On 21/02/2023 10:06, 'Munira Tursunova' via blink-dev wrote:
>> Is there a way to feature detect the synthesis functionality or not? How
>> a web author will be able to differentiate between Gecko vs
>> Chromium/WebKit behaviors? Would the lack of this feature confuse
>> authors? Maybe having some console message information when
>> font-variant-position doesn't have any effect due to missing synthesis
>> functionality, dunno if that makes sense.
>>
>> Do we have an use counter for the cases where we're not using
>> synthesized glyphs due to lack of functionality? So we can track how
>> common that situation is and understand the priority of such feature in
>> the future.
>
> I’m not sure I completely understand your question, but I suppose
> identifying cases when the feature is requested and the font does not
> have subscript/superscript glyphs might not be possible since we perform
> the checking of the font features in the shaping stage in Harfbuzz and
> we check different fonts in the shaping process without knowing what
> font will be finally used in the page. So, for example, we can trigger
> on some system font that does not have sub/superscript glyphs (so this
> glyphs should be synthesised) however, in the end, this font won’t be
> used in the page but a different web font will be used instead.
>
> One of the ways to detect whether a font has super/subscript glyphs is
> to check whether the font with the feature has loaded (using
> document.fonts for instance) and if it did then we won’t synthesise.
Mmmm, I'm not sure if I'm understanding properly.
In the first email you wrote:
> Currently font-variant-position is implemented without synthesis
functionality and affects only fonts that have superscript or subscript
glyphs (“sups”/”subs” opentype feature); i.e. if the font doesn’t have
superscript/subscript then setting font-variant-position to
“super”/“sub” won’t synthesize superscript and subscript glyphs,
therefore won’t change anything.
I understood that if the font has super/subscript glyphs we'll use them,
but if the font doesn't have them, we won't synthesize them, so the user
will see no difference between a text with `font-variant-position:
normal;` vs `font-variant-position: super;`. Am I getting this wrong?
If I'm right, my question was how to feature detect if the browser is
synthesizing things or not. For example we have this:
x<span style="font-variant-position: super;">2</span>
In Firefox that will always look as "x²". In Chromium/WebKit I
understand that depending on the font it'll look as "x²" or "x2".
Is there any way the author can detect what's going on so they can use a
different method to do the superscript here?
Isn't this going to be confusing to web authors why this is not working
in Chromium, while working in Firefox? Are they going to be able to
understand this is because the selected font doesn't have the proper
glyphs (even when it's the same font in Firefox)?
I was wondering about this kind of things, but I'm not sure if I
understood properly the original message.
Cheers,
Rego
>> I'm curious how this relates to the "old" way of doing superscript. If
> I understand correctly (and I might not!), then x<span
> style="font-variant-position: super">2</span> will render as "x²",
> somehow finding > the "super" variant of 2 in the font? The old way of
> doing this would be with x<span style="vertical-align: super; font-size:
> 0.83em">2</span> which will use the normal glyph for 2, but smaller and
> differently > positioned?
>
> Not exactly, vertical-align always does synthesis, so even if the font
> has subscript or superscript opentype features vertical-align would
> still synthesize the glyphs. The old way of activation
> superscript/subscript is through font-feature-settings, i.e. setting it
> to “sups” or ”subs”.
>
> On Wednesday, February 15, 2023 at 6:08:20 PM UTC+1 Daniel Bratell wrote:
>
> I'm curious how this relates to the "old" way of doing superscript.
>
> If I understand correctly (and I might not!), then
>
> x<span style="font-variant-position: super">2</span>
>
> will render as "x²", somehow finding the "super" variant of 2 in the
> font?
>
> The old way of doing this would be with
>
> x<span style="vertical-align: super; font-size: 0.83em">2</span>
>
> which will use the normal glyph for 2, but smaller and differently
> positioned?
>
> /Daniel
>
> On 2023-02-14 22:26, Manuel Rego Casasnovas wrote:
> > Is there a way to feature detect the synthesis functionality or
> not? How
> > a web author will be able to differentiate between Gecko vs
> > Chromium/WebKit behaviors? Would the lack of this feature confuse
> > authors? Maybe having some console message information when
> > font-variant-position doesn't have any effect due to missing
> synthesis
> > functionality, dunno if that makes sense.
> >
> > Do we have an use counter for the cases where we're not using
> > synthesized glyphs due to lack of functionality? So we can track how
> > common is that situation and understand the priority of such
> feature in
> > the future.
> >
> > Cheers,
> > Rego
> >
> > On 14/02/2023 17:08, Philip Jägenstedt wrote:
> >> I will recuse myself from this one since I have an interest in the
> >> success of Interop 2022 (and 2023), but I think shipping this makes
> >> sense. Chrome is the last browser to not support it at all, and
> we've
> >> seen with other features that the time it becomes available in all
> >> browsers can be an inflection point in usage.
