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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: Mon, 08 Jun 2020 18:24:48 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-640795040-1591640687-sysbot+gh@w3.org>
> So you are suggesting that same browser, same page, same font, should invoke different opsz value on different operating systems.

If the resulting actual size of type displayed is different, yes. That's the whole point of opsz instance selection, it should be as close as possible to the optical size of the text displayed. As Myles pointed out early in the thread, the actual size of the same nominal size text does display at different sizes on different platforms, and displays larger on Mac than on Windows. What platforms are _supposed_ to do with the point unit scale of opsz is to translate to that from whatever scale they use internally to size type, and select an appropriate instance, and since a CSS pt is not necessarily equivalent to the physical point of the opsz scale, that means simply passing CSS pt values to opsz isn't always the appropriate thing to do. So what Apple are doing makes sense because, on their platform, 16 opsz units is the correct selection for the size at which they display 12 CSS pt text. If another platform is displaying 12 CSS pt text at something close to 12 physical points, then that platform should be using the 12 opsz instance. The specified size of the text is the same, but the platforms are differently scaling the type and hence need to use different methods to select an appropriate opsz instance.

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Received on Monday, 8 June 2020 18:24:50 UTC

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