class Primer::Alpha::Banner

For more information about the focus management technique, visit the [Staff only: Accessible Banner Prototype docs](github.com/github/accessibility/blob/main/docs/coaching-recommendations/toast-flash-banner/accessible-banner-prototype.md#consideration). This guidance is subject to change.
To properly focus a banner, add a ‘tabindex=“-1”` to the Banner container, and focus that container (one way is using the [`focus()` API](developer.mozilla.org/en-US/docs/Web/API/HTMLElement/focus)).
Focusing a Banner when it appears helps to maximize discoverability of the message, especially in critical scenarios.
### Focusing a Banner
For more information about either technique, visit [Staff only: Challenges with live regions](github.com/github/accessibility/blob/main/docs/coaching-recommendations/toast-flash-banner/accessible-banner-prototype.md#challenges-with-dynamically-inserted-live-region). This guidance is subject to change.
To ensure a Banner is announced reliably, make sure that there’s a live region container that is already on the page. When the Banner is shown, populate the live region container with the content of the Banner. This can be done in one of two ways. The first is to rely on a global live region container that is guaranteed to be on the page. When the Banner appears, populate this global live region container with the Banner content. The second technique is to hide or show the Banner within a live region wrapper that is guaranteed to always be on the page.
Live regions can be finicky and don’t work well when injected dynamically. Setting a live region attribute on the Banner itself is discouraged as it will not announce as expected for most screen readers.
When a Banner is used to communicate non-critical feedback, or is used in critical scenarios where moving focus is considered too disruptive, use a live region announcement to announce the content of the Banner to screen reader users.
### Announcing a Banner
A Banner can be used in one of two ways – to highlight information on a page, or to communicate an urgent message/feedback for a user action. For the latter scenario, it may be necessary to use a live region or focus management technique to ensure that the Banner is discoverable and accessible for all users. Otherwise, the Banner can easily be missed, including by those using magnification software or screen reader users who may not realize that a Banner has appeared. The appropriate technique to use is highly context-dependent. Visit the [Banner’s Accessibility section](primer.style/components/banner#accessibility) or defer to the accessibility team to determine if your scenario requires either techniques.
Given that Banner is made visually prominent to sighted users through the use of icons and color, consider providing a heading and designating the Banner as a region landmark to improve navigability and discoverability of the Banner of assistive technology users. At this time, the PVC Banner does not render a heading nor render as a region landmark by default. This may be introduced in the future [as a breaking API change](github.com/primer/view_components/issues/2619). For now, consider providing an appropriate heading inside of the Banner and rendering the Banner as a ‘<section>` tag with `aria-labelledby=“switch-this-with-banner-heading-id”` to implicitly designate the Banner as a region landmark.
@accessibility
Use `Banner` to highlight important information.

def catalyst_action(event:, function:)

def catalyst_action(event:, function:)
  "#{event}:#{custom_element_name}##{function}"
end

def catalyst_target(field:)

def catalyst_target(field:)
  "#{custom_element_name}.#{field}"
end

def custom_element_name

def custom_element_name
  "x-banner"
end

def initialize(tag: DEFAULT_TAG, full: false, full_when_narrow: false, dismiss_scheme: DEFAULT_DISMISS_SCHEME, dismiss_label: DEFAULT_DISMISS_LABEL, description: nil, icon: nil, scheme: DEFAULT_SCHEME, **system_arguments)

Parameters:

system_arguments (Hash) -- <%= link_to_system_arguments_docs %>
scheme (Symbol) -- <%= one_of(Primer::Alpha::Banner::SCHEME_MAPPINGS.keys) %>
icon (Symbol) -- The name of an <%= link_to_octicons %> icon to use. If no icon is provided, a default one will be chosen based on the scheme.
description (String) -- Description text rendered underneath the message.
dismiss_label (String) -- The aria-label text of the dismiss "x" button
dismiss_scheme (Symbol) -- Whether the component can be dismissed with an "x" button. <%= one_of(Primer::Alpha::Banner::DISMISS_SCHEMES) %>
full_when_narrow (Boolean) -- Whether the component should take up the full width of the screen when rendered inside smaller viewports.
full (Boolean) -- Whether the component should take up the full width of the screen.
tag (Symbol) -- <%= one_of(Primer::Alpha::Banner::TAG_OPTIONS) %>

def initialize(tag: DEFAULT_TAG, full: false, full_when_narrow: false, dismiss_scheme: DEFAULT_DISMISS_SCHEME, dismiss_label: DEFAULT_DISMISS_LABEL, description: nil, icon: nil, scheme: DEFAULT_SCHEME, **system_arguments)
  @scheme = fetch_or_fallback(SCHEME_MAPPINGS.keys, scheme, DEFAULT_SCHEME)
  @icon = icon || DEFAULT_ICONS[@scheme]
  @dismiss_scheme = dismiss_scheme
  @dismiss_label = dismiss_label
  @description = description
  @system_arguments = system_arguments
  @system_arguments[:tag] = fetch_or_fallback(TAG_OPTIONS, tag, DEFAULT_TAG)
  @system_arguments[:classes] = class_names(
    @system_arguments[:classes],
    "Banner",
    "flash", # legacy
    SCHEME_MAPPINGS[@scheme],
    LEGACY_SCHEME_MAPPINGS[@scheme],
    "Banner--full": full,
    "flash-full": full, # legacy
    "Banner--full-whenNarrow": full_when_narrow
  )
  @message_arguments = {
    tag: :div,
    classes: "Banner-message"
  }
  @wrapper_arguments = {
    tag: custom_element_name,
    data: { dismiss_scheme: @dismiss_scheme }
  }
end