test(menu): test all positioning values

docs/components/figures/menu/usage-popover.html

@@ -0,0 +1,30 @@
+<div class="figure-wrapper">
+  <figure
+    style="justify-content: center"
+    aria-label="A filled button that says open popover menu. Interact with the button to open a popover menu."
+  >
+    <div>
+      <div style="margin: 16px">
+        <md-filled-button id="usage-popover-anchor">Open popover menu</md-filled-button>
+      </div>
+      <md-menu positioning="popover" id="usage-popover" anchor="usage-popover-anchor">
+        <md-menu-item>
+          <div slot="headline">Apple</div>
+        </md-menu-item>
+        <md-menu-item>
+          <div slot="headline">Banana</div>
+        </md-menu-item>
+        <md-menu-item>
+          <div slot="headline">Cucumber</div>
+        </md-menu-item>
+      </md-menu>
+    </div>
+    <script type="module">
+      const anchorEl = document.body.querySelector("#usage-popover-anchor");
+      const menuEl = document.body.querySelector("#usage-popover");
+      anchorEl.addEventListener("click", () => {
+        menuEl.open = !menuEl.open;
+      });
+    </script>
+  </figure>
+</div>

docs/components/menu.md

@@ -215,14 +215,69 @@ Granny Smith, and Red Delicious."](images/menu/usage-submenu.webp)
 </script>
 ```
 
-### Fixed-positioned menus
+### Popover-positioned menus
 
 Internally menu uses `position: absolute` by default. Though there are cases
 when the anchor and the node cannot share a common ancestor that is `position:
 relative`, or sometimes, menu will render below another item due to limitations
-with `position: absolute`. In most of these cases, you would want to use the
-`positioning="fixed"` attribute to position the menu relative to the window
-instead of relative to the element.
+with `position: absolute`.
+
+Popover-positioned menus use the native
+[Popover API](https://developer.mozilla.org/en-US/docs/Web/API/Popover_API)<!-- {.external} -->
+to render above all other content. This may fix most issues where the default
+menu positioning (`positioning="absolute"`) is not positioning as expected by
+rendering into the
+[top layer](google3/third_party/javascript/material/web/g3doc/docs/components/figures/menu/usage-fixed.html)<!-- {.external} -->.
+
+> Warning: Popover API support was added in Chrome 114 and Safari 17. At the
+> time of writing, Firefox does not support the Popover API
+> ([see latest browser compatiblity](#fixed-positioned-menus)<!-- {.external} -->).
+>
+> For browsers that do not support the Popover API, `md-menu` will fall back to
+> using [fixed-positioned menus](#fixed-positioned-menus).
+
+<!-- no-catalog-start -->
+
+!["A filled button that says open popover menu. There is an open menu anchored
+to the bottom of the button with three items, Apple, Banana, and
+Cucumber."](images/menu/usage-popover.webp)
+
+<!-- no-catalog-end -->
+<!-- catalog-include "figures/menu/usage-fixed.html" -->
+
+```html
+<!-- Note the lack of position: relative parent. -->
+<div style="margin: 16px;">
+  <md-filled-button id="usage-popover-anchor">Open popover menu</md-filled-button>
+</div>
+
+<!-- popover menus do not require a common ancestor with the anchor. -->
+<md-menu positioning="popover" id="usage-popover" anchor="usage-popover-anchor">
+  <md-menu-item>
+    <div slot="headline">Apple</div>
+  </md-menu-item>
+  <md-menu-item>
+    <div slot="headline">Banana</div>
+  </md-menu-item>
+  <md-menu-item>
+    <div slot="headline">Cucumber</div>
+  </md-menu-item>
+</md-menu>
+
+<script type="module">
+  const anchorEl = document.body.querySelector('#usage-popover-anchor');
+  const menuEl = document.body.querySelector('#usage-popover');
+
+  anchorEl.addEventListener('click', () => { menuEl.open = !menuEl.open; });
+</script>
+```
+
+### Fixed-positioned menus
+
+This is the fallback implementation of
+[popover-positioned menus](#popover-positioned-menus) and uses `position: fixed`
+rather than the default `position: absolute` which calculates its position
+relative to the window rather than the element.
