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dialog-patterns

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Native HTML dialog patterns for Rails with Turbo and Stimulus. Use when building modals, confirmations, alerts, or any overlay UI. Triggers on modal, dialog, popup, confirmation, alert, or toast patterns.

Design

What this skill does


# Native Dialog Patterns for Rails

Build accessible, modern dialog UIs using the native HTML `<dialog>` element with Turbo Frames and Stimulus. No JavaScript frameworks or heavy libraries required.

## When to Use This Skill

- Building modal dialogs for forms, confirmations, or content
- Creating toast/alert notifications
- Implementing confirmation dialogs (delete, destructive actions)
- Any overlay UI that needs focus management and accessibility

## Why Native `<dialog>`?

| Feature | Native `<dialog>` | Custom Modal |
|---------|-------------------|--------------|
| Focus trapping | Built-in | Manual implementation |
| ESC to close | Built-in | Manual implementation |
| Backdrop | Built-in (`::backdrop`) | Manual overlay |
| Accessibility | Native `role="dialog"` | Manual ARIA |
| Top layer | Automatic (above all content) | z-index battles |
| Scroll lock | Automatic | Manual `overflow: hidden` |

## Zero-JavaScript Confirmation Dialogs (Recommended)

Modern browsers support the **Invoker Commands API** for declarative dialog control—no JavaScript required. See [references/zero-js-patterns.md](references/zero-js-patterns.md) for complete examples.

### Quick Reference

```erb
<%= button_tag "Delete", commandfor: "delete-#{post.id}", command: "show-modal" %>

<dialog id="delete-<%= post.id %>" closedby="any" role="alertdialog">
  <h3>Delete "<%= post.title %>"?</h3>
  <button commandfor="delete-<%= post.id %>" command="close">Cancel</button>
  <%= button_to "Delete", post, method: :delete %>
</dialog>
```

### Key Attributes

| Attribute | Purpose |
|-----------|---------|
| `commandfor="id"` | References the dialog to control |
| `command="show-modal"` | Opens as modal (backdrop, focus trap) |
| `command="close"` | Closes the dialog |
| `closedby="any"` | Enables backdrop click and ESC to close |

### When to Use Zero-JS vs Stimulus

| Scenario | Approach |
|----------|----------|
| Simple confirmations | Zero-JS (Invoker Commands) |
| Modals with async content | Stimulus + Turbo Frames |
| Complex multi-step dialogs | Stimulus controller |
| Animations | CSS `@starting-style` |

### Additional Patterns (see references/)

- **CSS animations** with `@starting-style` for enter/exit transitions
- **Turbo.config.forms.confirm** to replace ugly browser dialogs
- **Progressive enhancement** for cross-browser compatibility

## Core Pattern: Async Modal with Turbo Frames

The recommended pattern for Rails modals combines three technologies:

1. **Turbo Frame** - Async content loading without page reload
2. **Native `<dialog>`** - Accessible modal presentation
3. **Stimulus controller** - Lifecycle management

### Step 1: Layout Container

Add a modal turbo-frame to your layout:

```erb
<%# app/views/layouts/application.html.erb %>
<body>
  <%= yield %>

  <%# Modal injection point %>
  <%= turbo_frame_tag :modal %>
</body>
```

### Step 2: Trigger Links

Target the modal frame from any link:

```erb
<%# Any view %>
<%= link_to "New Post", new_post_path, data: { turbo_frame: :modal } %>
<%= link_to "Edit", edit_post_path(@post), data: { turbo_frame: :modal } %>
<%= link_to "Confirm Delete", confirm_delete_post_path(@post), data: { turbo_frame: :modal } %>
```

### Step 3: Modal Content View

Wrap modal content in matching turbo-frame with nested inner frame:

```erb
<%# app/views/posts/new.html.erb %>
<%= turbo_frame_tag :modal do %>
  <%# Inner frame prevents flash during form validation %>
  <%= turbo_frame_tag :modal_content do %>
    <dialog data-controller="dialog" data-action="click->dialog#clickOutside" open>
      <article>
        <header>
          <h2>New Post</h2>
          <button data-action="dialog#close" aria-label="Close">&times;</button>
        </header>

        <%= render "form", post: @post %>
      </article>
    </dialog>
  <% end %>
<% end %>
```

### Step 4: Stimulus Controller

Key behaviors: `showModal()` on connect, `replaceChildren()` on disconnect (prevents stale content), `clickOutside` for backdrop close.

