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Re: [csswg-drafts] [css-fonts] Proposal to extend CSS font-optical-sizing (#4430)

From: John Hudson via GitHub <sysbot+gh@w3.org>
Date: Wed, 03 Jun 2020 04:09:04 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-637940257-1591157343-sysbot+gh@w3.org>
@frivoal The same document that defines these 'absolute lengths' goes on to say that 
> All of the absolute length units are compatible, and px is their canonical unit.
From which I take it that the actual size of any of these units is ultimately dependent on the size of px, and that can vary quite a lot.

The concept of px is really nice — it's something close to the concept of measuring visual angle, since it ostensibly takes into account viewing distance—, but interpretation and implementation seems more varied than needed for size-specific design for text. Hence, earlier in the thread, I was suggesting that _if_ we were to redefine the unit scale of the opsz axis, we would need to more precisely define it than CSS px seems to be defined, and in effect that means locking in a standard viewing distance, such that one could say e.g. the unit is 1/96 of a standard/industrial/physical inch or, as Nick suggests, a degree of visual angle at that standard distance. That's what we need to be able to do the type design work. If we don't have something that precisely defined, then we're not doing size-specific type design any more.

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Received on Wednesday, 3 June 2020 04:09:06 UTC

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