 
 > Note: Fixed menu positions are positioned relative to the window and not the
 > document. This means that the menu will not scroll with the anchor as the page

menu/demo/demo.ts

@@ -64,11 +64,12 @@ const collection = new MaterialCollection<KnobTypesToKnobs<StoryKnobs>>(
     }),
     new Knob('positioning', {
       defaultValue: 'absolute' as const,
-      ui: selectDropdown<'absolute' | 'fixed' | 'document'>({
+      ui: selectDropdown<'absolute' | 'fixed' | 'document' | 'popover'>({
         options: [
           {label: 'absolute', value: 'absolute'},
           {label: 'fixed', value: 'fixed'},
           {label: 'document', value: 'document'},
+          {label: 'popover', value: 'popover'},
         ],
       }),
     }),

menu/demo/stories.ts

@@ -22,7 +22,7 @@ export interface StoryKnobs {
   anchorCorner: Corner | undefined;
   menuCorner: Corner | undefined;
   defaultFocus: FocusState | undefined;
-  positioning: 'absolute' | 'fixed' | 'document' | undefined;
+  positioning: 'absolute' | 'fixed' | 'document' | 'popover' | undefined;
   open: boolean;
   quick: boolean;
   hasOverflow: boolean;

menu/internal/_menu.scss

@@ -60,6 +60,12 @@
   .menu {
     border-radius: map.get($tokens, 'container-shape');
     display: none;
+    inset: auto;
+    border: none;
+    padding: 0px;
+    overflow: visible;
+    // [popover] adds a canvas background
+    background-color: transparent;
     opacity: 0;
     z-index: 20;
     position: absolute;
@@ -70,6 +76,10 @@
     max-width: inherit;
   }
 
+  .menu::backdrop {
+    display: none;
+  }
+
   .fixed {
     position: fixed;
   }
@@ -93,10 +103,11 @@
     padding-block: 8px;
   }
 
-  .has-overflow .items {
+  .has-overflow:not([popover]) .items {
     overflow: visible;
   }
 
+  .has-overflow.animating .items,
   .animating .items {
     overflow: hidden;
   }

menu/internal/controllers/surfacePositionController.ts

@@ -196,6 +196,14 @@ export class SurfacePositionController implements ReactiveController {
     this.host.requestUpdate();
     await this.host.updateComplete;
 
+    // Safari has a bug that makes popovers render incorrectly if the node is
+    // made visible + Animation Frame before calling showPopover().
+    // https://bugs.webkit.org/show_bug.cgi?id=264069
+    // also the cast is required due to differing TS types in Google and OSS.
+    if ((surfaceEl as unknown as {popover: string}).popover) {
+      (surfaceEl as unknown as {showPopover: () => void}).showPopover();
+    }
+
     const surfaceRect = surfaceEl.getSurfacePositionClientRect
       ? surfaceEl.getSurfacePositionClientRect()
       : surfaceEl.getBoundingClientRect();
@@ -600,5 +608,12 @@ export class SurfacePositionController implements ReactiveController {
       'display': 'none',
     };
     this.host.requestUpdate();
+    const surfaceEl = this.getProperties().surfaceEl;
+
+    // The following type casts are required due to differing TS types in Google
+    // and open source.
+    if ((surfaceEl as unknown as {popover?: string})?.popover) {
+      (surfaceEl as unknown as {hidePopover: () => void}).hidePopover();
+    }
   }
 }

menu/internal/menu.ts

@@ -7,7 +7,7 @@
 import '../../elevation/elevation.js';
 import '../../focus/md-focus-ring.js';
 
-import {html, isServer, LitElement, PropertyValues} from 'lit';
+import {LitElement, PropertyValues, html, isServer, nothing} from 'lit';
 import {property, query, queryAssignedElements, state} from 'lit/decorators.js';
 import {ClassInfo, classMap} from 'lit/directives/class-map.js';
 import {styleMap} from 'lit/directives/style-map.js';
@@ -16,7 +16,7 @@ import {
   polyfillARIAMixin,
   polyfillElementInternalsAria,
 } from '../../internal/aria/aria.js';
-import {createAnimationSignal, EASING} from '../../internal/motion/animation.js';
+import {EASING, createAnimationSignal} from '../../internal/motion/animation.js';
 import {
   ListController,
   NavigableKeys,
@@ -107,9 +107,12 @@ export abstract class Menu extends LitElement {
   @property() anchor = '';
   /**
    * Whether the positioning algorithim should calculate relative to the parent
-   * of the anchor element (absolute) or relative to the window (fixed).
