Roving Tabindex

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: #0a0a0a;
  color: #e5e5e5;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding: 3rem 1.5rem;
}

.demo-wrapper {
  width: 100%;
  max-width: 680px;
}

.demo-title {
  font-size: 1.75rem;
  font-weight: 700;
  color: #f5f5f5;
  margin-bottom: 0.375rem;
}

.demo-subtitle {
  font-size: 0.9rem;
  color: #888;
  margin-bottom: 2rem;
  line-height: 1.5;
}

/* ── Info Panel ───────────────────────────────────── */

.info-panel {
  background: #111827;
  border: 1px solid #1e3a5f;
  border-radius: 10px;
  padding: 20px 24px;
  margin-bottom: 2.5rem;
}

.info-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: #93c5fd;
  margin-bottom: 8px;
}

.info-panel p {
  font-size: 0.85rem;
  color: #94a3b8;
  line-height: 1.6;
}

.info-panel code {
  background: #1e293b;
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.8rem;
  color: #c4b5fd;
}

.info-panel kbd {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 24px;
  height: 22px;
  padding: 0 6px;
  background: #1a1a1a;
  border: 1px solid #333;
  border-bottom-width: 2px;
  border-radius: 4px;
  font-family: inherit;
  font-size: 0.7rem;
  font-weight: 600;
  color: #ccc;
}

/* ── Section ──────────────────────────────────────── */

.example-section {
  margin-bottom: 2.5rem;
}

.section-title {
  font-size: 1.05rem;
  font-weight: 600;
  color: #d4d4d4;
  margin-bottom: 14px;
}

/* ── Toolbar ──────────────────────────────────────── */

.toolbar {
  display: flex;
  align-items: center;
  gap: 4px;
  background: #161616;
  border: 1px solid #262626;
  border-radius: 10px;
  padding: 6px 8px;
}

.toolbar-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 36px;
  background: transparent;
  border: none;
  border-radius: 7px;
  color: #999;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, box-shadow 0.15s;
}

.toolbar-btn:hover {
  background: #222;
  color: #d4d4d4;
}

.toolbar-btn:focus-visible {
  outline: 2px solid #6366f1;
  outline-offset: -2px;
  color: #f5f5f5;
}

.toolbar-btn[aria-pressed="true"] {
  background: #2d2d5e;
  color: #a5b4fc;
}

.toolbar-separator {
  width: 1px;
  height: 24px;
  background: #333;
  margin: 0 4px;
  flex-shrink: 0;
}

/* ── Radio Group ──────────────────────────────────── */

.radio-group {
  display: flex;
  gap: 6px;
  background: #161616;
  border: 1px solid #262626;
  border-radius: 10px;
  padding: 6px 8px;
}

.radio-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  border-radius: 7px;
  cursor: pointer;
  transition: background 0.15s;
  font-size: 0.875rem;
  color: #999;
}

.radio-item:hover {
  background: #222;
  color: #d4d4d4;
}

.radio-item:focus-visible {
  outline: 2px solid #6366f1;
  outline-offset: -2px;
  color: #f5f5f5;
}

.radio-item[aria-checked="true"] {
  background: #1e1e2e;
  color: #e5e5e5;
}

.radio-indicator {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 18px;
  height: 18px;
  border: 2px solid #444;
  border-radius: 50%;
  flex-shrink: 0;
  transition: border-color 0.15s;
}

.radio-item[aria-checked="true"] .radio-indicator {
  border-color: #6366f1;
}

.radio-item[aria-checked="true"] .radio-indicator::after {
  content: "";
  width: 8px;
  height: 8px;
  background: #6366f1;
  border-radius: 50%;
}

.radio-label {
  font-weight: 500;
}

/* ── Color Grid ───────────────────────────────────── */

.color-grid {
  display: inline-flex;
  flex-direction: column;
  gap: 6px;
  background: #161616;
  border: 1px solid #262626;
  border-radius: 10px;
  padding: 12px;
}

.color-row {
  display: flex;
  gap: 6px;
}

.color-swatch {
  width: 40px;
  height: 40px;
  background: var(--swatch);
  border-radius: 8px;
  cursor: pointer;
  transition: transform 0.15s, box-shadow 0.15s;
  border: 2px solid transparent;
}

.color-swatch:hover {
  transform: scale(1.1);
}

.color-swatch:focus-visible {
  outline: 2px solid #6366f1;
  outline-offset: 2px;
}

