1659258 - Ensure that SetupFamilyCharmap always sets the mCharacterMap pointer

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect, P2)

Description

[Jonathan Kew [:jfkthame]]

Currently if SetupFamilyCharmap finds a face that is lacking a shared-cmap record, it bails out, leaving the family's charmap unset. This is bad because we will then repeatedly try to set the family's charmap during font fallback searches, killing performance.

Instead we should ensure we always set the family charmap, even if we're setting it to empty because all the faces had broken/unusable cmaps; this just means the family will be skipped during searches, which is fine -- it doesn't have any faces we can actually use.

(This can happen on Linux where fontconfig may expose fonts in legacy formats that don't actually have cmap tables. We probably want to exclude these from the font list earlier if we can do so reliably, but in any case fixing SetupFamilyCharmap means they won't cripple fallback searches.)

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1659258 - Ensure that SetupFamilyCharmap always sets the mCharacterMap pointer, even if empty, so that we don't repeatedly call it for fonts we can't actually use. r=jwatt

Depends on D87175

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/92b5dfe764cc
Ensure that SetupFamilyCharmap always sets the mCharacterMap pointer, even if empty, so that we don't repeatedly call it for fonts we can't actually use. r=jwatt

Comment 3

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/92b5dfe764cc