Refactor shadowdom

README.md

@@ -16,11 +16,9 @@ import '@github/tab-container-element'
 
 ```html
 <tab-container>
-  <div role="tablist">
-    <button type="button" id="tab-one" role="tab" aria-selected="true">Tab one</button>
-    <button type="button" id="tab-two" role="tab" tabindex="-1">Tab two</button>
-    <button type="button" id="tab-three" role="tab" tabindex="-1">Tab three</button>
-  </div>
+  <button type="button" id="tab-one" role="tab" aria-selected="true">Tab one</button>
+  <button type="button" id="tab-two" role="tab" tabindex="-1">Tab two</button>
+  <button type="button" id="tab-three" role="tab" tabindex="-1">Tab three</button>
   <div role="tabpanel" aria-labelledby="tab-one">
     Panel 1
   </div>
@@ -35,8 +33,17 @@ import '@github/tab-container-element'
 
 ### Events
 
-- `tab-container-change` (bubbles, cancelable): fired on `<tab-container>` before a new tab is selected and visibility is updated. `event.detail.relatedTarget` is the tab panel that will be selected if the event isn't cancelled.
-- `tab-container-changed` (bubbles): fired on `<tab-container>` after a new tab is selected and visibility is updated. `event.detail.relatedTarget` is the newly visible tab panel.
+- `tab-container-change` (bubbles, cancelable): fired on `<tab-container>` before a new tab is selected and visibility is updated. `event.tab` is the tab that will be focused and `tab.panel` is the panel that will be shown if the event isn't cancelled.
+- `tab-container-changed` (bubbles): fired on `<tab-container>` after a new tab is selected and visibility is updated. `event.tab` is the tab that is now active (and will be focused right after this event) and `event.panel` is the newly visible tab panel.
+
+### Parts
+
+- `::part(tablist)` is the container which wraps all tabs. This element appears in ATs as it is `role=tablist`.
+- `::part(panel)` is the container housing the currently active tabpanel.
+- `::part(before-tabs)` is the container housing any elements that appear before the first `role=tab`. This also can be directly slotted with `slot=before-tabs`. This container lives outside the element with role=tablist to adhere to ARIA guidelines.
+- `::part(after-tabs)` is the container housing any elements that appear after the last `role=tab`. This also can be directly slotted with `slot=after-tabs`. This container lives outside the element with role=tablist to adhere to ARIA guidelines.
+- `::part(after-panels)` is the container housing any elements that appear after the last `role=tabpanel`. This can be useful if you want to add a visual treatment to the container but have content always appear visually below the active panel.
+
 
 ### When tab panel contents are controls
 
@@ -46,10 +53,33 @@ In those cases, apply `data-tab-container-no-tabstop` to the `tabpanel` element.
 
 ```html
 <tab-container>
-  <div role="tablist">
-    <button type="button" id="tab-one" role="tab" aria-selected="true">Tab one</button>
-    <button type="button" id="tab-two" role="tab" tabindex="-1">Tab two</button>
+  <button type="button" id="tab-one" role="tab" aria-selected="true">Tab one</button>
+  <button type="button" id="tab-two" role="tab" tabindex="-1">Tab two</button>
+  <div role="tabpanel" aria-labelledby="tab-one" data-tab-container-no-tabstop>
+    <ul role="menu" aria-label="Branches">
+      <li tabindex="0">branch-one</li>
+      <li tabindex="0">branch-two</li>
+    </ul>
   </div>
+  <div role="tabpanel" aria-labelledby="tab-two" data-tab-container-no-tabstop hidden>
+    <ul role="menu" aria-label="Commits">
+      <li tabindex="0">Commit One</li>
+      <li tabindex="0">Commit Two</li>
+    </ul>
+  </div>
+</tab-container>
+```
+
+### Vertical tabs
+
+If `<tab-container>` is given the `vertical` attribute it will apply the `aria-orientation=vertical` attribute to the tablist. This will present to ATs as a vertical tablist, and you can use the attribute to style the tabs accordingly.
+
+In those cases, apply `data-tab-container-no-tabstop` to the `tabpanel` element.
+
+```html
+<tab-container vertical>
+  <button type="button" id="tab-one" role="tab" aria-selected="true">Tab one</button>
+  <button type="button" id="tab-two" role="tab" tabindex="-1">Tab two</button>
   <div role="tabpanel" aria-labelledby="tab-one" data-tab-container-no-tabstop>
     <ul role="menu" aria-label="Branches">
       <li tabindex="0">branch-one</li>

