833297 - ensure graphite shaper does not overwrite cluster information

Status: RESOLVED FIXED

(Core :: Graphics: Text, defect)

Description

[Jonathan Kew [:jfkthame]]

Discovered through word/line-breaking reftests with a font configuration where fallback chooses a graphite font for combining marks that are not supported in the main font. When deciding whether to use a 'simple' glyph record, the shaper needs to check that the non-cluster-start flag has not been set at the current position in the shaped text; if it's a cluster continuation, then we must not overwrite it with a simple glyph.

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: patch, check that we're at a cluster start before using a simple-glyph record

Comment 2

[John Daggett (:jtd)]

r+ with the inclusion of a reftest for this case

Comment 3

[Jonathan Kew [:jfkthame]]

Attachment: reftest for preserving clusters across font-shaping boundary with graphite

Reftest for the issue here; without the patch, it will incorrectly line-break before the combining marks (when graphite shaping is enabled).

Comment 4

[Jonathan Kew [:jfkthame]]

Attachment: reftest for preserving clusters across font-shaping boundary with graphite

And now with HTTP(..) in the manifest, so that it will actually load the intended fonts (oops!)

Comment 5

[Jonathan Kew [:jfkthame]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/011d0b0befdc
https://hg.mozilla.org/integration/mozilla-inbound/rev/363a34802aef

Comment 6

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/011d0b0befdc
https://hg.mozilla.org/mozilla-central/rev/363a34802aef