[cirdes]

The shadcn audit of the Codeblock found one visual gap and one behavior difference. This PR fixes both and widens the audit fixture so every part of the component gets checked in the browser.

What changes

• CodeblockContent gets shadcn's scroll-fade-x scrollbar-thin data-wrap:scroll-fade-y. When a line is wider than the block, the cut edge fades out (and the start fades too once you scroll), and the scrollbar is thin. With wrap: true the fade runs top and bottom.
• The scroll-fade-x and scroll-fade-y utilities are ported from shadcn's tailwind.css (MIT) into the installer template (tailwind.css.erb) and the docs CSS, next to the scroll-fade-b MessageScroller already uses. scrollbar-thin comes with Tailwind 4.3.
• A failed copy shows nothing, as in shadcn. Before, the button and the live region said "Copy failed" for 2s.

Deprecated

• Codeblock(clipboard_error:) and CodeblockCopyButton(error_label:) are still accepted but ignored, with a deprecation warning. They can be removed in the next major.

Audit

• The fixture now renders three blocks: the floating copy button, a header (title and copy button) with a footer, and numbered lines using the removed, added and highlighted variants. The map gains selectors for CodeblockHeader, CodeblockTitle, CodeblockLine and CodeblockFooter, which the audit never rendered before.
• The map lists style on CodeblockContent and onClick on CodeblockCopyButton. onClick is a registered divergence (audit/divergences/codeblock.yml): Ruby has no React event prop, and a data: {action: ...} passed in runs next to the copy.
• Baseline moved to shadcn 8a353667.
• One tooling gap, left for another PR: collect doesn't compare mask-image or scrollbar-width, so on main it reported the content as matching. I checked both by hand here.

Before / after

A line wider than the block, light mode, pointer over the block (the copy button only shows on hover or focus):

Audit on main (before)