examples/index.html

@@ -10,7 +10,24 @@
 
     <h1>Tab Container Examples</h1>
 
-    <h2>Horizontal</h2>
+    <h2>Horizontal (shadow tablist)</h2>
+
+    <tab-container>
+      <button type="button" id="tab-one" role="tab">Tab one</button>
+      <button type="button" id="tab-two" role="tab">Tab two</button>
+      <button type="button" id="tab-three" role="tab">Tab three</button>
+      <div role="tabpanel" aria-labelledby="tab-one">
+        Panel 1
+      </div>
+      <div role="tabpanel" aria-labelledby="tab-two" hidden>
+        Panel 2
+      </div>
+      <div role="tabpanel" aria-labelledby="tab-three" hidden>
+        Panel 3
+      </div>
+    </tab-container>
+
+    <h2>Horizontal (custom tablist)</h2>
 
     <tab-container>
       <div role="tablist" aria-label="Horizontal Tabs Example">
@@ -29,7 +46,25 @@ <h2>Horizontal</h2>
       </div>
     </tab-container>
 
-    <h2>Vertical</h2>
+    <h2>Vertical (shadow tablist)</h2>
+
+    <tab-container>
+      <button type="button" id="tab-one" role="tab">Tab one</button>
+      <button type="button" id="tab-two" role="tab">Tab two</button>
+      <button type="button" id="tab-three" role="tab">Tab three</button>
+      <div role="tabpanel" aria-labelledby="tab-one">
+        Panel 1
+      </div>
+      <div role="tabpanel" aria-labelledby="tab-two" hidden>
+        Panel 2
+      </div>
+      <div role="tabpanel" aria-labelledby="tab-three" hidden>
+        Panel 3
+      </div>
+    </tab-container>
+
+
+    <h2>Vertical (custom tablist)</h2>
 
     <tab-container>
       <div role="tablist" aria-label="Vertical Tabs Example" aria-orientation="vertical">
@@ -51,16 +86,12 @@ <h2>Vertical</h2>
     <h2>Panel with extra buttons</h2>
 
     <tab-container>
-      <div style="display: flex">
-        <button>Left button, not a tab!</button>
-        <button>2nd Left button, not a tab!</button>
-        <div role="tablist" aria-label="Tabs Example with extra buttons">
-          <button type="button" id="tab-one" role="tab">Tab one</button>
-          <button type="button" id="tab-two" role="tab">Tab two</button>
-          <button type="button" id="tab-three" role="tab">Tab three</button>
-        </div>
-        <button>Right button, not a tab!</button>
-      </div>
+      <button>Left button, not a tab!</button>
+      <button type="button" id="tab-one" role="tab">Tab one</button>
+      <button type="button" id="tab-two" role="tab">Tab two</button>
+      <button type="button" id="tab-three" role="tab">Tab three</button>
+      <button>Right button, not a tab!</button>
+      <button slot="before-tabs">2nd Left button, not a tab!</button>
       <div role="tabpanel" aria-labelledby="tab-one">
         Panel 1
       </div>

src/tab-container-element.ts

@@ -66,18 +66,90 @@ export class TabContainerElement extends HTMLElement {
     }
   }
 
