Slate v2 Embeds Spacing Regression

Status

Complete.

Goal

Restore /examples/embeds visual parity with legacy Slate: the paragraph after the Vimeo void must sit below the URL input with normal block spacing, not visually glued to the input.

Scope

• Code repo: /Users/zbeyens/git/slate-v2.
• Plan repo: /Users/zbeyens/git/plate-2.
• Primary route: /examples/embeds.
• Keep existing selectable-void keyboard behavior intact.

Current Evidence

• User screenshot shows the new renderer on the left and legacy on the right.
• Regression is visual/layout parity around the video void and following paragraph.
• Existing embeds keyboard-navigation plan already fixed atomic selectable void traversal; do not regress that.
• Browser metrics before the fix:
  • input bottom: 730.4296875
  • following paragraph top: 768.828125
  • input-to-paragraph gap: 38.390625
  • void wrapper bottom: 752.828125
  • extra void height after input: about 22.4px
• Owner: site/examples/ts/embeds.tsx hand-rolled the void wrapper and rendered children directly after the URL input. That made the required Slate void spacer participate in layout.
• Fix: render the Vimeo block with VoidElement, passing the app-owned video UI as content and Slate children as spacer.
• Captured the reusable learning in docs/solutions/logic-errors/2026-04-26-slate-react-custom-voids-must-render-children-through-spacer.md.
• Browser metrics after the fix:
  • input bottom: 730.4296875
  • following paragraph top: 746.4296875
  • input-to-paragraph gap: 16
  • extra void height after input: 0

Plan

1. Reproduce the layout with browser metrics on /examples/embeds. Done.
2. Identify whether the owner is example markup, reusable void rendering, or global editor CSS. Done: example markup bypassed VoidElement.
3. Add a focused browser regression assertion for the gap after the URL input. Done.
4. Fix the owner without weakening selectable void behavior or internal control ownership. Done.
5. Run focused Playwright, typecheck, lint, dev-browser proof, and completion check. Done except completion check is next.

Verification

• Red proof: PLAYWRIGHT_BASE_URL=http://localhost:3100 bunx playwright test ./playwright/integration/examples/embeds.test.ts --project=chromium --workers=1 --retries=0 failed with Received: 38.390625, expected <= 24.
• Green proof: PLAYWRIGHT_BASE_URL=http://localhost:3100 bunx playwright test ./playwright/integration/examples/embeds.test.ts --project=chromium --workers=1 --retries=0 passed, 3 tests.
• Dev-browser proof: dev-browser --connect http://127.0.0.1:9222 on /examples/embeds measured gapInputToParagraph: 16 and extraVoidHeightAfterInput: 0.
• bun typecheck:root passed.
• bun typecheck:site passed.
• bun lint:fix passed, formatted 2 files.
• bun lint passed.