.color-swatch[aria-selected="true"] {
  border-color: #fff;
  box-shadow: 0 0 0 2px #6366f1;
  transform: scale(1.05);
}

.color-selected {
  margin-top: 12px;
  font-size: 0.85rem;
  color: #888;
}

/* ── Tab Order Visualizer ─────────────────────────── */

.tab-order-info {
  font-size: 0.85rem;
  color: #888;
  line-height: 1.6;
  margin-bottom: 14px;
}

.tab-order-info kbd {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 24px;
  height: 22px;
  padding: 0 6px;
  background: #1a1a1a;
  border: 1px solid #333;
  border-bottom-width: 2px;
  border-radius: 4px;
  font-family: inherit;
  font-size: 0.7rem;
  font-weight: 600;
  color: #ccc;
}

.tabindex-display {
  background: #111;
  border: 1px solid #222;
  border-radius: 10px;
  padding: 16px 20px;
  font-family: "SF Mono", "Fira Code", "Cascadia Code", monospace;
  font-size: 0.78rem;
  color: #888;
  line-height: 1.8;
  white-space: pre-wrap;
  word-break: break-all;
}

.tabindex-display .active-tab {
  color: #22c55e;
  font-weight: 600;
}

.tabindex-display .inactive-tab {
  color: #555;
}

.tabindex-display .group-label {
  color: #6366f1;
  font-weight: 600;
}

/* ── Responsive ── */
@media (max-width: 600px) {
  body {
    padding: 1.25rem 0.75rem;
  }

  .demo-title {
    font-size: 1.35rem;
  }

  .demo-subtitle {
    font-size: 0.82rem;
    margin-bottom: 1.25rem;
  }

  .info-panel {
    padding: 14px 16px;
    margin-bottom: 1.5rem;
  }

  .info-title {
    font-size: 0.88rem;
  }

  .info-panel p {
    font-size: 0.8rem;
  }

  .example-section {
    margin-bottom: 1.5rem;
  }

  .section-title {
    font-size: 0.95rem;
    margin-bottom: 10px;
  }

  /* Toolbar: allow wrap */
  .toolbar {
    flex-wrap: wrap;
    padding: 6px;
  }

  .toolbar-btn {
    width: 36px;
    height: 34px;
  }

  /* Radio group: wrap into rows */
  .radio-group {
    flex-wrap: wrap;
    gap: 4px;
    padding: 6px;
  }

  .radio-item {
    padding: 7px 12px;
    font-size: 0.82rem;
    gap: 6px;
  }

  .radio-indicator {
    width: 16px;
    height: 16px;
  }

  .radio-item[aria-checked="true"] .radio-indicator::after {
    width: 7px;
    height: 7px;
  }

  /* Color grid: smaller swatches */
  .color-grid {
    padding: 8px;
    gap: 4px;
    max-width: 100%;
  }

  .color-row {
    gap: 4px;
  }

  .color-swatch {
    width: 34px;
    height: 34px;
    border-radius: 6px;
  }

  .color-selected {
    font-size: 0.8rem;
  }

  /* Tab order visualizer */
  .tabindex-display {
    padding: 12px 14px;
    font-size: 0.7rem;
    overflow-x: auto;
  }

  .tab-order-info {
    font-size: 0.8rem;
    margin-bottom: 10px;
  }
}

@media (max-width: 360px) {
  .color-swatch {
    width: 28px;
    height: 28px;
  }

  .toolbar-btn {
    width: 32px;
    height: 30px;
  }

  .toolbar-btn svg {
    width: 15px;
    height: 15px;
  }
}

(() => {
  const groups = document.querySelectorAll("[data-roving-group]");
  const tabindexDisplay = document.getElementById("tabindexDisplay");
  const colorSelected = document.getElementById("colorSelected");

  /* ── Roving Tabindex Core ───────────────────────── */

  function getItems(group) {
    // For grid, get all gridcells; for toolbar, get buttons; for radiogroup, get radios
    if (group.hasAttribute("data-grid")) {
      return [...group.querySelectorAll('[role="gridcell"]')];
    }
    if (group.getAttribute("role") === "radiogroup") {
      return [...group.querySelectorAll('[role="radio"]')];
    }
    // Toolbar: skip separators
    return [...group.querySelectorAll('button:not([role="separator"])')];
  }

  function setRovingFocus(group, targetItem) {
    const items = getItems(group);
    items.forEach((item) => item.setAttribute("tabindex", "-1"));
    targetItem.setAttribute("tabindex", "0");
    targetItem.focus();
    updateDisplay();
  }

  function getCurrentIndex(group) {
    const items = getItems(group);
    return items.findIndex((item) => item.getAttribute("tabindex") === "0");
  }

