Integrate with ElementInternals

Closes [basecamp#1023][]

Replace the requirement for an `<input type="hidden">` element with
direct `<form>` integration through built-in support for
[ElementInternals][].

According to the [Form-associated custom elements][] section of [More
capable form controls][], various behaviors that the `<trix-editor>`
element was recreating are provided out of the box.

For example, the `<input type="hidden">`-`[input]` attribute pairing can
be achieved through [ElementInternals.setFormValue][]. Similarly, the
`<label>` element support can be achieved through
[ElementInternals.labels][].

[basecamp#1023]: basecamp#1023
[ElementInternals]: https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals
[Form-associated custom elements]: https://web.dev/articles/more-capable-form-controls#form-associated_custom_elements
[More capable form controls]: https://web.dev/articles/more-capable-form-controls
[ElementInternals.setFormValue]: https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals/setFormValue
[ElementInternals.labels]: https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals/labels

.github/workflows/ci.yml

@@ -8,8 +8,13 @@ on:
 
 jobs:
   build:
-    name: Browser tests
+    name: "Browser tests (ElementInternals: ${{ matrix.elementInternals }})"
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        elementInternals: [false, true]
+    env:
+      EDITOR_ELEMENT_INTERNALS: "${{ matrix.elementInternals }}"
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3

README.md

@@ -19,7 +19,7 @@ This is the approach that all modern, production ready, WYSIWYG editors now take
 
 <details><summary>Trix supports all evergreen, self-updating desktop and mobile browsers.</summary><img src="https://app.saucelabs.com/browser-matrix/basecamp_trix.svg"></details>
 
-Trix is built with established web standards, notably [Custom Elements](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements), [Mutation Observer](https://dom.spec.whatwg.org/#mutation-observers), and [Promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise).
+Trix is built with established web standards, notably [Custom Elements](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements), [Element Internals](https://developer.mozilla.org/en-US/docs/Web/API/ElementInternals), [Mutation Observer](https://dom.spec.whatwg.org/#mutation-observers), and [Promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise).
 
 # Getting Started
 
@@ -49,12 +49,26 @@ document.addEventListener("trix-before-initialize", () => {
 
 ## Creating an Editor
 
-Place an empty `<trix-editor></trix-editor>` tag on the page. Trix will automatically insert a separate `<trix-toolbar>` before the editor.
+Place an empty `<trix-editor></trix-editor>` tag on the page. If the `<trix-editor>` element is rendered with a `[toolbar]` attribute that references the element by its `[id]`, it will treat that element as its toolbar:
+
+```html
+<trix-toolbar id="editor_toolbar"></trix-toolbar>
+
+<trix-editor toolbar="editor_toolbar"></trix-editor>
+```
+
+Otherwise, Trix will automatically insert a separate `<trix-toolbar>` before the editor.
 
 Like an HTML `<textarea>`, `<trix-editor>` accepts `autofocus` and `placeholder` attributes. Unlike a `<textarea>`, `<trix-editor>` automatically expands vertically to fit its contents.
 