+  static observedAttributes = ['vertical']
+
   get #tabList() {
-    return this.querySelector<HTMLElement>('[role=tablist]')
+    const slot = this.#tabListSlot
+    if (this.#tabListSlot.hasAttribute('role')) {
+      return slot
+    } else {
+      return slot.assignedNodes()[0] as HTMLElement
+    }
+  }
+
+  get #beforeTabsSlot() {
+    return this.shadowRoot!.querySelector<HTMLSlotElement>('slot[part="before-tabs"]')!
+  }
+
+  get #afterTabsSlot() {
+    return this.shadowRoot!.querySelector<HTMLSlotElement>('slot[part="after-tabs"]')!
+  }
+
+  get #afterPanelsSlot() {
+    return this.shadowRoot!.querySelector<HTMLSlotElement>('slot[part="after-panels"]')!
+  }
+
+  get #tabListSlot() {
+    return this.shadowRoot!.querySelector<HTMLSlotElement>('slot[part="tablist"]')!
+  }
+
+  get #panelSlot() {
+    return this.shadowRoot!.querySelector<HTMLSlotElement>('slot[part="panel"]')!
   }
 
   get #tabs() {
+    if (this.#tabListSlot.matches('[role=tablist]')) {
+      return this.#tabListSlot.assignedNodes() as HTMLElement[]
+    }
     return Array.from(this.#tabList?.querySelectorAll<HTMLElement>('[role="tab"]') || []).filter(
       tab => tab instanceof HTMLElement && tab.closest(this.tagName) === this,
     )
   }
 
-  #setup = false
+  get activePanel() {
+    return this.#panelSlot.assignedNodes()[0] as HTMLElement
+  }
+
+  get vertical(): boolean {
+    return this.#tabList?.getAttribute('aria-orientation') === 'vertical'
+  }
+
+  set vertical(isVertical: boolean) {
+    const tabList = this.#tabList
+    if (tabList && isVertical) {
+      tabList.setAttribute('aria-orientation', 'vertical')
+    } else {
+      tabList.setAttribute('aria-orientation', 'horizontal')
+    }
+  }
+
+  #setupComplete = false
+  #internals!: ElementInternals | null
   connectedCallback(): void {
+    this.#internals ||= this.attachInternals ? this.attachInternals() : null
+    const shadowRoot = this.shadowRoot || this.attachShadow({mode: 'open', slotAssignment: 'manual'})
+    const tabListContainer = document.createElement('div')
+    tabListContainer.style.display = 'flex'
+    const tabListSlot = document.createElement('slot')
+    tabListSlot.setAttribute('part', 'tablist')
+    const panelSlot = document.createElement('slot')
+    panelSlot.setAttribute('part', 'panel')
+    panelSlot.setAttribute('role', 'presentation')
+    const beforeTabSlot = document.createElement('slot')
+    beforeTabSlot.setAttribute('part', 'before-tabs')
+    const afterTabSlot = document.createElement('slot')
+    afterTabSlot.setAttribute('part', 'after-tabs')
+    tabListContainer.append(beforeTabSlot, tabListSlot, afterTabSlot)
+    const afterSlot = document.createElement('slot')
+    afterSlot.setAttribute('part', 'after-panels')
+    shadowRoot.replaceChildren(tabListContainer, panelSlot, afterSlot)
+
+    if (this.#internals && 'role' in this.#internals) {
+      this.#internals.role = 'presentation'
+    } else {
+      this.setAttribute('role', 'presentation')
+    }
+
     this.addEventListener('keydown', this)
     this.addEventListener('click', this)
     this.selectTab(
@@ -86,7 +158,14 @@ export class TabContainerElement extends HTMLElement {
         0,
       ),
     )
-    this.#setup = true
+    this.#setupComplete = true
+  }
+
+  attributeChangedCallback(name: string) {
+    if (!this.isConnected || !this.shadowRoot) return
+    if (name === 'vertical') {
+      this.vertical = this.hasAttribute('vertical')
+    }
   }
 
   handleEvent(event: Event) {
@@ -130,7 +209,56 @@ export class TabContainerElement extends HTMLElement {
     if (index >= 0) this.selectTab(index)
   }
 
