LGTM3
On 09/09/2022 07:02, Mike Taylor wrote:
LGTM2
On Thursday, September 8, 2022 at 9:42:54 AM UTC-4 [email protected] wrote:
Hi Yoav,
On Thursday, September 8, 2022 at 4:35:58 PM UTC+3
[email protected] <mailto:[email protected]> wrote:
OK, so sounds like there's urgency here, or at least we need to
coordinate shipping.
LGTM1 to ship in the same release as `tech()`.
Thanks!
Does that mean that if we'd want to ship a future enhancement to
colrv1, we'd need to give it its own tech() signifier? e.g.
"colrv1-foobar"?
Yes, either that or call an update to the format COLRv2 for example.
We have some requests for functionality as additoins to COLRv1, such
as mesh gradients, blur filters (for shadows) and such, but none of
that is spec'ed as of today.
Dominik
On Monday, September 5, 2022 at 4:36:01 PM UTC+2 Dominik
Röttsches wrote:
Contact emails
[email protected]
Explainer
https://github.com/googlefonts/colr-gradients-spec/blob/main/OFF_AMD2_WD.md#changes-to-off-5711---color-table
<https://github.com/googlefonts/colr-gradients-spec/blob/main/OFF_AMD2_WD.md#changes-to-off-5711---color-table>
Specification
https://docs.microsoft.com/en-us/typography/opentype/otspec191alpha/colr
<https://docs.microsoft.com/en-us/typography/opentype/otspec191alpha/colr>
Summary
COLRv1 color vector fonts have been previously
released in Chrome 98
https://developer.chrome.com/blog/colrv1-fonts/
<https://developer.chrome.com/blog/colrv1-fonts/>
but this release supported only static functionality
of the COLRv1 table. (Previous I2S
<https://groups.google.com/a/chromium.org/g/blink-dev/c/kDfj3rcA6sc/m/77Ary8NVBwAJ>).
The COLRv1 specification defined integration with
OpenType Variations
<https://medium.com/variable-fonts/https-medium-com-tiro-introducing-opentype-variable-fonts-12ba6cd2369#:~:text=An%20OpenType%20variable%20font%20is,font%20instances%20can%20be%20interpolated.>
from the beginning. This allows modifying the color elements of a font, parameters of
gradients and transforms by means of changing font variable axis parameters. This I2S here
is for bringing implementation support and adding variations to COLRv1 in Blink (see demo
video <https://www.youtube.com/watch?v=H-ulJ04cODE>, or demo links below)
Blink component
Blink>Fonts
<https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EFonts>
Search tags
colrv1
<https://chromestatus.com/features#tags:colrv1>,
variations
<https://chromestatus.com/features#tags:variations>,
variable fonts
<https://chromestatus.com/features#tags:variable%20fonts>, color
<https://chromestatus.com/features#tags:color>, emoji
<https://chromestatus.com/features#tags:emoji>, gradients
<https://chromestatus.com/features#tags:gradients>
TAG review
The COLRv1 specification is developed outside of
W3C, slated for inclusion in OpenType and ISO/MPEG
Open Font Format. Before the previous I2S
<https://groups.google.com/a/chromium.org/g/blink-dev/c/kDfj3rcA6sc/m/77Ary8NVBwAJ>,
I started a thread on blink-api-owners-discuss asking whether TAG review for such a font
format would be needed. This discussion concluded that a TAG review is not required (thread
<https://groups.google.com/a/chromium.org/g/blink-api-owners-discuss/c/k7eMJh0kRDk/m/WKXoDhmHAAAJ>).
TAG review status
Not applicable
Risks
Interoperability and Compatibility
I see an interoperability risk mainly by not
shipping variable COLRv1 support. Here's why:
Firefox is already in the process of shipping COLRv1
support (#1740530)
<https://bugzilla.mozilla.org/show_bug.cgi?id=1740530>, and
their initial release will immediately include COLRv1 variations support.
