Htmx/docs/Components/DropdownMenu.md

# DropdownMenu

A button that reveals a floating list of links or actions when clicked. Closes when the user clicks outside or presses Escape. Positioned below the trigger by default.

---

## HTML structure

```
div.relative.inline-block         ← anchor for absolute positioning
  {trigger rendered inline}       ← any IHtmxComponent (usually a Button)
  div.dropdown-menu.absolute...   ← the floating panel; hidden by default
    div.w-48.rounded-md.border.bg-popover.shadow-md.p-1
      a.dropdown-item             ← link item
      hr.dropdown-separator       ← separator (when isSeparator=true)
```

---

## CSS mechanics

| Class | Effect |
|---|---|
| `hidden` (initial) on panel | Hides the dropdown until toggled by JS |
| `absolute z-50` | Floats above surrounding content |
| `top-full mt-1` | Placed below the trigger with a small gap |
| `right-0` / `left-0` | Controlled by the `position` parameter |
| `dropdown-item` | `flex items-center px-2 py-1.5 text-sm rounded hover:bg-accent cursor-pointer` |

---

## JavaScript (delegated click in `components.js`)

Set up once on `document` — works for HTMX-swapped dropdowns.

**Open / close toggle:**
1. Click on the trigger element (`[data-dropdown-trigger]`) → toggle `.hidden` on the sibling `.dropdown-menu`
2. Click outside the dropdown root → close all open dropdowns
3. `Escape` keydown → close all open dropdowns
4. Click on a `.dropdown-item` link → close the parent dropdown and follow the link

---

## Constructor signature

```csharp
public DropdownMenu(
    IHtmxComponent trigger,
    IEnumerable<(string Label, string Href, bool IsSeparator)> items,
    string position = "right")
```

| Parameter | Description |
|---|---|
| `trigger` | Any `IHtmxComponent` — shown as the visible toggle element |
| `items` | Menu items; `IsSeparator=true` renders an `<hr>` (Label/Href ignored) |
| `position` | `"right"` (default) aligns panel right edge; `"left"` aligns left edge |

---

## Usage examples

### User menu

```csharp
new DropdownMenu(
    trigger: new Button("Account", variant: "outline"),
    items: new[]
    {
        ("Profile",  "/profile",  false),
        ("Settings", "/settings", false),
        ("",          "",          true),   // separator
        ("Sign out",  "/logout",   false),
    })
```

### Icon-button dropdown

```csharp
new DropdownMenu(
    trigger: new Button("⋯", size: "icon", variant: "ghost"),
    items: new[]
    {
        ("Edit",   "/items/42/edit",   false),
        ("Delete", "/items/42/delete", false),
    })
```

### Left-aligned dropdown (useful when near the right edge of the viewport)

```csharp
new DropdownMenu(
    trigger: new Button("Actions"),
    items: actions,
    position: "left")
```

### HTMX action items

Items use `<a href>` — if you need HTMX requests, override by building the HTML manually:

```csharp
// Pass a synthetic IHtmxComponent for trigger and use a raw slot override
// for items that need hx-delete / hx-post, since items only support href links.
// Alternatively, use a Dialog for confirmation dialogs linked from the dropdown.
```

---

## Tips and tricks

- The `trigger` is any `IHtmxComponent` — pass a `Button`, an `Avatar`, or any custom component.
- All items are rendered as `<a href>` links. For actions that should POST/DELETE, either route them through normal GET links to a form redirect, or pair them with a confirmation Dialog.
- For a context menu that appears at a table row, pass `new Button("⋯", size: "icon", variant: "ghost")` as the trigger.
- Setting `position: "left"` prevents the dropdown from overflowing the right side of the viewport when the trigger is near the right edge.
- Multiple dropdowns on the same page are handled independently — clicking one will close others.
- Multiple dropdowns on the same page are handled independently — clicking one will close others.

---

## Complete page example

**`Templates/UserHeaderPage.htmx`**
```html
<header class="border-b px-6 py-3 flex items-center justify-between">
  <a href="/" class="font-bold text-lg">MyApp</a>
  <div class="flex items-center gap-4">
    <a href="/dashboard" class="text-sm text-muted-foreground hover:text-foreground">Dashboard</a>
    $$UserMenu$$
  </div>
</header>
<main class="max-w-3xl mx-auto py-10">
  $$Body$$
</main>
```

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

public sealed class UserHeaderPage : UserHeaderPageBase
{
    private readonly IHtmxComponent _userMenu;
    private readonly IHtmxComponent _body;

    public UserHeaderPage(AppUser user, IHtmxComponent body)
    {
        _body = body;

        var trigger = new Components.Avatar(
            fallback: GetInitials(user.DisplayName),
            size: "sm");

        _userMenu = new Components.DropdownMenu(
            trigger: trigger,
            items: new[]
            {
                ("Profile",       "/profile",  false),
                ("Settings",      "/settings", false),
                ("",              "",           true),   // separator
                ("Sign out",      "/logout",   false),
            });
    }

    private static string GetInitials(string? name)
    {
        if (string.IsNullOrWhiteSpace(name)) return "?";
        var parts = name.Split(' ', StringSplitOptions.RemoveEmptyEntries);
        return parts.Length >= 2 ? $"{parts[0][0]}{parts[^1][0]}" : name[..1].ToUpperInvariant();
    }

    protected override void RenderUserMenu(HtmxRenderContext ctx) => _userMenu.Render(ctx.Next());
    protected override void RenderBody(HtmxRenderContext ctx)     => _body.Render(ctx.Next());
}
```

**GET handler**
```csharp
[Handler]
[MapGet("/home")]
public static partial class GetHomeHandler
{
    public record Query();

    private static async Task<IResult> HandleAsync(
        Query _, HttpContext ctx, MongoDbService db, CancellationToken ct)
    {
        var email = ctx.User.FindFirst(ClaimTypes.Email)?.Value ?? "";
        var user  = await db.FindByNormalizedEmailAsync(email.ToUpperInvariant(), ct)
                    ?? new AppUser { Email = email };

        // The inner body can be any page component
        var innerBody = new WelcomePage(user);
        var page = new UserHeaderPage(user, innerBody);
        return await ctx.WriteHtmxPage(page, title: "Home");
    }
}
```