> >>
> >> On Tue, Feb 14, 2023 at 4:56 PM 'Munira Tursunova' via blink-dev
> >> <blin...@chromium.org <mailto:blin...@chromium.org>> wrote:
> >>
> >>
> >> Contact emails
> >>
> >> moo...@google.com <mailto:moo...@google.com>, dr...@google.com
> >> <mailto:dr...@google.com>
> >>
> >>
> >> Explainer
> >>
> >>
> https://developer.mozilla.org/en-US/docs/Web/CSS/font-variant-position
> <https://developer.mozilla.org/en-US/docs/Web/CSS/font-variant-position>
> <https://developer.mozilla.org/en-US/docs/Web/CSS/font-variant-position
> <https://developer.mozilla.org/en-US/docs/Web/CSS/font-variant-position>>
> >>
> >>
> >> Specification
> >>
> >>
> https://drafts.csswg.org/css-fonts-4/#propdef-font-variant-position
> <https://drafts.csswg.org/css-fonts-4/#propdef-font-variant-position>
> >>
> <https://drafts.csswg.org/css-fonts-4/#propdef-font-variant-position
> <https://drafts.csswg.org/css-fonts-4/#propdef-font-variant-position>>
> >>
> >>
> >> Summary
> >>
> >> The font-variant-position CSS property controls the use of
> >> alternate, smaller glyphs that are positioned as superscript or
> >> subscript.
> >>
> >>
> >> Motivation
> >>
> >> Font-variant-position property allows users to control usage of
> >> typographic superscript and subscript glyphs.
> >>
> >> Currently font-variant-position is implemented without synthesis
> >> functionality and affects only fonts that have superscript or
> >> subscript glyphs (“sups”/”subs” opentype feature); i.e. if the font
> >> doesn’t have superscript/subscript then setting
> >> font-variant-position to “super”/“sub” won’t synthesize superscript
> >> and subscript glyphs, therefore won’t change anything.
> >>
> >> Subscript and superscript glyphs can be also activated using the
> >> font-feature-settings property, however using font-variant-position
> >> property might be more reasonable since it cascades like a regular
> >> CSS property and with the font-feature-settings, if the element
> >> inherits the “sups” or “subs” value, users need to
> >> activate/deactivate other features that were also defined in
> >> font-feature-settings of the parent element.
> >>
> >> Implementing the synthesis part would be complex and it is
> >> questionable if it is worth the cost since synthesized glyphs may
> >> look unnatural and synthesis of the font-variant-position property
> >> is at risk in the spec
> >>
>
> <https://drafts.csswg.org/css-fonts-4/#:~:text=The%20following%20features,variant%2Dposition%20property
>
> <https://drafts.csswg.org/css-fonts-4/#:~:text=The%20following%20features,variant%2Dposition%20property>>.
> Also Safari supports font-variant-position property without synthesis
> functionality as well.
> >>
> >> This feature is implemented behind the ‘experimental’ flag and is
> >> part of Interop 2022. Shipping this feature will provide a higher
> >> stable score for Interop and will decrease the stable vs.
> >> experimental score difference.Since Chrome is the last browser to
> >> ship this, this will enable broader usage of the feature on the web.
> >>
> >>
> >> Blink component
> >>
> >> Blink>Fonts
> >>
>
> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EFonts
> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EFonts>>
> >>
> >>
> >> Search tags
> >>
> >> font-variant-position
> >> <https://chromestatus.com/features#tags:font-variant-position
> <https://chromestatus.com/features#tags:font-variant-position>>,
> >> subscript glyphs
> >> <https://chromestatus.com/features#tags:subscript%20glyphs
> <https://chromestatus.com/features#tags:subscript%20glyphs>>,
> >> superscript glyphs
> >> <https://chromestatus.com/features#tags:superscript%20glyphs
> <https://chromestatus.com/features#tags:superscript%20glyphs>>, sub
> >> <https://chromestatus.com/features#tags:sub
> <https://chromestatus.com/features#tags:sub>>, super
> >> <https://chromestatus.com/features#tags:super
> <https://chromestatus.com/features#tags:super>>
> >>
> >>
> >> TAG review
> >>
> >> Already shipped in other browsers, see below, no TAG review
> required.
> >>
> >>
> >> TAG review status
> >>
> >> Not applicable, existing standard, shipped in other UAs
> >>
> >>
> >> Risks
> >>
> >>
> >>
> >> Interoperability and Compatibility
> >>
> >>
> >> Gecko: Shipped/Shipping
> >>
> >> https://bugzilla.mozilla.org/show_bug.cgi?id=1024804
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1024804>
> >> <https://bugzilla.mozilla.org/show_bug.cgi?id=1024804
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1024804>>Gecko has
> >> implemented the feature with the synthesis functionality.