shadcn audit  ruby-ui/ruby_ui
  base 1fd93db0  head 1fd93db0  shadcn 8a353667
⚠️ Environment  font: "Inter Variable", "system-ui", -apple-system, "system-ui", "Segoe UI", Roboto, "Helvetica Neue", Arial, "sans-serif" vs "Inter Variable", sans-serif (light)
⚠️ Environment  font: "Inter Variable", "system-ui", -apple-system, "system-ui", "Segoe UI", Roboto, "Helvetica Neue", Arial, "sans-serif" vs "Inter Variable", sans-serif (dark)
✅ Theme  neutral tokens match shadcn
Codeblock  (ref: bases/base/ui/code-block.tsx + style-vega.css @ 8a353667)
  ❌ Look       CodeblockContent: no scroll-fade-x / data-wrap:scroll-fade-y / scrollbar-thin (mask-image: none, scrollbar-width: auto)
               vega: scroll-fade-x scrollbar-thin data-wrap:scroll-fade-y (mask-image linear-gradient fading the overflowing edge up to min(12%, 40px), scrollbar-width: thin)
               Override of collect's 'CodeblockContent: computed styles match': collect doesn't compare mask-image or scrollbar-width. Verified with getComputedStyle at 1280x800 and by injecting an overflowing line on both sides (screens/codeblock-overflow-*): shadcn fades the cut-off end of the line, RubyUI cuts it hard. The utilities come from shadcn's tailwind.css (@utility scroll-fade-x/-y); RubyUI's install template ports only scroll-fade-b. Other computed properties match. Requested: add scroll-fade-x scrollbar-thin data-wrap:scroll-fade-y to CodeblockContent and port @utility scroll-fade-x/-y (+ scroll-fade-reveal-* keyframes) to the installer tailwind.css.erb and the docs CSS. Requested: run `baseline codeblock 8a3536678a528cc012b9e62484290e79d0be410f` in this PR.
               ↳ bases/base/ui/code-block.tsx:169
  ⏸ Look       CodeblockHeader: no selector in the component map. Static compare: RubyUI class string equals reference effective classes (style-vega.css:1705); not rendered by the fixture. Requested: extend audit/fixtures/codeblock (header with title + actions, footer, line_numbers, added/removed lines) on both sides and add selectors for these parts to audit/component_map/codeblock.yml.
  ⏸ Look       CodeblockTitle: no selector in the component map. Static compare: class string equals reference effective classes (style-vega.css:1713); not rendered by the fixture. Requested: extend audit/fixtures/codeblock (header with title + actions, footer, line_numbers, added/removed lines) on both sides and add selectors for these parts to audit/component_map/codeblock.yml.
  ⏸ Look       CodeblockLine: no selector in the component map. Static compare: base classes and added/removed/highlighted variants equal the reference (style-vega.css:1728-1741); not rendered by the fixture. Requested: extend audit/fixtures/codeblock (header with title + actions, footer, line_numbers, added/removed lines) on both sides and add selectors for these parts to audit/component_map/codeblock.yml.
  ⏸ Look       CodeblockFooter: no selector in the component map. Static compare: class string equals reference effective classes (style-vega.css:1709); not rendered by the fixture. Requested: extend audit/fixtures/codeblock (header with title + actions, footer, line_numbers, added/removed lines) on both sides and add selectors for these parts to audit/component_map/codeblock.yml.
  ✅ Look       CodeblockActions, CodeblockCopyButton (hovered): absolute top/end 12px, 24x24, bg-background, ring-1 ring-foreground/10, radius 8px, 12px icon
               Override of collect's 'no visible element in any reached state': collect only reaches closed (actions sit at opacity 0 until hover/focus). Driven by hand with hover; computed styles match. Copy button: shadcn size-6 vs RubyUI h-6 w-6, same 24px. Settles the reference warning (copy button rendered through <Button>).
               ↳ sandbox DOM + getComputedStyle (hover state, by hand)
  ⏸ Look       properties: font-family
               Codeblock — explained by environment diff: font Kept as is: environment diff, not a Codeblock finding.
  ✅ ARIA       CodeblockActions, CodeblockCopyButton: button "Copy" (type=button) + aria-live=polite sr-only region; "Copied" in both after a copy, reset after 2s
               Override of collect's 'no visible element' lines for both parts: verified by snapshot and by reading aria-label/live region before and after the click. shadcn's button also has tabindex=0 (Base UI), RubyUI relies on the native button; same tab order.
               ↳ accessibility tree (by hand, hover + click)
  ✅ ARIA       Codeblock, CodeblockContent: accessibility tree matches
               ↳ accessibility tree (shadcn-audit collect)
  ✅ Props      variant, size (Codeblock); wrap, line_numbers, start_line (CodeblockContent); value, variant, size (CodeblockCopyButton); variant (CodeblockLine)
               rubyui_only: syntax (Rouge), clipboard / clipboard_success / clipboard_error and the content kwargs on the Codeblock shorthand, label / copied_label / error_label on CodeblockCopyButton. value is optional in RubyUI (falls back to the block's code); required in shadcn.
               ↳ bases/base/ui/code-block.tsx:25-31,147-159,85-92,208-213
  ⏸ Props      Map gap: the .tsx declares style (CodeblockContent) and onClick (CodeblockCopyButton), absent from audit/component_map/codeblock.yml. RubyUI takes style: (merged after counter-reset, caller wins, as shadcn) and onClick has no Ruby counterpart (data-action passes through attrs). Requested: add style: style to CodeblockContent props in audit/component_map/codeblock.yml and record onClick as having no Ruby counterpart (data-action via attrs).
  ✅ Behavior   Copy writes the code to the clipboard, icon copy→check, aria-label + live region "Copied", reset after 2s; actions revealed on hover and focus-within; Tab: copy button → content (<pre tabindex=0>), content focus shows ring-3 ring-ring/50 + border-ring on the root
               Light theme, 1280x800.
               ↳ bases/base/ui/code-block.tsx:93-145, browser run (clipboard.writeText recorded on both sides)
  ⚠️ Behavior   writeText rejects (or no Clipboard API) → aria-label and live region "Copy failed" for 2s
               shadcn: writeText rejects → nothing (.catch(() => {})), label stays "Copy"
               Verified in the browser by making writeText reject on both sides. RubyUI's behavior is the more useful one (failure announced to screen readers); deliberate extra, not registered as a divergence. Requested: align with shadcn — swallow copy failures (no error label or announcement). Removing clipboard_error:/error_label: is a public API change; deprecate or note it in the changelog.
               ↳ bases/base/ui/code-block.tsx:113-119
  ✅ Animation  actions: transition-property opacity, 150ms, opacity 0 → 1 on hover/focus-within, always on pointer:coarse
               Computed transition on both sides.
               ↳ bases/base/ui/code-block.tsx:77
  ✅ Native     Stimulus controller only calls navigator.clipboard.writeText; scrolling via native overflow + tabindex=0 on <pre> — native
               No hand-rolled behavior with a native replacement in native-html.md.
               ↳ https://developer.mozilla.org/en-US/docs/Web/API/Clipboard/writeText
  ✅ Spec       scrollable <pre> reachable by keyboard (tabindex=0); copy result announced through aria-live=polite
               No spec violation observed on shadcn's side.
               ↳ https://www.w3.org/TR/WCAG22/#keyboard

