Partial Mitigation for Samsung TextInput Hangs (facebook#35967)

Summary:
Pull Request resolved: facebook#35967

In facebook#35936 we observed that the presence of AbsoluteSizeSpan may lead to hangs when using the Grammarly keyboard on Samsung.

This mitigation makes it so that we do not emit this span in the most common cases, when it is sufficient to set `android:textSize`. In simple cases, it causes typing into the TextInput to no longer hang.

This does not resolve the issue for TextInputs which meaningfully use layout-effecting spans (or at least font size), such as non-uniform text size within the input. We could potentially do further work to reduce the number of spans emitted in these scenarios, but this may be fighting a losing battle against the platform.

Changelog:
[Android][Fixed] - Partial Mitigation for Samsung TextInput Hangs (Paper)

Reviewed By: cortinico

Differential Revision: D42721684

fbshipit-source-id: 1b6935014c8055c3bd547c7ba5294bb9975479c2

ReactAndroid/src/main/java/com/facebook/react/views/textinput/ReactEditText.java

@@ -585,6 +585,10 @@ public void maybeSetText(ReactTextUpdate reactTextUpdate) {
         new SpannableStringBuilder(reactTextUpdate.getText());
 
     manageSpans(spannableStringBuilder, reactTextUpdate.mContainsMultipleFragments);
+
+    // Mitigation for https://github.com/facebook/react-native/issues/35936 (S318090)
+    stripAbsoluteSizeSpans(spannableStringBuilder);
+
     mContainsImages = reactTextUpdate.containsImages();
 
     // When we update text, we trigger onChangeText code that will
@@ -658,6 +662,31 @@ private void manageSpans(
     }
   }
 
+  private void stripAbsoluteSizeSpans(SpannableStringBuilder sb) {
+    // We have already set a font size on the EditText itself. We can safely remove sizing spans
+    // which are the same as the set font size, and not otherwise overlapped.
+    final int effectiveFontSize = mTextAttributes.getEffectiveFontSize();
+    ReactAbsoluteSizeSpan[] spans = sb.getSpans(0, sb.length(), ReactAbsoluteSizeSpan.class);
+
+    outer:
+    for (ReactAbsoluteSizeSpan span : spans) {
+      if (span.getSize() != effectiveFontSize) {
+        continue;
+      }
+
+      ReactAbsoluteSizeSpan[] overlappingSpans =
+          sb.getSpans(sb.getSpanStart(span), sb.getSpanEnd(sb), ReactAbsoluteSizeSpan.class);
+
+      for (ReactAbsoluteSizeSpan overlappingSpan : overlappingSpans) {
+        if (span.getSize() != effectiveFontSize) {
+          continue outer;
+        }
+      }
+
+      sb.removeSpan(span);
+    }
+  }
+
   private static boolean sameTextForSpan(
       final Editable oldText,
       final SpannableStringBuilder newText,