commit e1400ef4581676b52364c3c7b9587c705c564ab9
author Yoshifuim Inoue <yosin@chromium.org> Fri Dec 02 07:05:51 2022
committer Blink WPT Bot <blink-w3c-test-autoroller@chromium.org> Fri Dec 02 07:20:40 2022
tree e19f3019aa668d6bdb782c7f46bbce49a6985426
parent 8646f9fc564439fe5c7582ce5d73a86427a57cf2

[initial-letter] Use baseline alignment for drop, raise, sunken initial

This patch changes `ComputeInitialLetterBoxBlockOffset()` to use
baseline alignment instead of line-under alignment when initial-letter
size >= sink, e.g. `initial-letter: 3 drop`, `initial-letter: 3 raise`,
`initial-letter: 3 2` to match the spec[1][2].

This patch also introduces new test:
 `initial-letter-text-decoration-underline.html`
for verifying baseline alignment and underline for the open issue
887[5].

# Details

The spec says[2]:

If its size is greater than or equal to its sink, the initial letter is
positioned to satisfy its under alignment, and then shifted by
--------------------------^^^^^^^^^^^^^^^
(sink - 1) × line-height of containing block towards the containing
block’s block end.

The spec says[3]:

This property specifies the alignment points used to size and position
an initial letter. Two sets of alignment points are necessary:
the over and under alignment points of the initial letter are matched to
-------------^^^^^^^^^^^^^^^
corresponding over and under points of the root inline box.

Before this patch, Blink uses "line-under"[4], the link is pointed to.
After this patch, Blink uses "baseline" as
`initial-letter-align: alphabetic`[1].

[1] https://drafts.csswg.org/css-inline-3/#valdef-initial-letter-align-alphabetic
[2] https://drafts.csswg.org/css-inline-3/#initial-letter-block-position
[3] https://drafts.csswg.org/css-inline-3/#aligning-initial-letter
[4] https://drafts.csswg.org/css-writing-modes-4/#under
[5] https://github.com/w3c/csswg-drafts/issues/887

Bug: 1276900
Change-Id: I99e0b535f13350856187a5d2af8136c7eef78f80
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4067085
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1078467}