commit e5cfd27e4a082ec75151f98f2ffcc99376b656e8
author Javier Fernández García-Boente <jfernandez@igalia.com> Wed Jan 19 20:13:40 2022
committer Blink WPT Bot <blink-w3c-test-autoroller@chromium.org> Wed Jan 19 20:30:11 2022
tree 22a59fa60889f23634ab0b7370bdeccc2492305f
parent 0b54c5a86bd34917a8114ce57043140deac652b4

Compute the NGLineInfo hang_width even if ignored in text alignment

The NGLineInfo class has an attribute hang_width_ to store the width
of the preserved trailing spaces. Theoretically, this value is intended
to be used during text alignment, following the rules discussed and
resolved in the CSS WG issue 3440 [1]. In this issue it's been
discussed how to handle end-of-line pre-wrap spaces, which may hang and
could affect the final result of the text alignment.

However, we also use the NGLineInfo's attribute to compute the line
box's inline size, as part of the NGInlineLayoutAlgorithm::CreateLine
logic. Since we ignore the hanging spaces when using 'center'
alignment, we don't compute it; this leads to an incorrect inline size
of the fist line in the test case described in the bug 782638, which
incorrectly overflows the box's fixed size, causing the scrollbar to be
activated when it shouldn't.

Since we always compute the hang_width now, we need to consider it also
in the case of RTL scenarios, where we were assuming it was ignored
depending on certain values of the text alignment. In order to avoid
regressions, this CL also simplifies the line_box's inline_size
computation performed in the CreateLine function, ignoring for now the
text direction, we always subtract the hang_width

Then, the inclusion or not of the hang_width will be decided where it
should; the function NGInlineLayoutAlgorithm::ApplyTextAlign is the one
responsible of implementing the rules agreed in the CSS WG issue
mentioned before.

https://github.com/w3c/csswg-drafts/issues/3440

Bug: 782638, 1278559
Change-Id: Ib1950533169fb9cabc6b7bb9e6925451eff2a767
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3360876
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Javier Fernandez <jfernandez@igalia.com>
Cr-Commit-Position: refs/heads/main@{#961084}