row-rule-* properties should inherit to an anonymous fieldset content box

[kbabbitt]

What is the issue with the HTML Standard?

The <fieldset> element is specified to generate an anonymous fieldset content box which inherits a set of properties from the <fieldset> element. Among that list of properties is column-rule which will then apply if the content box is a grid, flexbox, or multicol container.

CSS Gap Decorations introduces row-rule and subproperties row-rule-width, row-rule-style, and row-rule-color which function exactly the same as the corresponding column-rule-* properties, but in the row direction. As such, I suggest adding row-rule to the list of properties that inherit from a <fieldset> to its anonymous fieldset content box.

[annevk]

cc @whatwg/css @zcorpan

[zcorpan]

Gecko: https://searchfox.org/mozilla-central/rev/9c6e9ca72d4a59267d985fb35ba259fb937c8503/layout/style/res/forms.css#12

These rules exist in Gecko that are not in the spec:

  overflow-clip-box: inherit;
  resize: inherit;
  box-decoration-break: inherit;
  content: inherit;
  -moz-box-orient: inherit;
  -moz-box-direction: inherit;
  -moz-box-pack: inherit;
  -moz-box-align: inherit;

Also the note

  /* Please keep the declarations below in sync with ::-moz-scrolled-content in
     ua.css and ::-moz-button-content below. */

...suggests the spec is missing a list of properties that should inherit in https://html.spec.whatwg.org/multipage/rendering.html#anonymous-button-content-box