+  #reflectAttributeToShadow(name: string, node: Element) {
+    if (this.hasAttribute(name)) {
+      node.setAttribute(name, this.getAttribute(name)!)
+      this.removeAttribute(name)
+    }
+  }
+
   selectTab(index: number): void {
+    if (!this.#setupComplete) {
+      const tabListSlot = this.#tabListSlot
+      const customTabList = this.querySelector('[role=tablist]')
+      if (customTabList && customTabList.closest(this.tagName) === this) {
+        tabListSlot.assign(customTabList)
+      } else {
+        tabListSlot.assign(...[...this.children].filter(e => e.matches('[role=tab]')))
+        tabListSlot.role = 'tablist'
+        tabListSlot.style.display = 'block'
+      }
+      const tabList = this.#tabList
+      this.#reflectAttributeToShadow('aria-description', tabList)
+      this.#reflectAttributeToShadow('aria-label', tabList)
+      if (this.vertical) {
+        this.#tabList.setAttribute('aria-orientation', 'vertical')
+      }
+      const beforeSlotted: Element[] = []
+      const afterTabSlotted: Element[] = []
+      const afterSlotted: Element[] = []
+      let autoSlotted = beforeSlotted
+      for (const child of this.children) {
+        if (child.getAttribute('role') === 'tab' || child.getAttribute('role') === 'tablist') {
+          autoSlotted = afterTabSlotted
+          continue
+        }
+        if (child.getAttribute('role') === 'tabpanel') {
+          autoSlotted = afterSlotted
+          continue
+        }
+        if (child.getAttribute('slot') === 'before-tabs') {
+          beforeSlotted.push(child)
+        } else if (child.getAttribute('slot') === 'after-tabs') {
+          afterTabSlotted.push(child)
+        } else {
+          autoSlotted.push(child)
+        }
+      }
+      this.#beforeTabsSlot.assign(...beforeSlotted)
+      this.#afterTabsSlot.assign(...afterTabSlotted)
+      this.#afterPanelsSlot.assign(...afterSlotted)
+    }
+
     const tabs = this.#tabs
     const panels = Array.from(this.querySelectorAll<HTMLElement>('[role="tabpanel"]')).filter(
       panel => panel.closest(this.tagName) === this,
@@ -146,7 +274,7 @@ export class TabContainerElement extends HTMLElement {
     const selectedTab = tabs[index]
     const selectedPanel = panels[index]
 
-    if (this.#setup) {
+    if (this.#setupComplete) {
       const cancelled = !this.dispatchEvent(
         new TabContainerChangeEvent('tab-container-change', {
           bubbles: true,
@@ -163,17 +291,17 @@ export class TabContainerElement extends HTMLElement {
       tab.setAttribute('tabindex', '-1')
     }
     for (const panel of panels) {
-      panel.hidden = true
       if (!panel.hasAttribute('tabindex') && !panel.hasAttribute('data-tab-container-no-tabstop')) {
         panel.setAttribute('tabindex', '0')
       }
     }
 
     selectedTab.setAttribute('aria-selected', 'true')
     selectedTab.setAttribute('tabindex', '0')
+    this.#panelSlot.assign(selectedPanel)
     selectedPanel.hidden = false
 
-    if (this.#setup) {
+    if (this.#setupComplete) {
       selectedTab.focus()
       this.dispatchEvent(
         new TabContainerChangeEvent('tab-container-changed', {

test/test.js

@@ -3,7 +3,7 @@ import '../src/index.ts'
 
 describe('tab-container', function () {
   const isSelected = e => e.matches('[aria-selected=true]')
-  const isHidden = e => e.hidden
+  const isHidden = e => !e.assignedSlot
   let tabContainer = null
   let tabs = []
   let panels = []