1533448 - Create a shared-memory-friendly version of gfxSparseBitSet to store font character coverage

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, enhancement, P3)

Description

[Jonathan Kew [:jfkthame]]

gfxSparseBitSet is not suited to storing in shared memory, because of its use of nsTArray<> members. For the cross-process font list, we want to store character coverage data in the shared memory, so it will be useful to have an object like gfxSparseBitSet, but designed to be usable regardless of the address where it is mapped.

For simplicity, the SharedBitSet introduced here will be frozen once initialized, unlike gfxSharedBitSet which can be updated with set()/clear() operations. The intention is to use gfxSharedBitSet as an accumulator while reading the character coverage info for a font (as we currently do), and then "snapshot" the result into a frozen SharedBitSet for storage in the shared font list.

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1533448 - Provide a version of gfxSparseBitSet that is better suited to shared-memory use. r?jwatt

Depends on D22935

Comment 2

[Jonathan Kew [:jfkthame]]

(This is migrated from patch 8 in bug 1514869.)

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

There's a r+ patch which didn't land and no activity in this bug for 2 weeks.
:jfkthame, could you have a look please?

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/cfbec1b8ef40
Provide a version of gfxSparseBitSet that is better suited to shared-memory use. r=jwatt

Comment 5

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/cfbec1b8ef40