use android QwertyKeyListener for deleting backward

Author: DeMonkeyCoder

shell/platform/android/io/flutter/plugin/editing/InputConnectionAdaptor.java

@@ -16,6 +16,8 @@
 import android.text.Layout;
 import android.text.Selection;
 import android.text.TextPaint;
+import android.text.method.QwertyKeyListener;
+import android.text.method.TextKeyListener.Capitalize;
 import android.view.KeyEvent;
 import android.view.View;
 import android.view.inputmethod.BaseInputConnection;
@@ -237,53 +239,12 @@ public boolean sendKeyEvent(KeyEvent event) {
           updateEditingState();
           return true;
         } else if (selStart > 0) {
-          // Delete to the left/right of the cursor depending on direction of text.
-          // TODO(garyq): Explore how to obtain per-character direction. The
-          // isRTLCharAt() call below is returning blanket direction assumption
-          // based on the first character in the line.
-
-          Boolean selectedCharIsEmoji = false;
-          if (selStart > 1) {
-            final String emo_regex =
-                "([\\u20a0-\\u32ff\\ud83c\\udc00-\\ud83d\\udeff\\udbb9\\udce5-\\udbb9\\udcee])";
-            String lastChars = mLayout.getText().subSequence(selStart - 2, selStart).toString();
-            selectedCharIsEmoji = lastChars.matches(emo_regex);
-          }
-
-          // The Selection.extendLeft and extendRight calls have some problems
-          // when mixing RTL and LTR text so if selected character is not emoji
-          // simply select that character
-          if (selectedCharIsEmoji) {
-            boolean isRtl =
-                mLayout.isRtlCharAt(mLayout.getLineStart(mLayout.getLineForOffset(selStart)));
-            Log.i("isRtl", Boolean.toString(isRtl));
-            try {
-              if (isRtl) {
-                Selection.extendRight(mEditable, mLayout);
-              } else {
-                Selection.extendLeft(mEditable, mLayout);
-              }
-            } catch (IndexOutOfBoundsException e) {
-              // On some Chinese devices (primarily Huawei, some Xiaomi),
-              // on initial app startup before focus is lost, the
-              // Selection.extendLeft and extendRight calls always extend
-              // from the index of the initial contents of mEditable. This
-              // try-catch will prevent crashing on Huawei devices by falling
-              // back to a simple way of deletion, although this a hack and
-              // will not handle emojis.
-              Selection.setSelection(mEditable, selStart, selStart - 1);
-            }
-          } else {
-            Selection.setSelection(mEditable, selStart, selStart - 1);
+          QwertyKeyListener qwertyKeyListener = new QwertyKeyListener(Capitalize.NONE, false);
+          if (qwertyKeyListener.onKeyDown(null, mEditable, event.getKeyCode(), event)) {
+            updateEditingState();
+            return true;
           }
-          int newStart = clampIndexToEditable(Selection.getSelectionStart(mEditable), mEditable);
-          int newEnd = clampIndexToEditable(Selection.getSelectionEnd(mEditable), mEditable);
-          Selection.setSelection(mEditable, Math.min(newStart, newEnd));
-          // Min/Max the values since RTL selections will start at a higher
-          // index than they end at.
-          mEditable.delete(Math.min(newStart, newEnd), Math.max(newStart, newEnd));
-          updateEditingState();
-          return true;
+          return false;
         }
       } else if (event.getKeyCode() == KeyEvent.KEYCODE_DPAD_LEFT) {
         int selStart = Selection.getSelectionStart(mEditable);

shell/platform/android/test/io/flutter/plugin/editing/InputConnectionAdaptorTest.java

@@ -256,15 +256,44 @@ public void testSendKeyEvent_downKeyMovesCaretDown() {
     assertTrue(Selection.getSelectionStart(editable) > selStart);
   }
 
+  @Test
+  public void testSendKeyEvent_delKeyDeletesBackward() {
+    int selStart = 29;
+    Editable editable = sampleRtlEditable(selStart, selStart);
+    InputConnectionAdaptor adaptor = sampleInputConnectionAdaptor(editable);
+
+    KeyEvent downKeyDown = new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DEL);
+
+    for (int i = 0; i < 9; i++) {
+      boolean didConsume = adaptor.sendKeyEvent(downKeyDown);
+      assertTrue(didConsume);
+    }
+    assertEquals(Selection.getSelectionStart(editable), 19);
+
+    for (int i = 0; i < 9; i++) {
+      boolean didConsume = adaptor.sendKeyEvent(downKeyDown);
+      assertTrue(didConsume);
+    }
+    assertEquals(Selection.getSelectionStart(editable), 10);
+  }
+
   private static final String SAMPLE_TEXT =
       "Lorem ipsum dolor sit amet," + "\nconsectetur adipiscing elit.";
 
+  private static final String SAMPLE_RTL_TEXT = "متن ساختگی" + "\nبرای تستfor test😊";
+
   private static Editable sampleEditable(int selStart, int selEnd) {
     SpannableStringBuilder sample = new SpannableStringBuilder(SAMPLE_TEXT);
     Selection.setSelection(sample, selStart, selEnd);
     return sample;
   }
 
+  private static Editable sampleRtlEditable(int selStart, int selEnd) {
+    SpannableStringBuilder sample = new SpannableStringBuilder(SAMPLE_RTL_TEXT);
+    Selection.setSelection(sample, selStart, selEnd);
+    return sample;
+  }
+
   private static InputConnectionAdaptor sampleInputConnectionAdaptor(Editable editable) {
     View testView = new View(RuntimeEnvironment.application);
     int client = 0;