[MPEG-OTSPEC] fvar and hoi updated

[Laurence Penney]

WG03-fvar-2024-04.pdf

I’ve done a rewrite, which resolves a few issues.

* "font to use multiple" -> "font to have multiple"
* "user interfaces or API access" -> "user interfaces and API access"
* It was not defined which axis’s range and defaultValue would be used if all axes are hidden.
* To avoid scope issues, I’ve made it all one paragraph.
* Clamping noted last, since it may override what happened with setting default.
* Also added a final sentence clarifying that independent adjustment is never allowed.

----

For smooth animation, and for non-linear interpolation, it may be necessary for a font to have multiple axes with the same axisTag. In such a font, at most one of those axes shall be visible (i.e. have its HIDDEN_AXIS bit set to zero). The VariationAxisRecord for such a visible axis shall appear first in the array of axes, before the records for any of the other axes with that same axisTag. For an axisTag used by multiple axes, the range of values exposed to user interfaces and API access for that axisTag shall be taken from the minValue and maxValue of the first axis having that axisTag; similarly, if a user interface or API requires a default, then the defaultValue of the first axis having that axisTag shall be used. Where the ranges of the axes with a given axisTag differ in minValue or maxValue, the value shall be clamped to be within the minValue and maxValue of each axis. Independent adjustment of multiple axes with the same axisTag must not be offered or processed under any circumstances.

- Laurence

> On 4 Apr 2024, at 05:44, Liam R. E. Quin via mpeg-otspec <mpeg-otspec at lists.aau.at> wrote:
> 
> I keep thinking of koi carp for some reason.
> 
> https://github.com/harfbuzz/boring-expansion-spec/tree/main/iso_docs
> 
> The new text says what happens (based on what Harfbuzz does) if the
> min/max values for duplicated axisTags are different.
> 
> (scroll down past the list of files to get to
> WG03-fvar-2024-04.pdf
> and the Markdown and LibreOffice files)
> 
> liam
> 
> 
> -- 
> Liam Quin, https://www.delightfulcomputing.com/
> Available for XML/Document/Information Architecture/XSLT/
> XSL/XQuery/Web/Text Processing/A11Y training, work & consulting.
> Barefoot Web-slave, antique illustrations:  http://www.fromoldbooks.org
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