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Re: [csswg-drafts] [css-values] Ability to address actual physical size (#614)

From: Mike Bremford via GitHub <sysbot+gh@w3.org>
Date: Thu, 17 Oct 2019 23:19:08 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-543404142-1571354346-sysbot+gh@w3.org>
Bit late to this. I can't speak for screen output at all, but if you specify units of 1in, 96px or 72pt in the CSS, that is absolutely the length that can - and should - be written to any product creating PDF or PostScript output from CSS.

That is exactly what happens with *all* CSS to PDF products. It's not always the case when printing from browsers, but that's an implementation - not a spec - issue, as is any scaling introduced by the print dialog that means an inch in PDF is not an inch on the page.

But I do need to take issue with this:

> print media is already supposed to anchor on physical sizes. the spec has been saying that for ages.

We initially anchored our CSS-to-PDF engine on points, which worked fine until we came to implement css-transforms. The matrix() transform is unitless, but the translate components have to be treated as pixels. So even as a print-based implementation, we found it simpler to work from pixels. They are defined to be 96 pixels per inch, so are as much as of a physical size as points or cm.

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Received on Thursday, 17 October 2019 23:19:11 UTC

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