github · keithamus · Oct 20, 2023 · Oct 20, 2023
@@ -1,13 +1,22 @@
-<!DOCTYPE html>
+<!doctype html>
 <html>
   <head>
     <title>GitHub Feature Support Table</title>
     <meta charset="utf-8" />
     <link rel="shortcut icon" href="favicon.ico" type="image/x-icon" />
     <style>
       html {
-        font-family: 'Alliance No.1', -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif,
-          'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';
+        font-family:
+          'Alliance No.1',
+          -apple-system,
+          BlinkMacSystemFont,
+          'Segoe UI',
+          Helvetica,
+          Arial,
+          sans-serif,
+          'Apple Color Emoji',
+          'Segoe UI Emoji',
+          'Segoe UI Symbol';
         font-weight: 400;
         line-height: 28px;
       }
@@ -630,6 +639,20 @@ <h1>GitHub Feature Support Table</h1>
             <td data-supported="true"><div>78+</div></td>
             <td data-supported="true"><div>16.0+</div></td>
           </tr>
+          <tr>
+            <th>
+              <a href="https://developer.mozilla.org/en-US/docs/Web/API/Element/checkVisibility">
+                <code>Element.checkVisibility</code>
+              </a>
+            </th>
+            <td data-polyfill="elementCheckVisibility"><div>*</div></td>
+            <td data-supported="true"><div>105+</div></td>
+            <td data-supported="true"><div>105+</div></td>
+            <td data-supported="true"><div>106+</div></td>
+            <td data-supported="false"><div>*</div></td>
+            <td data-supported="true"><div>91+</div></td>
+            <td data-supported="true"><div>20.0+</div></td>
+          </tr>
           <tr>
             <th>
               <a

@@ -0,0 +1,50 @@
+declare global {
+  interface Element {
+    checkVisibility(options?: Partial<CheckVisibilityOptions>): boolean
+  }
+}
+
+interface CheckVisibilityOptions {
+  checkOpacity: boolean
+  checkVisibilityCSS: boolean
+}
+
+export function checkVisibility(
+  this: Element,
+  {checkOpacity = false, checkVisibilityCSS = false}: Partial<CheckVisibilityOptions> = {},
+) {
+  if (!this.isConnected) return false
+  const styles = getComputedStyle(this)
+  if (styles.getPropertyValue('display') === 'contents') return false
+  if (checkVisibilityCSS && styles.getPropertyValue('visibility') !== 'visible') return false
+  // eslint-disable-next-line @typescript-eslint/no-this-alias
+  let node: Element | null = this
+  while (node) {
+    const nodeStyles = node === this ? styles : getComputedStyle(node)
+    if (nodeStyles.getPropertyValue('display') === 'none') return false
+    if (checkOpacity && nodeStyles.getPropertyValue('opacity') === '0') return false
+    if (node !== this && nodeStyles.getPropertyValue('content-visibility') === 'hidden') {
+      return false
+    }
+    if (!node.parentElement && node.getRootNode() instanceof ShadowRoot) {
+      node = (node.getRootNode() as ShadowRoot).host
+    } else {
+      node = node.parentElement
+    }
+  }
+  return true
+}
+
+export function isSupported(): boolean {
+  return 'checkVisibility' in Element.prototype && typeof Element.prototype.checkVisibility === 'function'
+}
+
+export function isPolyfilled(): boolean {
+  return Element.prototype.checkVisibility === checkVisibility
+}
+
+export function apply(): void {
+  if (!isSupported()) {
+    Element.prototype.checkVisibility = checkVisibility
+  }
+}
@@ -3,6 +3,7 @@ import * as abortSignalTimeout from './abortsignal-timeout.js'
 import * as arrayAt from './arraylike-at.js'
 import * as clipboardItem from './clipboarditem.js'
 import * as cryptoRandomUUID from './crypto-randomuuid.js'
+import * as elementCheckVisibility from './element-checkvisibility.js'
 import * as eventAbortSignal from './event-abortsignal.js'
 import * as navigatorClipboard from './navigator-clipboard.js'
 import * as formRequestSubmit from './form-requestsubmit.js'
@@ -58,6 +59,7 @@ export const polyfills = {
   arrayAt,
   clipboardItem,
   cryptoRandomUUID,
+  elementCheckVisibility,
   eventAbortSignal,
   navigatorClipboard,
   formRequestSubmit,

@@ -0,0 +1,95 @@
+import {apply, isPolyfilled, isSupported, checkVisibility} from '../lib/element-checkvisibility.js'
+
+describe('checkVisibility', () => {
+  it('has standard isSupported, isPolyfilled, apply API', () => {
+    expect(isSupported).to.be.a('function')
+    expect(isPolyfilled).to.be.a('function')
+    expect(apply).to.be.a('function')
+    expect(isSupported()).to.be.a('boolean')
+    expect(isPolyfilled()).to.equal(false)
+  })
+