See [references/dialog-examples.md](references/dialog-examples.md) for full Stimulus controller, CSS styling, and Tailwind variant.

## Why Nested Turbo Frames?

The nested frame pattern (`modal` > `modal_content`) prevents content flashing:

```erb
<%= turbo_frame_tag :modal do %>
  <%= turbo_frame_tag :modal_content do %>
    <dialog>...</dialog>
  <% end %>
<% end %>
```

**Problem without nested frame:**
When a form inside the modal has validation errors and re-renders, the outer frame briefly shows the old content before replacing it.

**Solution with nested frame:**
The inner frame handles form re-renders independently, keeping the modal structure stable.

## Form Handling in Modals

### Successful Submission

Redirect with Turbo to close modal and update page:

```ruby
# app/controllers/posts_controller.rb
def create
  @post = Post.new(post_params)

  if @post.save
    redirect_to posts_path, notice: "Post created!"
  else
    render :new, status: :unprocessable_entity
  end
end
```

The redirect navigates `_top` (full page), effectively closing the modal.

### Validation Errors

Re-render the form with `422` status to keep modal open:

```ruby
render :new, status: :unprocessable_entity
```

### Turbo Stream Response (Stay in Modal)

Use `turbo_stream.update("modal", "")` to clear modal without full redirect. See [references/dialog-examples.md](references/dialog-examples.md) for full example.

## Confirmation Dialog Pattern

For destructive actions: add a `confirm_delete` member route, render a dialog in a turbo frame, trigger via `link_to` with `data: { turbo_frame: :modal }`.

See [references/dialog-examples.md](references/dialog-examples.md) for full confirmation dialog view, route, and trigger.

## Alert/Toast Pattern

For flash messages and notifications. Use `show()` instead of `showModal()` for non-modal presentation. See [references/toast-slideover-patterns.md](references/toast-slideover-patterns.md) for complete implementation.

```erb
<dialog class="toast" data-controller="toast" data-toast-duration-value="5000">
  <p><%= message %></p>
</dialog>
```

Key difference: `show()` opens without backdrop or focus trap (toasts), `showModal()` centers with backdrop (modals).

## Slideover Panel Pattern

For side panels (settings, filters, details). See [references/toast-slideover-patterns.md](references/toast-slideover-patterns.md) for styling and animations.

```erb
<dialog class="slideover" data-controller="dialog" data-action="click->dialog#clickOutside">
  <aside>
    <header><h2>Filters</h2></header>
    <%= render "filters" %>
  </aside>
</dialog>
```

## Accessibility

Native `<dialog>` provides focus trapping, ESC close, background inert, and top layer automatically. Additionally ensure:

- Visible close button (not just ESC)
- `aria-labelledby` / `aria-describedby` for descriptive context
- Focus return to trigger element on close (store `document.activeElement` in `connect()`)

See [references/dialog-examples.md](references/dialog-examples.md) for enhanced accessibility and focus return examples.

## Common Patterns Summary

| Pattern | Container | Stimulus | `show` method |
|---------|-----------|----------|---------------|
| Modal form | `turbo_frame_tag :modal` | `dialog` | `showModal()` |
| Confirmation | `turbo_frame_tag :modal` | `dialog` | `showModal()` |
| Toast/Alert | Fixed position | `toast` | `show()` |
| Slideover | `turbo_frame_tag :modal` | `dialog` | `showModal()` |

## Anti-Patterns to Avoid

| Anti-Pattern | Problem | Solution |
|--------------|---------|----------|
| Custom modal without `<dialog>` | No native accessibility | Use native `<dialog>` |
| Missing nested turbo-frame | Content flash on validation | Add inner frame |
| Not clearing frame on close | Stale content on reopen | Clear with `replaceChildren()` in `disconnect()` |
| z-index for stacking | Battles with other elements | `<dialog>` uses top layer |
| Manual focus trap | Complex, error-prone | `showModal()` handl

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