Fix: duplicated newlines when using dictation on iOS 18+.

This fixes a bug that started to happen with iOS 18, where you would get duplicated newlines
after completing the dictation.

The bug happens because, upon dictation completion, iOS sends the sequence of `beforeinput` events
very quickly. With the `insertParagraph` ones, it can happen that the internal document range fails
to update, resulting in duplicated newlines and missed content.

This workaround is necessary due to the inability to distinguish text entered in dictation mode, as
iOS WebKit doesn’t trigger composition events during dictation (https://bugs.webkit.org/show_bug.cgi?id=261764).

src/test/system/level_2_input_test.js

@@ -52,11 +52,18 @@ const performInputTypeUsingExecCommand = async (command, { inputType, data }) =>
 
   await nextFrame()
 
+  const isInsertParagraph = inputType === "insertParagraph"
+
   triggerInputEvent(document.activeElement, "beforeinput", { inputType, data })
-  document.execCommand(command, false, data)
-  assert.equal(inputEvents.length, 2)
+
+  // See `shouldRenderInmmediately` to deal with iOS 18+ dictation bug.
+  if (!isInsertParagraph) {
+    document.execCommand(command, false, data)
+    assert.equal(inputEvents[1].type, "input")
+  }
+
+  assert.equal(inputEvents.length, isInsertParagraph ? 1 : 2)
   assert.equal(inputEvents[0].type, "beforeinput")
-  assert.equal(inputEvents[1].type, "input")
   assert.equal(inputEvents[0].inputType, inputType)
   assert.equal(inputEvents[0].data, data)
 

src/test/test_helpers/input_helpers.js

@@ -276,9 +276,8 @@ const simulateKeypress = async (keyName) => {
       await deleteInDirection("right")
       break
     case "return":
-      await nextFrame()
       triggerInputEvent(document.activeElement, "beforeinput", { inputType: "insertParagraph" })
-      await insertNode(document.createElement("br"))
+      break
   }
 }
 

src/trix/controllers/level_2_input_controller.js

@@ -1,4 +1,4 @@
-import { getAllAttributeNames, squishBreakableWhitespace } from "trix/core/helpers"
+import { getAllAttributeNames, shouldRenderInmmediately, squishBreakableWhitespace } from "trix/core/helpers"
 import InputController from "trix/controllers/input_controller"
 import * as config from "trix/config"
 
@@ -80,7 +80,12 @@ export default class Level2InputController extends InputController {
 
       if (handler) {
         this.withEvent(event, handler)
-        this.scheduleRender()
+
+        if (shouldRenderInmmediately(event)) {
+          this.render()
+        } else {
+          this.scheduleRender()
+        }
       }
     },
 

src/trix/core/helpers/events.js

@@ -43,3 +43,16 @@ export const keyEventIsKeyboardCommand = (function() {
     return (event) => event.ctrlKey
   }
 })()
+
+export function shouldRenderInmmediately(inputEvent) {
+  if (/iPhone|iPad/.test(navigator.userAgent)) {
+    // Handle duplicated newlines when using dictation on iOS 18+. Upon dictation completion, iOS sends
+    // the list of insertText / insertParagraph events in a quick sequence. For newlines, if we don't render
+    // the editor synchronously, the internal range fails to update and results in duplicated newlines.
+    // This workaround is necessary because iOS doesn't send composing events as expected while dictating:
+    // https://bugs.webkit.org/show_bug.cgi?id=261764
+    return inputEvent.inputType === "insertParagraph"
+  } else {
+    return false
+  }
+}