  /* ── Toolbar navigation (horizontal) ────────────── */

  function handleLinearNav(group, e) {
    const items = getItems(group);
    const current = getCurrentIndex(group);
    let next;

    switch (e.key) {
      case "ArrowRight":
      case "ArrowDown":
        e.preventDefault();
        next = (current + 1) % items.length;
        setRovingFocus(group, items[next]);
        break;
      case "ArrowLeft":
      case "ArrowUp":
        e.preventDefault();
        next = (current - 1 + items.length) % items.length;
        setRovingFocus(group, items[next]);
        break;
      case "Home":
        e.preventDefault();
        setRovingFocus(group, items[0]);
        break;
      case "End":
        e.preventDefault();
        setRovingFocus(group, items[items.length - 1]);
        break;
    }
  }

  /* ── Grid navigation (2D) ───────────────────────── */

  function handleGridNav(group, e) {
    const items = getItems(group);
    const cols = parseInt(group.dataset.cols) || 5;
    const current = getCurrentIndex(group);
    const row = Math.floor(current / cols);
    const col = current % cols;
    let next;

    switch (e.key) {
      case "ArrowRight":
        e.preventDefault();
        next = col + 1 < cols && current + 1 < items.length ? current + 1 : row * cols;
        setRovingFocus(group, items[next]);
        break;
      case "ArrowLeft":
        e.preventDefault();
        next = col - 1 >= 0 ? current - 1 : Math.min(row * cols + cols - 1, items.length - 1);
        setRovingFocus(group, items[next]);
        break;
      case "ArrowDown": {
        e.preventDefault();
        const nextRow = current + cols;
        next = nextRow < items.length ? nextRow : col;
        setRovingFocus(group, items[next]);
        break;
      }
      case "ArrowUp": {
        e.preventDefault();
        const prevRow = current - cols;
        const totalRows = Math.ceil(items.length / cols);
        next = prevRow >= 0 ? prevRow : Math.min((totalRows - 1) * cols + col, items.length - 1);
        setRovingFocus(group, items[next]);
        break;
      }
      case "Home":
        e.preventDefault();
        setRovingFocus(group, items[0]);
        break;
      case "End":
        e.preventDefault();
        setRovingFocus(group, items[items.length - 1]);
        break;
      case "Enter":
      case " ":
        e.preventDefault();
        selectColor(items[current]);
        break;
    }
  }

  /* ── Radio group selection ──────────────────────── */

  function handleRadioNav(group, e) {
    const items = getItems(group);
    const current = getCurrentIndex(group);
    let next;

    switch (e.key) {
      case "ArrowRight":
      case "ArrowDown":
        e.preventDefault();
        next = (current + 1) % items.length;
        selectRadio(group, items[next]);
        break;
      case "ArrowLeft":
      case "ArrowUp":
        e.preventDefault();
        next = (current - 1 + items.length) % items.length;
        selectRadio(group, items[next]);
        break;
      case "Home":
        e.preventDefault();
        selectRadio(group, items[0]);
        break;
      case "End":
        e.preventDefault();
        selectRadio(group, items[items.length - 1]);
        break;
    }
  }

  function selectRadio(group, item) {
    getItems(group).forEach((el) => el.setAttribute("aria-checked", "false"));
    item.setAttribute("aria-checked", "true");
    setRovingFocus(group, item);
  }

  /* ── Color swatch selection ─────────────────────── */

  function selectColor(swatch) {
    document
      .querySelectorAll(".color-swatch")
      .forEach((s) => s.setAttribute("aria-selected", "false"));
    swatch.setAttribute("aria-selected", "true");
    const color = swatch.dataset.color;
    const name = swatch.getAttribute("aria-label");
    colorSelected.innerHTML = `Selected: <span style="color: ${color}; font-weight: 600;">${name} (${color})</span>`;
  }

  /* ── Toolbar button toggle ──────────────────────── */

  function handleToolbarAction(button) {
    const pressed = button.getAttribute("aria-pressed");
    if (pressed !== null) {
      button.setAttribute("aria-pressed", pressed === "true" ? "false" : "true");
    }
  }