+  it('checks visibility of elements', async () => {
+    // These tests originate from
+    // https://github.com/web-platform-tests/wpt/blob/master/css/cssom-view/checkVisibility.html
+    const el = document.createElement('div')
+    // eslint-disable-next-line github/no-inner-html
+    el.innerHTML = `
+      <div id=visibilityhidden style="visibility:hidden">hello</div>
+      <div style="content-visibility:hidden">
+        <div id=cvhidden>hello</div>
+      </div>
+      <div style="content-visibility:auto">
+        <div id=cvauto>hello</div>
+      </div>
+      <div id=displaynone style="display:none">hello</div>
+      <div style="display:none" class="shadow-host-with-slot">
+        <div id="slottedindisplaynone" slot="slot">slotted</div>
+      </div>
+      <div id=displaycontents style="display:contents">
+        <div id=displaycontentschild>hello</div>
+      </div>
+      <div id=opacityzero style="opacity:0">hello</div>
+      <div style="opacity:0" class="shadow-host-with-slot">
+        <div id="slottedinopacityzero" slot="slot">slotted</div>
+      </div>
+      <div style="content-visibility:hidden">
+        <div id=cvhiddenchildwithupdate></div>
+      </div>
+      <div style="content-visibility:hidden" id=cvhiddenwithupdate></div>
+      <div style="content-visibility:hidden" class="shadow-host-with-slot">
+        <div id="slottedincvhidden" slot="slot">slotted</div>
+      </div>
+      <div style="height:10000px">spacer</div>
+      <div style="content-visibility:auto">
+        <div id=cvautooffscreen>hello</div>
+      </div>
+      <div id=cvautocontainer>
+        <div id=cvautochild></div>
+      </div>
+      <div style="content-visibility:auto">
+        <div style="content-visibility:auto">
+          <div id=nestedcvautochild></div>
+        </div>
+    `
+    document.body.append(el)
+    for (const host of document.querySelectorAll('.shadow-host-with-slot')) {
+      const shadowRoot = host.attachShadow({mode: 'open'})
+      const slot = document.createElement('slot')
+      slot.name = 'slot'
+      shadowRoot.appendChild(slot)
+    }
+    expect(checkVisibility.call(document.getElementById('visibilityhidden'), {checkVisibilityCSS: true})).to.equal(
+      false,
+    )
+    expect(checkVisibility.call(document.getElementById('visibilityhidden'), {checkVisibilityCSS: false})).to.equal(
+      true,
+    )
+    expect(checkVisibility.call(document.getElementById('cvhidden'))).to.equal(false)
+    expect(checkVisibility.call(document.getElementById('slottedincvhidden'))).to.equal(false)
+    expect(checkVisibility.call(document.getElementById('cvauto'))).to.equal(true)
+    expect(checkVisibility.call(document.getElementById('cvautooffscreen'))).to.equal(true)
+    expect(checkVisibility.call(document.getElementById('displaynone'))).to.equal(false)
+    expect(checkVisibility.call(document.getElementById('slottedindisplaynone'))).to.equal(false)
+    expect(checkVisibility.call(document.getElementById('displaycontents'))).to.equal(false)
+    expect(checkVisibility.call(document.getElementById('displaycontentschild'))).to.equal(true)
+    expect(checkVisibility.call(document.getElementById('opacityzero'), {checkOpacity: true})).to.equal(false)
+    expect(checkVisibility.call(document.getElementById('opacityzero'), {checkOpacity: false})).to.equal(true)
+    expect(checkVisibility.call(document.getElementById('slottedinopacityzero'), {checkOpacity: true})).to.equal(false)
+    expect(checkVisibility.call(document.getElementById('slottedinopacityzero'), {checkOpacity: false})).to.equal(true)
+    const cvautocontainer = document.getElementById('cvautocontainer')
+    const cvautochild = document.getElementById('cvautochild')
+    cvautocontainer.style.contentVisibility = 'auto'
+    cvautochild.style.visibility = 'hidden'
+    expect(checkVisibility.call(cvautochild, {checkVisibilityCSS: true})).to.equal(false)
+    cvautochild.style.visibility = 'visible'
+    expect(checkVisibility.call(cvautochild, {checkVisibilityCSS: true})).to.equal(true)
+    expect(checkVisibility.call(document.getElementById('nestedcvautochild'))).to.equal(true)
+    const cvhiddenchildwithupdate = document.getElementById('cvhiddenchildwithupdate')
+    cvhiddenchildwithupdate.getBoundingClientRect()
+    expect(checkVisibility.call(cvhiddenchildwithupdate)).to.equal(false)
+    const cvhiddenwithupdate = document.getElementById('cvhiddenwithupdate')
+    cvhiddenwithupdate.getBoundingClientRect()
+    expect(checkVisibility.call(cvhiddenwithupdate)).to.equal(true)
+  })
+})