[Webkit-unassigned] [Bug 96470] [Chromium] Japanese characters should not be rotated in vertical writing-mode and text-rendering:optimizelegibility

Wed Sep 12 09:55:39 PDT 2012

https://bugs.webkit.org/show_bug.cgi?id=96470

--- Comment #1 from Koji Ishii <kojiishi at gmail.com>  2012-09-12 09:56:04 PST ---
Thank you for putting this bug, I noted complex path is not supported in bug 51450 but didn't put a bug to track it further.

I had some discussions with Bashi and Takuya, but didn't share with anyone else, sorry about that. Here it is.

Linux and Windows have different restrictions. On Windows, Chrome and Safari uses Uniscribe for complex code path. Unfortunately, Uniscribe doesn't support vertical flow, nor MS has any plans to do so in future. Uniscribe is deprecated and MS's plan is for DirectWrite to support both shaping and vertical flow.

So, if we want to fix this now using GDI-based code base, we could modify complex path to two paths by code points; one for Uniscribe and the other not to use Uniscribe, but the ideal solution is to look into this after we have moved to DirectWrite.

On Mac, Core Text supports both shaping and vertical flow, but it has a bug when both are used. Given it's not working properly on Mac either, and given the low demand for the combination of vertical flow in complex code path, I prefer waiting for the move to DirectWrite to complete.

Linux has similar but slightly different situation; harfbuzz doesn't support vertical flow today, but it's an open source and we could fix this. If I understand correctly, the move to harfbuzz-ng is going on. I quickly looked at harfbuzz-ng and I believe it's not too hard to add vertical flow feature to harfbuzz-ng. But since the move isn't done yet, again, I guess waiting for the move and work on harfbuzz-ng after the move looks more reasonable to me.

Does this sound reasonable?

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