  /* ── Bind events ────────────────────────────────── */

  groups.forEach((group) => {
    const isGrid = group.hasAttribute("data-grid");
    const isRadio = group.getAttribute("role") === "radiogroup";

    group.addEventListener("keydown", (e) => {
      if (isGrid) {
        handleGridNav(group, e);
      } else if (isRadio) {
        handleRadioNav(group, e);
      } else {
        handleLinearNav(group, e);
        // Toggle on Enter/Space for toolbar
        if ((e.key === "Enter" || e.key === " ") && !isGrid && !isRadio) {
          e.preventDefault();
          const items = getItems(group);
          const current = getCurrentIndex(group);
          if (current >= 0) handleToolbarAction(items[current]);
        }
      }
    });

    // Click handlers
    getItems(group).forEach((item) => {
      item.addEventListener("click", () => {
        setRovingFocus(group, item);
        if (isRadio) {
          selectRadio(group, item);
        } else if (isGrid) {
          selectColor(item);
        } else {
          handleToolbarAction(item);
        }
      });
    });

    // Radio items also select on click
    if (isRadio) {
      getItems(group).forEach((item) => {
        item.addEventListener("click", () => selectRadio(group, item));
      });
    }
  });

  /* ── Tabindex Display ───────────────────────────── */

  function updateDisplay() {
    if (!tabindexDisplay) return;

    let html = "";
    const labels = ["Toolbar", "Radio Group", "Color Grid"];

    groups.forEach((group, gi) => {
      const items = getItems(group);
      html += `<span class="group-label">${labels[gi]}:</span> `;
      html += items
        .map((item) => {
          const val = item.getAttribute("tabindex");
          const cls = val === "0" ? "active-tab" : "inactive-tab";
          const label =
            item.getAttribute("aria-label") || item.textContent.trim() || item.dataset.color || "?";
          const short = label.length > 8 ? label.slice(0, 8) : label;
          return `<span class="${cls}">[${val}] ${short}</span>`;
        })
        .join("  ");
      html += "\n";
    });

    tabindexDisplay.innerHTML = html;
  }

  // Update display on any focus change
  document.addEventListener("focusin", () => {
    requestAnimationFrame(updateDisplay);
  });

  // Initial display
  updateDisplay();
})();

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Roving Tabindex</title>
  <link rel="stylesheet" href="style.css" />
</head>
<body>

  <div class="demo-wrapper">
    <h1 class="demo-title">Roving Tabindex</h1>
    <p class="demo-subtitle">Single Tab stop per widget group &mdash; arrow keys navigate within, Tab moves between groups</p>

    <div class="info-panel">
      <h2 class="info-title">How it works</h2>
      <p>Only one element per group has <code>tabindex="0"</code>; all others have <code>tabindex="-1"</code>. Pressing an arrow key moves <code>tabindex="0"</code> to the next item and focuses it. <kbd>Tab</kbd> moves to the next group, not the next item.</p>
    </div>

    <!-- Example 1: Toolbar -->
    <section class="example-section">
      <h2 class="section-title">Formatting Toolbar</h2>
      <div class="toolbar" role="toolbar" aria-label="Text formatting" data-roving-group>
        <button type="button" class="toolbar-btn" tabindex="0" data-action="bold" aria-label="Bold" aria-pressed="false">
          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round"><path d="M6 4h8a4 4 0 0 1 4 4 4 4 0 0 1-4 4H6z"/><path d="M6 12h9a4 4 0 0 1 4 4 4 4 0 0 1-4 4H6z"/></svg>
        </button>
        <button type="button" class="toolbar-btn" tabindex="-1" data-action="italic" aria-label="Italic" aria-pressed="false">
          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round"><line x1="19" y1="4" x2="10" y2="4"/><line x1="14" y1="20" x2="5" y2="20"/><line x1="15" y1="4" x2="9" y2="20"/></svg>
        </button>
        <button type="button" class="toolbar-btn" tabindex="-1" data-action="underline" aria-label="Underline" aria-pressed="false">
          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round"><path d="M6 4v6a6 6 0 0 0 12 0V4"/><line x1="4" y1="20" x2="20" y2="20"/></svg>
        </button>
        <span class="toolbar-separator" role="separator" aria-orientation="vertical"></span>
        <button type="button" class="toolbar-btn" tabindex="-1" data-action="align-left" aria-label="Align left" aria-pressed="true">
          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round"><line x1="17" y1="10" x2="3" y2="10"/><line x1="21" y1="6" x2="3" y2="6"/><line x1="21" y1="14" x2="3" y2="14"/><line x1="17" y1="18" x2="3" y2="18"/></svg>
        </button>
        <button type="button" class="toolbar-btn" tabindex="-1" data-action="align-center" aria-label="Align center" aria-pressed="false">
          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round"><line x1="18" y1="10" x2="6" y2="10"/><line x1="21" y1="6" x2="3" y2="6"/><line x1="21" y1="14" x2="3" y2="14"/><line x1="18" y1="18" x2="6" y2="18"/></svg>
        </button>
        <button type="button" class="toolbar-btn" tabindex="-1" data-action="align-right" aria-label="Align right" aria-pressed="false">
          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round"><line x1="21" y1="10" x2="7" y2="10"/><line x1="21" y1="6" x2="3" y2="6"/><line x1="21" y1="14" x2="3" y2="14"/><line x1="21" y1="18" x2="7" y2="18"/></svg>
        </button>
      </div>
    </section>

