BTW, this bug is the cause of the following WPT:

https://github.com/w3c/web-platform-tests/blob/master/css/css-text-3/white-space/pre-wrap-002.html

It passes when loaded in Gecko/Firefox and Webkit/Safari

I think you meant 'word-break: break-all' applied to the div? I can then reproduce in the current layout engine but not with LayoutNG.

We should probably import these tests too.

Attached a new test case to reproduce the bug.

Deleted: pre-wrap-bug.html 267 bytes

pre-wrap-bug.html 267 bytes View Download

Thank you for the updated test. Confirmed in Canary, and confirmed this was fixed in LayoutNG.

Given this is fixed in LayoutNG and we expect the switch isn't too far, I'm not planning to work on this. But if anyone wants to work on, or have reasons to raise the priority, I'd be happy to hear/advice/review. I guess this is about break-after-space mode, which isn't the first class citizen in the current line breaker, but we refactored in LayoutNG. The fix shouldn't be too hard.

I'm planning to work on this now.

Thank you!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3c9ddfebad716cd1aed2386175bdd1870efa0217

commit 3c9ddfebad716cd1aed2386175bdd1870efa0217
Author: Javier Fernandez <jfernandez@igalia.com>
Date: Tue Nov 13 10:43:28 2018

[css-text] Skip trailing spaces for pre-wrap even if word can be broken

According to the specs, preserved white-spaces should hang, or visually
collapse, when white-space is set to pre-wrap; even if word-break allows
breaing the word at any point.

https://www.w3.org/TR/css-text-3/#line-break-details

Bug:  768363 
Change-Id: I7ab356ed6f789ecef087ff469ad97c50e7af49be
Reviewed-on: https://chromium-review.googlesource.com/c/1318694
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Javier Fernandez <jfernandez@igalia.com>
Cr-Commit-Position: refs/heads/master@{#607550}
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/TestExpectations
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/editing/deleting/delete-across-editable-content-boundaries-2.html
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/external/wpt/css/css-text/white-space/pre-wrap-002.html
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/platform/linux/editing/style/table-selection-expected.png
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/platform/linux/editing/style/table-selection-expected.txt
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/platform/linux/fast/forms/textarea/basic-textareas-expected.png
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/platform/mac/editing/style/table-selection-expected.png
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/platform/mac/editing/style/table-selection-expected.txt
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/platform/win/editing/style/table-selection-expected.png
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/platform/win/editing/style/table-selection-expected.txt
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/WebKit/LayoutTests/platform/win/fast/forms/textarea/basic-textareas-expected.png
[modify] https://crrev.com/3c9ddfebad716cd1aed2386175bdd1870efa0217/third_party/blink/renderer/core/layout/line/breaking_context_inline_headers.h

This issue should be FIXED now.