blocks cause several miscalculations: - The positions of the anchored boxes are wrong. - They attach to the wrong element (always the last one) when multiple anchors share an anchor name. H. Anchored boxes with 'position: fixed' aren't scroll-adjusted. I. Boxes anchored to an anchored box that is scroll-adjusted aren't scroll-adjusted along with their anchor. J. Element.offset* is not updated by scroll-adjustments. K. IntersectionObserver is not fired when scroll-adjustment changes visibility. Other bugs noticed during triage: - anchor-scope changes don't cause style/layout invalidation, but should.

Analysis of WPT Failures Part 2! https://wpt.fyi/results/css/css-anchor-position?label=experimental&label=master&aligned anchor-scroll-position-try-* - Scrolling doesn't trigger fallback for anchor(). (J) anchor-scroll-to-sticky-00[34] - Anchored box painted underneath scrollbars in sibling. (K) anchor-scroll-update-003 - Seems to pass on trunk. anchor-scroll-update-00[56] - Zero-height anchor treated as invisible. (L) Also test seems to be wrong? anchor-scroll-update-007 - Seems to pass on trunk. anchor-transition-focus - Seems to pass on trunk. anchor-transition-name - Seems to pass on trunk. at-position-try-cssom - Seems to pass on trunk. last-successful-* - Successful option not remembered across style change. (M) popover-implicit-anchor - WPT harness failure. Test actually seems to pass on trunk. position-area-inline-container - Inline containing blocks not supported. position-area-pseudo-element-implicit-anchor - Passes on trunk. position-area-scrolling-00[123].tentative.html - Paints correctly, unsure about offset*. (O) position-area-scrolling-00[567].html - Container, not scrollable area, needs to trigger fallbacks. (P) position-try-backdrop - position-try on ::backdrop not supported. (Q) position-try-cascade-layer-reorder - @position-try changes don't invalidate correctly. (R) position-try-cascade - revert-layer should revert the @position-try origin only (S) position-try-container - container query height fails to cycle back into position-try fallback choice (T) position-try-fallbacks-003 - Fallback not triggered by scrolling CB. (P) position-try-grid-001 - anchor() fails to account for grid area (U) position-try-ident-function - Requires support for ident(). position-try-pseudo-elements - position-try not supported on ::before/::after (V) position-try-switch-to-fixed-anchor - fixed position scrolling not handled (H) position-try-tree-scoped - Open shadow DOM fails to inherit @position-try (W) position-visibility-anchors-valid - 'position-visibility: anchors-valid' unsupported (ZB) position-visibility-anchors-visible-chained - Chained visibility change invalidation failure (Z) position-visibility-anchors-visible-change-anchor - Change invalidation failure (Z) position-visibility-remove-*no-overflow* - 'position-visibility: no-overflow' unsupported (ZA) position-visibility-anchors-visible-with-position - Seems to be an incorrect test? position-visibility-remove-anchors-visible - Seems to be an incorrect test? transform-00*.tentative - Anchor rect fails to account for anchor transforms. (X) try-tactic-position-area - Need to simplify position-area serialization. (Y) Bugs related to anchor positioning that cause us to fail tests in this directory (continued): J. Scrolling the anchor doesn't trigger fallback when needed for anchor()-positioned box whose containing block is scroller. (Related to P.) K. Anchoring a box to the child of a sibling scroller paints it underneath that scroller's scrollbars. L. Zero-height anchors treated as invisible even if within visible range. M. Earlier try options are ignored if a previous layout attempt adopted a successful option further down the list. N. Inline absolute positioning containing blocks not supported. O. Tests check offsetTop/Left/Width/Height, but unclear these should change. P. Scrolling doesn't trigger fallback when needed for position-area box whose containing block is scroller. (Related to J.) Q. Missing support for anchor positioning on ::backdrop. R. @position-try changes don't invalidate and recalculate style correctly. S. revert-layer reverts the top author layer in addition to the position-try origin T. height from container query fails to cycle back into fallback choice U. anchor() functions don't account for grid area insets V. position-try-fallbacks not supported on ::before/::after W. Open shadow roots are unable to see @position-try rules from outer scopes (but correctly ignore inner scopes). X. Test expects anchor rect to reflect anchor box transforms. Y. https://bugs.webkit.org/show_bug.cgi?id=291004 Z. Anchoring a box to an anchored box fails to hide or to invalidate correctly when the original anchor's visibility changes. ZA. 'position-visibility: no-overflow' unsupported ZB. 'position-visibility: anchors-valid' unsupported Other bugs noticed during triage: b. Scrolling the anchor partially out of view causes the anchored box to detach from the anchor. (anchor-scroll-position-try-001) c. Grid area insets don't trigger fallbacks. (position-try-grid variant) Possible spec issues: - Behavior required in J & P might not be well specified, and might conflict with other expecations, see e.g. https://software.hixie.ch/utilities/js/live-dom-viewer/?%3C!DOCTYPE%20html%3E%0A%3Cdiv%20style%3D%22width%3A%20100px%3B%20height%3A%20100px%3B%20border%3A%20solid%3B%20overflow%3A%20scroll%3B%20position%3A%20relative%22%3E%0A%20%20%3Cdiv%20style%3D%22width%3A%20200px%3B%20height%3A%20200px%3B%20background%3A%20aqua%3B%22%3E%3C%2Fdiv%3E%0A%20%20%3Cdiv%20style%3D%22border%3A%20solid%20orange%2010px%3B%20position%3A%20absolute%3B%20top%3A%200%3B%20left%3A%200%3B%20right%3A%200%3B%20bottom%3A%200%22%3E%3C%2Fdiv%3E and position-visibility-anchors-visible-with-position.html