# Tabs

A row of clickable tabs that each reveal different content. Only one tab is visible at a time. Think of it like a filing cabinet with labelled dividers — you flip between sections without leaving the page.

---

## Quick example

```csharp
new Tabs(
    id: "settings-tabs",
    tabs: new[]
    {
        ("general",  "General",  "<p>General settings here.</p>"),
        ("security", "Security", "<p>Password and 2FA here.</p>"),
        ("billing",  "Billing",  "<p>Payment details here.</p>"),
    })
```

The first tab is active by default.

---

## All the options

```csharp
public Tabs(
    string id,
    IEnumerable<(string Id, string Label, string Content)> tabs)
```

| Parameter | What it does |
|---|---|
| `id` | A unique identifier for this tabs widget. Required if you have more than one `Tabs` on the same page. |
| `tabs` | The list of tabs. Each is a `(Id, Label, Content)` tuple. |

**Tab tuple fields:**

| Field | What it does |
|---|---|
| `Id` | A unique identifier for this tab within the widget. Used internally to link the trigger to the panel. |
| `Label` | The text shown on the tab button. |
| `Content` | The HTML content shown when this tab is active. |

---

## Real-world examples

### User profile page with tabbed sections

```csharp
new Tabs(
    id: "profile-tabs",
    tabs: new[]
    {
        ("overview",  "Overview",  $"<p>Joined {user.CreatedAt:MMMM yyyy}</p>"),
        ("activity",  "Activity",  activityHtml),
        ("settings",  "Settings",  settingsFormHtml),
    })
```

### Tab containing a full component

Pre-render inner components to HTML strings before embedding them:

```csharp
string Render(IHtmxComponent c)
{
    var buf = new System.Buffers.ArrayBufferWriter<byte>();
    c.Render(new HtmxRenderContext(buf));
    return System.Text.Encoding.UTF8.GetString(buf.WrittenSpan);
}

new Tabs(
    id: "report",
    tabs: new[]
    {
        ("table",  "Table",  Render(new Table(headers: cols, rows: rows))),
        ("summary", "Summary", summaryHtml),
    })
```

### Code samples in multiple languages

```csharp
new Tabs(
    id: "code-example",
    tabs: new[]
    {
        ("csharp", "C#",     "<pre><code>var x = 42;</code></pre>"),
        ("fsharp", "F#",     "<pre><code>let x = 42</code></pre>"),
    })
```

---

## How it works

All tab panels are present in the HTML on page load. JavaScript in `components.js` hides all but the first using the HTML `hidden` attribute. When a tab button is clicked, its matching panel has `hidden` removed and all others get it added back. No server request is made — this is pure client-side switching.
    {
        ("summary", "Summary", "<p>High level numbers.</p>"),
        ("detail",  "Detail",  tableHtml),
    })
```

### Multiple independent tab groups

```csharp
new Tabs(id: "tabs-a", tabs: setA)
new Tabs(id: "tabs-b", tabs: setB)
```

The `id` scopes JS initialization — each Tabs instance is independent.

---

## Tips and tricks

- The `Id` of each tab tuple is used as the `data-tab` attribute — keep it URL-safe and unique within the instance.
- The first tab is always activated on page load regardless of which tab was active before navigation.
- Tab `Content` is raw HTML — HTML-encode any user-supplied values.
- For lazy-loaded tab content, place HTMX attributes in the `Content` string and use `hx-trigger="revealed"` to load content when the panel becomes visible.
- Tabs do not push to the URL hash by default. If you need deep-linkable tabs, listen to the `click` event on `.tabs-trigger` elements and update `location.hash`.
- Tabs do not push to the URL hash by default. If you need deep-linkable tabs, listen to the `click` event on `.tabs-trigger` elements and update `location.hash`.

---

## Complete page example

**`Templates/ProfileSettingsPage.htmx`**
```html
<div class="max-w-2xl mx-auto py-10">
  <h1 class="text-2xl font-bold mb-6">Profile settings</h1>
  $$SettingsTabs$$
</div>
```

**`Templates/ProfileSettingsPage.htmx.cs`**
```csharp
namespace Htmx.ApiDemo.Templates;

public sealed class ProfileSettingsPage : ProfileSettingsPageBase
{
    private readonly IHtmxComponent _tabs;

    public ProfileSettingsPage(ApplicationUser user, IAntiforgery af, HttpContext ctx)
    {
        var tokens = af.GetAndStoreTokens(ctx);
        var afHtml = $"""<input type="hidden" name="{tokens.FormFieldName}" value="{tokens.RequestToken}">""";

        // Build each tab's content as raw HTML strings rendered into the Tabs component
        var generalContent = $"""
            <form method="post" action="/profile/general">
              {afHtml}
              <label class="block mb-1 text-sm">Display name</label>
              <input name="displayName" value="{System.Net.WebUtility.HtmlEncode(user.DisplayName ?? "")}"
                     class="input mb-4 w-full">
              <button class="btn" type="submit">Save</button>
            </form>
            """;

        var securityContent = $"""
            <form method="post" action="/profile/password">
              {afHtml}
              <label class="block mb-1 text-sm">New password</label>
              <input name="newPassword" type="password" class="input mb-4 w-full">
              <button class="btn" type="submit">Change password</button>
            </form>
            """;

        _tabs = new Components.Tabs(
            defaultValue: "general",
            tabs: new[]
            {
                new TabItem(Value: "general",  Label: "General",  Content: generalContent),
                new TabItem(Value: "security", Label: "Security", Content: securityContent),
            });
    }

    protected override void RenderSettingsTabs(HtmxRenderContext ctx) => _tabs.Render(ctx.Next());
}
```

**GET handler**
```csharp
[Handler]
[MapGet("/profile")]
public static partial class GetProfileSettingsHandler
{
    public record Query();
    private static async Task<IResult> HandleAsync(
        Query _, HttpContext ctx, MongoDbService db, IAntiforgery af, CancellationToken ct)
    {
        var user = await db.GetCurrentUserAsync(ctx, ct);
        return await ctx.WriteHtmxPage(
            new ProfileSettingsPage(user, af, ctx), title: "Profile settings");
    }
}
```