initial dialog implementation

app/components/primer/alpha/dialog.html.erb

@@ -0,0 +1,8 @@
+<%= show_button %>
+<div class="Overlay--hidden Overlay-backdrop--center Overlay-backdrop--full-whenNarrow" data-modal-dialog-overlay>
+  <%= render Primer::BaseComponent.new(**@system_arguments) do %>
+    <%= header %>
+    <%= body %>
+    <%= footer %>
+  <% end %>
+</div>

app/components/primer/alpha/dialog.rb

@@ -0,0 +1,127 @@
+# frozen_string_literal: true
+
+module Primer
+  module Alpha
+    # A `Dialog` is used to remove the user from the main application flow,
+    # to confirm actions, ask for disambiguation or to present small forms.
+    #
+    # @accessibility
+    #   - **Dialog Accessible Name**: A dialog should have an accessible name,
+    #   so screen readers are aware of the purpose of the dialog when it opens.
+    #   Give an accessible name setting `:title`. The accessible name will be
+    #   used as the main heading inside the dialog.
+    #   - **Dialog unique id**: A dialog should be unique. Give a unique id
+    #   setting `:dialog_id`. If no `:dialog_id` is given, a default randomize
+    #   hex id is generated.
+    #
+    #   The combination of both `:title` and `:dialog_id` establishes an
+    #   `aria-labelledby` relationship between the title and the unique id of
+    #   the dialog.
+    class Dialog < Primer::Component
+      DEFAULT_WIDTH = :medium
+      WIDTH_MAPPINGS = {
+        :small => "Overlay--width-small",
+        DEFAULT_WIDTH => "Overlay--width-medium",
+        :large => "Overlay--width-large",
+        :xlarge => "Overlay--width-xlarge",
+        :xxlarge => "Overlay--width-xxlarge"
+      }.freeze
+      WIDTH_OPTIONS = WIDTH_MAPPINGS.keys
+
+      # Optional button to open the dialog.
+      #
+      # @param system_arguments [Hash] The same arguments as <%= link_to_component(Primer::ButtonComponent) %>.
+      renders_one :show_button, lambda { |**system_arguments|
+        system_arguments[:classes] = class_names(
+          system_arguments[:classes]
+        )
+        system_arguments[:id] = "dialog-show-#{@system_arguments[:id]}"
+        system_arguments["data-show-dialog-id"] = @system_arguments[:id]
+        system_arguments[:data] = (system_arguments[:data] || {}).merge({ "show-dialog-id": @system_arguments[:id] })
+        Primer::ButtonComponent.new(**system_arguments)
+      }
+
+      # Header content.
+      #
+      # @param hide_divider [Boolean] If true the visual dividing line between the header and body will be hidden
+      # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
+      renders_one :header, lambda { |hide_divider: false, **system_arguments|
+        if @subtitle.present?
+          subtitle_id = "#{id}-description"
+        end
+        Primer::Alpha::Dialog::Header.new(
+          title: @title,
+          subtitle: @subtitle,
+          subtitle_id: subtitle_id,
+          hide_divider: hide_divider,
+          **system_arguments
+        )
+      }
+
+      # Required body content.
+      #
+      # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
+      renders_one :body, "Body"
+
+      # Footer content.
+      #
+      # @param hide_divider [Boolean] If true the visual dividing line between the body and footer will be hidden
+      # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
+      renders_one :footer, lambda { |hide_divider: false, **system_arguments|
+        Primer::Alpha::Dialog::Footer.new(hide_divider: hide_divider, **system_arguments)
+      }
+
+      # @example Dialog with Cancel and Submit buttons
+      #   @description
+      #     An ID is provided which enables wiring of the open and close buttons to the dialog.
+      #   @code
+      #     <%= render(Primer::Alpha::Dialog.new(
+      #       title: "Dialog Example",
+      #     )) do |d| %>
+      #       <% d.show_button { "Show Dialog" } %>
+      #       <% d.body do %>
+      #         <p>Some content</p>
+      #       <% end %>
+      #       <% d.footer do %>
+      #         <%= render(Primer::ButtonComponent.new(data: { "close-dialog-id": "my-dialog" })) { "Cancel" } %>
+      #         <%= render(Primer::ButtonComponent.new(scheme: :primary)) { "Submit" } %>
+      #       <% end %>
+      #     <% end %>
+      # @param id [String] The id of the dialog.
+      # @param title [String] The title of the dialog.
+      # @param subtitle [String] The subtitle of the dialog. This will also set the `aria-describedby` attribute.
+      # @param width [Symbol] The width of the dialog. <%= one_of(Primer::Alpha::Dialog::WIDTH_OPTIONS) %>
+      # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
+      # @param body_padding_variant??
+      def initialize(
+        title:,
+        subtitle: nil,
+        width: DEFAULT_WIDTH,
+        id: "dialog-#{(36**3 + rand(36**4)).to_s(36)}",
+        **system_arguments
+      )
+        @system_arguments = deny_tag_argument(**system_arguments)
+
+        @system_arguments[:tag] = "modal-dialog"
+        @system_arguments[:role] = "dialog"
+        @system_arguments[:id] = id.to_s
+        @system_arguments[:aria] = { modal: true }
+        @system_arguments[:classes] = class_names(
+          "Overlay",
+          WIDTH_MAPPINGS[fetch_or_fallback(WIDTH_OPTIONS, width, DEFAULT_WIDTH)],
+          "Overlay--height-auto",
+          "Overlay--motion-scaleFade",
+          system_arguments[:classes]
+        )
+
+        @subtitle = subtitle
+        if subtitle.present?
+          @system_arguments[:aria].describedby ||= @description
+        end
+
+        @id = id.to_s
+        @title = title
+      end
+    end
+  end
+end