> >>
> >>
> >> WebKit: Shipped/Shipping
> >>
> >> https://bugs.webkit.org/show_bug.cgi?id=148413
> <https://bugs.webkit.org/show_bug.cgi?id=148413>
> >> <https://bugs.webkit.org/show_bug.cgi?id=148413
> <https://bugs.webkit.org/show_bug.cgi?id=148413>>WebKit has
> >> implemented the feature without the synthesis functionality.
> >>
> >>
> >> Web developers: No signals
> >>
> >>
> >> Other signals: -
> >>
> >>
> >>
> >> Activation
> >>
> >> None expected; Feature already implemented in other browsers.
> >>
> >>
> >>
> >> Debuggability
> >>
> >> Same as any other CSS property, css_properties.json will be rolled
> >> to DevTools during development.
> >>
> >>
> >>
> >> Will this feature be supported on all six Blink platforms
> >> (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?
> >>
> >> Yes
> >>
> >>
> >> Is this feature fully tested by web-platform-tests
> >>
>
> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md
>
> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>>?
> >>
> >> Yes, following tests are testing property implementation:
> >>
> >> https://wpt.fyi/results/css/css-fonts/font-variant-position.html
> <https://wpt.fyi/results/css/css-fonts/font-variant-position.html>
> >> <https://wpt.fyi/results/css/css-fonts/font-variant-position.html
> <https://wpt.fyi/results/css/css-fonts/font-variant-position.html>>
> >>
> >>
> https://wpt.fyi/results/css/css-fonts/font-variant-position-01.html
> <https://wpt.fyi/results/css/css-fonts/font-variant-position-01.html>
> >>
> <https://wpt.fyi/results/css/css-fonts/font-variant-position-01.html
> <https://wpt.fyi/results/css/css-fonts/font-variant-position-01.html>>
> >>
> >>
> https://wpt.fyi/results/css/css-fonts/font-variant-position-02.html
> <https://wpt.fyi/results/css/css-fonts/font-variant-position-02.html>
> >>
> <https://wpt.fyi/results/css/css-fonts/font-variant-position-02.html
> <https://wpt.fyi/results/css/css-fonts/font-variant-position-02.html>>
> >>
> >>
> https://wpt.fyi/results/css/css-fonts/font-variant-position-03.html
> <https://wpt.fyi/results/css/css-fonts/font-variant-position-03.html>
> >>
> <https://wpt.fyi/results/css/css-fonts/font-variant-position-03.html
> <https://wpt.fyi/results/css/css-fonts/font-variant-position-03.html>>
> >>
> >>
>
> https://wpt.fyi/results/css/css-fonts/parsing/font-variant-position-valid.html
>
> <https://wpt.fyi/results/css/css-fonts/parsing/font-variant-position-valid.html>
>
> <https://wpt.fyi/results/css/css-fonts/parsing/font-variant-position-valid.html
>
> <https://wpt.fyi/results/css/css-fonts/parsing/font-variant-position-valid.html>>
> >>
> >>
>
> https://wpt.fyi/results/css/css-fonts/parsing/font-variant-position-computed.html
>
> <https://wpt.fyi/results/css/css-fonts/parsing/font-variant-position-computed.html>
>
> <https://wpt.fyi/results/css/css-fonts/parsing/font-variant-position-computed.html
>
> <https://wpt.fyi/results/css/css-fonts/parsing/font-variant-position-computed.html>>
> >>
> >>
> https://wpt.fyi/results/css/css-fonts/parsing/font-variant-valid.html
> <https://wpt.fyi/results/css/css-fonts/parsing/font-variant-valid.html>
> <https://wpt.fyi/results/css/css-fonts/parsing/font-variant-valid.html
> <https://wpt.fyi/results/css/css-fonts/parsing/font-variant-valid.html>>
> >>
> >>
> >> Flag name
> >>
> >> FontVariantPosition
> >>
> >>
> >> Requires code in //chrome?
> >>
> >> False
> >>
> >>
> >> Tracking bug
> >>
> >> https://bugs.chromium.org/p/chromium/issues/detail?id=1212668
> <https://bugs.chromium.org/p/chromium/issues/detail?id=1212668>
> >> <https://bugs.chromium.org/p/chromium/issues/detail?id=1212668
> <https://bugs.chromium.org/p/chromium/issues/detail?id=1212668>>
> >>
> >>
> >> Estimated milestones
> >>
> >> No milestones specified
> >>
> >>
> >>
> >> Anticipated spec changes
> >>
> >> None expected
> >>
> >>
> >>
> >> Link to entry on the Chrome Platform Status
> >>
> >> https://chromestatus.com/feature/5067180721307648
> <https://chromestatus.com/feature/5067180721307648>
> >> <https://chromestatus.com/feature/5067180721307648
> <https://chromestatus.com/feature/5067180721307648>>
> >>
> >>
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