tree 73ce0d9bef7bf89b17a456f8d5a4c6f0358860b2
parent 8f92feb2de04e3fca8801732848f0085372fa043
author Koji Ishii <kojii@chromium.org> 1539082874 +0000
committer Commit Bot <commit-bot@chromium.org> 1539082874 +0000

Revert "Improve performance of PreviousBreakOpportunity"

This reverts commit 99d504fd35a7e07c4cf16bbbe1464044e2195b4e.

Reason for revert:

crbug.com/883963 bisected to this CL. I'm not sure how this
affects print preview, reverting to see the effect.

This revert may affect LayoutNG performance, but should not
affect the currently shipping line breaker.

Original change's description:
> Improve performance of PreviousBreakOpportunity
>
> In the current layout engine, PreviousBreakOpportunity is used
> only when mid-word break (break-all or break-word), but it is
> much more heavily used in LayoutNG.
>
> LazyLineBreakIterator is designed for forward only.
> PreviousBreakOpportunity is implemented by repeatedly calling
> NextBreakablePosition, but since NextBreakablePosition look
> for the next break opportunity until the end of the string,
> when a very long word without break opportunity is given,
> PreviousBreakOpportunity is O(n!).
>
> This patch changes it to O(n) by limiting the end position
> NextBreakablePosition can look for.
>
> blink/perf_tests/layout/word-break-break-word.html consumes
> 78% of the total time in LayoutNG. The average run is:
>   Current engine:    469ms
>   LayoutNG:       26,644ms
>   This patch:      2,250ms
>
> It's still 4-5 times slower, more improvements will be in
> following patches.
>
> Bug: 636993
> Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
> Change-Id: I814e2c45c8030aa682c7f5e3a3b785b3c0733c84
> Reviewed-on: https://chromium-review.googlesource.com/1095894
> Commit-Queue: Koji Ishii <kojii@chromium.org>
> Reviewed-by: Emil A Eklund <eae@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#567133}

TBR=eae@chromium.org,kojii@chromium.org

Bug: 636993, 883963
Change-Id: I2c453a011208b014e342d7b44646eb90b5b7bbd2
Reviewed-on: https://chromium-review.googlesource.com/c/1270396
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597876}