app/components/primer/alpha/dialog/body.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module Primer
+  module Alpha
+    class Dialog
+      # A `Dialog::Body` is a compositional component, used to render the
+      # Body of a dialog. See <%= link_to_component(Primer::Alpha::Dialog) %>.
+      class Body < Primer::Component
+        # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
+        def initialize(**system_arguments)
+          deny_tag_argument(**system_arguments)
+          system_arguments[:tag] = :header
+          system_arguments[:classes] = class_names(
+            "Overlay-body",
+            system_arguments[:classes]
+          )
+          render(Primer::BaseComponent.new(**system_arguments))
+        end
+      end
+    end
+  end
+end

app/components/primer/alpha/dialog/footer.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Primer
+  module Alpha
+    class Dialog
+      # A `Dialog::Footer` is a compositional component, used to render the
+      # Footer of a dialog. See <%= link_to_component(Primer::Alpha::Dialog) %>.
+      class Footer < Primer::Component
+        # @param hide_divider [Boolean] If true the visual dividing line between the body and footer will be hidden
+        # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
+        def initialize(hide_divider: false, **system_arguments)
+          deny_tag_argument(**system_arguments)
+          system_arguments[:tag] = :div
+          system_arguments[:classes] = class_names(
+            "Overlay-footer",
+            "Overlay-footer--alignEnd",
+            { "Overlay-footer--divided": !hide_divider },
+            system_arguments[:classes]
+          )
+          render(Primer::BaseComponent.new(**system_arguments))
+        end
+      end
+    end
+  end
+end

app/components/primer/alpha/dialog/header.html.erb

@@ -0,0 +1,13 @@
+<%= render Primer::BaseComponent.new(**@system_arguments) do %>
+  <div class="Overlay-headerContentWrap">
+    <div class="Overlay-titleWrap">
+      <h1 class="Overlay-title"><%= @title %></h1>
+      <% if @subtitle.present? %>
+        <h2 id="<%= @subtitle_id %>" class="Overlay-description"><%= @subtitle %></h2>
+      <% end %>
+    </div>
+    <div class="Overlay-actionWrap">
+      <%= render Primer::CloseButton.new(classes: "Overlay-closeButton", "data-close-dialog-id": @system_arguments[:id]) %>
+    </div>
+  </div>
+<% end %>

app/components/primer/alpha/dialog/header.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module Primer
+  module Alpha
+    class Dialog
+      # A `Dialog::Header` is a compositional component, used to render the
+      # Header of a dialog. See <%= link_to_component(Primer::Alpha::Dialog) %>.
+      class Header < Primer::Component
+        # @param title [String] The title of the dialog.
+        # @param subtitle [String] The subtitle of the dialog. This will also set the `aria-describedby` attribute.
+        # @param hide_divider [Boolean] If true the visual dividing line between the body and footer will be hidden
+        # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
+        def initialize(
+          title:,
+          subtitle: nil,
+          sbutitle_id: nil,
+          hide_divider: false,
+          **system_arguments
+        )
+          deny_tag_argument(**system_arguments)
+          system_arguments[:tag] = :header
+          system_arguments[:classes] = class_names(
+            "Overlay-header",
+            { "Overlay-header--divided": !hide_divider },
+            system_arguments[:classes]
+          )
+          render(Primer::BaseComponent.new(**system_arguments))
+        end
+      end
+    end
+  end
+end

