Intent to implement: OpenType Variation Fonts

[Jonathan Kew]

We're proposing to implement support for OpenType Variation Fonts in Gecko.

From the Microsoft announcement[1] of Font Variations technology:

"...make use of a variety of font weights and styles to make your
message stand out clearly. The problem has been that all those weights
and styles—bold, semibold, regular, display, caption—are separate font
files, which increases application size and slows down web page load
times, especially on mobile phones. OpenType Font Variations provide all
the weights and styles of a full font family in a single, compact file
to improve applications size and web site responsiveness."

Other companies and designers have also been posting about the
technology, which is arousing a good deal of interest in the font and
web design communities.[2,3,4]

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1302685

Link to standard: https://drafts.csswg.org/css-fonts-4/, particularly
https://drafts.csswg.org/css-fonts-4/#low-level-font-variation-settings-control-the-font-variation-settings-property.

Platform coverage: All platforms, although implementation may proceed at
different speeds depending on native font back-ends involved.

Estimated or target release: Not yet determined.

Preference behind which this will be implemented:
layout.css.font-variations.enabled

DevTools bug: It's not yet clear to me whether specific DevTools work
will be needed, beyond the support we'll automatically get for a new CSS
property.

Do other browser engines implement this?
Blink: Google has discussed the intention to support variation fonts in
Chrome (see [2]); I'm not sure if a formal "Intent to implement" mail is
on file.
Edge: The Microsoft announcement[1] indicates a clear intention to
support this technology.
WebKit: Experimental support is in WebKit nightly builds on OS X (see
https://webkit.org/blog/7051/variable-fonts-on-the-web/).

Tests: Not yet written.

(Because of the already-existing support for font variations in the
macOS font system, this will probably be the first platform backend to
be implemented in Gecko. There's a try build linked from
https://bugzilla.mozilla.org/show_bug.cgi?id=1321031#c5 for anyone who
cares to play around with it already.)

JK


[1]
https://www.microsoft.com/en-us/Typography/FontVariationsAnnouncement.aspx
[2]
https://opensource.googleblog.com/2016/09/introducing-opentype-font-variations.html
[3]
https://medium.com/@tiro/https-medium-com-tiro-introducing-opentype-variable-fonts-12ba6cd2369
[4]
http://blog.typekit.com/2016/09/14/variable-fonts-a-new-kind-of-font-for-flexible-design/

[Boris Zbarsky]

On 12/5/16 4:28 AM, Jonathan Kew wrote:
> Blink: Google has discussed the intention to support variation fonts in
> Chrome (see [2]); I'm not sure if a formal "Intent to implement" mail is
> on file.

I think
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/GAhY5gl8bIs
is the relevant intent to implement.

Makes sense to me to implement this.

-Boris

[Benjamin Smedberg]

I want to make sure that our test plan includes fairly comprehensive
fuzzing coverage, since this appears to be a new attack surface.

--BDS

> Blink: Google has discussed the intention to support variation fonts in
> Chrome (see [2]); I'm not sure if a formal "Intent to implement" mail is on
> file.

> Edge: The Microsoft announcement[1] indicates a clear intention to support
> this technology.
> WebKit: Experimental support is in WebKit nightly builds on OS X (see
> https://webkit.org/blog/7051/variable-fonts-on-the-web/).
>
> Tests: Not yet written.
>
> (Because of the already-existing support for font variations in the macOS
> font system, this will probably be the first platform backend to be
> implemented in Gecko. There's a try build linked from
> https://bugzilla.mozilla.org/show_bug.cgi?id=1321031#c5 for anyone who
> cares to play around with it already.)
>
> JK
>
>
> [1] https://www.microsoft.com/en-us/Typography/FontVariationsAnn
> ouncement.aspx
> [2] https://opensource.googleblog.com/2016/09/introducing-openty
> pe-font-variations.html
> [3] https://medium.com/@tiro/https-medium-com-tiro-introducing-
> opentype-variable-fonts-12ba6cd2369
> [4] http://blog.typekit.com/2016/09/14/variable-fonts-a-new-kind
> -of-font-for-flexible-design/
>

> _______________________________________________
> dev-platform mailing list
> dev-pl...@lists.mozilla.org
> https://lists.mozilla.org/listinfo/dev-platform
>

[Xidorn Quan]

On Tue, Dec 6, 2016, at 01:28 AM, Jonathan Kew wrote:
> DevTools bug: It's not yet clear to me whether specific DevTools work
> will be needed, beyond the support we'll automatically get for a new CSS
> property.

I think DevTools may want to display a panel which lists all available
variation axis supported by the font, and allow developers to adjust
them. I think there is some discussion about adding this kind of
detection to Font Loading API. Before that API gets stable I guess we
can implement an internal thing listing that for DevTools and as an
experiment for the future standard API.

> (Because of the already-existing support for font variations in the
> macOS font system, this will probably be the first platform backend to
> be implemented in Gecko. There's a try build linked from
> https://bugzilla.mozilla.org/show_bug.cgi?id=1321031#c5 for anyone who
> cares to play around with it already.)

Great work \o/

- Xidorn

[Jonathan Kew]

On 06/12/2016 19:04, Xidorn Quan wrote:
> On Tue, Dec 6, 2016, at 01:28 AM, Jonathan Kew wrote:
>> DevTools bug: It's not yet clear to me whether specific DevTools work
>> will be needed, beyond the support we'll automatically get for a new CSS
>> property.
>
> I think DevTools may want to display a panel which lists all available
> variation axis supported by the font, and allow developers to adjust
> them.

Yes, perhaps something like that would be useful. Though we don't do
anything along those lines for OpenType font features at present. If
DevTools is to start exposing details of "font capabilities", both
features and variations should be treated similarly.

I think that makes it a broader topic, not directly linked to
variations, which would be just one among various details that could be
exposed via a DevTools "font inspector".

JK

[Patrick Brosset]

The inspector in DevTools has a Fonts panel already. For now, it only lists
the fonts currently used by the selected element. It can also list all
fonts used on the page.
We would love to make this panel more useful and expose things like
variations. As Xidorn said, if we could have an API that lists those for
us, then we could pretty easily add a UI to the panel that lets people
explore the fonts.
It sounds like that could be very useful.

Finally, this bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1280162 is
about exposing OpenType features like ligature for a given font in the
Fonts panel.

And, related to this, we also have this bug:
https://bugzilla.mozilla.org/show_bug.cgi?id=1280163 where we would like to
have the Fonts panel list all the glyphs that a font contains.

I'll file a specific bug for the variations technology and will cc Jonathan.

Thanks,
Patrick

[Patrick Brosset]

Here's the bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1323743

On Thu, Dec 15, 2016 at 4:02 PM, Patrick Brosset <pbro...@mozilla.com>
wrote: