1882790 - Optimize bidi resolution where possible

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, enhancement)

Description

[Jonathan Kew [:jfkthame]]

Profiling and reading the nsBidiPresUtils code, I've noticed some minor inefficiencies that we can improve; patches incoming.

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1882790 - Cleanup and optimize BidiLineData handling. r=#layout-reviewers

We don't need to explicitly drop bidi-control frames from the original list in BidiLineData,
and make the corresponding updates to the Levels and IndexMap arrays; instead, we can just
skip over them when building the VisualFrames array.

Also, in nsBidiPresUtils::ReorderFrames we don't need a BidiLineData at all if there's only
a single frame on the line; we can just call RepositionFrame directly.

Comment 2

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1882790 - Use a custom ReplaceSeparators function in place of nsString::ReplaceChar during bidi resolution. r=#layout-reviewers

In nsBidiPresUtils::ResolveParagraph, we replace any block or segment separators
with space characters before bidi resolution. The use of nsString::ReplaceChar
here can appear in profiles, so it seems worth having a custom accelerated version
to handle the fixed set of separator codes. My local testing indicates this runs
between 5 and 10 times faster than the general-purpose function that has to
iterate over the provided set of characters at runtime.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6e0be8c8b999
Cleanup and optimize BidiLineData handling. r=layout-reviewers,emilio
https://hg.mozilla.org/integration/autoland/rev/ccd673b111a7
Use a custom ReplaceSeparators function in place of nsString::ReplaceChar during bidi resolution. r=layout-reviewers,emilio

Comment 4

[Norisz Fay [:noriszfay]]

Backed out for causing build bustage on nsBidiPresUtils.cpp

Backout link

Push with failures

Failure log

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/cb08b842d8fd
Cleanup and optimize BidiLineData handling. r=layout-reviewers,emilio
https://hg.mozilla.org/integration/autoland/rev/300643546ea8
Use a custom ReplaceSeparators function in place of nsString::ReplaceChar during bidi resolution. r=layout-reviewers,emilio

Comment 6

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/cb08b842d8fd
https://hg.mozilla.org/mozilla-central/rev/300643546ea8