app/components/primer/alpha/modal-dialog-element.ts

@@ -0,0 +1,150 @@
+import {focusTrap} from '@primer/behaviors'
+import {getFocusableChild} from '@primer/behaviors/utils'
+
+function focusIfNeeded(elem?: HTMLElement) {
+  if (document.activeElement !== elem) {
+    elem?.focus()
+  }
+}
+
+export class ModalDialogElement extends HTMLElement {
+  //TODO: Do we remove the abortController from focusTrap?
+  #focusAbortController = new AbortController()
+  #abortController: AbortController | null = null
+  #openButton: HTMLButtonElement | undefined
+  #shouldTryLoadingFragment = true
+
+  get open() {
+    return this.hasAttribute('open')
+  }
+  set open(value: boolean) {
+    if (value) {
+      if (this.open) return
+      this.setAttribute('open', '')
+      this.#overlayBackdrop?.classList.remove('Overlay--hidden')
+      document.body.style.overflow = 'hidden'
+      if (this.#focusAbortController.signal.aborted) {
+        this.#focusAbortController = new AbortController()
+      }
+      focusTrap(this, undefined, this.#focusAbortController.signal)
+    } else {
+      if (!this.open) return
+      this.removeAttribute('open')
+      this.#overlayBackdrop?.classList.add('Overlay--hidden')
+      document.body.style.overflow = 'initial'
+      this.#focusAbortController.abort()
+      // if #openButton is a child of a menu, we need to focus a suitable child of the menu
+      // element since it is expected for the menu to close on click
+      const menu = this.#openButton?.closest('details') || this.#openButton?.closest('action-menu')
+      if (menu) {
+        focusIfNeeded(getFocusableChild(menu))
+      } else {
+        focusIfNeeded(this.#openButton)
+      }
+      this.#openButton = undefined
+    }
+  }
+
+  get #overlayBackdrop(): HTMLElement | null {
+    if (this.parentElement?.hasAttribute('data-modal-dialog-overlay')) {
+      return this.parentElement
+    }
+
+    return null
+  }
+
+  get showButtons(): NodeList {
+    // Dialogs may also be opened from any arbitrary button with a matching show-dialog-id data attribute
+    return document.querySelectorAll(`button[data-show-dialog-id='${this.id}']`)
+  }
+
+  connectedCallback(): void {
+    if (!this.hasAttribute('role')) this.setAttribute('role', 'dialog')
+
+    const {signal} = (this.#abortController = new AbortController())
+
+    this.ownerDocument.addEventListener(
+      'click',
+      event => {
+        const target = event.target as HTMLElement
+        const clickOutsideDialog = target.closest(this.tagName) !== this
+        const button = target?.closest('button')
+        // go over this logic:
+        if (!button) {
+          if (clickOutsideDialog) {
+            // This click is outside the dialog
+            this.close()
+          }
+          return
+        }
+
+        let dialogId = button.getAttribute('data-close-dialog-id')
+        if (dialogId === this.id) {
+          this.close()
+        }
+
+        dialogId = button.getAttribute('data-submit-dialog-id')
+        if (dialogId === this.id) {
+          this.close(true)
+        }
+
+        dialogId = button.getAttribute('data-show-dialog-id')
+        if (dialogId === this.id) {
+          //TODO: see if I can remove this
+          event.stopPropagation()
+          this.#openButton = button
+          this.show()
+        }
+      },
+      {signal}
+    )
+
+    this.addEventListener('keydown', e => this.#keydown(e))
+  }
+
+  disconnectedCallback(): void {
+    this.#abortController?.abort()
+  }
+
+  show() {
+    this.open = true
+  }
+
+  close(closed = false) {
+    if (this.open === false) return
+    const eventType = closed ? 'close' : 'cancel'
+    const dialogEvent = new Event(eventType)
+    this.dispatchEvent(dialogEvent)
+    this.open = false
+  }
+
+  #keydown(event: Event) {
+    if (!(event instanceof KeyboardEvent)) return
+    if (event.isComposing) return
+
+    switch (event.key) {
+      case 'Escape':
+        if (this.open) {
+          this.close()
+          event.preventDefault()
+          event.stopPropagation()
+        }
+        break
+    }
+  }
+}
+
+declare global {
+  interface Window {
+    ModalDialogElement: typeof ModalDialogElement
+  }
+  interface HTMLElementTagNameMap {
+    'modal-dialog': ModalDialogElement
+  }
+}
+
+if (!window.customElements.get('modal-dialog')) {
+  window.ModalDialogElement = ModalDialogElement
+  window.customElements.define('modal-dialog', ModalDialogElement)
+}
+

app/components/primer/primer.ts

@@ -6,3 +6,4 @@ import './local_time'
 import './image_crop'
 import './dropdown'
 import './alpha/tool-tip-element'
+import './alpha/modal-dialog-element'

docs/src/@primer/gatsby-theme-doctocat/nav.yml

@@ -45,6 +45,8 @@
     url: "/components/counter"
   - title: Details
     url: "/components/details"
+  - title: Dialog
+    url: "/components/alpha/dialog"
   - title: Dropdown
     url: "/components/dropdown"
   - title: DropdownMenu