[css-cascade] User stylesheets, UA stylesheets - still something we expect to be real?

[svgeesus]

CSS 2.2 section 3.2 UA conformance:

UAs must allow users to specify a file that contains the user style sheet. UAs that run on devices without any means of writing or specifying files are exempted from this requirement. Additionally, UAs may offer other means to specify user preferences, for example, through a GUI.
https://drafts.csswg.org/css2/conform.html#conformance

Microsoft Edge does not support User Stylesheets.
https://msdn.microsoft.com/en-us/library/hh674753(v=vs.85).aspx

Chrome removed User stylesheets ages ago (chrome 33)
https://bugs.chromium.org/p/chromium/issues/detail?id=347016
https://news.ycombinator.com/item?id=7329855

The conformance section does not mention UA default stylesheets at all, but they are listed in section 6.4 the cascade:

User agent: Conforming user agents must apply a default style sheet (or behave as if they did). A user agent's default style sheet should present the elements of the document language in ways that satisfy general presentation expectations for the document language (e.g., for visual browsers, the EM element in HTML is presented using an italic font). See A sample style sheet for HTML for a recommended default style sheet for HTML documents.

I came across this again recently in the context of test for Fonts 3. A couple of tests require a particular font to be set in the UA stylesheet. For example font-052 and font-family-rule-004a. Everyone fails those tests, and they have less results than other tests (I guess skipping is easier than finding how to change the UA stylesheet, restarting the browser, then changing it back again for one test).

Do we want to still
a) say that UA stylesheets are a thing
b) insist that they be modifiable by users (as a stylesheet, not as prefs in a dialog box)

If not, then CSS2 should be modified.

if we do, then we need browser vendors on board to expose UA styles to user editing. Otherwise, how can we pass tests like these?

[svgeesus]

User stylesheets (not UA stylesheets, I think) are also a WAI UA Accessibility Guidelines requirement
https://www.w3.org/TR/UAAG20/#gl-style-sheets-config

[emilio]

Also, Blink was adding them back last time I checked, see https://bugs.chromium.org/p/chromium/issues/detail?id=632009.

[svgeesus]

Great link! Interesting to see that extensions rely on injecting user stylesheets.

[fantasai]

There's no requirement that UA stylesheets be modifiable by users; in fact they are most definitely not intended to be modifiable by users--the users should be modifying the user stylesheet. There's also no requirement that the UA represent the user stylesheet as CSS syntax--if it wants to inject rules directly into the cascade internally, that's fine and allowable. So I'm not sure what the problem is that you're asking us to fix.

Update: Nm, noticed that 3.2 and 6.4 conflict--3.2 requires a file for the user style sheet, and 6.4 says “may”. We should fix that.

[fantasai]

I also don't see why those two tests need the UA's default font to be set to anything? The test should just specify div { font-family: whatever-the-default-was-supposed-to-be } if it needs a specific font to be specified earlier in the cascade.

[Nadya678]

@fantasai: But due to possibility of tracking users, I propose Helvetica, Arial, Liberation Sans 16px (=12pt) as default font. Or other with character width compatible with Arial/Helvetica.

[svgeesus]

No, it needs to be the specific font required by the test. Helvetica etc as you suggest would not suit the test purpose.