Bug 210468

Summary:

axis in scroll-snap-type should be required

Product:

WebKit

Reporter:

Simon Fraser (smfr) <simon.fraser>

Component:

Scrolling

Assignee:

Martin Robinson <mrobinson>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

esprehn+autocc, ews-watchlist, fred.wang, glenn, gyuyoung.kim, macpherson, majidvp, menard, mrobinson, simon.fraser, webkit-bug-importer, wenson_hsieh

Priority:

Keywords:

BrowserCompat, InRadar, WebExposed

Version:

Safari Technology Preview

Hardware:

Unspecified

OS:

Unspecified

Attachments:

Description	Flags
Patch	none

Description Simon Fraser (smfr) 2020-04-13 17:07:10 PDT

We don't parse scroll-snap-type according to the spec:
https://drafts.csswg.org/css-scroll-snap-1/#scroll-snap-type

which means we're not compatible with Firefox and Chrome.

Comment 1 Radar WebKit Bug Importer 2020-04-13 17:11:00 PDT

<rdar://problem/61746766>

Comment 2 Simon Fraser (smfr) 2020-04-13 18:28:28 PDT

Actually we do parse it:

    auto firstValue = consumeIdent<CSSValueX, CSSValueY, CSSValueBlock, CSSValueInline, CSSValueBoth>(range);
    if (firstValue)
        secondValue = consumeIdent<CSSValueProximity, CSSValueMandatory>(range);
    else
        firstValue = consumeIdent<CSSValueNone, CSSValueProximity, CSSValueMandatory>(range);

but we treat the axis optional, when it should be required.

Comment 3 Martin Robinson 2020-10-15 06:34:11 PDT

Created attachment 411435 [details]
Patch

Comment 4 Martin Robinson 2020-10-15 07:26:35 PDT

*** Bug 187697 has been marked as a duplicate of this bug. ***

Comment 5 Simon Fraser (smfr) 2020-10-15 10:12:03 PDT

Comment on attachment 411435 [details]
Patch

I'm concerned about web compat here. Does the snapping on https://music.apple.com still work?

Comment 6 Majid Valipour 2020-10-15 17:58:13 PDT

FWIW, apple music scroll snapping works in Chrome which requires the new syntax.
Quick check on their home page showed they are using "scroll-snap-type: x mandatory".


Unfortunately chrome css data stats (https://chromestatus.com/metrics/css/popularity) do not tell you much about the value. But we can use it to compare usage of attributes that exclusively belong to the old syntax vs the new syntax: 


[exclusively old] <= 0.000001%
   scroll-snap-points-{x,y}, scroll-snap-coordinates, scroll-snap-destinations

[common in both] 2.090845%
  scroll-snap-types

[exclusively new] 2.090845%
  scroll-snap-align


This does suggest that old syntax is not being used much compared to the new one which could indicate that it is rare to have a single value that is not an axis as that is from old syntax and not valid in Chrome, Firefox, or Edge.

None of this is hard data on compat but hopefully helps.

Comment 7 Majid Valipour 2020-10-15 18:00:38 PDT

scroll-snap-align usage should be 2.119231%

so
[exclusively old] <= 0.000001%
   scroll-snap-points-{x,y}, scroll-snap-coordinates, scroll-snap-destinations

[common in both] 2.090845%
  scroll-snap-type

[exclusively new] 2.119231%
  scroll-snap-align

Comment 8 EWS 2020-10-19 02:24:53 PDT

Committed r268665: <https://trac.webkit.org/changeset/268665>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 411435 [details].