 ## Integrating With Forms
 
+There are two styles of integrating with `<form>` element submissions.
+
+### Legacy integration with `<input type="hidden">`
+
+Legacy support is provided through an `<input type="hidden">` element paired with an `[input]` attribute on the `<trix-editor>` element.
+
 To submit the contents of a `<trix-editor>` with a form, first define a hidden input field in the form and assign it an `id`. Then reference that `id` in the editor’s `input` attribute.
 
 ```html
@@ -66,7 +80,7 @@ To submit the contents of a `<trix-editor>` with a form, first define a hidden i
 
 Trix will automatically update the value of the hidden input field with each change to the editor.
 
-## Populating With Stored Content
+#### Populating With Stored Content
 
 To populate a `<trix-editor>` with stored content, include that content in the associated input element’s `value` attribute.
 
@@ -79,6 +93,71 @@ To populate a `<trix-editor>` with stored content, include that content in the a
 
 Always use an associated input element to safely populate an editor. Trix won’t load any HTML content inside a `<trix-editor>…</trix-editor>` tag.
 
+### Integration with Element Internals
+
+Trix can also be configured to integrate with forms through the `<trix-editor>` element's `ElementInternals` instance.
+
+First, configure Trix to opt-into its Element Internals support by rendering a `<meta>` element into the document's `<head>`:
+
+```html
+<head>
+  <!-- … -->
+  <meta name="trix-config-editor-element-internals" content="true">
+</head>
+```
+
+Then, to submit the contents of a `<trix-editor>` with a `<form>`, render the element with a `[name]` attribute and its initial value as its inner HTML.
+
+```html
+<form …>
+  <trix-editor name="content"></trix-editor>
+</form>
+```
+
+To associate the element with a `<form>` that isn't an ancestor, render the element with a `[form]` attribute that references the `<form>` element by its `[id]`:
+
+```html
+<form id="a-form-element" …></form>
+<trix-editor name="content" form="a-form-element"></trix-editor>
+```
+
+#### Populating With Stored Content
+
+To populate a `<trix-editor>` with stored content, include that content as HTML inside the element’s inner HTML.
+
+```html
+<form …>
+  <trix-editor>Editor content goes here</trix-editor>
+</form>
+```
+
+## Providing an Accessible Name
+
+Like other form controls, `<trix-editor>` elements should have an accessible name. The `<trix-editor>` element integrates with `<label>` elements and The `<trix-editor>` supports two styles of integrating with `<label>` elements:
+
+1. render the `<trix-editor>` element with an `[id]` attribute that the `<label>` element references through its `[for]` attribute:
+
+```html
+<label for="editor">Editor</label>
+<trix-editor id="editor"></trix-editor>
+```
+
+2. render the `<trix-editor>` element as a child of the `<label>` element:
+
+```html
+<trix-toolbar id="editor-toolbar"></trix-toolbar>
+<label>
+  Editor
+
+  <trix-editor toolbar="editor-toolbar"></trix-editor>
+</label>
+```
+
+> [!WARNING]
+> When rendering the `<trix-editor>` element as a child of the `<label>` element, [explicitly render](#creating-an-editor) the corresponding `<trix-toolbar>` element outside of the `<label>` element.
+
+In addition to integrating with `<label>` elements, `<trix-editor>` elements support `[aria-label]` and `[aria-labelledby]` attributes.
+
 ## Styling Formatted Content
 
 To ensure what you see when you edit is what you see when you save, use a CSS class name to scope styles for Trix formatted content. Apply this class name to your `<trix-editor>` element, and to a containing element when you render stored Trix content for display in your application.

assets/index.html

@@ -12,7 +12,7 @@
         box-sizing: border-box;
       }
 
-      main {
+      main, nav {
         margin: 20px auto;
         max-width: 700px;
       }
@@ -69,10 +69,30 @@
         }
       });
     </script>
+    <script>
+      const searchParams = new URLSearchParams(location.search)
+
+      if (searchParams.get("editor") === "elementInternals") {
+        document.head.insertAdjacentHTML(
+          "beforeend",
+          `<meta name="trix-config-editor-element-internals" content="true">`
+        )
+
+        document.addEventListener("trix-change", function(event) {
+          var input = document.getElementById("input")
+          input.value = event.target.value
+        })
+      }
+    </script>
   </head>
   <body>
+    <nav>
+      <a href="/">Legacy support</a>
+      <a href="/?editor=elementInternals">ElementInternals support</a>
+    </nav>
     <main>
-      <trix-editor autofocus class="trix-content" input="input"></trix-editor>
+      <label for="editor">Input</label>
+      <trix-editor autofocus class="trix-content" id="editor"></trix-editor>
       <details id="output">
         <summary>Output</summary>
