[css-writing-modes] writing-mode on form control elements

[josepharhar]

The spec says that user agents "should" instead of "must" respect writing mode in replaced elements. I suppose this makes sense for native form control picker popups that don't support being rotated for writing mode on some native platforms.

However, there are parts of the controls that the user agent can control because they are actually rendered inside the page and don't use native platform code to render, such as the button to open a picker for various input types, the <button> element, the <textarea> element, etc.

There are also several WPTs which have been included in interop2023 to test this behavior (for the part rendered inside the page), but they all have optional in their name (which seems like a contradiction to me), and I'm guessing it's because the spec says "should" instead of "must": https://wpt.fyi/results/css/css-writing-modes/forms?label=master&label=experimental&product=chrome&product=firefox&product=safari&aligned&view=interop&q=label%3Ainterop-2022-forms%20or%20label%3Ainterop-2023-forms cc @nt1m who has worked on these tests

I don't know about the other browsers, but in chromium we even have a user agent stylesheet rule to disable writing-mode for certain form control elements and I don't know why we have it: https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/html/resources/html.css;l=410-413;drc=5fa2480334f68dbe19ee6591cba86dde6bb25603

In discussions for the new <selectmenu> element, this was also raised as an issue with interest in changing the "should" to a "must": https://github.com/openui/open-ui/issues/600#issuecomment-1231181295

Should the spec say "must" instead of "should"? Should user-agent stylesheets disable writing-mode on form control elements like chromium is doing or not?

[tabatkins]

The "should" is indeed because replaced elements might be out of the UA's direct control, yeah. Still, "should" means "do it unless there's a good reason not to", so if we can support writing-mode, we, uh, "should".

[nt1m]

The reason I marked them as optional is because each platform may choose to different things in terms of form controls, e.g. iOS uses a button for <select multiple> instead of a listbox, so some of the tests don't necessarily apply.

[fantasai]

SHOULD is an RFC2119 keyword defined thus:

3. SHOULD This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.

I agree with Tab that the spec is correct as-is.

Should user-agent stylesheets disable writing-mode on form control elements like chromium is doing or not?

The answer to this is clearly no. The UA should support writing-mode on any form control elements that it can.

@josepharhar Do you have enough information here to close the issue, or do you still think something needs to change?

[nt1m]

I don't know about the other browsers, but in chromium we even have a user agent stylesheet rule to disable writing-mode for certain form control elements and I don't know why we have it:

This is historical and inherits from WebKit, WebKit has the same CSS rule because no one at the time had time to make form controls writing mode compatible.

[josepharhar]

I agree with Tab that the spec is correct as-is.

Sounds good

Do you have enough information here to close the issue, or do you still think something needs to change?

Sounds like we don't need anything in css to change. I just wonder if we can remove that user agent style in chromium, and if we can enforce writing-mode for <selectmenu> when I try to get it specced and tested since it will not be rendering any native OS stuff, despite it technically being a form control element.

This is historical and inherits from WebKit, WebKit has the same CSS rule because no one at the time had time to make form controls writing mode compatible.

Do you think we should remove that rule?

[nt1m]

Do you think we should remove that rule?

Yeah, I think this rule shouldn't have been added and form controls should have been made writing mode compatible (and the folks who wrote this rule at the time seem to agree this was temporary)