    <!-- Example 2: Radio Group -->
    <section class="example-section">
      <h2 class="section-title">Theme Selection</h2>
      <div class="radio-group" role="radiogroup" aria-label="Choose a theme" data-roving-group>
        <div class="radio-item" role="radio" aria-checked="true" tabindex="0" data-value="dark">
          <span class="radio-indicator"></span>
          <span class="radio-label">Dark</span>
        </div>
        <div class="radio-item" role="radio" aria-checked="false" tabindex="-1" data-value="light">
          <span class="radio-indicator"></span>
          <span class="radio-label">Light</span>
        </div>
        <div class="radio-item" role="radio" aria-checked="false" tabindex="-1" data-value="dim">
          <span class="radio-indicator"></span>
          <span class="radio-label">Dim</span>
        </div>
        <div class="radio-item" role="radio" aria-checked="false" tabindex="-1" data-value="auto">
          <span class="radio-indicator"></span>
          <span class="radio-label">System</span>
        </div>
      </div>
    </section>

    <!-- Example 3: Color Swatch Grid -->
    <section class="example-section">
      <h2 class="section-title">Color Palette</h2>
      <div class="color-grid" role="grid" aria-label="Choose accent color" data-roving-group data-grid data-cols="5">
        <div class="color-row" role="row">
          <div class="color-swatch" role="gridcell" tabindex="0" data-color="#ef4444" style="--swatch: #ef4444" aria-label="Red" aria-selected="false"></div>
          <div class="color-swatch" role="gridcell" tabindex="-1" data-color="#f97316" style="--swatch: #f97316" aria-label="Orange" aria-selected="false"></div>
          <div class="color-swatch" role="gridcell" tabindex="-1" data-color="#eab308" style="--swatch: #eab308" aria-label="Yellow" aria-selected="false"></div>
          <div class="color-swatch" role="gridcell" tabindex="-1" data-color="#22c55e" style="--swatch: #22c55e" aria-label="Green" aria-selected="false"></div>
          <div class="color-swatch" role="gridcell" tabindex="-1" data-color="#06b6d4" style="--swatch: #06b6d4" aria-label="Cyan" aria-selected="false"></div>
        </div>
        <div class="color-row" role="row">
          <div class="color-swatch" role="gridcell" tabindex="-1" data-color="#3b82f6" style="--swatch: #3b82f6" aria-label="Blue" aria-selected="false"></div>
          <div class="color-swatch" role="gridcell" tabindex="-1" data-color="#8b5cf6" style="--swatch: #8b5cf6" aria-label="Violet" aria-selected="false"></div>
          <div class="color-swatch" role="gridcell" tabindex="-1" data-color="#d946ef" style="--swatch: #d946ef" aria-label="Fuchsia" aria-selected="false"></div>
          <div class="color-swatch" role="gridcell" tabindex="-1" data-color="#ec4899" style="--swatch: #ec4899" aria-label="Pink" aria-selected="false"></div>
          <div class="color-swatch" role="gridcell" tabindex="-1" data-color="#f5f5f5" style="--swatch: #f5f5f5" aria-label="White" aria-selected="false"></div>
        </div>
      </div>
      <p class="color-selected" id="colorSelected">No color selected</p>
    </section>

    <section class="example-section">
      <h2 class="section-title">Tab Order Visualizer</h2>
      <p class="tab-order-info">Press <kbd>Tab</kbd> to see how focus jumps between the three groups above &mdash; never between items within a group. The current tabindex values are shown below.</p>
      <div class="tabindex-display" id="tabindexDisplay"></div>
    </section>
  </div>

  <script src="script.js"></script>
</body>
</html>