EmojiCompat TextWatcher that supports rendering glyphs when text is replaced in an EditText widget - https://issuetracker.google.com/issues/257225296

EmojiTextWatcherReplacementSupport.kt

import android.annotation.SuppressLint
import android.text.Editable
import android.text.Selection
import android.text.Spannable
import android.text.TextWatcher
import android.widget.EditText
import androidx.emoji2.text.EmojiCompat
import androidx.emoji2.text.EmojiCompat.InitCallback
import java.lang.ref.Reference
import java.lang.ref.WeakReference

/** Shameless copy of Androidx's EmojiTextWatcher, fixes EmojiCompat process when replacing text with Emoji glyphs */
class EmojiTextWatcherReplacementSupport(private val editText: EditText) : TextWatcher {

  private val initCallback: InitCallback by lazy { InitCallbackImpl(WeakReference(editText)) }

  @SuppressLint("CheckResult")
  override fun onTextChanged(text: CharSequence?, start: Int, before: Int, after: Int) {
    if (before <= after) {
      // Google's EmojiTextWatcher handles this case, so we don't need to.
      return
    }

    when (EmojiCompat.get().loadState) {
      EmojiCompat.LOAD_STATE_SUCCEEDED -> {
        EmojiCompat.get().process(text, start, start + after, maxEmojiCount, emojiReplaceStrategy)
      }
      EmojiCompat.LOAD_STATE_LOADING,
      EmojiCompat.LOAD_STATE_DEFAULT -> EmojiCompat.get().registerInitCallback(initCallback)
      EmojiCompat.LOAD_STATE_FAILED -> {}
      else -> {}
    }
  }

  override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
    // do nothing
  }

  override fun afterTextChanged(s: Editable?) {
    // do nothing
  }

  private class InitCallbackImpl(private val editTextReference: Reference<EditText>) :
    InitCallback() {

    @SuppressLint("CheckResult")
    override fun onInitialized() {
      val editText = editTextReference.get()
      if (editText?.isAttachedToWindow == true) {
        val text: Editable = editText.editableText
        val selectionStart = Selection.getSelectionStart(text)
        val selectionEnd = Selection.getSelectionEnd(text)
        EmojiCompat.get().process(text)
        updateSelection(text, selectionStart, selectionEnd)
      }
    }

    override fun onFailed(throwable: Throwable?) {
      super.onFailed(throwable)
      throw RuntimeException(throwable)
    }

    fun updateSelection(spannable: Spannable?, start: Int, end: Int) {
      if (start >= 0 && end >= 0) {
        Selection.setSelection(spannable, start, end)
      } else if (start >= 0) {
        Selection.setSelection(spannable, start)
      } else if (end >= 0) {
        Selection.setSelection(spannable, end)
      }
    }
  }

  companion object {
    private const val maxEmojiCount = Int.MAX_VALUE
    private const val emojiReplaceStrategy = EmojiCompat.REPLACE_STRATEGY_ALL
  }
}