1471584 - Avoid using a virtual call within gfxHarfBuzzShaper::HBGetGlyphHAdvance

Status: RESOLVED FIXED

(Core :: Graphics: Text, enhancement, P3)

Description

[Jonathan Kew [:jfkthame]]

This is a very hot function when doing text layout -- it's called for every glyph the shaper processes. Currently, it calls the gfxFont's ProvidesGlyphWidths() method, which is a virtual function, to determine which implementation to use. We should avoid that.

The result of ProvidesGlyphWidths() is already cached in the shaper object, so by just checking that flag instead we can avoid the virtual call here in the inner loop of text shaping.

(The perf benefit will be lost in the noise for normal cases, but with an extreme testcase that involves shaping multiple megabytes of text, I'm measuring a definite improvement in total reflow time, from ~6200ms to ~5950ms.)

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: Micro-optimize text shaping by avoiding an unnecessary virtual method call

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/1b9dcb1b80dd
Micro-optimize text shaping by avoiding an unnecessary virtual method call. r=lsalzman

Comment 3

[Tiberius Oros[:tiberius_oros]]

https://hg.mozilla.org/mozilla-central/rev/1b9dcb1b80dd