Audit on this PR (after)

shadcn audit  ruby-ui/ruby_ui
  base 1fd93db0  head 67fc7e8e  shadcn 8a353667
⚠️ Environment  font: "Inter Variable", "system-ui", -apple-system, "system-ui", "Segoe UI", Roboto, "Helvetica Neue", Arial, "sans-serif" vs "Inter Variable", sans-serif (light)
⚠️ Environment  font: "Inter Variable", "system-ui", -apple-system, "system-ui", "Segoe UI", Roboto, "Helvetica Neue", Arial, "sans-serif" vs "Inter Variable", sans-serif (dark)
✅ Theme  neutral tokens match shadcn
Codeblock  (ref: bases/base/ui/code-block.tsx + style-vega.css @ 8a353667)
  ⏸ Look       properties: font-family
               Codeblock, CodeblockHeader, CodeblockTitle, CodeblockActions, CodeblockCopyButton, CodeblockFooter — explained by environment diff: font
  ✅ Look       CodeblockContent, CodeblockLine: computed styles match
               Rendered preview: 162a9832 (67fc7e8e only adds audit/divergences/codeblock.yml). Fixture now covers header, title, footer and numbered added/removed/highlighted lines. mask-image and scrollbar-width (not in collect's property list) checked by hand: identical gradient strings at scrollLeft 0 and 150 with an overflowing line (screens/codeblock-overflow-*-now.png), scrollbar-width: thin on both.
               ↳ computed styles (shadcn-audit collect)
  ✅ ARIA       Codeblock, CodeblockHeader, CodeblockTitle, CodeblockActions, CodeblockCopyButton, CodeblockContent, CodeblockLine, CodeblockFooter: accessibility tree matches
               ↳ accessibility tree (shadcn-audit collect)
  ✅ Look       CodeblockActions, CodeblockCopyButton (hovered): absolute top/end 12px, 24x24, bg-background, ring-1 ring-foreground/10, radius 8px, 12px icon
               Floating actions sit at opacity 0 until hover/focus, so collect sees them only inside the header; the floating state was driven by hand. Unchanged by this PR.
               ↳ sandbox DOM + getComputedStyle (hover state, by hand)
  ✅ Props      variant, size (Codeblock); style, wrap, line_numbers, start_line (CodeblockContent); value, variant, size (CodeblockCopyButton); variant (CodeblockLine)
               rubyui_only: syntax, clipboard, clipboard_success, label, copied_label; clipboard_error / error_label are deprecated and ignored.
               ↳ bases/base/ui/code-block.tsx:25-31,147-159,85-92,208-213
  ✅ Props      no onClick on CodeblockCopyButton; a data-action passed through attrs runs alongside the copy — intentional
               Server-rendered component: there is no React event prop. Extra behavior hooks in through Stimulus with data: {action: "click->my-controller#method"}, merged with the button's own copy action.
               ↳ audit/divergences/codeblock.yml
  ✅ Behavior   Copy writes the code, icon copy→check, aria-label + live region "Copied", reset after 2s; a failed copy (writeText rejects or no Clipboard API) shows nothing; actions revealed on hover and focus-within
               Success and failure driven in the browser on both sides (writeText stubbed to resolve / reject).
               ↳ bases/base/ui/code-block.tsx:93-145, browser run
  ✅ Animation  actions: transition-property opacity, 150ms; content scroll fade driven by scroll-timeline animations scroll-fade-reveal-s/-e
               Computed on both sides.
               ↳ bases/base/ui/code-block.tsx:77,169
  ✅ Native     Stimulus controller only calls navigator.clipboard.writeText; scroll fade is CSS scroll-driven animation; scrolling via native overflow + tabindex=0 on <pre> — native
               No hand-rolled behavior with a native replacement in native-html.md.
               ↳ https://developer.mozilla.org/en-US/docs/Web/API/Clipboard/writeText
  ✅ Spec       scrollable <pre> reachable by keyboard (tabindex=0); copy result announced through aria-live=polite
               No spec violation observed on shadcn's side.
               ↳ https://www.w3.org/TR/WCAG22/#keyboard

Test steps

1. cd gem && bundle exec rake (tests and standardrb).
2. cd docs && bin/dev, open /docs/codeblock and narrow the window until a line overflows. The cut edge fades, and scrolling right fades the start as well.
3. Click a copy button on localhost: the check and "Copied" show for 2s. Opened over plain http from another machine (no Clipboard API), the click changes nothing.
4. With Warning[:deprecated] = true, Codeblock(code, clipboard_error: "x") prints a deprecation warning.

🤖 Generated with Claude Code

---

Summary by cubic

Closes the last visual and behavioral gaps between the Codeblock and shadcn's: overflowing lines now fade at the cut edge instead of being clipped, and a failed copy shows nothing instead of announcing "Copy failed".

Migration

• clipboard_error: and error_label: are ignored and emit a deprecation warning; remove them in the next major.
• The new scroll-fade-x / scroll-fade-y utilities were added to the installer template and the manual install docs CSS, so existing projects must regenerate their Tailwind CSS or copy the utilities to get the fade.

Audit

• The fixture now renders a header, title, footer, and numbered diff lines; the map gains selectors for CodeblockHeader, CodeblockTitle, CodeblockLine, and CodeblockFooter.
• Registered onClick as a divergence: a Ruby data: {action: ...} runs alongside the copy.

^{Written for commit 844118e. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 13 files

<sub>Reply with feedback, questions, or to request a fix.

View guided diff | Turn on auto-fix | Re-trigger cubic</sub>