In the past few weeks, I've worked closely with
Jonathan Kew from the Mozilla side to ensure
interoperability of the resulting variable COLRv1
glyph renderings. To that end, I developed an
extensive variable COLRv1 test font, for which we
have compared results.
https://github.com/googlefonts/color-fonts/blob/main/fonts/test_glyphs-glyf_colr_1_variable.ttf
<https://github.com/googlefonts/color-fonts/blob/main/fonts/test_glyphs-glyf_colr_1_variable.ttf>
Additional interoperability efforts are underways: I would like to get to a point
where we can have at least pixel comparisons of text stack rendering results for
COLRv1. This is below the level of testing that WPT covers and likely needs separate
infrastructure. For now, rendering results based on the test font have been manually
compared.
/Gecko/: In development
(https://bugzilla.mozilla.org/show_bug.cgi?id=1740530
<https://bugzilla.mozilla.org/show_bug.cgi?id=1740530>) The standards position was
already "worth implementing" and no a fast-paced effort to deliver COLRv1 including
variations support to users is driven by Jonathan Kew. The high quality implementation can
already be tested in FF Nightly.
/WebKit/: Neutral
(https://groups.google.com/a/chromium.org/g/blink-dev/c/kDfj3rcA6sc/m/77Ary8NVBwAJ
<https://groups.google.com/a/chromium.org/g/blink-dev/c/kDfj3rcA6sc/m/77Ary8NVBwAJ>) See
discussion in previous COLRv1 intent-to-ship. Since then, I would estimate their stance towards
COLRv1 has changed from negative to "observing".
/Web developers/: Positive Google Fonts,
Underware.nl and other type foundry partners are
anticipating this feature.
/Other signals/:
Activation
Similar to the initial release of COLRv1, the issue
of feature detection remains. See separate I2S for
tech() in src: line of @font-face. This, plus
@supports(font-tech()) are intended to solve that.
Security
In addition to the initial COLRv1 release, which
already had fuzzing for the FreeType parts, a fuzzer
that fuzzes the Skia level code has been introduced
<https://bugs.chromium.org/p/skia/issues/detail?id=13675>
and a few smaller issues that this fuzzer found have been addressed.
WebView application risks
Does this intent deprecate or change behavior of
existing APIs, such that it has potentially high
risk for Android WebView-based applications?
No.
Debuggability
Decoding errors of COLRv1 fonts show up as decode
failure messages in the console, which is equivalent
to the level of debugging of font format support for
other font technologies. External tooling exists for
creating, analyzing and testing COLRv1 fonts, such
as https://github.com/fonttools/fonttools/
<https://github.com/fonttools/fonttools/> and
https://github.com/BlackFoundryCom/black-renderer
<https://github.com/BlackFoundryCom/black-renderer>
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>?
No
It is covered extensively by Skia gold regression
tests, the variable COLRv1 test font has been
developed and been used for ensuring consistent
rendering results between FF's and our implementation.
Flag name
chrome://flags/#variable-colrv1
Requires code in //chrome?
False
Tracking bug
https://crbug.com/1311241 <https://crbug.com/1311241>
Sample links
(Remember to activate chrome://flags/#variable-colrv1)
* Video of variable COLRv1 test font rendering
<https://www.youtube.com/watch?v=H-ulJ04cODE>
* https://roettsch.es/var_colrv1.html
<https://roettsch.es/var_colrv1.html> based on
variable COLRv1 test font
* Underware's Plakato Moire Demo:
https://www.underware.nl/blog/2022/07/plakato-moire/
<https://www.underware.nl/blog/2022/07/plakato-moire/>
Estimated milestones
107
Anticipated spec changes
One spec issue (#367)
<https://github.com/googlefonts/colr-gradients-spec/issues/367> is being
discussed for handling an edge case in radial gradients and radii becoming negative
under variations. Jonathan Kew and I have already found consensus on the
implementation approach and I consider this issue mostly needing updated spec
wording, but otherwise resolved.
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/6326528091095040
<https://chromestatus.com/feature/6326528091095040>
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