         <textarea readonly id="input"></textarea>

karma.conf.js

@@ -3,7 +3,7 @@ const config = {
   frameworks: [ "qunit" ],
   files: [
     { pattern: "dist/test.js", watched: false },
-    { pattern: "src/test_helpers/fixtures/*.png", watched: false, included: false, served: true }
+    { pattern: "src/test/test_helpers/fixtures/*.png", watched: false, included: false, served: true }
   ],
   proxies: {
     "/test_helpers/fixtures/": "/base/src/test_helpers/fixtures/"
@@ -101,6 +101,10 @@ if (process.env.SAUCE_ACCESS_KEY) {
   }
 }
 
+if (process.env.EDITOR_ELEMENT_INTERNALS === "true") {
+  config.files.unshift({ pattern: "src/test/test_helpers/fixtures/element_internals.js", watched: false, included: true })
+}
+
 function buildId() {
   const { GITHUB_WORKFLOW, GITHUB_RUN_NUMBER, GITHUB_RUN_ID } = process.env
   return GITHUB_WORKFLOW && GITHUB_RUN_NUMBER && GITHUB_RUN_ID

src/test/system/accessibility_test.js

@@ -1,4 +1,5 @@
-import { assert, test, testGroup, triggerEvent } from "test/test_helper"
+import * as config from "trix/config"
+import { assert, test, testGroup, testIf, testUnless, triggerEvent } from "test/test_helper"
 
 testGroup("Accessibility attributes", { template: "editor_default_aria_label" }, () => {
   test("sets the role to textbox", () => {
@@ -22,17 +23,26 @@ testGroup("Accessibility attributes", { template: "editor_default_aria_label" },
     assert.equal(editor.getAttribute("aria-labelledby"), "aria-labelledby-id")
   })
 
-  test("assigns aria-label to the text of the element's <label> elements", () => {
+  testUnless(config.editor.elementInternals, "assigns aria-label to the text of the element's <label> elements", () => {
     const editor = document.getElementById("editor-with-labels")
     assert.equal(editor.getAttribute("aria-label"), "Label 1 Label 2 Label 3")
   })
 
-  test("updates the aria-label on focus", () => {
+  testUnless(config.editor.elementInternals, "updates the aria-label on focus", () => {
     const editor = document.getElementById("editor-with-modified-label")
     const label = document.getElementById("modified-label")
 
     label.innerHTML = "<span>New Value</span>"
     triggerEvent(editor, "focus")
     assert.equal(editor.getAttribute("aria-label"), "New Value")
   })
+
+  testIf(config.editor.elementInternals, "does not set [aria-label] for a <label> element", () => {
+    const editor = document.getElementById("editor-with-labels")
+    const labels = Array.from(editor.labels)
+    const text = labels.map((label) => label.textContent.trim())
+
+    assert.deepEqual(text, [ "Label 1", "Label 2", "Label 3" ])
+    assert.equal(editor.getAttribute("aria-label"), null)
+  })
 })

src/test/system/custom_element_test.js

@@ -1,3 +1,4 @@
+import * as config from "trix/config"
 import { rangesAreEqual } from "trix/core/helpers"
 
 import {
@@ -13,6 +14,7 @@ import {
   test,
   testGroup,
   testIf,
+  testUnless,
   triggerEvent,
   typeCharacters,
   typeInToolbarDialog,
@@ -391,12 +393,6 @@ testGroup("Custom element API", { template: "editor_empty" }, () => {
     })
   })
 
-  test("element returns empty string when value is missing", async () => {
-    const element = getEditorElement()
-
-    assert.equal(element.value, "")
-  })
-
   test("element serializes HTML after attribute changes", async () => {
     const element = getEditorElement()
     let serializedHTML = element.value
@@ -446,14 +442,6 @@ testGroup("Custom element API", { template: "editor_empty" }, () => {
     return promise
   })
 
-  test("editor resets to its original value on element reset", async () => {
-    const element = getEditorElement()
-
-    await typeCharacters("hello")
-    element.reset()
-    expectDocument("\n")
-  })
-
   test("editor resets to its original value on form reset", async () => {
     const element = getEditorElement()
     const { form } = element
@@ -485,6 +473,26 @@ testGroup("Custom element API", { template: "editor_empty" }, () => {
     form.removeEventListener("reset", preventDefault, false)
     expectDocument("hello\n")
   })
+
+  test("editor resets to its original value on element reset", async () => {
+    const element = getEditorElement()
+
+    await typeCharacters("hello")
+    element.reset()
+    expectDocument("\n")
+  })
+
+  test("element returns empty string when value is missing", async () => {
+    const element = getEditorElement()
+
+    assert.equal(element.value, "")
+  })
+
+  test("editor returns its type", async() => {
+    const element = getEditorElement()
+
+    assert.equal("trix-editor", element.type)
+  })
 })
 
 testGroup("HTML sanitization", { template: "editor_html" }, () => {
@@ -501,15 +509,15 @@ testGroup("HTML sanitization", { template: "editor_html" }, () => {
 testGroup("<label> support", { template: "editor_with_labels" }, () => {
   test("associates all label elements", () => {
