[css-color-adjust] Should forced-colors override `border-image`?

[tigt]

CSS Color Adjustment Module Level 1

I recently worked on a component library to make it play nice with Windows High-Contrast Mode, and I noticed HCM left its border-image styles untouched, which rendered some components visually inaccessible. I added the following CSS to fix the problem:

@media (-ms-high-contrast: active) {
  *, ::before, ::after {
    border-image: none !important;
    list-style-image: none !important; /* IE/Edge didn’t override this either at the time */
  }
}

Since border-image is specced to require a fallback border-style in order for the image to display at all (and I think Chromium patched their bug about that), it seems like it would be safe to include this as part of forced-color rendering.

I wrote some more about this at the time I encountered it:

• Writing CSS for High-Contrast Mode — what I thought when I encountered the problem
• High-Contrast Mode Styles tester pen — Reduced test case for properties I was suspicious of, like border-image, content: url(), and filter.

[css-meeting-bot]

The CSS Working Group just discussed . [css-color-adjust] Should forced-colors override `border-image`?, and agreed to the following:

• RESOLVED: forced-color does not override border-image

The full IRC log of that discussion

<dael> Topic: . [css-color-adjust] Should forced-colors override `border-image`?
<dael> github: https://github.com//issues/5469
<dael> Rossen_: For historic PoV we did preserve border-images as part of the forced colors
<dael> Rossen_: I think it's a valid expectation that forced colors don't override images for same reason why we fought to bring back bg images and added things like backing plate behind text
<dael> Rossen_: For similar reasons I think we can continue to allow images that are part of decorations like borders
<dael> Rossen_: Prop is forced-colors should not override border-image
<dael> Rossen_: Unless there's a new requirement or use case to provoke that
<dael> Rossen_: Not hearing anything
<dael> Rossen_: Prop: forced-color does not override border-image
<dael> RESOLVED: forced-color does not override border-image

[atanassov]

@tigt thank you for opening this issue. The above discussion with the broader CSS working group captures our consensus to keep the existing behavior of forced-colors, which is to not override border-image. The reason behind this behavior is similar to the reason we don't override background-image by setting it to a background-color. There is a lot of rich semantic information provided by background or border images and removing this degrades the user experience a lot. We tried to do that in early versions of IE and the results weren't good.

Hope this provides the additional reasoning you were looking for.

[fantasai]

@atanassov Did MSFT evaluate border-images separately from background-images? I imagine it's less likely for border-images to be used for semantic information.

[css-meeting-bot]

The CSS Working Group just discussed CSS Color Adjust.

The full IRC log of that discussion

<fantasai> Topic: CSS Color Adjust
<fantasai> github: https://github.com//issues/5469#issuecomment-707918323
<fantasai> TabAtkins: This is the only issue open to block us from CR
<fantasai> TabAtkins: we pinged you repeatedly for the answer, and no response
<fantasai> TabAtkins: So put it on the agenda.
<fantasai> Rossen_: Have some colleagues closer to the implementation, will tag them.
<fremy> fremy: wouldn't mind keeping the border image, just in case
<fantasai> Rossen_: hopefully close on this before the end of the week
<fantasai> Rossen_: horizontal review issue?
<fantasai> fantasai: We only have the one issue open. Horizontal review is done. We want to transition to CR, once the border-image issue is closed.
<fantasai> Rossen_: should we resolve provisionally, or resolve next week?
<fantasai> TabAtkins: up to the chair :)
<fantasai> Rossen_: Current spec doesn't override border-image?
<fantasai> TabAtkins: current spec calls for that I believe
<fantasai> TabAtkins: border-image is not on the list of properties getting overridden
<fantasai> Rossen_: That reflects current implementations. Don't see why we'd want to change it. Does anyone have a different opinion?
<fantasai> TabAtkins: We're not trying to resolve on the open question right now.
<fantasai> TabAtkins: Question is do we want to move to CR?
<fantasai> Rossen_: Current spec matches our expectations
<fremy> +1 to what Rossen_ said; also border-image is quite rare, it's tough to say why it's used because it can be creative
<fantasai> TabAtkins: Question is, do we want to resolve regardless of how that issue is resolved, or do we want to wait for that issue before deciding?
<tantek> q?
<fantasai> Rossen_: Currently we can proceed with CR. I will follow up with folks here today and have closing arguments in the issue by end of week
<fantasai> Rossen_: if we end up changing, let's handle it later
<fantasai> tantek: Is the issue linked in the draft?
<fantasai> TabAtkins: no
<fantasai> Rossen_: if we can't close this, put a link in there
<tantek> perhaps in the status section
<fantasai> Rossen_: OK, calling for provisional CR transition resolution
<fantasai> Rossen_: any last concerns to moving forward with transition?

[FremyCompany]

Now that a backplate is rendered under text, it's no longer necessary to remove images of any kind, so I would be in favor of keeping them, just in case they might carry semantics. border-image is quite rare, it's tough to say why it's used because it can be creative. Creative usages are difficult to predict.

[atanassov]

We had a chance to review the issue internally and wanted to confirm we are OK closing the issue without further discussion - per our provisional resolution from last call.