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

> Perhaps I should say 'quantization' rather than 'rasterization' as the point is that the glyph outline design (what I just called the '1000 UPM grid') is resolved to a 'css px' grid, that has a varying "resolution", and that grid, not a physical size, is what MUST be targeted - because the actual physical size has been abstracted away, along with ppem raster sizes and real pixels.

And yet it isn't really abstracted away, because there is an actual physical size to a piece of text that is displayed to a reader. There may be difficulties in determining what that size is going to be from an upstream perspective, given the variety of devices, platforms, libraries involved, and there may even be difficulties in determining what that size _is_, given the variety of resolutions involved. But the text is an actual, physical size, which is what the optics of the reader is seeing, and which optical size is supposed to address. If it really can't address that physical size any more, maybe the thing to do — given all those givens — is to throw out the concept of optical size as it is currently understood by type designers and typographers, to throw out all the analogues to size-specific metal fonts, and to instead embrace a more vague, less size-specific concept of 'size tuning' of design: smallest, smaller, small, smallish.... That suggests the possibility of a properly abstracted ‘size’ axis scale like that we have for wght, in which CSS might define what big round number equals 'Smallest' then 'Smaller' etc.. Then we could stop worrying about points and pixels, and just avar map our design spaces to the abstract scale.

>The opsz scale HAS ALREADY been redefined to use 'px' as a unit.

What we disagree about, I think, is the implication of that decision. It isn't just a change to a different unit, but from an absolute, physical unit to an uncertain flexi-unit. Redefining the opsz scale to use px as a unit means redefining it as not optical. Yes, we can say that Mac OS is the oddity in the way it makes a kind of px and a kind of pt equivalent, and hence the size of px on that platform vs other platforms, but I'm not left with any reassurance that it is the only oddity or will remain the only oddity. Once you have a flexi-unit, you really can't make any assumptions or predictions.

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Received on Wednesday, 27 May 2020 21:57:01 UTC