     const labels = [ document.getElementById("label-1"), document.getElementById("label-3") ]
-    assert.deepEqual(getEditorElement().labels, labels)
+    assert.deepEqual(Array.from(getEditorElement().labels), labels)
   })
 
-  test("focuses when <label> clicked", () => {
+  testUnless(config.editor.elementInternals, "focuses when <label> clicked", () => {
     document.getElementById("label-1").click()
     assert.equal(getEditorElement(), document.activeElement)
   })
 
-  test("focuses when <label> descendant clicked", () => {
+  testUnless(config.editor.elementInternals, "focuses when <label> descendant clicked", () => {
     document.getElementById("label-1").querySelector("span").click()
     assert.equal(getEditorElement(), document.activeElement)
   })
@@ -529,7 +537,7 @@ testGroup("form property references its <form>", { template: "editors_with_forms
     assert.equal(editor.form, form)
   })
 
-  test("transitively accesses its related <input> element's <form>", () => {
+  test("transitively accesses its related <form>", () => {
     const form = document.getElementById("input-form")
     const editor = document.getElementById("editor-with-input-form")
     assert.equal(editor.form, form)
@@ -539,10 +547,4 @@ testGroup("form property references its <form>", { template: "editors_with_forms
     const editor = document.getElementById("editor-with-no-form")
     assert.equal(editor.form, null)
   })
-
-  test("editor returns its type", async() => {
-    const element = getEditorElement()
-
-    assert.equal("trix-editor", element.type)
-  })
 })

src/test/system/installation_process_test.js

@@ -1,6 +1,7 @@
+import * as config from "trix/config"
 import EditorController from "trix/controllers/editor_controller"
 
-import { assert, test, testGroup } from "test/test_helper"
+import { assert, test, testGroup, testUnless } from "test/test_helper"
 import { nextFrame } from "../test_helpers/timing_helpers"
 
 testGroup("Installation process", { template: "editor_html" }, () => {
@@ -20,23 +21,27 @@ testGroup("Installation process", { template: "editor_html" }, () => {
   })
 })
 
-testGroup("Installation process without specified elements", { template: "editor_empty" }, () =>
-  test("creates identified toolbar and input elements", () => {
+testGroup("Installation process without specified elements", { template: "editor_empty" }, () => {
+  test("creates identified toolbar", () => {
     const editorElement = getEditorElement()
 
     const toolbarId = editorElement.getAttribute("toolbar")
     assert.ok(/trix-toolbar-\d+/.test(toolbarId), `toolbar id not assert.ok ${JSON.stringify(toolbarId)}`)
     const toolbarElement = document.getElementById(toolbarId)
     assert.ok(toolbarElement, "toolbar element not assert.ok")
     assert.equal(editorElement.toolbarElement, toolbarElement)
+  })
+
+  testUnless(config.editor.elementInternals, "creates identified input elements", () => {
+    const editorElement = getEditorElement()
 
     const inputId = editorElement.getAttribute("input")
     assert.ok(/trix-input-\d+/.test(inputId), `input id not assert.ok ${JSON.stringify(inputId)}`)
     const inputElement = document.getElementById(inputId)
     assert.ok(inputElement, "input element not assert.ok")
     assert.equal(editorElement.inputElement, inputElement)
   })
-)
+})
 
 testGroup("Installation process with specified elements", { template: "editor_with_toolbar_and_input" }, () => {
   test("uses specified elements", () => {

src/test/test_helpers/fixtures/editor_html.js

@@ -1,3 +1,8 @@
+import * as config from "trix/config"
+
 export default () =>
-  `<input id="my_input" type="hidden" value="&lt;div&gt;Hello world&lt;/div&gt;">
-  <trix-editor input="my_input" autofocus placeholder="Say hello..."></trix-editor>`
+  config.editor.elementInternals ?
+    `<trix-editor autofocus placeholder="Say hello..."><div>Hello world</div></trix-editor>
+    ` :
+    `<input id="my_input" type="hidden" value="&lt;div&gt;Hello world&lt;/div&gt;">
+    <trix-editor input="my_input" autofocus placeholder="Say hello..."></trix-editor>`

src/test/test_helpers/fixtures/editor_with_image.js

@@ -1,5 +1,9 @@
+import * as config from "trix/config"
 import { TEST_IMAGE_URL } from "./test_image_url"
 
 export default () =>
-  `<trix-editor input="my_input" autofocus placeholder="Say hello..."></trix-editor>
-  <input id="my_input" type="hidden" value="ab&lt;img src=&quot;${TEST_IMAGE_URL}&quot; width=&quot;10&quot; height=&quot;10&quot;&gt;">`
+  config.editor.elementInternals ?
+    `<trix-editor autofocus placeholder="Say hello...">ab<img src="${TEST_IMAGE_URL}" width="10" height="10"></trix-editor>
+    ` :
+    `<trix-editor input="my_input" autofocus placeholder="Say hello..."></trix-editor>
+    <input id="my_input" type="hidden" value="ab&lt;img src=&quot;${TEST_IMAGE_URL}&quot; width=&quot;10&quot; height=&quot;10&quot;&gt;">`