1994193 - Try to avoid applying per-glyph Spacing adjustments if they are known to all be zero

Status: RESOLVED FIXED

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

Description

[Jonathan Kew [:jfkthame]]

If the TEXT_ENABLE_SPACING flag is set, but we are able to determine that all the values we computed in the spacing array turned out to be zero, we may be able to optimize measurement/drawing slightly by skipping the application of these values.

This is particularly relevant when the text-autospace property is enabled, as this will force spacing values to be computed for many text frames that previously were able to omit the TEXT_ENABLE_SPACING flag and skip all this processing.

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1994193 - Try to skip applying spacing if all values are zero. r=#layout

No behavior change is expected; this is just skipping some work
when we know it would be a no-op.

Comment 2

[Jonathan Kew [:jfkthame]]

Not sure if this will visibly move the needle on any of the reported text-autospace perf regressions (e.g. bug 1991421), but it seems worth doing in general.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/f4ed96250592
https://hg.mozilla.org/integration/autoland/rev/6ed83aef5a49
Try to skip applying spacing if all values are zero. r=layout-reviewers,TYLin

Comment 4

[Serban Stanca [:SerbanS]]

Reverted this because it was causing assertion failures in nsTextFrame.cpp.

• Revert link
• Push with failures
• Failure Log
• Failure line: Assertion failure: aISize >= 0 (unexpected negative hangable advance), at /builds/worker/checkouts/gecko/layout/generic/nsTextFrame.cpp:X

Also, please check these wpt failures.

• Failure Log

Comment 5

[Jonathan Kew [:jfkthame]]

The failures were from bug 1994197, which landed in the same push; this should be fine by itself, so re-landing.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/f86d3e5a2b91
https://hg.mozilla.org/integration/autoland/rev/3e11bcb731df
Try to skip applying spacing if all values are zero. r=layout-reviewers,TYLin

Comment 7

[Cristina Horotan [:chorotan]]

https://hg.mozilla.org/mozilla-central/rev/3e11bcb731df