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

image-editor/lib/src/main/java/org/signal/imageeditor/core/HiddenEditText.java

@@ -17,6 +17,10 @@ import androidx.annotation.Nullable;
 import org.signal.imageeditor.core.model.EditorElement;
 import org.signal.imageeditor.core.renderers.MultiLineTextRenderer;
 
+import java.util.Collection;
+import java.util.LinkedList;
+import java.util.List;
+
 /**
  * Invisible {@link android.widget.EditText} that is used during in-image text editing.
  */
@@ -37,6 +41,8 @@ public final class HiddenEditText extends androidx.appcompat.widget.AppCompatEdi
   @Nullable
   private OnEditOrSelectionChange onEditOrSelectionChange;
 
+  private List<TextFilter> textFilters = new LinkedList<>();
+
   public HiddenEditText(Context context) {
     super(context);
     setAlpha(0);
@@ -54,7 +60,11 @@ public final class HiddenEditText extends androidx.appcompat.widget.AppCompatEdi
   protected void onTextChanged(CharSequence text, int start, int lengthBefore, int lengthAfter) {
     super.onTextChanged(text, start, lengthBefore, lengthAfter);
     if (currentTextEntity != null) {
-      currentTextEntity.setText(text.toString());
+      String filtered = text.toString();
+      for (TextFilter filter : textFilters) {
+        filtered = filter.filter(filtered);
+      }
+      currentTextEntity.setText(filtered);
       postEditOrSelectionChange();
     }
   }
@@ -79,6 +89,18 @@ public final class HiddenEditText extends androidx.appcompat.widget.AppCompatEdi
     }
   }
 
+  public void addTextFilter(@NonNull TextFilter filter) {
+    textFilters.add(filter);
+  }
+
+  public void addTextFilters(@NonNull Collection<TextFilter> filters) {
+    textFilters.addAll(filters);
+  }
+
+  public void removeTextFilter(@NonNull TextFilter filter) {
+    textFilters.remove(filter);
+  }
+
   private void endEdit() {
     if (onEndEdit != null) {
       onEndEdit.run();
@@ -173,4 +195,11 @@ public final class HiddenEditText extends androidx.appcompat.widget.AppCompatEdi
   public interface OnEditOrSelectionChange {
     void onChange(@NonNull EditorElement editorElement, @NonNull MultiLineTextRenderer textRenderer);
   }
+
+  public interface TextFilter {
+    /**
+     * Given an input string, return a filtered version.
+     */
+    String filter(@NonNull String text);
+  }
 }

image-editor/lib/src/main/java/org/signal/imageeditor/core/ImageEditorView.java

@@ -24,6 +24,9 @@ import org.signal.imageeditor.core.renderers.BezierDrawingRenderer;
 import org.signal.imageeditor.core.renderers.MultiLineTextRenderer;
 import org.signal.imageeditor.core.renderers.TrashRenderer;
 
+import java.util.LinkedList;
+import java.util.List;
+
 /**
  * ImageEditorView
  * <p>
@@ -71,6 +74,8 @@ public final class ImageEditorView extends FrameLayout {
   @Nullable
   private DragListener dragListener;
 
+  private final List<HiddenEditText.TextFilter> textFilters = new LinkedList<>();
+
   private final Matrix viewMatrix      = new Matrix();
   private final RectF  viewPort        = Bounds.newFullBounds();
   private final RectF  visibleViewPort = Bounds.newFullBounds();
@@ -116,6 +121,8 @@ public final class ImageEditorView extends FrameLayout {
     editText.clearFocus();
     editText.setOnEndEdit(this::doneTextEditing);
     editText.setOnEditOrSelectionChange(this::zoomToFitText);
+    editText.addTextFilters(textFilters);
+
     return editText;
   }
 
@@ -150,6 +157,16 @@ public final class ImageEditorView extends FrameLayout {
     this.typefaceProvider = typefaceProvider;
   }
 
+  public void addTextInputFilter(@NonNull HiddenEditText.TextFilter inputFilter) {
+    textFilters.add(inputFilter);
+    editText = createAHiddenTextEntryField();
+  }
+
+  public void removeTextInputFilter(@NonNull HiddenEditText.TextFilter inputFilter) {
+    textFilters.remove(inputFilter);
+    editText = createAHiddenTextEntryField();
+  }
+
   @Override
   protected void onDraw(Canvas canvas) {
     if (rendererContext == null || rendererContext.canvas != canvas || rendererContext.typefaceProvider != typefaceProvider) {