1137588 - Text in vertical writing mode is lower than its containing inline box

Status: RESOLVED FIXED

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

Description

[Xidorn Quan [:xidorn] UTC+10]

Attachment: testcase

See attachment. On Android and B2G, the position of the text in vertical writing mode is a little lower than the inline box containing it. It seems to happen only for upright characters.

Comment 1

[Xidorn Quan [:xidorn] UTC+10]

Attachment: screenshot

Comment 2

[Xidorn Quan [:xidorn] UTC+10]

I suspect that this bug probably causes bug 1136067.

Comment 3

[Jonathan Kew [:jfkthame]]

Yes, that looks likely.

I wonder if this may also be related to the incorrect sizing described in bug 1137582. I'll try to look into this next week, when I'm back from PTO.

Comment 4

[Xidorn Quan [:xidorn] UTC+10]

Though bug 1137582 has been fixed, it seems this bug still exists.

Comment 5

[Jonathan Kew [:jfkthame]]

This appears to be an issue with particular fonts. I can reproduce a it on OS X desktop by explicitly using the Droid Sans Fallback font, for example, or MotoyaLMaru; but TakaoPGothic, in contrast, renders fine.

Comment 6

[Jonathan Kew [:jfkthame]]

Attachment: patch 1 - Read the second array in 'vmtx' correctly to get glyph vertical origins

Turns out there are two bugs here. First, gfxHarfBuzzShaper doesn't read 'vmtx' tables correctly -- it ignores the second (sidebearing-only) array, if present. Fixing this gives us correct results with fonts like MotoyaLMaru, which make use of the monospaced optimization.

Comment 7

[Jonathan Kew [:jfkthame]]

Attachment: patch 2 - Use a better default vOrigin in fonts without real vertical metrics

Second problem is that when no 'vmtx' table is present, we return a vertical origin based on the 'hhea' ascent, which is often too large because we're using the em height as the default advance. Adjusting this gives us a better result with fonts like Droid Sans Fallback that lack any 'vmtx' table.

Comment 8

[Jonathan Kew [:jfkthame]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=174b5f8d4ca3

Comment 9

[Jonathan Kew [:jfkthame]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=1096b81b8847

Comment 10

[Jonathan Kew [:jfkthame]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/44625300e010
https://hg.mozilla.org/integration/mozilla-inbound/rev/986f5faf4655

Comment 11

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/44625300e010
https://hg.mozilla.org/mozilla-central/rev/986f5faf4655