Do not allow emoji in image editing if device doesn't support it.

core-util/src/main/java/org/signal/core/util/FontUtil.kt

@@ -0,0 +1,40 @@
+package org.signal.core.util
+
+import android.graphics.Bitmap
+import android.graphics.Canvas
+import android.graphics.Color
+import android.graphics.Paint
+import android.graphics.PorterDuff
+import kotlin.math.abs
+
+
+object FontUtil {
+  private const val SAMPLE_EMOJI = "\uD83C\uDF0D" // 🌍
+
+  /**
+   * Certain platforms cannot render emoji above a certain font size.
+   *
+   * This will attempt to render an emoji at the specified font size and tell you if it's possible.
+   * It does this by rendering an emoji into a 1x1 bitmap and seeing if the resulting pixel is non-transparent.
+   *
+   * https://stackoverflow.com/a/50988748
+   */
+  @JvmStatic
+  fun canRenderEmojiAtFontSize(size: Float): Boolean {
+    val bitmap: Bitmap = Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888)
+    val canvas = Canvas(bitmap)
+    val paint = Paint()
+
+    paint.textSize = size
+    paint.textAlign = Paint.Align.CENTER
+
+    val ascent: Float = abs(paint.ascent())
+    val descent: Float = abs(paint.descent())
+    val halfHeight = (ascent + descent) / 2.0f
+
+    canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR)
+    canvas.drawText(SAMPLE_EMOJI, 0.5f, 0.5f + halfHeight - descent, paint)
+
+    return bitmap.getPixel(0, 0) != 0
+  }
+}

core-util/src/main/java/org/signal/core/util/ListUtil.java

@@ -3,7 +3,9 @@ package org.signal.core.util;
 import androidx.annotation.NonNull;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
+import java.util.stream.Stream;
 
 public final class ListUtil {
   private ListUtil() {}
@@ -18,4 +20,15 @@ public final class ListUtil {
 
     return chunks;
   }
+
+  @SafeVarargs
+  public static <T> List<T> concat(Collection<T>... items) {
+    final List<T> concat = new ArrayList<>(Stream.of(items).map(Collection::size).reduce(0, Integer::sum));
+
+    for (Collection<T> list : items) {
+      concat.addAll(list);
+    }
+
+    return concat;
+  }
 }