+   * of the anchor element (`absolute`), relative to the window (`fixed`), or
+   * relative to the document (`document`). `popover` will use the popover API
+   * to render the menu in the top-layer. If your browser does not support the
+   * popover API, it will revert to `fixed`.
    *
-   * Examples for `position = 'fixed'`:
+   * __Examples for `position = 'fixed'`:__
    *
    * - If there is no `position:relative` in the given parent tree and the
    *   surface is `position:absolute`
@@ -118,7 +121,7 @@ export abstract class Menu extends LitElement {
    * - The anchor and the surface do not share a common `position:relative`
    *   ancestor
    *
-   * When using positioning = fixed, in most cases, the menu should position
+   * When using `positioning=fixed`, in most cases, the menu should position
    * itself above most other `position:absolute` or `position:fixed` elements
    * when placed inside of them. e.g. using a menu inside of an `md-dialog`.
    *
@@ -134,8 +137,14 @@ export abstract class Menu extends LitElement {
    *   end of the `<body>` to render over everything or in a top-layer.
    * - You are reusing a single `md-menu` element that dynamically renders
    *   content.
+   *
+   * __Examples for `position = 'popover'`:__
+   *
+   * - Your browser supports `popover`.
+   * - Most cases. Once popover is in browsers, this will become the default.
    */
-  @property() positioning: 'absolute' | 'fixed' | 'document' = 'absolute';
+  @property() positioning: 'absolute' | 'fixed' | 'document' | 'popover' =
+    'absolute';
   /**
    * Skips the opening and closing animations.
    */
@@ -362,7 +371,8 @@ export abstract class Menu extends LitElement {
         surfaceCorner: this.menuCorner,
         surfaceEl: this.surfaceEl,
         anchorEl: this.anchorElement,
-        positioning: this.positioning,
+        positioning:
+          this.positioning === 'popover' ? 'document' : this.positioning,
         isOpen: this.open,
         xOffset: this.xOffset,
         yOffset: this.yOffset,
@@ -372,7 +382,10 @@ export abstract class Menu extends LitElement {
         // We can't resize components that have overflow like menus with
         // submenus because the overflow-y will show menu items / content
         // outside the bounds of the menu. (to be fixed w/ popover API)
-        repositionStrategy: this.hasOverflow ? 'move' : 'resize',
+        repositionStrategy:
+          this.hasOverflow && this.positioning !== 'popover'
+            ? 'move'
+            : 'resize',
       };
     },
   );
@@ -407,13 +420,25 @@ export abstract class Menu extends LitElement {
       }
     }
 
+    // Firefox does not support popover. Fall-back to using fixed.
+    if (
+      changed.has('positioning') &&
+      this.positioning === 'popover' &&
+      // type required for Google JS conformance
+      !(this as unknown as {showPopover?: () => void}).showPopover
+    ) {
+      this.positioning = 'fixed';
+    }
+
     super.update(changed);
   }
 
   private readonly onWindowResize = () => {
     if (
       this.isRepositioning ||
-      (this.positioning !== 'document' && this.positioning !== 'fixed')
+      (this.positioning !== 'document' &&
+        this.positioning !== 'fixed' &&
+        this.positioning !== 'popover')
     ) {
       return;
     }
@@ -445,7 +470,8 @@ export abstract class Menu extends LitElement {
     return html`
       <div
         class="menu ${classMap(this.getSurfaceClasses())}"
-        style=${styleMap(this.menuPositionController.surfaceStyles)}>
+        style=${styleMap(this.menuPositionController.surfaceStyles)}
+        popover=${this.positioning === 'popover' ? 'manual' : nothing}>
         ${this.renderElevation()}
         <div class="items">
           <div class="item-padding"> ${this.renderMenuItems()} </div>